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Author name code: dravins
ADS astronomy entries on 2022-09-14
author:"Dravins, Dainis"
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Title: CTA – the World's largest ground-based gamma-ray observatory
Authors: Zanin, R.; Abdalla, H.; Abe, H.; Abe, S.; Abusleme, A.;
Acero, F.; Acharyya, A.; Acin Portella, V.; Ackley, K.; Adam, R.;
Adams, C.; Adhikari, S. S.; Aguado Ruesga, I.; Agudo, I.; Aguilera,
R.; Aguirre Santaella, A.; Aharonian, F.; Alberdi, A.; Alfaro, R.;
Alfaro, J.; Alispach, C.; Aloisio, R.; Alves Batista, R.; Amans,
J. P.; Amati, L.; Amato, E.; Ambrogi, L.; Ambrosi, G.; Ambrosio, M.;
Ammendola, R.; Anderson, J.; Anduze, M.; Anguner, E. O.; Antonelli,
L. A.; Antonuccio, V.; Antoranz, P.; Anutarawiramkul, R.; Aragunde
Gutierrez, J.; Aramo, C.; Araudo, A.; Araya, M.; Arbet Engels, A.;
Arcaro, C.; Arendt, V.; Armand, C.; Armstrong, T.; Arqueros, F.;
Arrabito, L.; Arsioli, B.; Artero, M.; Asano, K.; Ascasibar, Y.;
Aschersleben, J.; Ashley, M.; Attina, P.; Aubert, P.; Singh, C. B.;
Baack, D.; Babic, A.; Backes, M.; Baena, V.; Bajtlik, S.; Baktash,
A.; Balazs, C.; Balbo, M.; Ballester, O.; Ballet, J.; Balmaverde, B.;
Bamba, A.; Bandiera, R.; Baquero Larriva, A.; Barai, P.; Barbier, C.;
Barbosa Martins, V.; Barcelo, M.; Barkov, M.; Barnard, M.; Baroncelli,
L.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Batista, P. I.;
Batkovic, I.; Bauer, C.; Bautista González, R.; Baxter, J.; Becciani,
U.; Becerra González, J.; Becherini, Y.; Beck, G.; Becker Tjus, J.;
Bednarek, W.; Belfiore, A.; Bellizzi, L.; Belmont, R.; Benbow, W.;
Berge, D.; Bernardini, E.; Bernardos, M. I.; Bernlöhr, K.; Berti,
A.; Berton, M.; Bertucci, B.; Beshley, V.; Bhatt, N.; Bhattacharyya,
S.; Bhattacharyya, W.; Bhattacharyya, S.; Bi, B. Y.; Bicknell, G.;
Biederbeck, N.; Bigongiari, C.; Biland, A.; Bird, R.; Bissaldi, E.;
Biteau, J.; Bitossi, M.; Blanch, O.; Blank, M.; Blazek, J.; Bobin,
J.; Boccato, C.; Bocchino, F.; Boehm, C.; Bohacova, M.; Boisson, C.;
Boix, J.; Bolle, J. P.; Bolmont, J.; Bonanno, G.; Bonavolontà, C.;
Bonneau Arbeletche, L.; Bonnoli, G.; Bordas, P.; Borkowski, J.; Bose,
R.; Bose, D.; Bosnjak, Z.; Bottacini, E.; Böttcher, M.; Botticella,
M. T.; Boutonnet, C.; Bouyjou, F.; Bozhilov, V.; Bozzo, E.; Brahimi,
L.; Braiding, C.; Brau Nogue, S.; Breen, S.; Bregeon, J.; Breuhaus,
M.; Brill, A.; Brisken, W.; Brocato, E.; Brown, A. M.; Brügge, K.;
Brun, P.; Brun, F.; Brunetti, L.; Brunetti, G.; Bruno, P.; Bruno,
A.; Bruzzese, A.; Bucciantini, N.; Buckley, J. H.; Bühler, R.;
Bulgarelli, A.; Bulik, T.; Bünning, M.; Bunse, M.; Burton, M.;
Burtovoi, A.; Buscemi, M.; Buschjager, S.; Busetto, G.; Buss, J.;
Byrum, K.; Caccianiga, A.; Cadoux, F.; Calanducci, A.; Calderon,
C.; Calvo Tovar, J.; Cameron, R. A.; Campana, P.; Canestrari, R.;
Cangemi, F.; Cantlay, B.; Capalbi, M.; Capasso, M.; Cappi, M.;
Caproni, A.; Capuzzo Dolcetta, R.; Caraveo, P.; Cárdenas, V.;
Cardiel, L.; Cardillo, M.; Carlile, C.; Caroff, S.; Carosi, R.;
Carosi, A.; Carquin, E.; Carrere, M.; Casandjian, J. M.; Casanova,
S.; Cassol, F.; Catalani, F.; Catalano, O.; Cauz, D.; Ceccanti, A.;
Celestino Silva, C.; Cerny, K.; Cerruti, M.; Chabanne, E.; Chadwick,
P.; Chai, Y.; Chambery, P.; Champion, C.; Chaty, S.; Chen, A.; Cheng,
K.; Chernyakova, M.; Chiaro, G.; Chiavassa, A.; Chikawa, M.; Chitnis,
V. R.; Chudoba, J.; Chytka, L.; Cikota, S.; Circiello, A.; Clark,
P.; Colak, M.; Colombo, E.; Colonges, S.; Comastri, A.; Compagnino,
A.; Conforti, V.; Congiu, E.; Coniglione, R.; Conrad, J.; Conte,
F.; Contreras, J. L.; Coppi, P.; Cornat, R.; Coronado Blazquez,
J.; Cortina, J.; Costa, A.; Costantini, H.; Cotter, G.; Courty, B.;
Covino, S.; Crestan, S.; Cristofari, P.; Crocker, R.; Croston, J.;
Cubuk, K.; Cuevas, O.; Cui, X.; Cusumano, G.; Cutini, S.; D'Amico,
G.; D'Ammando, F.; D'Avanzo, P.; Da Vela, P.; Dadina, M.; Dai, S.;
Dalchenko, M.; Dall'Ora, M.; Daniel, M. K.; Dauguet, J.; Davids, I.;
Davies, J.; Dawson, B.; De Angelis, A.; de Araujo Carvalho, A. E.;
de Bony de Lavergne, M.; De Cesare, G.; de Frondat, F.; de la Calle,
I.; de Gouveia Dal Pino, E.; De Lotto, B.; De Luca, A.; De Martino,
D.; de Naurois, M.; de Ona Wilhelmi, E.; De Palma Persio, F.; De
Simone, N.; de Souza Valle, V.; Delagnes, E.; Deleglise Reznicek,
G.; Delgado, C.; Delgado Giler, A. G.; Delgado Mengual Valle, J.;
della Volpe, D.; Depaoli, D.; Devin, J.; Di Girolamo, T.; Di Giulio
Pierro, C.; Di Venere, L.; Díaz, C.; Dib, C.; Diebold, S.; Digel,
S.; Djannati Atai, A.; Djuvsland, J.; Dmytriiev, A.; Docher, K.;
Domínguez, A.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro,
M.; dos Anjos, R. d. C.; Dournaux, J. L.; Downes, T.; Drake, G.;
Drass, H.; Dravins, D.; Duangchan, C.; Duara, A.; Dubus, G.; Ducci,
L.; Duffy, C.; Dumora, D.; Dundas Mora, K.; Durkalec, A.; Dwarkadas,
V. V.; Ebr, J.; Eckner, C.; Eder, J.; Edy, E.; Egberts, K.; Einecke,
S.; Eleftheriadis, C.; Elsässer, D.; Emery, G.; Emmanoulopoulos, D.;
Ernenwein, J. P.; Errando, M.; Escarate, P.; Escudero, J.; Espinoza,
C.; Ettori, S.; Eungwanichayapant, A.; Evans, P.; Evoli, C.; Fairbairn,
M.; Falceta Goncalves, D.; Falcone, A.; Fallah Ramazanı, V.; Falomo,
R.; Farakos, K.; Fasola, G.; Fattorini, A.; Favre, Y.; Fedora, R.;
Fedorova, E.; Feijen, K.; Feng, Q.; Ferrand, G.; Ferrara, G.; Ferreira,
O.; Fesquet, M.; Fiandrini, E.; Fiasson, A.; Filipovic, M.; Fink, D.;
Finley, J. P.; Fioretti, V.; Fiorillo, D. F. G.; Fiorini, M.; Flis, S.;
Flores, H.; Foffano, L.; Fohr, C.; Fonseca, M. V.; Font, L.; Fontaine,
G.; Fornieri, O.; Fortin, P.; Fortson, L.; Fouque, N.; Fraga, B.;
Franceschini, A.; Franco, F. J.; Freixas Coromina, L.; Fresnillo, L.;
Fugazza, D.; Fujita, Y.; Fukami, S.; Fukazawa, Y.; Fulla, D.; Funk,
S.; Furniss, A.; Gabici, S.; Gaggero, D.; Galanti, G.; Galdemard,
P.; Gallant, Y. A.; Galloway, D.; Gallozzi, S.; Gammaldi, V.; Garcia,
R.; Garcia, E.; Garcia Lopez, E.; Gargano, F.; Gargano, C.; Garozzo,
S.; Gascon, D.; Gasparetto, T.; Gasparrini, D.; Gasparyan, H.; Gaug,
M.; Geffroy, N.; Gent, A.; Germani, S.; Ghalumyan, A.; Ghedina, A.;
Ghirlanda, G.; Gianotti, F.; Giarrusso, S.; Giarrusso, M.; Giavitto,
G.; Giebels, B.; Giglietto, N.; Gika, V.; Gillardo, F.; Gimenes,
R.; Giordano, F.; Giro, E.; Giroletti, M.; Giuliani, A.; Gjaja,
M.; Glicenstein, J. F.; Gliwny, P.; Goksu, H.; Goldoni, P.; Gomez,
J. L.; Gonzalez, M. M.; Gonzalez, J. M.; Gothe, K. S.; Gotz Coelho,
D.; Grabarczyk, T.; Graciani, R.; Grandi, P.; Grasseau, G.; Grasso,
D.; Green, D.; Green, J.; Greenshaw, T.; Grespan, P.; Grillo, A.;
Grondin, M. H.; Grube, J.; Guarino, V.; Guest, B.; Gueta, O.; Günduz,
M.; Gunji, S.; Gyuk, G.; Hackfeld, J.; Hadasch, D.; Hagge, L.; Hahn,
A.; Hajlaoui, J. E.; Halim, A.; Hamal, P.; Hanlon, W.; Harada, Y.;
Hardcastle, M. J.; Collado, M. Harvey; Haubold, T.; Haupt, A.; Havelka,
M.; Hayashi, K.; Hayashi, K.; Hayashida, M.; He, H.; Heckmann, L.;
Heller, M.; Henault, F.; Henri, G.; Hermann, G.; Hernández Cadena, S.;
Herrera Llorente, J.; Hervet, O.; Hinton, J.; Hiramatsu, A.; Hirotani,
K.; Hnatyk, B.; Hnatyk, R.; Hoang, J. K.; Hoffmann, D. H. H.; Hoischen,
C.; Holder, J.; Holler, M.; Hona, B.; Horan, D.; Horns, D.; Horvath,
P.; Houles, J.; Hrabovsky, M.; Hrupec, D.; Huang, Y.; Huet, J. M.;
Hughes, G.; Hull, G.; Humensky, T. B.; Hütten, M.; Iarlori, M.; Illa,
J. M.; Imazawa, R.; Inada, T.; Incardona, F.; Ingallinera, A.; Inoue,
S.; Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Ionica, M.; Iovenitti,
S.; Iriarte, A.; Ishio, K.; Ishizaki, W.; Iwamura, Y.; Jacquemier, J.;
Jacquemont, M.; Jamrozy, M.; Janecek, P.; Jankowsky, F.; JardinBlicq,
A.; Jarnot, C.; Martínez, P. Jean; Jocou, L.; Jordana, N.; Josselin,
M.; JungRichardt, I.; Junqueira, F. J. P. A.; Juramy Gilles, C.;
Kaaret, P.; Kadowaki, L. H. S.; Kagaya, M.; Kankanyan, R.; Kantzas, D.;
Karas, V.; Karastergiou, A.; Karkar, S.; Kasperek, J.; Katagiri, H.;
Kataoka, J.; Katarzynski, K.; Katsuda, S.; Kawanaka, N.; Kazanas, D.;
Kerszberg, D.; Khélifi, B.; Kherlakian, M. C.; Kian, T. P.; Kieda,
D. B.; Kihm, T.; Kim, S.; Kisaka, S.; Kissmann, R.; Kleijwegt, R.;
Kluge, G.; Kluźniak, W.; Knapp, J.; Kobakhidze, A.; Kobayashi, Y.;
Koch, B.; Kocot, J.; Kohri, K.; Komin, N.; Kong, A.; Kosack, K.; Krack,
F.; Krause, M.; Krennrich, F.; Kubo, H.; Kudryavtsev, V. N.; Kunwar,
S.; Kushida, J.; Kushwaha, P.; Parola, B.; La Rosa, G.; Lahmann, R.;
Lamastra, A.; Landoni, M.; Landriu, D.; Lang, R. G.; Lapington, J.;
Laporte, P.; Lason, P.; Lasuik, J.; Lazendic Galloway, J.; Le Flour,
T.; Le Sidaner, P.; Leach, S.; Lee, S. H.; Lee, W. H.; Oliveira,
S. Lee; Lemiere, A.; Lemoine Goumard, M.; Lenain, J. P.; Leone,
F.; Leray, V.; Leto, G.; Leuschner, F.; Lindemann, R.; Lindfors,
E.; Linhoff, L.; Liodakis, I.; Lipniacka, A.; Lobo, M.; Lohse, T.;
Lombardi, S.; Lopez, A.; Lopez, M.; Lopez Coto, R.; Louis, F.; Louys,
M.; Lucarelli, F.; Boudi, H. Ludwig; Luque Escamilla, P. L.; Maccarone,
M. C.; Mach, E.; Maciejewski, A. J.; Mackey, J.; Maeght, P.; Maggio,
C.; Maier, G.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Malta Nunes
de Almeida, R.; Malyshev, D.; Malyshev, D.; Mandat, D.; Maneva, G.;
Manganaro, M.; Manigot, P.; Mannheim, K.; Maragos, N.; Marano, D.;
Marconi, M.; Marcowith, A.; Marculewicz, M.; Marcun, B.; Marin, J.;
Marinello, N.; Marinos, P.; Markoff, S.; Marquez, P.; Marsella, G.;
Martin, J. M.; Martin, P. G.; Martinez, M.; Martinez, G.; Martinez,
O.; Martinez Huerta, H.; Marty, C.; Marx, R.; Masetti, N.; Massimino,
P.; Matsumoto, H.; Matthews, N.; Maurin, G.; Moerbeck, W. Max; Maxted,
N.; Mazziotta, M. N.; Mazzola, S. M.; Mbarubucyeye, J. D.; Mc Comb,
L.; McHardy, I.; McKeague, S.; McMuldroch, S.; Medina, E.; Medina
Miranda, D.; Melandri, A.; Melioli, C.; Melkumyan, D.; Menchiari,
S.; Mereghetti, S.; Merino Arevalo, G.; Mestre, E.; Meunier, J. L.;
Meures, T.; Micanovic, S.; Miceli, M.; Michailidis, M.; Michalowski,
J.; Miener, T.; Mievre, I.; Miller, J. D.; Mineo, T.; Minev, M.;
Miranda, J. M.; Mitchell, A.; Mizuno, T.; Mode, B. A.; Moderski, R.;
Mohrmann, L.; Molinari, E.; Montaruli, T.; Monteiro, I.; Moore, C.;
Moralejo, A.; Morcuende Parrilla, D.; Moretti, E.; Mori, K.; Moriarty,
P.; Morik, K.; Morris, P.; Morselli, A.; Mosshammer, K.; Mukherjee,
R.; Muller, J.; Mundell, C.; Mundet, J.; Murach, T.; Muraczewski,
A.; Muraishi, H.; Musella, I.; Musumarra, A.; Nagai, A.; Nagataki,
S.; Naito, T.; Nakamori, T.; Nakashima, K.; Nakayama, K.; Nakhjiri,
N.; Naletto, G.; Naumann, D.; Nava, L.; Nawaz, M. A.; Ndiyavala,
H.; Neise, D.; Nellen, L.; Nemmen, R.; Neyroud, N.; Ngernphat, K.;
Nguyen Trung, T.; Nicastro, L.; Nickel, L.; Niemiec, J.; Nieto, D.;
Nigro, C.; Nikołajuk, M.; Ninci, D.; Noda, K.; Nogami, Y.; Nolan,
S.; Norris, R. P.; Nosek, D.; Nöthe, M.; Novotny, V.; Nozaki, S.;
Nunio, F.; O'Brien, P.; Obara, K.; Ohira, Y.; Ohishi, M.; Ohm, S.;
Oka, T.; Okazaki, N.; Okumura, A.; Oliver, C.; Olivera, G.; Olmi, B.;
Orienti, M.; Orito, R.; Orlandini, M.; Orlando, E.; Osborne, J. P.;
Ostrowski, M.; Otte, N.; Ovcharov, E.; Owen, E.; Oya, I.; Ozieblo, A.;
Padovani, M.; Pagliaro, A.; Paizis, A.; Palatiello, M.; Palatka, M.;
Palazzi, E.; Panazol, J. L.; Paneque, D.; Panny, S.; Pantaleo, F. R.;
Panter, M.; Paolillo, M.; Papitto, A.; Paravac, A.; Paredes, J. M.;
Pareschi, G.; Parmiggiani, N.; Parsons, R. D.; Paśko, P.; Patel,
S. R.; Patricelli, B.; Pavletic, L.; Pavy, S.; Peer, A.; Pecimotika,
M.; Pellegriti, M. G.; Peñil Del Campo, P.; Pepato, A.; Perard, S.;
Perennes, C.; Peresano, M.; Perez Aguilera, A.; Perez Romero, J.;
Perez Torres, M. A.; Persic, M.; Petrucci, P. O.; Petruk, O.; Peyaud,
B.; Pfrang, K.; Pian, E.; Piatteli, P.; Pietropaolo, E.; Pillera, R.;
Pimentel, D.; Pintore, F.; Garcia, C. Pio; Pirola, G.; Piron, F.; Pita,
S.; Pohl, M.; Poireau, V.; Pollo, A.; Polo, M.; Pongkitivanichkul, C.;
Porthault, J.; Powell, J.; Pozo, D.; Prado, R. R.; Prandini, E.; Prast,
J.; Pressard, K.; Principe, G.; Produit, N.; Prokhorov, D.; Prokoph,
H.; Przybilski, H.; Pueschel, E.; Pühlhofer, G.; Puljak, I.; Pumo,
M. L.; Punch, M.; Queiroz, F.; Quinn, J.; Quirrenbach, A.; Rajda,
P. J.; Rando, R.; Razzaque, S.; Recchia, S.; Reichherzer, P.; Reimer,
O.; Reisenegger, A.; Remy, Q.; Renaud, M.; Reposeur, T.; Reville,
B.; Reymond, J. M.; Reynolds, J.; Ribeiro, D.; Ribo, M.; Richards,
G.; Rico, J.; Rieger, F.; Riitano, L.; Riquelme, M.; Riquelme, D.;
Rivoire, S.; Rizi, V.; Roache, E.; Roche, M.; Rodriguez, J.; Rodriguez
Fernandez, G.; Rodriguez Ramirez, J. C.; Rodriguez Vazquez, J. J.;
Rojas, G.; Romano, P.; Romeo Lobato, G.; Romoli, C.; Roncadelli,
M.; Rosado, J.; Rosales de Leon, A.; Rowell, G.; Rugliancich, A.;
Ruiz del Mazo, J. E.; Rulten, C.; Russell, C.; Russo Hatlen, F.;
Safi Harb, S.; Saha, L.; Sahakian, V.; Sailer, S.; Saito, T.; Sakaki,
N.; Sakurai, S.; Salina, G.; Salzmann, H.; Sanchez, D.; Sandaker, H.;
Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.; Santander, M.;
Santangelo, A.; Santos Lima, R.; Sanuy, A.; Sapozhnikov, L.; Saric,
T.; Sarkar, S.; Sasaki, H.; Sasaki, N.; Sato, Y.; Saturni, F. G.;
Sawada, M.; Schaefer, J.; Scherer, A.; Scherpenberg, J.; Schipani,
P.; Schleicher, B.; Schmoll, J.; Schneider, M.; Schoorlemmer, H.;
Schovanek, P.; Schussler, F.; Schwab, B.; Schwanke, U.; Schwarz, J.;
Sciacca, E.; Scuderi, S.; Seglar Arroyo, M.; Seitenzahl, I.; Semikoz,
D.; Sergijenko, O.; Serna Franco, J. E.; Seweryn, K.; Sguera, V.;
Shalchi, A.; Shang, R. Y.; Sharma, P.; Sidoli, L.; Sieiro, J.;
Siejkowski, H.; Sillanpaa, A.; Singh, B. B.; Singh, K. K.; Sinha,
A.; Siqueira, C.; Sitarek, J.; Sizun, P.; Sliusar, V.; Sobczynska,
D.; Sobrinho, R. W.; Sol, H.; Sottile, G.; Spackman, H.; Spencer,
S.; Spengler, G.; Spiga, D.; Springer, W.; Stamerra, A.; Stanic, S.;
Starling, R.; Stawarz, Ł.; Stefanik, S.; Stegmann, C.; Steiner, A.;
Steinmassl, S.; Stella, C.; Sternberger, R.; Sterzel, M.; Stevens, C.;
Stevenson, B.; Stolarczyk, T.; Stratta, G.; Straumann, U.; Striskovic,
J.; Strzys, M.; Stuik, R.; Suchenek, M.; Sunada, Y.; Suomijarvi,
T.; Suric, T.; Suzuki, H.; Swierk, P.; Szepieniec, T.; Tachihara,
K.; Tagliaferri, G.; Tajima, H.; Tajima, N.; Tak, D.; Takahashi, H.;
Takahashi, M.; Takata, J.; Takeishi, R.; Tam, T.; Tanaka, M.; Tanaka,
T.; Tanaka, S.; Tavani, M.; Tavecchio, F.; Tavernier, T.; Taylor,
A. R.; Tejedor, L. A.; Temnikov, P.; Terauchi, K.; Terrazas, J. C.;
Terrier, R.; Terzic, T.; Teshima, M.; Thibaut, D.; Thocquenne, F.;
Tian, W.; Tibaldo, L.; Tiengo, A.; Tluczykont, M.; Todero Peixoto,
C. J.; Toma, K.; Tomankova, L.; Tomastik, J.; Tornikoski, M.; Torres,
D. F.; Torresi, E.; Tosti, G.; Tosti, L.; Tothill, N.; Toussenel,
F.; Tovmassian, G.; Trichard, C.; Trifoglio, M.; Trois, A.; Truzzi,
S.; Tsiahina, A.; Turk, B.; Tutone, A.; Uchiyama, Y.; Utayarat,
P.; Vaclavek, L.; Vacula, M.; Vagelli, V.; Vagnetti, F.; Valdivia,
J. A.; Valentino, M.; Valio, A.; Vallage, B.; Vallania Quispe, P.;
van den Berg, A. M.; van Driel, W.; van Eldik, C.; van Rensburg,
C.; van Soelen, B.; Vandenbroucke, J.; Vasileiadis, G.; Vassiliev,
V.; Vazquez Acosta, M.; Vecchi, M.; Vega, A.; Veh, J.; Veitch, P.;
Venter, C.; Ventura, S.; Vercellone, S.; Verguilov, V.; Verna, G.;
Vernetto, S.; Verzi, V.; Vettolani, G. P.; Veyssiere, C.; Viale, I.;
Viana, A.; Viaux, N.; Vignatti, J.; Vigorito, C. F.; Villanueva, J.;
Vitale, V.; Vittorini, V.; Vodeb, V.; Vogel, N.; Voisin, V.; Vorobiov,
S.; Vrastil, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wakazono,
K.; Wakely, S. P.; Ward, M.; Warren, D.; Watson, J.; Wechakama, M.;
Wegner, P.; Weinstein, A.; Weniger, C.; Werner, F.; Wetteskind, H.;
White, M. L.; Wierzcholska, A.; Wiesand, S.; Wijers, R.; Wilkinson,
M.; Will, M.; Williams, J.; Williamson, T. J.; Wolter, A.; Wong,
Y. W.; Wood, M.; Yamamoto, T.; Yamamoto, H.; Yamane, Y.; Yamazaki,
R.; Yanagita, S.; Yang, L.; Yoo, S.; Yoshida, T.; Yoshikoshi, T.;
Yu, P.; Yusafzai, A.; Zacharias, M.; Zaldivar, B.; Zampieri, L.;
Zanin, R.; Zanmar Sanchez, R.; Zaric, D.; Zavrtanik, M.; Zavrtanik,
D.; Zdziarski, A.; Zech, A.; Zechlin, H.; Zenin, A.; Zerwekh, A.;
Ziętara, K.; Zink, A.; Ziolkowski, J.; Zivec, M.; Zmija, A.
2022icrc.confE...5Z Altcode: 2022PoS...395E...5Z
No abstract at ADS
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Title: Astrometric radial velocities for nearby stars
Authors: Lindegren, Lennart; Dravins, Dainis
2021A&A...652A..45L Altcode: 2021arXiv210509014L
Context. Under certain conditions, stellar radial velocities can be
determined from astrometry, without any use of spectroscopy. This
enables us to identify phenomena, other than the Doppler effect,
that are displacing spectral lines. <BR /> Aims: The change of
stellar proper motions over time (perspective acceleration) is used
to determine radial velocities from accurate astrometric data, which
are now available from the Gaia and HIPPARCOS missions. <BR /> Methods:
Positions and proper motions at the epoch of HIPPARCOS are compared with
values propagated back from the epoch of the Gaia Early Data Release
3. This propagation depends on the radial velocity, which obtains its
value from an optimal fit assuming uniform space motion relative to the
solar system barycentre. <BR /> Results: For 930 nearby stars we obtain
astrometric radial velocities with formal uncertainties better than
100 km s<SUP>−1</SUP>; for 55 stars the uncertainty is below 10 km
s<SUP>−1</SUP>, and for seven it is below 1 km s<SUP>−1</SUP>. Most
stars that are not components of double or multiple systems show
good agreement with available spectroscopic radial velocities. <BR />
Conclusions: Astrometry offers geometric methods to determine stellar
radial velocity, irrespective of complexities in stellar spectra. This
enables us to segregate wavelength displacements caused by the radial
motion of the stellar centre-of-mass from those induced by other
effects, such as gravitational redshifts in white dwarfs.
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Title: Intensity Interferometry
Authors: Dravins, Dainis
2021hai3.book...31D Altcode:
No abstract at ADS
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Title: Spatially resolved spectroscopy across stellar surfaces. IV. F,
G, and K-stars: Synthetic 3D spectra at hyper-high resolution
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Freytag, Bernd
2021A&A...649A..16D Altcode: 2021arXiv210303880D
Context. High-precision stellar analyses require hydrodynamic 3D
modeling. Such models predict changes across stellar disks of spectral
line shapes, asymmetries, and wavelength shifts. For testing models in
stars other than the Sun, spatially resolved observations are feasible
from differential spectroscopy during exoplanet transits, retrieving
spectra of those stellar surface segments that successively become
hidden behind the transiting planet, as demonstrated in Papers I, II,
and III. <BR /> Aims: Synthetic high-resolution spectra over extended
spectral regions are now available from 3D models. Similar to other ab
initio simulations in astrophysics, these data contain patterns that
have not been specifically modeled but may be revealed after analyses
to be analogous to those of a large volume of observations. <BR />
Methods: From five 3D models spanning T<SUB>eff</SUB> = 3964-6726 K
(spectral types ~K8 V-F3 V), synthetic spectra at hyper-high resolution
(λ/Δλ >1 000 000) were analyzed. Selected Fe I and Fe II lines at
various positions across stellar disks were searched for characteristic
patterns between different types of lines in the same star and for
similar lines between different stars. <BR /> Results: Spectral-line
patterns are identified for representative photospheric lines of
different strengths, excitation potentials, and ionization levels,
thereby encoding the hydrodynamic 3D structure. Line profiles and
bisectors are shown for various stars at different positions across
stellar disks. Absolute convective wavelength shifts are obtained
as differences to 1D models, where such shifts do not occur. <BR />
Conclusions: Observable relationships for line properties are retrieved
from realistically complex synthetic spectra. Such patterns may also
test very detailed 3D modeling, including non-LTE effects. While present
results are obtained at hyper-high spectral resolution, the subsequent
Paper V examines their practical observability at realistically lower
resolutions, and in the presence of noise.
---------------------------------------------------------
Title: Spatially resolved spectroscopy across stellar
surfaces. V. Observational prospects: toward Earth-like exoplanet
detection
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Freytag, Bernd
2021A&A...649A..17D Altcode: 2021arXiv210304996D
Context. High-precision stellar analyses require hydrodynamic 3D
modeling. Testing such models is feasible by retrieving spectral line
shapes across stellar disks, using differential spectroscopy during
exoplanet transits. Observations were presented in Papers I, II, and
III, while Paper IV explored synthetic data at hyper-high spectral
resolution for different classes of stars, identifying characteristic
patterns for Fe I and Fe II lines. <BR /> Aims: Anticipating future
observations, the observability of patterns among photospheric lines
of different strength, excitation potential and ionization level are
examined from synthetic spectra, as observed at ordinary spectral
resolutions and at different levels of noise. Time variability in 3D
atmospheres induces changes in spectral-line parameters, some of which
are correlated. An adequate calibration could identify proxies for
the jitter in apparent radial velocity to enable adjustments to actual
stellar radial motion. <BR /> Methods: We used spectral-line patterns
identified in synthetic spectra at hyper-high resolution in Paper IV
from 3D models spanning T<SUB>eff</SUB> = 3964-6726 K (spectral types
~K8 V-F3 V) to simulate practically observable signals at different
stellar disk positions at various lower spectral resolutions, down
to λ/Δλ = 75 000. We also examined the center-to-limb temporal
variability. <BR /> Results: Recovery of spatially resolved line
profiles with fitted widths and depths is shown for various noise
levels, with gradual degradation at successively lower spectral
resolutions. Signals during exoplanet transit are simulated. In
addition to Rossiter-McLaughlin type signatures in apparent radial
velocity, analogous effects are shown for line depths and widths. In
a solar model, temporal variability in line profiles and apparent
radial velocity shows correlations between jittering in apparent
radial velocity and fluctuations in line depth. <BR /> Conclusions:
Spatially resolved spectroscopy using exoplanet transits is feasible
for main-sequence stars. Overall line parameters of width, depth and
wavelength position can be retrieved already with moderate efforts,
but a very good signal-to-noise ratio is required to reveal the more
subtle signatures between subgroups of spectral lines, where finer
details of atmospheric structure are encoded. Fluctuations in line depth
correlate with those in wavelength, and because both can be measured
from the ground, searches for low-mass exoplanets should explore these
to adjust apparent radial velocities to actual stellar motion.
---------------------------------------------------------
Title: Spatially Resolved Stellar Disk Spectra at Hyper-high
Resolution: Toward Earth-like Exoplanet Detection
Authors: Dravins, D.; Ludwig, H.
2020AAS...23613002D Altcode:
High-precision spectroscopy might find 'truly' Earth-like
exoplanets. Instrumental precisions are close to being achieved
but limitations arise in the complexities of spectral-line
formation. Spectral lines become somewhat asymmetric by being
formed in dynamic gas flows. Radial-velocity signatures differ
between different types of lines, change between stars, vary across
stellar disks, and are modulated by magnetic activity. Spectroscopy
across spatially resolved stellar disks has become possible by using
transiting exoplanets as occulting spatial probes, permitting to
test center-to-limb atmospheric hydrodynamics in stars also other
than the Sun. Additional suitable target stars will likely be found
in exoplanet surveys, and simulated observations are in progress to
identify strategies for their near-future observations. From a grid
of 3-D hydrodynamic CO5BOLD model atmospheres for solar-type stars,
synthetic spectra have been computed at hyper-high spectral resolution
(R greater than 1 million), for several center-to-limb locations across
stellar disks. (The term 'hyper-high' is used since 'ultra-high'
is already taken for lower-resolution data.) Such resolutions are
required to fully resolve intrinsic line asymmetries. To segregate
those from such arising due to blends, and also to obtain absolute
wavelength shifts irrespective of errors in laboratory wavelengths,
3-D spectra are matched against similar data from 1-D models. There,
unblended lines appear symmetric at their laboratory wavelength
positions, and differences to 3-D profiles isolate effects arising in
the dynamic photospheres. Synthetic spectra are surveyed for unblended
lines with different strengths, excitation potentials, and ionization
levels, each of which contribute characteristic signatures of line
asymmetries and apparent Doppler shifts. The hyper-high resolution
data are degraded to common spectrometer values to appreciate what
signatures may realistically be observed. An adequate understanding
of both line formation and of spectrometer performance should enable
to disentangle effects from variable stellar atmospheres from those
induced by even small Earth-like exoplanets.
---------------------------------------------------------
Title: State of the Profession: Intensity Interferometry
Authors: Kieda, David; Anton, Gisela; Barbano, Anastasia; Benbow,
Wystan; Carlile, Colin; Daniel, Michael; Dravins, Dainis; Griffin,
Sean; Hassan, Tarek; Holder, Jamie; LeBohec, Stephan; Matthews, Nolan;
Montaruli, Theresa; Produit, Nicolas; Reynolds, Josh; Walter, Roland;
Zampieri, Luca
2019BAAS...51g.227K Altcode: 2019astro2020U.227K; 2019arXiv190713181K
This paper describes validation tests of Stellar Intensity
Interferometry (SII) in the laboratory and SII measurements on nearby
stars that have been completed as a technology demonstrator. The
paper describes current and future observatories that will advance
the impact and increase the instrumental resolution of SII during the
upcoming decade.
---------------------------------------------------------
Title: Science opportunities enabled by the era of Visible Band
Stellar Imaging with sub-100 {\mu}arc-sec angular resolution
Authors: Kieda, D.; Acosta, Monica; Barbano, Anastasia; Carlile,
Colin; Daniel, Michael; Dravins, Dainis; Holder, Jamie; Matthews,
Nolan; Montaruli, Teresa; Walter, Roland; Zampieri, Luca
2019arXiv190803164K Altcode:
This white paper briefly summarizes stellar science opportunities
enabled by ultra-high resolution (sub-100 {\mu} arc-sec) astronomical
imaging in the visible (U/V) wavebands. Next generation arrays of
Imaging Cherenkov telescopes, to be constructed in the next decade,
can provide unprecedented visible band imaging of several thousand
bright (m< 6), hot (O/B/A) stars using a modern implementation of
Stellar Intensity Interferometry (SII). This white paper describes the
astrophysics/astronomy science opportunities that may be uncovered in
this new observation space during the next decade.
---------------------------------------------------------
Title: Science opportunities enabled by the era of Visible Band
Stellar Imaging with sub-100 μarc-sec angular resolution.
Authors: Kieda, David; Acosta, Monica; Barbano, Anastasia; Carlile,
Colin; Daniel, Michael; Dravins, Dainis; Holder, Jamie; Matthews,
Nolan; Montaruli, Teresa; Walter, Roland; Zampieri, Luca
2019BAAS...51c.275K Altcode: 2019astro2020T.275K
This white paper briefly summarizes stellar science opportunities
enabled by ultra-high resolution (sub-100 μarc-sec) astronomical
imaging in the visible (U/V) wavebands. We describe the science impact
of imaging of several thousand bright (m < 6), hot (O/B/A) stars
using a modern implementation of Stellar Intensity Interferometry (SII).
---------------------------------------------------------
Title: Science with the Cherenkov Telescope Array
Authors: Cherenkov Telescope Array Consortium; Acharya, B. S.; Agudo,
I.; Al Samarai, I.; Alfaro, R.; Alfaro, J.; Alispach, C.; Alves
Batista, R.; Amans, J. -P.; Amato, E.; Ambrosi, G.; Antolini, E.;
Antonelli, L. A.; Aramo, C.; Araya, M.; Armstrong, T.; Arqueros, F.;
Arrabito, L.; Asano, K.; Ashley, M.; Backes, M.; Balazs, C.; Balbo, M.;
Ballester, O.; Ballet, J.; Bamba, A.; Barkov, M.; Barres de Almeida,
U.; Barrio, J. A.; Bastieri, D.; Becherini, Y.; Belfiore, A.; Benbow,
W.; Berge, D.; Bernardini, E.; Bernardini, M. G.; Bernardos, M.;
Bernlöhr, K.; Bertucci, B.; Biasuzzi, B.; Bigongiari, C.; Biland,
A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Blazek, J.; Boisson, C.;
Bolmont, J.; Bonanno, G.; Bonardi, A.; Bonavolontà, C.; Bonnoli,
G.; Bosnjak, Z.; Böttcher, M.; Braiding, C.; Bregeon, J.; Brill, A.;
Brown, A. M.; Brun, P.; Brunetti, G.; Buanes, T.; Buckley, J.; Bugaev,
V.; Bühler, R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.;
Busetto, G.; Canestrari, R.; Capalbi, M.; Capitanio, F.; Caproni, A.;
Caraveo, P.; Cárdenas, V.; Carlile, C.; Carosi, R.; Carquín, E.;
Carr, J.; Casanova, S.; Cascone, E.; Catalani, F.; Catalano, O.; Cauz,
D.; Cerruti, M.; Chadwick, P.; Chaty, S.; Chaves, R. C. G.; Chen, A.;
Chen, X.; Chernyakova, M.; Chikawa, M.; Christov, A.; Chudoba, J.;
Cieślar, M.; Coco, V.; Colafrancesco, S.; Colin, P.; Conforti, V.;
Connaughton, V.; Conrad, J.; Contreras, J. L.; Cortina, J.; Costa,
A.; Costantini, H.; Cotter, G.; Covino, S.; Crocker, R.; Cuadra, J.;
Cuevas, O.; Cumani, P.; D'Aì, A.; D'Ammando, F.; D'Avanzo, P.; D'Urso,
D.; Daniel, M.; Davids, I.; Dawson, B.; Dazzi, F.; De Angelis, A.;
de Cássia dos Anjos, R.; De Cesare, G.; De Franco, A.; de Gouveia
Dal Pino, E. M.; de la Calle, I.; de los Reyes Lopez, R.; De Lotto,
B.; De Luca, A.; De Lucia, M.; de Naurois, M.; de Oña Wilhelmi,
E.; De Palma, F.; De Persio, F.; de Souza, V.; Deil, C.; Del Santo,
M.; Delgado, C.; della Volpe, D.; Di Girolamo, T.; Di Pierro, F.;
Di Venere, L.; Díaz, C.; Dib, C.; Diebold, S.; Djannati-Ataï, A.;
Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Drass,
H.; Dravins, D.; Dubus, G.; Dwarkadas, V. V.; Ebr, J.; Eckner, C.;
Egberts, K.; Einecke, S.; Ekoume, T. R. N.; Elsässer, D.; Ernenwein,
J. -P.; Espinoza, C.; Evoli, C.; Fairbairn, M.; Falceta-Goncalves,
D.; Falcone, A.; Farnier, C.; Fasola, G.; Fedorova, E.; Fegan, S.;
Fernandez-Alonso, M.; Fernández-Barral, A.; Ferrand, G.; Fesquet,
M.; Filipovic, M.; Fioretti, V.; Fontaine, G.; Fornasa, M.; Fortson,
L.; Freixas Coromina, L.; Fruck, C.; Fujita, Y.; Fukazawa, Y.; Funk,
S.; Füßling, M.; Gabici, S.; Gadola, A.; Gallant, Y.; Garcia,
B.; Garcia López, R.; Garczarczyk, M.; Gaskins, J.; Gasparetto,
T.; Gaug, M.; Gerard, L.; Giavitto, G.; Giglietto, N.; Giommi, P.;
Giordano, F.; Giro, E.; Giroletti, M.; Giuliani, A.; Glicenstein,
J. -F.; Gnatyk, R.; Godinovic, N.; Goldoni, P.; Gómez-Vargas, G.;
González, M. M.; González, J. M.; Götz, D.; Graham, J.; Grandi,
P.; Granot, J.; Green, A. J.; Greenshaw, T.; Griffiths, S.; Gunji,
S.; Hadasch, D.; Hara, S.; Hardcastle, M. J.; Hassan, T.; Hayashi,
K.; Hayashida, M.; Heller, M.; Helo, J. C.; Hermann, G.; Hinton,
J.; Hnatyk, B.; Hofmann, W.; Holder, J.; Horan, D.; Hörandel, J.;
Horns, D.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.;
Humensky, T. B.; Hütten, M.; Iarlori, M.; Inada, T.; Inome, Y.;
Inoue, S.; Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.;
Ishio, K.; Iwamura, Y.; Jamrozy, M.; Janecek, P.; Jankowsky, D.;
Jean, P.; Jung-Richardt, I.; Jurysek, J.; Kaaret, P.; Karkar, S.;
Katagiri, H.; Katz, U.; Kawanaka, N.; Kazanas, D.; Khélifi, B.;
Kieda, D. B.; Kimeswenger, S.; Kimura, S.; Kisaka, S.; Knapp, J.;
Knödlseder, J.; Koch, B.; Kohri, K.; Komin, N.; Kosack, K.; Kraus,
M.; Krause, M.; Krauß, F.; Kubo, H.; Kukec Mezek, G.; Kuroda, H.;
Kushida, J.; La Palombara, N.; Lamanna, G.; Lang, R. G.; Lapington,
J.; Le Blanc, O.; Leach, S.; Lees, J. -P.; Lefaucheur, J.; Leigui
de Oliveira, M. A.; Lenain, J. -P.; Lico, R.; Limon, M.; Lindfors,
E.; Lohse, T.; Lombardi, S.; Longo, F.; López, M.; López-Coto,
R.; Lu, C. -C.; Lucarelli, F.; Luque-Escamilla, P. L.; Lyard, E.;
Maccarone, M. C.; Maier, G.; Majumdar, P.; Malaguti, G.; Mandat, D.;
Maneva, G.; Manganaro, M.; Mangano, S.; Marcowith, A.; Marín, J.;
Markoff, S.; Martí, J.; Martin, P.; Martínez, M.; Martínez, G.;
Masetti, N.; Masuda, S.; Maurin, G.; Maxted, N.; Mazin, D.; Medina,
C.; Melandri, A.; Mereghetti, S.; Meyer, M.; Minaya, I. A.; Mirabal,
N.; Mirzoyan, R.; Mitchell, A.; Mizuno, T.; Moderski, R.; Mohammed,
M.; Mohrmann, L.; Montaruli, T.; Moralejo, A.; Morcuende-Parrilla,
D.; Mori, K.; Morlino, G.; Morris, P.; Morselli, A.; Moulin, E.;
Mukherjee, R.; Mundell, C.; Murach, T.; Muraishi, H.; Murase, K.;
Nagai, A.; Nagataki, S.; Nagayoshi, T.; Naito, T.; Nakamori, T.;
Nakamura, Y.; Niemiec, J.; Nieto, D.; Nikołajuk, M.; Nishijima, K.;
Noda, K.; Nosek, D.; Novosyadlyj, B.; Nozaki, S.; O'Brien, P.; Oakes,
L.; Ohira, Y.; Ohishi, M.; Ohm, S.; Okazaki, N.; Okumura, A.; Ong,
R. A.; Orienti, M.; Orito, R.; Osborne, J. P.; Ostrowski, M.; Otte,
N.; Oya, I.; Padovani, M.; Paizis, A.; Palatiello, M.; Palatka, M.;
Paoletti, R.; Paredes, J. M.; Pareschi, G.; Parsons, R. D.; Pe'er,
A.; Pech, M.; Pedaletti, G.; Perri, M.; Persic, M.; Petrashyk, A.;
Petrucci, P.; Petruk, O.; Peyaud, B.; Pfeifer, M.; Piano, G.; Pisarski,
A.; Pita, S.; Pohl, M.; Polo, M.; Pozo, D.; Prandini, E.; Prast, J.;
Principe, G.; Prokhorov, D.; Prokoph, H.; Prouza, M.; Pühlhofer, G.;
Punch, M.; Pürckhauer, S.; Queiroz, F.; Quirrenbach, A.; Rainò,
S.; Razzaque, S.; Reimer, O.; Reimer, A.; Reisenegger, A.; Renaud,
M.; Rezaeian, A. H.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richtler, T.;
Rico, J.; Rieger, F.; Riquelme, M.; Rivoire, S.; Rizi, V.; Rodriguez,
J.; Rodriguez Fernandez, G.; Rodríguez Vázquez, J. J.; Rojas, G.;
Romano, P.; Romeo, G.; Rosado, J.; Rovero, A. C.; Rowell, G.; Rudak,
B.; Rugliancich, A.; Rulten, C.; Sadeh, I.; Safi-Harb, S.; Saito, T.;
Sakaki, N.; Sakurai, S.; Salina, G.; Sánchez-Conde, M.; Sandaker,
H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.; Santander,
M.; Sarkar, S.; Satalecka, K.; Saturni, F. G.; Schioppa, E. J.;
Schlenstedt, S.; Schneider, M.; Schoorlemmer, H.; Schovanek, P.;
Schulz, A.; Schussler, F.; Schwanke, U.; Sciacca, E.; Scuderi, S.;
Seitenzahl, I.; Semikoz, D.; Sergijenko, O.; Servillat, M.; Shalchi,
A.; Shellard, R. C.; Sidoli, L.; Siejkowski, H.; Sillanpää, A.;
Sironi, G.; Sitarek, J.; Sliusar, V.; Slowikowska, A.; Sol, H.;
Stamerra, A.; Stanič, S.; Starling, R.; Stawarz, Ł.; Stefanik, S.;
Stephan, M.; Stolarczyk, T.; Stratta, G.; Straumann, U.; Suomijarvi,
T.; Supanitsky, A. D.; Tagliaferri, G.; Tajima, H.; Tavani, M.;
Tavecchio, F.; Tavernet, J. -P.; Tayabaly, K.; Tejedor, L. A.;
Temnikov, P.; Terada, Y.; Terrier, R.; Terzic, T.; Teshima, M.;
Testa, V.; Thoudam, S.; Tian, W.; Tibaldo, L.; Tluczykont, M.; Todero
Peixoto, C. J.; Tokanai, F.; Tomastik, J.; Tonev, D.; Tornikoski,
M.; Torres, D. F.; Torresi, E.; Tosti, G.; Tothill, N.; Tovmassian,
G.; Travnicek, P.; Trichard, C.; Trifoglio, M.; Troyano Pujadas, I.;
Tsujimoto, S.; Umana, G.; Vagelli, V.; Vagnetti, F.; Valentino, M.;
Vallania, P.; Valore, L.; van Eldik, C.; Vandenbroucke, J.; Varner,
G. S.; Vasileiadis, G.; Vassiliev, V.; Vázquez Acosta, M.; Vecchi,
M.; Vega, A.; Vercellone, S.; Veres, P.; Vergani, S.; Verzi, V.;
Vettolani, G. P.; Viana, A.; Vigorito, C.; Villanueva, J.; Voelk,
H.; Vollhardt, A.; Vorobiov, S.; Vrastil, M.; Vuillaume, T.; Wagner,
S. J.; Wagner, R.; Walter, R.; Ward, J. E.; Warren, D.; Watson,
J. J.; Werner, F.; White, M.; White, R.; Wierzcholska, A.; Wilcox,
P.; Will, M.; Williams, D. A.; Wischnewski, R.; Wood, M.; Yamamoto,
T.; Yamazaki, R.; Yanagita, S.; Yang, L.; Yoshida, T.; Yoshiike, S.;
Yoshikoshi, T.; Zacharias, M.; Zaharijas, G.; Zampieri, L.; Zandanel,
F.; Zanin, R.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A. A.; Zech,
A.; Zechlin, H.; Zhdanov, V. I.; Ziegler, A.; Zorn, J.
2019scta.book.....C Altcode: 2017arXiv170907997C
The Cherenkov Telescope Array, CTA, will be the major global
observatory for very high energy gamma-ray astronomy over the next
decade and beyond. The scientific potential of CTA is extremely broad:
from understanding the role of relativistic cosmic particles to the
search for dark matter. CTA is an explorer of the extreme universe,
probing environments from the immediate neighbourhood of black holes to
cosmic voids on the largest scales. Covering a huge range in photon
energy from 20 GeV to 300 TeV, CTA will improve on all aspects of
performance with respect to current instruments. The observatory
will operate arrays on sites in both hemispheres to provide full sky
coverage and will hence maximize the potential for the rarest phenomena
such as very nearby supernovae, gamma-ray bursts or gravitational
wave transients. With 99 telescopes on the southern site and 19
telescopes on the northern site, flexible operation will be possible,
with sub-arrays available for specific tasks. CTA will have important
synergies with many of the new generation of major astronomical and
astroparticle observatories. Multi-wavelength and multi-messenger
approaches combining CTA data with those from other instruments will
lead to a deeper understanding of the broad-band non-thermal properties
of target sources. The CTA Observatory will be operated as an open,
proposal-driven observatory, with all data available on a public archive
after a pre-defined proprietary period. Scientists from institutions
worldwide have combined together to form the CTA Consortium. This
Consortium has prepared a proposal for a Core Programme of highly
motivated observations. The programme, encompassing approximately
40% of the available observing time over the first ten years of CTA
operation, is made up of individual Key Science Projects (KSPs),
which are presented in this document.
---------------------------------------------------------
Title: Capabilities beyond Gamma Rays
Authors: Bühler, R.; Dravins, D.; Egberts, K.; Hinton, J. A.; Parsons,
R. D.; Cherenkov Telescope Array Consortium
2019scta.book..291B Altcode:
Although designed as a gamma-ray observatory, CTA is a powerful tool
for a range of other astrophysics and astroparticle physics. For
example, CTA can make precision studies of charged cosmic rays in
the energy range from ∼100 GeV up to PeV energies, and it can
be used as an instrument for optical intensity interferometry, to
provide unprecedented angular resolution in the optical for bright
sources. Below, we briefly summarise these possibilities. Most of
the topics we discuss can be explored in parallel with gamma-ray
data-taking, without interfering with the major science operations of
CTA. Those studies (such as intensity interferometry) which require
specific observations can likely make use of bright moonlight time,
thus enhancing the CTA science return without negative impact on the
key science goals.
---------------------------------------------------------
Title: Spatially resolved spectroscopy across stellar
surfaces. III. Photospheric Fe I lines across HD 189733A (K1 V)
Authors: Dravins, Dainis; Gustavsson, Martin; Ludwig, Hans-Günter
2018A&A...616A.144D Altcode: 2018arXiv180600012D
Context. Spectroscopy across spatially resolved stellar surfaces reveals
spectral line profiles free from rotational broadening, whose gradual
changes from disk center toward the stellar limb reflect an atmospheric
fine structure that is possible to model by 3D hydrodynamics. <BR />
Aims: Previous studies of photospheric spectral lines across stellar
disks exist for the Sun and <ASTROBJ>HD 209458</ASTROBJ> (G0 V) and
are now extended to the planet-hosting <ASTROBJ>HD 189733A</ASTROBJ>
to sample a cooler K-type star and explore the future potential of
the method. <BR /> Methods: During exoplanet transit, stellar surface
portions successively become hidden and differential spectroscopy
between various transit phases uncovers spectra of small surface
segments temporarily hidden behind the planet. The method was elaborated
in Paper I, in which observable signatures were predicted quantitatively
from hydrodynamic simulations. <BR /> Results: From observations of
<ASTROBJ>HD 189733A</ASTROBJ> with the ESO HARPS spectrometer at
λ/Δλ 115 000, profiles for stronger and weaker Fe I lines are
retrieved at several center-to-limb positions, reaching adequate
S/N after averaging over numerous similar lines. <BR /> Conclusions:
Retrieved line profile widths and depths are compared to synthetic
ones from models with parameters bracketing those of the target star
and are found to be consistent with 3D simulations. Center-to-limb
changes strongly depend on the surface granulation structure and much
greater line-width variation is predicted in hotter F-type stars
with vigorous granulation than in cooler K-types. Such parameters,
obtained from fits to full line profiles, are realistic to retrieve
for brighter planet-hosting stars, while their hydrodynamic modeling
offers previously unexplored diagnostics for stellar atmospheric fine
structure and 3D line formation. Precise modeling may be required in
searches for Earth-analog exoplanets around K-type stars, whose more
tranquil surface granulation and lower ensuing microvariability may
enable such detections.
---------------------------------------------------------
Title: Intensity Interferometry: Imaging Stars with Kilometer
Baselines
Authors: Dravins, Dainis
2018iss..confE...6D Altcode:
Microarcsecond imaging will reveal stellar surfaces but requires
kilometer-scale interferometers. Intensity interferometry circumvents
atmospheric turbulence by correlating intensity fluctuations between
independent telescopes. Telescopes connect only electronically,
and the error budget relates to electronic timescales of nanoseconds
(light-travel distances on the order of a meter), enabling the use of
imperfect optics in a turbulent atmosphere. Once pioneered by Hanbury
Brown and Twiss, digital versions have now been demonstrated in the
laboratory, reconstructing diffraction-limited images from hundreds
of optical baselines. Arrays of Cherenkov telescopes (primarily
erected for gamma-ray studies) will extend over a few km, enabling
an optical equivalent of radio interferometers. Resolutions in the
tens of microarcseconds will resolve rotationally flattened stars with
their circumstellar disks and winds, or possibly even the silhouettes
of transiting exoplanets. Applying the method to mirror segments in
extremely large telescopes (even with an incompletely filled main
mirror, poor seeing, no adaptive optics), the diffraction limit in
the blue may be reached.
---------------------------------------------------------
Title: Seeing Stars - Intensity Interferometry in the Laboratory &
on the Ground
Authors: Carlile, Colin; Dravins, Dainis
2018iss..confE...3C Altcode:
In many ways it is a golden age for astronomy. Spectacular new
discoveries, for example the detection of gravitational waves, are
very dependent upon instrumental development. The specific instrument
development we propose, Intensity Interferometry (II), aims toimprove
the spatial resolution of optical telescopes by 100x to 50µas [1]. This
is impractical to achieve by increasing the size of telescopes or by
extending the capabilities of phase interferometry. II, if implemented
on the Cherenkov Telescope Array (CTA) currently being installed in La
Palma and Paranal, would record the light intensity - the photon train
- from many different telescopes, up to 2 km apart, on a nanosecond
timescale and compare them. The signal from the many pairs of telescopes
would quantify the degree of correlation by extracting the second-order
correlation function, and thus create an image. This is not a real space
image. However we can invert the data by Fourier Transform and create a
real image. The more telescopes, the better resolved and more physical
is the image, enabling the study of sunspots on nearby stars; orbiting
binary stars; or exoplanets traversing the disc of their own star. We
understand the Sun well but we have little experimental knowledge of
how representative it is of main sequence stars. To test the II method,
at Lund Observatory we have set up a laboratory analogue comprising ten
small telescopes observing an artificial star created by light from a
laser. The method has been shown to work [2] and the telescope array
has now been extended to two dimensions. We are in discussion with
other groups to explore the possibility of implementing this method
on real telescopes observing actual stars. We plan to do this with
the prototype Small Size Telescopes being built by groups in Europe,
and ultimately with the CTA itself. A Science Working Group for II has
now been set up within the CTA Consortium, of which Lund University is
an integral part. A Letter of Intent has been sent to CTA expressing
these intentions. An attractive aspect of II is its complementarity to
the principle goal of CTA - the exploration of high energy cosmic rays
via the Cherenkov light they generate in the atmosphere. This can only
be observed under the most demanding atmospheric conditions whereas II
can be recorded when conditions are poor: with a bright Moon, during
periods of turbulence; in hazy conditions; or after dusk and before
dawn. Two further advantages of implementing an II option on CTA are the
minimal marginal costs incurred to an already 400M€ investment and,
secondly, that even a few telescopes would produce unique scientific
results even in the early days when the CTA array is far from
complete. [1] Dainis Dravins and Colin Carlile, SPIE Newsroom (2016),
http://spie.org/newsroom/6504-kilometer-baseline-optical-intensity-interferometry-for-stellar-surface-observations
[2] D. Dravins, T. Lagadec, P.D. Nuñez, Nature Communications 6, 6852
(2015)
---------------------------------------------------------
Title: Revealing Stellar Surface Structure Behind Transiting
Exoplanets
Authors: Dravins, Dainis
2018iss..confE...7D Altcode:
During exoplanet transits, successive stellar surface portions become
hidden and differential spectroscopy between various transit phases
provide spectra of small surface segments temporarily hidden behind the
planet. Line profile changes across the stellar disk offer diagnostics
for hydrodynamic modeling, while exoplanet analyses require stellar
background spectra to be known along the transit path. Since even
giant planets cover only a small fraction of any main-sequence star,
very precise observations are required, as well as averaging over
numerous spectral lines with similar parameters. Spatially resolved
Fe I line profiles across stellar disks have now been retrieved for
HD209458 (G0V) and HD189733A (K1V), using data from the UVES and HARPS
spectrometers. Free from rotational broadening, spatially resolved
profiles are narrower and deeper than in integrated starlight. During
transit, the profiles shift towards longer wavelengths, illustrating
both stellar rotation at the latitude of transit and the prograde
orbital motion of the exoplanets. This method will soon become
applicable to more stars, once additional bright exoplanet hosts have
been found.
---------------------------------------------------------
Title: Stellar atmospheres behind transiting exoplanets
Authors: Dravins, D.; Ludwig, H. -G.; Dahlén, E.; Gustavsson, M.;
Pazira, H.
2017EPSC...11...21D Altcode:
Stellar surfaces are covered with brighter and darker structures, just
like on the Sun. While solar surface details can be easily studied
with telescopes, stellar surfaces cannot thus be resolved. However,
one can use planets that happen to pass in front of distant stars as
"shades" that successively block out small portions of the stellar
surface behind. By measuring how the light from the star changes during
such a transit, one can deduce stellar surface properties. Knowing those
is required not only to study the star as such, but also to deduce the
chemical composition of the planet that is passing in front of it,
where some of the detected starlight has been filtered through the
planet's atmosphere.
---------------------------------------------------------
Title: Cherenkov Telescope Array Contributions to the 35th
International Cosmic Ray Conference (ICRC2017)
Authors: Acero, F.; Acharya, B. S.; Acín Portella, V.; Adams, C.;
Agudo, I.; Aharonian, F.; Samarai, I. Al; Alberdi, A.; Alcubierre,
M.; Alfaro, R.; Alfaro, J.; Alispach, C.; Aloisio, R.; Alves Batista,
R.; Amans, J. -P.; Amato, E.; Ambrogi, L.; Ambrosi, G.; Ambrosio, M.;
Anderson, J.; Anduze, M.; Angüner, E. O.; Antolini, E.; Antonelli,
L. A.; Antonuccio, V.; Antoranz, P.; Aramo, C.; Araya, M.; Arcaro, C.;
Armstrong, T.; Arqueros, F.; Arrabito, L.; Arrieta, M.; Asano, K.;
Asano, A.; Ashley, M.; Aubert, P.; Singh, C. B.; Babic, A.; Backes,
M.; Bajtlik, S.; Balazs, C.; Balbo, M.; Ballester, O.; Ballet, J.;
Ballo, L.; Balzer, A.; Bamba, A.; Bandiera, R.; Barai, P.; Barbier,
C.; Barcelo, M.; Barkov, M.; Barres de Almeida, U.; Barrio, J. A.;
Bastieri, D.; Bauer, C.; Becciani, U.; Becherini, Y.; Becker Tjus,
J.; Bednarek, W.; Belfiore, A.; Benbow, W.; Benito, M.; Berge, D.;
Bernardini, E.; Bernardini, M. G.; Bernardos, M.; Bernhard, S.;
Bernlöhr, K.; Bertinelli Salucci, C.; Bertucci, B.; Besel, M. -A.;
Beshley, V.; Bettane, J.; Bhatt, N.; Bhattacharyya, W.; Bhattachryya,
S.; Biasuzzi, B.; Bicknell, G.; Bigongiari, C.; Biland, A.; Bilinsky,
A.; Bird, R.; Bissaldi, E.; Biteau, J.; Bitossi, M.; Blanch, O.;
Blasi, P.; Blazek, J.; Boccato, C.; Bockermann, C.; Boehm, C.;
Bohacova, M.; Boisson, C.; Bolmont, J.; Bonanno, G.; Bonardi, A.;
Bonavolontà, C.; Bonnoli, G.; Borkowski, J.; Bose, R.; Bosnjak,
Z.; Böttcher, M.; Boutonnet, C.; Bouyjou, F.; Bowman, L.; Bozhilov,
V.; Braiding, C.; Brau-Nogué, S.; Bregeon, J.; Briggs, M.; Brill,
A.; Brisken, W.; Bristow, D.; Britto, R.; Brocato, E.; Brown, A. M.;
Brown, S.; Brügge, K.; Brun, P.; Brun, P.; Brun, F.; Brunetti, L.;
Brunetti, G.; Bruno, P.; Bryan, M.; Buckley, J.; Bugaev, V.; Bühler,
R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.; Busetto, G.;
Buson, S.; Buss, J.; Byrum, K.; Caccianiga, A.; Cameron, R.; Canelli,
F.; Canestrari, R.; Capalbi, M.; Capasso, M.; Capitanio, F.; Caproni,
A.; Capuzzo-Dolcetta, R.; Caraveo, P.; Cárdenas, V.; Cardenzana,
J.; Cardillo, M.; Carlile, C.; Caroff, S.; Carosi, R.; Carosi, A.;
Carquín, E.; Carr, J.; Casandjian, J. -M.; Casanova, S.; Cascone, E.;
Castro-Tirado, A. J.; Castroviejo Mora, J.; Catalani, F.; Catalano, O.;
Cauz, D.; Celestino Silva, C.; Celli, S.; Cerruti, M.; Chabanne, E.;
Chadwick, P.; Chakraborty, N.; Champion, C.; Chatterjee, A.; Chaty, S.;
Chaves, R.; Chen, A.; Chen, X.; Cheng, K.; Chernyakova, M.; Chikawa,
M.; Chitnis, V. R.; Christov, A.; Chudoba, J.; Cieślar, M.; Clark,
P.; Coco, V.; Colafrancesco, S.; Colin, P.; Colombo, E.; Colome, J.;
Colonges, S.; Conforti, V.; Connaughton, V.; Conrad, J.; Contreras,
J. L.; Cornat, R.; Cortina, J.; Costa, A.; Costantini, H.; Cotter, G.;
Courty, B.; Covino, S.; Covone, G.; Cristofari, P.; Criswell, S. J.;
Crocker, R.; Croston, J.; Crovari, C.; Cuadra, J.; Cuevas, O.; Cui,
X.; Cumani, P.; Cusumano, G.; D'Aì, A.; D'Ammando, F.; D'Avanzo,
P.; D'Urso, D.; Da Vela, P.; Dale, Ø.; Dang, V. T.; Dangeon, L.;
Daniel, M.; Davids, I.; Dawson, B.; Dazzi, F.; De Angelis, A.; De
Caprio, V.; de Cássia dos Anjos, R.; De Cesare, G.; De Franco, A.;
De Frondat, F.; de Gouveia Dal Pino, E. M.; de la Calle, I.; De Lisio,
C.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; De Lucia, M.;
de Mello Neto, J. R. T.; de Naurois, M.; de Oña Wilhelmi, E.; De
Palma, F.; De Persio, F.; de Souza, V.; Decock, J.; Deil, C.; Deiml,
P.; Del Santo, M.; Delagnes, E.; Deleglise, G.; Delfino Reznicek, M.;
Delgado, C.; Delgado Mengual, J.; Della Ceca, R.; della Volpe, D.;
Detournay, M.; Devin, J.; Di Girolamo, T.; Di Giulio, C.; Di Pierro,
F.; Di Venere, L.; Diaz, L.; Díaz, C.; Dib, C.; Dickinson, H.;
Diebold, S.; Digel, S.; Djannati-Ataï, A.; Doert, M.; Domínguez,
A.; Dominis Prester, D.; Donnarumma, I.; Dorner, D.; Doro, M.;
Dournaux, J. -L.; Downes, T.; Drake, G.; Drappeau, S.; Drass, H.;
Dravins, D.; Drury, L.; Dubus, G.; Dundas Morå, K.; Durkalec, A.;
Dwarkadas, V.; Ebr, J.; Eckner, C.; Edy, E.; Egberts, K.; Einecke,
S.; Eisch, J.; Eisenkolb, F.; Ekoume, T. R. N.; Eleftheriadis, C.;
Elsässer, D.; Emmanoulopoulos, D.; Ernenwein, J. -P.; Escarate,
P.; Eschbach, S.; Espinoza, C.; Evans, P.; Evoli, C.; Fairbairn, M.;
Falceta-Goncalves, D.; Falcone, A.; Fallah Ramazani, V.; Farakos, K.;
Farrell, E.; Fasola, G.; Favre, Y.; Fede, E.; Fedora, R.; Fedorova,
E.; Fegan, S.; Fernandez-Alonso, M.; Fernández-Barral, A.; Ferrand,
G.; Ferreira, O.; Fesquet, M.; Fiandrini, E.; Fiasson, A.; Filipovic,
M.; Fink, D.; Finley, J. P.; Finley, C.; Finoguenov, A.; Fioretti,
V.; Fiorini, M.; Flores, H.; Foffano, L.; Föhr, C.; Fonseca, M. V.;
Font, L.; Fontaine, G.; Fornasa, M.; Fortin, P.; Fortson, L.; Fouque,
N.; Fraga, B.; Franco, F. J.; Freixas Coromina, L.; Fruck, C.; Fugazza,
D.; Fujita, Y.; Fukami, S.; Fukazawa, Y.; Fukui, Y.; Funk, S.; Furniss,
A.; Füßling, M.; Gabici, S.; Gadola, A.; Gallant, Y.; Galloway, D.;
Gallozzi, S.; Garcia, B.; Garcia, A.; García Gil, R.; Garcia López,
R.; Garczarczyk, M.; Gardiol, D.; Gargano, F.; Gargano, C.; Garozzo,
S.; Garrido-Ruiz, M.; Gascon, D.; Gasparetto, T.; Gaté, F.; Gaug,
M.; Gebhardt, B.; Gebyehu, M.; Geffroy, N.; Genolini, B.; Ghalumyan,
A.; Ghedina, A.; Ghirlanda, G.; Giammaria, P.; Gianotti, F.; Giebels,
B.; Giglietto, N.; Gika, V.; Gimenes, R.; Giommi, P.; Giordano, F.;
Giovannini, G.; Giro, E.; Giroletti, M.; Gironnet, J.; Giuliani, A.;
Glicenstein, J. -F.; Gnatyk, R.; Godinovic, N.; Goldoni, P.; Gómez,
J. L.; Gómez-Vargas, G.; González, M. M.; González, J. M.; Gothe,
K. S.; Gotz, D.; Goullon, J.; Grabarczyk, T.; Graciani, R.; Graham,
J.; Grandi, P.; Granot, J.; Grasseau, G.; Gredig, R.; Green, A. J.;
Greenshaw, T.; Grenier, I.; Griffiths, S.; Grillo, A.; Grondin, M. -H.;
Grube, J.; Guarino, V.; Guest, B.; Gueta, O.; Gunji, S.; Gyuk, G.;
Hadasch, D.; Hagge, L.; Hahn, J.; Hahn, A.; Hakobyan, H.; Hara, S.;
Hardcastle, M. J.; Hassan, T.; Haubold, T.; Haupt, A.; Hayashi, K.;
Hayashida, M.; He, H.; Heller, M.; Helo, J. C.; Henault, F.; Henri, G.;
Hermann, G.; Hermel, R.; Herrera Llorente, J.; Herrero, A.; Hervet, O.;
Hidaka, N.; Hinton, J.; Hiroshima, N.; Hirotani, K.; Hnatyk, B.; Hoang,
J. K.; Hoffmann, D.; Hofmann, W.; Holder, J.; Horan, D.; Hörandel,
J.; Hörbe, M.; Horns, D.; Horvath, P.; Houles, J.; Hovatta, T.;
Hrabovsky, M.; Hrupec, D.; Huet, J. -M.; Hughes, G.; Hui, D.; Hull,
G.; Humensky, T. B.; Hussein, M.; Hütten, M.; Iarlori, M.; Ikeno,
Y.; Illa, J. M.; Impiombato, D.; Inada, T.; Ingallinera, A.; Inome,
Y.; Inoue, S.; Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Ionica,
M.; Iori, M.; Iriarte, A.; Ishio, K.; Israel, G. L.; Iwamura, Y.;
Jablonski, C.; Jacholkowska, A.; Jacquemier, J.; Jamrozy, M.; Janecek,
P.; Jankowsky, F.; Jankowsky, D.; Jansweijer, P.; Jarnot, C.; Jean, P.;
Johnson, C. A.; Josselin, M.; Jung-Richardt, I.; Jurysek, J.; Kaaret,
P.; Kachru, P.; Kagaya, M.; Kakuwa, J.; Kalekin, O.; Kankanyan, R.;
Karastergiou, A.; Karczewski, M.; Karkar, S.; Katagiri, H.; Kataoka,
J.; Katarzyński, K.; Katz, U.; Kawanaka, N.; Kaye, L.; Kazanas, D.;
Kelley-Hoskins, N.; Khélifi, B.; Kieda, D. B.; Kihm, T.; Kimeswenger,
S.; Kimura, S.; Kisaka, S.; Kishida, S.; Kissmann, R.; Kluźniak, W.;
Knapen, J.; Knapp, J.; Knödlseder, J.; Koch, B.; Kocot, J.; Kohri,
K.; Komin, N.; Kong, A.; Konno, Y.; Kosack, K.; Kowal, G.; Koyama,
S.; Kraus, M.; Krause, M.; Krauß, F.; Krennrich, F.; Kruger, P.;
Kubo, H.; Kudryavtsev, V.; Kukec Mezek, G.; Kumar, S.; Kuroda, H.;
Kushida, J.; Kushwaha, P.; La Palombara, N.; La Parola, V.; La Rosa,
G.; Lahmann, R.; Lalik, K.; Lamanna, G.; Landoni, M.; Landriu, D.;
Landt, H.; Lang, R. G.; Lapington, J.; Laporte, P.; Le Blanc, O.;
Le Flour, T.; Le Sidaner, P.; Leach, S.; Leckngam, A.; Lee, S. -H.;
Lee, W. H.; Lees, J. -P.; Lefaucheur, J.; Leigui de Oliveira, M. A.;
Lemoine-Goumard, M.; Lenain, J. -P.; Leto, G.; Lico, R.; Limon, M.;
Lindemann, R.; Lindfors, E.; Linhoff, L.; Lipniacka, A.; Lloyd, S.;
Lohse, T.; Lombardi, S.; Longo, F.; Lopez, M.; Lopez-Coto, R.; Louge,
T.; Louis, F.; Louys, M.; Lucarelli, F.; Lucchesi, D.; Luque-Escamilla,
P. L.; Lyard, E.; Maccarone, M. C.; Maccarone, T.; Mach, E.; Madejski,
G. M.; Maier, G.; Majczyna, A.; Majumdar, P.; Makariev, M.; Malaguti,
G.; Malouf, A.; Maltezos, S.; Malyshev, D.; Malyshev, D.; Mandat,
D.; Maneva, G.; Manganaro, M.; Mangano, S.; Manigot, P.; Mannheim,
K.; Maragos, N.; Marano, D.; Marcowith, A.; Marín, J.; Mariotti,
M.; Marisaldi, M.; Markoff, S.; Martí, J.; Martin, J. -M.; Martin,
P.; Martin, L.; Martínez, M.; Martínez, G.; Martínez, O.; Marx,
R.; Masetti, N.; Massimino, P.; Mastichiadis, A.; Mastropietro, M.;
Masuda, S.; Matsumoto, H.; Matthews, N.; Mattiazzo, S.; Maurin, G.;
Maxted, N.; Mayer, M.; Mazin, D.; Mazziotta, M. N.; Mc Comb, L.;
McHardy, I.; Medina, C.; Melandri, A.; Melioli, C.; Melkumyan, D.;
Mereghetti, S.; Meunier, J. -L.; Meures, T.; Meyer, M.; Micanovic, S.;
Michael, T.; Michałowski, J.; Mievre, I.; Miller, J.; Minaya, I. A.;
Mineo, T.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.; Mitchell, A.;
Mizuno, T.; Moderski, R.; Mohammed, M.; Mohrmann, L.; Molijn, C.;
Molinari, E.; Moncada, R.; Montaruli, T.; Monteiro, I.; Mooney, D.;
Moore, P.; Moralejo, A.; Morcuende-Parrilla, D.; Moretti, E.; Mori,
K.; Morlino, G.; Morris, P.; Morselli, A.; Moscato, F.; Motohashi,
D.; Moulin, E.; Mueller, S.; Mukherjee, R.; Munar, P.; Mundell, C.;
Mundet, J.; Murach, T.; Muraishi, H.; Murase, K.; Murphy, A.; Nagai,
A.; Nagar, N.; Nagataki, S.; Nagayoshi, T.; Nagesh, B. K.; Naito,
T.; Nakajima, D.; Nakamori, T.; Nakamura, Y.; Nakayama, K.; Naumann,
D.; Nayman, P.; Neise, D.; Nellen, L.; Nemmen, R.; Neronov, A.;
Neyroud, N.; Nguyen, T.; Nguyen, T. T.; Nguyen Trung, T.; Nicastro,
L.; Nicolau-Kukliński, J.; Niemiec, J.; Nieto, D.; Nievas-Rosillo,
M.; Nikołajuk, M.; Nishijima, K.; Nishikawa, K. -I.; Nishiyama, G.;
Noda, K.; Nogues, L.; Nolan, S.; Nosek, D.; Nöthe, M.; Novosyadlyj,
B.; Nozaki, S.; Nunio, F.; O'Brien, P.; Oakes, L.; Ocampo, C.; Ochoa,
J. P.; Oger, R.; Ohira, Y.; Ohishi, M.; Ohm, S.; Okazaki, N.; Okumura,
A.; Olive, J. -F.; Ong, R. A.; Orienti, M.; Orito, R.; Orlati, A.;
Osborne, J. P.; Ostrowski, M.; Otte, N.; Ou, Z.; Ovcharov, E.; Oya,
I.; Ozieblo, A.; Padovani, M.; Paiano, S.; Paizis, A.; Palacio, J.;
Palatiello, M.; Palatka, M.; Pallotta, J.; Panazol, J. -L.; Paneque,
D.; Panter, M.; Paoletti, R.; Paolillo, M.; Papitto, A.; Paravac, A.;
Paredes, J. M.; Pareschi, G.; Parsons, R. D.; Paśko, P.; Pavy, S.;
Pe'er, A.; Pech, M.; Pedaletti, G.; Peñil Del Campo, P.; Perez, A.;
Pérez-Torres, M. A.; Perri, L.; Perri, M.; Persic, M.; Petrashyk,
A.; Petrera, S.; Petrucci, P. -O.; Petruk, O.; Peyaud, B.; Pfeifer,
M.; Piano, G.; Piel, Q.; Pieloth, D.; Pintore, F.; García, C. Pio;
Pisarski, A.; Pita, S.; Pizarro, L.; Platos, Ł.; Pohl, M.; Poireau,
V.; Pollo, A.; Porthault, J.; Poutanen, J.; Pozo, D.; Prandini, E.;
Prasit, P.; Prast, J.; Pressard, K.; Principe, G.; Prokhorov, D.;
Prokoph, H.; Prouza, M.; Pruteanu, G.; Pueschel, E.; Pühlhofer,
G.; Puljak, I.; Punch, M.; Pürckhauer, S.; Queiroz, F.; Quinn, J.;
Quirrenbach, A.; Rafighi, I.; Rainò, S.; Rajda, P. J.; Rando, R.;
Rannot, R. C.; Razzaque, S.; Reichardt, I.; Reimer, O.; Reimer, A.;
Reisenegger, A.; Renaud, M.; Reposeur, T.; Reville, B.; Rezaeian,
A. H.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richer, M. G.; Richtler,
T.; Rico, J.; Rieger, F.; Riquelme, M.; Ristori, P. R.; Rivoire, S.;
Rizi, V.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodríguez Vázquez,
J. J.; Rojas, G.; Romano, P.; Romeo, G.; Roncadelli, M.; Rosado, J.;
Rosen, S.; Rosier Lees, S.; Rousselle, J.; Rovero, A. C.; Rowell, G.;
Rudak, B.; Rugliancich, A.; Ruíz del Mazo, J. E.; Rujopakarn, W.;
Rulten, C.; Russo, F.; Saavedra, O.; Sabatini, S.; Sacco, B.; Sadeh,
I.; Sæther Hatlen, E.; Safi-Harb, S.; Sahakian, V.; Sailer, S.; Saito,
T.; Sakaki, N.; Sakurai, S.; Salek, D.; Salesa Greus, F.; Salina, G.;
Sanchez, D.; Sánchez-Conde, M.; Sandaker, H.; Sandoval, A.; Sangiorgi,
P.; Sanguillon, M.; Sano, H.; Santander, M.; Santangelo, A.; Santos,
E. M.; Sanuy, A.; Sapozhnikov, L.; Sarkar, S.; Satalecka, K.; Sato,
Y.; Saturni, F. G.; Savalle, R.; Sawada, M.; Schanne, S.; Schioppa,
E. J.; Schlenstedt, S.; Schmidt, T.; Schmoll, J.; Schneider, M.;
Schoorlemmer, H.; Schovanek, P.; Schulz, A.; Schussler, F.; Schwanke,
U.; Schwarz, J.; Schweizer, T.; Schwemmer, S.; Sciacca, E.; Scuderi,
S.; Seglar-Arroyo, M.; Segreto, A.; Seitenzahl, I.; Semikoz, D.;
Sergijenko, O.; Serre, N.; Servillat, M.; Seweryn, K.; Shah, K.;
Shalchi, A.; Sharma, M.; Shellard, R. C.; Shilon, I.; Sidoli, L.;
Sidz, M.; Siejkowski, H.; Silk, J.; Sillanpää, A.; Simone, D.; Singh,
B. B.; Sironi, G.; Sitarek, J.; Sizun, P.; Sliusar, V.; Slowikowska,
A.; Smith, A.; Sobczyńska, D.; Sokolenko, A.; Sol, H.; Sottile, G.;
Springer, W.; Stahl, O.; Stamerra, A.; Stanič, S.; Starling, R.;
Staszak, D.; Stawarz, Ł.; Steenkamp, R.; Stefanik, S.; Stegmann,
C.; Steiner, S.; Stella, C.; Stephan, M.; Sternberger, R.; Sterzel,
M.; Stevenson, B.; Stodulska, M.; Stodulski, M.; Stolarczyk, T.;
Stratta, G.; Straumann, U.; Stuik, R.; Suchenek, M.; Suomijarvi, T.;
Supanitsky, A. D.; Suric, T.; Sushch, I.; Sutcliffe, P.; Sykes, J.;
Szanecki, M.; Szepieniec, T.; Tagliaferri, G.; Tajima, H.; Takahashi,
K.; Takahashi, H.; Takahashi, M.; Takalo, L.; Takami, S.; Takata, J.;
Takeda, J.; Tam, T.; Tanaka, M.; Tanaka, T.; Tanaka, Y.; Tanaka, S.;
Tanci, C.; Tavani, M.; Tavecchio, F.; Tavernet, J. -P.; Tayabaly,
K.; Tejedor, L. A.; Temme, F.; Temnikov, P.; Terada, Y.; Terrazas,
J. C.; Terrier, R.; Terront, D.; Terzic, T.; Tescaro, D.; Teshima, M.;
Testa, V.; Thoudam, S.; Tian, W.; Tibaldo, L.; Tiengo, A.; Tiziani, D.;
Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tokarz, M.; Toma,
K.; Tomastik, J.; Tonachini, A.; Tonev, D.; Tornikoski, M.; Torres,
D. F.; Torresi, E.; Tosti, G.; Totani, T.; Tothill, N.; Toussenel,
F.; Tovmassian, G.; Trakarnsirinont, N.; Travnicek, P.; Trichard,
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A. M.; van Driel, W.; van Eldik, C.; van Soelen, B.; Vandenbroucke,
J.; Vanderwalt, J.; Varner, G. S.; Vasileiadis, G.; Vassiliev, V.;
Vázquez, J. R.; Vázquez Acosta, M.; Vecchi, M.; Vega, A.; Veitch,
P.; Venault, P.; Venter, C.; Vercellone, S.; Veres, P.; Vergani,
S.; Verzi, V.; Vettolani, G. P.; Veyssiere, C.; Viana, A.; Vicha,
J.; Vigorito, C.; Villanueva, J.; Vincent, P.; Vink, J.; Visconti,
F.; Vittorini, V.; Voelk, H.; Voisin, V.; Vollhardt, A.; Vorobiov,
S.; Vovk, I.; Vrastil, M.; Vuillaume, T.; Wagner, S. J.; Wagner, R.;
Wagner, P.; Wakely, S. P.; Walstra, T.; Walter, R.; Ward, M.; Ward,
J. E.; Warren, D.; Watson, J. J.; Webb, N.; Wegner, P.; Weiner, O.;
Weinstein, A.; Weniger, C.; Werner, F.; Wetteskind, H.; White, M.;
White, R.; Wierzcholska, A.; Wiesand, S.; Wijers, R.; Wilcox, P.;
Wilhelm, A.; Wilkinson, M.; Will, M.; Williams, D. A.; Winter, M.;
Wojcik, P.; Wolf, D.; Wood, M.; Wörnlein, A.; Wu, T.; Yadav, K. K.;
Yaguna, C.; Yamamoto, T.; Yamamoto, H.; Yamane, N.; Yamazaki, R.;
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S.; Yoshikoshi, T.; Yu, P.; Zaborov, D.; Zacharias, M.; Zaharijas, G.;
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A.; Zechlin, H.; Zhdanov, V. I.; Ziegler, A.; Ziemann, J.; Ziętara,
K.; Zink, A.; Ziółkowski, J.; Zitelli, V.; Zoli, A.; Zorn, J.
2017arXiv170903483A Altcode: 2017arXiv170903483C
List of contributions from the Cherenkov Telescope Array Consortium
presented at the 35th International Cosmic Ray Conference, July 12-20
2017, Busan, Korea.
---------------------------------------------------------
Title: Spatially resolved spectroscopy across stellar
surfaces. II. High-resolution spectra across HD 209458 (G0 V)
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Dahlén, Erik;
Pazira, Hiva
2017A&A...605A..91D Altcode: 2017arXiv170801618D
Context. High-resolution spectroscopy across spatially resolved
stellar surfaces aims at obtaining spectral-line profiles that
are free from rotational broadening; the gradual changes of these
profiles from disk center toward the stellar limb reveal properties
of atmospheric fine structure, which are possible to model with 3D
hydrodynamics. <BR /> Aims: Previous such studies have only been
carried out for the Sun but are now extended to other stars. In this
work, profiles of photospheric spectral lines are retrieved across
the disk of the planet-hosting star HD 209458 (G0 V). <BR /> Methods:
During exoplanet transit, stellar surface portions successively become
hidden and differential spectroscopy provides spectra of small surface
segments temporarily hidden behind the planet. The method was elaborated
in Paper I, with observable signatures quantitatively predicted from
hydrodynamic simulations. <BR /> Results: From observations of HD
209458 with spectral resolution λ/ Δλ 80 000, photospheric Fe
I line profiles are obtained at several center-to-limb positions,
reaching adequately high S/N after averaging over numerous similar
lines. <BR /> Conclusions: Retrieved line profiles are compared
to synthetic line profiles. Hydrodynamic 3D models predict, and
current observations confirm, that photospheric absorption lines
become broader and shallower toward the stellar limb, reflecting that
horizontal velocities in stellar granulation are greater than vertical
velocities. Additional types of 3D signatures will become observable
with the highest resolution spectrometers at large telescopes.
---------------------------------------------------------
Title: Spatially resolved spectroscopy across stellar
surfaces. I. Using exoplanet transits to analyze 3D stellar
atmospheres
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Dahlén, Erik;
Pazira, Hiva
2017A&A...605A..90D Altcode: 2017arXiv170801616D
Context. High-precision stellar analyses require hydrodynamic modeling
to interpret chemical abundances or oscillation modes. Exoplanet
atmosphere studies require stellar background spectra to be known
along the transit path while detection of Earth analogs require
stellar microvariability to be understood. Hydrodynamic 3D models can
be computed for widely different stars but have been tested in detail
only for the Sun with its resolved surface features. Model predictions
include spectral line shapes, asymmetries, and wavelength shifts,
and their center-to-limb changes across stellar disks. <BR /> Aims: We
observe high-resolution spectral line profiles across spatially highly
resolved stellar surfaces, which are free from the effects of spatial
smearing and rotational broadening present in full-disk spectra,
enabling comparisons to synthetic profiles from 3D models. <BR />
Methods: During exoplanet transits, successive stellar surface portions
become hidden and differential spectroscopy between various transit
phases provides spectra of small surface segments temporarily hidden
behind the planet. Planets cover no more than 1% of any main-sequence
star, enabling high spatial resolution but demanding very precise
observations. Realistically measurable quantities are identified
through simulated observations of synthetic spectral lines. <BR />
Results: In normal stars, line profile ratios between various transit
phases may vary by 0.5%, requiring S/N ≳ 5000 for meaningful spectral
reconstruction. While not yet realistic for individual spectral lines,
this is achievable for cool stars by averaging over numerous lines
with similar parameters. <BR /> Conclusions: For bright host stars of
large transiting planets, spatially resolved spectroscopy is currently
practical. More observable targets are likely to be found in the near
future by ongoing photometric searches.
---------------------------------------------------------
Title: Contributions of the Cherenkov Telescope Array (CTA) to
the 6th International Symposium on High-Energy Gamma-Ray Astronomy
(Gamma 2016)
Authors: CTA Consortium, The; :; Abchiche, A.; Abeysekara, U.; Abril,
Ó.; Acero, F.; Acharya, B. S.; Adams, C.; Agnetta, G.; Aharonian,
F.; Akhperjanian, A.; Albert, A.; Alcubierre, M.; Alfaro, J.; Alfaro,
R.; Allafort, A. J.; Aloisio, R.; Amans, J. -P.; Amato, E.; Ambrogi,
L.; Ambrosi, G.; Ambrosio, M.; Anderson, J.; Anduze, M.; Angüner,
E. O.; Antolini, E.; Antonelli, L. A.; Antonucci, M.; Antonuccio,
V.; Antoranz, P.; Aramo, C.; Aravantinos, A.; Araya, M.; Arcaro, C.;
Arezki, B.; Argan, A.; Armstrong, T.; Arqueros, F.; Arrabito, L.;
Arrieta, M.; Asano, K.; Ashley, M.; Aubert, P.; Singh, C. B.; Babic,
A.; Backes, M.; Bais, A.; Bajtlik, S.; Balazs, C.; Balbo, M.; Balis,
D.; Balkowski, C.; Ballester, O.; Ballet, J.; Balzer, A.; Bamba,
A.; Bandiera, R.; Barber, A.; Barbier, C.; Barcelo, M.; Barkov,
M.; Barnacka, A.; Barres de Almeida, U.; Barrio, J. A.; Basso, S.;
Bastieri, D.; Bauer, C.; Becciani, U.; Becherini, Y.; Becker Tjus,
J.; Beckmann, V.; Bednarek, W.; Benbow, W.; Benedico Ventura, D.;
Berdugo, J.; Berge, D.; Bernardini, E.; Bernardini, M. G.; Bernhard,
S.; Bernlöhr, K.; Bertucci, B.; Besel, M. -A.; Beshley, V.; Bhatt,
N.; Bhattacharjee, P.; Bhattacharyya, W.; Bhattachryya, S.; Biasuzzi,
B.; Bicknell, G.; Bigongiari, C.; Biland, A.; Bilinsky, A.; Bilnik,
W.; Biondo, B.; Bird, R.; Bird, T.; Bissaldi, E.; Bitossi, M.;
Blanch, O.; Blasi, P.; Blazek, J.; Bockermann, C.; Boehm, C.; Bogacz,
L.; Bogdan, M.; Bohacova, M.; Boisson, C.; Boix, J.; Bolmont, J.;
Bonanno, G.; Bonardi, A.; Bonavolontà, C.; Bonifacio, P.; Bonnarel,
F.; Bonnoli, G.; Borkowski, J.; Bose, R.; Bosnjak, Z.; Böttcher, M.;
Bousquet, J. -J.; Boutonnet, C.; Bouyjou, F.; Bowman, L.; Braiding,
C.; Brantseg, T.; Brau-Nogué, S.; Bregeon, J.; Briggs, M.; Brigida,
M.; Bringmann, T.; Brisken, W.; Bristow, D.; Britto, R.; Brocato, E.;
Bron, S.; Brook, P.; Brooks, W.; Brown, A. M.; Brügge, K.; Brun, F.;
Brun, P.; Brun, P.; Brunetti, G.; Brunetti, L.; Bruno, P.; Buanes,
T.; Bucciantini, N.; Buchholtz, G.; Buckley, J.; Bugaev, V.; Bühler,
R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.; Busetto,
G.; Buson, S.; Buss, J.; Byrum, K.; Cadoux, F.; Calvo Tovar, J.;
Cameron, R.; Canelli, F.; Canestrari, R.; Capalbi, M.; Capasso, M.;
Capobianco, G.; Caproni, A.; Caraveo, P.; Cardenzana, J.; Cardillo,
M.; Carius, S.; Carlile, C.; Carosi, A.; Carosi, R.; Carquín, E.;
Carr, J.; Carroll, M.; Carter, J.; Carton, P. -H.; Casandjian, J. -M.;
Casanova, S.; Casanova, S.; Cascone, E.; Casiraghi, M.; Castellina,
A.; Castroviejo Mora, J.; Catalani, F.; Catalano, O.; Catalanotti,
S.; Cauz, D.; Cavazzani, S.; Cerchiara, P.; Chabanne, E.; Chadwick,
P.; Chaleil, T.; Champion, C.; Chatterjee, A.; Chaty, S.; Chaves, R.;
Chen, A.; Chen, X.; Chen, X.; Cheng, K.; Chernyakova, M.; Chiappetti,
L.; Chikawa, M.; Chinn, D.; Chitnis, V. R.; Cho, N.; Christov, A.;
Chudoba, J.; Cieślar, M.; Ciocci, M. A.; Clay, R.; Colafrancesco,
S.; Colin, P.; Colley, J. -M.; Colombo, E.; Colome, J.; Colonges, S.;
Conforti, V.; Connaughton, V.; Connell, S.; Conrad, J.; Contreras,
J. L.; Coppi, P.; Corbel, S.; Coridian, J.; Cornat, R.; Corona,
P.; Corti, D.; Cortina, J.; Cossio, L.; Costa, A.; Costantini, H.;
Cotter, G.; Courty, B.; Covino, S.; Covone, G.; Crimi, G.; Criswell,
S. J.; Crocker, R.; Croston, J.; Cuadra, J.; Cumani, P.; Cusumano,
G.; Da Vela, P.; Dale, Ø.; D'Ammando, F.; Dang, D.; Dang, V. T.;
Dangeon, L.; Daniel, M.; Davids, I.; Davids, I.; Dawson, B.; Dazzi,
F.; de Aguiar Costa, B.; De Angelis, A.; de Araujo Cardoso, R. F.;
De Caprio, V.; de Cássia dos Anjos, R.; De Cesare, G.; De Franco,
A.; De Frondat, F.; de Gouveia Dal Pino, E. M.; de la Calle, I.;
De Lisio, C.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de
Mello Neto, J. R. T.; de Naurois, M.; de Oña Wilhelmi, E.; De Palma,
F.; De Persio, F.; de Souza, V.; Decock, G.; Decock, J.; Deil, C.;
Del Santo, M.; Delagnes, E.; Deleglise, G.; Delgado, C.; Delgado, J.;
della Volpe, D.; Deloye, P.; Detournay, M.; Dettlaff, A.; Devin, J.;
Di Girolamo, T.; Di Giulio, C.; Di Paola, A.; Di Pierro, F.; Diaz,
M. A.; Díaz, C.; Dib, C.; Dick, J.; Dickinson, H.; Diebold, S.;
Digel, S.; Dipold, J.; Disset, G.; Distefano, A.; Djannati-Ataï, A.;
Doert, M.; Dohmke, M.; Domínguez, A.; Dominik, N.; Dominique, J. -L.;
Dominis Prester, D.; Donat, A.; Donnarumma, I.; Dorner, D.; Doro,
M.; Dournaux, J. -L.; Downes, T.; Doyle, K.; Drake, G.; Drappeau,
S.; Drass, H.; Dravins, D.; Drury, L.; Dubus, G.; Ducci, L.; Dumas,
D.; Dundas Morå, K.; Durand, D.; D'Urso, D.; Dwarkadas, V.; Dyks,
J.; Dyrda, M.; Ebr, J.; Edy, E.; Egberts, K.; Eger, P.; Egorov, A.;
Einecke, S.; Eisch, J.; Eisenkolb, F.; Eleftheriadis, C.; Elsaesser,
D.; Elsässer, D.; Emmanoulopoulos, D.; Engelbrecht, C.; Engelhaupt,
D.; Ernenwein, J. -P.; Escarate, P.; Eschbach, S.; Espinoza, C.;
Evans, P.; Fairbairn, M.; Falceta-Goncalves, D.; Falcone, A.; Fallah
Ramazani, V.; Fantinel, D.; Farakos, K.; Farnier, C.; Farrell, E.;
Fasola, G.; Favre, Y.; Fede, E.; Fedora, R.; Fedorova, E.; Fegan, S.;
Ferenc, D.; Fernandez-Alonso, M.; Fernández-Barral, A.; Ferrand, G.;
Ferreira, O.; Fesquet, M.; Fetfatzis, P.; Fiandrini, E.; Fiasson, A.;
Filipčič, A.; Filipovic, M.; Fink, D.; Finley, C.; Finley, J. P.;
Finoguenov, A.; Fioretti, V.; Fiorini, M.; Fleischhack, H.; Flores,
H.; Florin, D.; Föhr, C.; Fokitis, E.; Fonseca, M. V.; Font, L.;
Fontaine, G.; Fontes, B.; Fornasa, M.; Fornasa, M.; Förster, A.;
Fortin, P.; Fortson, L.; Fouque, N.; Franckowiak, A.; Franckowiak,
A.; Franco, F. J.; Freire Mota Albuquerque, I.; Freixas Coromina,
L.; Fresnillo, L.; Fruck, C.; Fuessling, M.; Fugazza, D.; Fujita, Y.;
Fukami, S.; Fukazawa, Y.; Fukuda, T.; Fukui, Y.; Funk, S.; Furniss, A.;
Gäbele, W.; Gabici, S.; Gadola, A.; Galindo, D.; Gall, D. D.; Gallant,
Y.; Galloway, D.; Gallozzi, S.; Galvez, J. A.; Gao, S.; Garcia, A.;
Garcia, B.; García Gil, R.; Garcia López, R.; Garczarczyk, M.;
Gardiol, D.; Gargano, C.; Gargano, F.; Garozzo, S.; Garrecht, F.;
Garrido, L.; Garrido-Ruiz, M.; Gascon, D.; Gaskins, J.; Gaudemard,
J.; Gaug, M.; Gaweda, J.; Gebhardt, B.; Gebyehu, M.; Geffroy, N.;
Genolini, B.; Gerard, L.; Ghalumyan, A.; Ghedina, A.; Ghislain, P.;
Giammaria, P.; Giannakaki, E.; Gianotti, F.; Giarrusso, S.; Giavitto,
G.; Giebels, B.; Gieras, T.; Giglietto, N.; Gika, V.; Gimenes, R.;
Giomi, M.; Giommi, P.; Giordano, F.; Giovannini, G.; Girardot, P.;
Giro, E.; Giroletti, M.; Gironnet, J.; Giuliani, A.; Glicenstein,
J. -F.; Gnatyk, R.; Godinovic, N.; Goldoni, P.; Gomez, G.; Gonzalez,
M. M.; González, A.; Gora, D.; Gothe, K. S.; Gotz, D.; Goullon, J.;
Grabarczyk, T.; Graciani, R.; Graham, J.; Grandi, P.; Granot, J.;
Grasseau, G.; Gredig, R.; Green, A. J.; Green, A. M.; Greenshaw, T.;
Grenier, I.; Griffiths, S.; Grillo, A.; Grondin, M. -H.; Grube, J.;
Grudzinska, M.; Grygorczuk, J.; Guarino, V.; Guberman, D.; Gunji, S.;
Gyuk, G.; Hadasch, D.; Hagedorn, A.; Hagge, L.; Hahn, J.; Hakobyan,
H.; Hara, S.; Hardcastle, M. J.; Hassan, T.; Hatanaka, K.; Haubold,
T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, M.; Heller,
R.; Helo, J. C.; Henault, F.; Henri, G.; Hermann, G.; Hermel, R.;
Herrera Llorente, J.; Herrera Llorente, J.; Herrero, A.; Hervet,
O.; Hidaka, N.; Hinton, J.; Hirai, W.; Hirotani, K.; Hnatyk, B.;
Hoang, J.; Hoffmann, D.; Hofmann, W.; Holch, T.; Holder, J.; Hooper,
S.; Horan, D.; Hörandel, J.; Hörbe, M.; Horns, D.; Horvath, P.;
Hose, J.; Houles, J.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Huet,
J. -M.; Huetten, M.; Hughes, G.; Hui, D.; Humensky, T. B.; Hussein,
M.; Iacovacci, M.; Ibarra, A.; Ikeno, Y.; Illa, J. M.; Impiombato,
D.; Inada, T.; Incorvaia, S.; Infante, L.; Inome, Y.; Inoue, S.;
Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.; Ishio, K.;
Ishio, K.; Israel, G. L.; Iwamura, Y.; Jablonski, C.; Jacholkowska,
A.; Jacquemier, J.; Jamrozy, M.; Janecek, P.; Janiak, M.; Jankowsky,
D.; Jankowsky, F.; Jean, P.; Jegouzo, I.; Jenke, P.; Jimenez, J. J.;
Jingo, M.; Jingo, M.; Jocou, L.; Jogler, T.; Johnson, C. A.; Jones,
M.; Josselin, M.; Journet, L.; Jung, I.; Kaaret, P.; Kagaya, M.;
Kakuwa, J.; Kalekin, O.; Kalkuhl, C.; Kamon, H.; Kankanyan, R.;
Karastergiou, A.; Kärcher, K.; Karczewski, M.; Karkar, S.; Karn, P.;
Kasperek, J.; Katagiri, H.; Kataoka, J.; Katarzyński, K.; Kato, S.;
Katz, U.; Kawanaka, N.; Kaye, L.; Kazanas, D.; Kelley-Hoskins, N.;
Kersten, J.; Khélifi, B.; Kieda, D. B.; Kihm, T.; Kimeswenger, S.;
Kisaka, S.; Kishida, S.; Kissmann, R.; Klepser, S.; Kluźniak, W.;
Knapen, J.; Knapp, J.; Knödlseder, J.; Koch, B.; Köck, F.; Kocot,
J.; Kohri, K.; Kokkotas, K.; Kokkotas, K.; Kolitzus, D.; Komin, N.;
Kominis, I.; Kong, A.; Konno, Y.; Kosack, K.; Koss, G.; Kossatz, M.;
Kowal, G.; Koyama, S.; Kozioł, J.; Kraus, M.; Krause, J.; Krause, M.;
Krawzcynski, H.; Krennrich, F.; Kretzschmann, A.; Kruger, P.; Kubo, H.;
Kudryavtsev, V.; Kukec Mezek, G.; Kuklis, M.; Kuroda, H.; Kushida, J.;
La Barbera, A.; La Palombara, N.; La Parola, V.; La Rosa, G.; Laffon,
H.; Lahmann, R.; Lakicevic, M.; Lalik, K.; Lamanna, G.; Landriu,
D.; Landt, H.; Lang, R. G.; Lapington, J.; Laporte, P.; Le Fèvre,
J. -P.; Le Flour, T.; Le Sidaner, P.; Lee, S. -H.; Lee, W. H.; Lees,
J. -P.; Lefaucheur, J.; Leffhalm, K.; Leich, H.; Leigui de Oliveira,
M. A.; Lelas, D.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.;
Leonard, R.; Leoni, R.; Lessio, L.; Leto, G.; Leveque, A.; Lieunard,
B.; Limon, M.; Lindemann, R.; Lindfors, E.; Linhoff, L.; Liolios,
A.; Lipniacka, A.; Lockart, H.; Lohse, T.; Łokas, E.; Lombardi, S.;
Longo, F.; Lopatin, A.; Lopez, M.; Loreggia, D.; Louge, T.; Louis,
F.; Louys, M.; Lucarelli, F.; Lucchesi, D.; Lüdecke, H.; Luigi, T.;
Luque-Escamilla, P. L.; Lyard, E.; Maccarone, M. C.; Maccarone, T.;
Maccarone, T. J.; Mach, E.; Madejski, G. M.; Madonna, A.; Magniette,
F.; Magniez, A.; Mahabir, M.; Maier, G.; Majumdar, P.; Majumdar, P.;
Makariev, M.; Malaguti, G.; Malaspina, G.; Mallot, A. K.; Malouf,
A.; Maltezos, S.; Malyshev, D.; Mancilla, A.; Mandat, D.; Maneva, G.;
Manganaro, M.; Mangano, S.; Manigot, P.; Mankushiyil, N.; Mannheim, K.;
Maragos, N.; Marano, D.; Marchegiani, P.; Marcomini, J. A.; Marcowith,
A.; Mariotti, M.; Marisaldi, M.; Markoff, S.; Martens, C.; Martí,
J.; Martin, J. -M.; Martin, L.; Martin, P.; Martínez, G.; Martínez,
M.; Martínez, O.; Martynyuk-Lototskyy, K.; Marx, R.; Masetti, N.;
Massimino, P.; Mastichiadis, A.; Mastroianni, S.; Mastropietro, M.;
Masuda, S.; Matsumoto, H.; Matsuoka, S.; Matthews, N.; Mattiazzo, S.;
Maurin, G.; Maxted, N.; Maxted, N.; Maya, J.; Mayer, M.; Mazin, D.;
Mazziotta, M. N.; Mc Comb, L.; McCubbin, N.; McHardy, I.; Medina,
C.; Mehrez, F.; Melioli, C.; Melkumyan, D.; Melse, T.; Mereghetti,
S.; Merk, M.; Mertsch, P.; Meunier, J. -L.; Meures, T.; Meyer, M.;
Meyrelles, J. L., jr; Miccichè, A.; Michael, T.; Michałowski, J.;
Mientjes, P.; Mievre, I.; Mihailidis, A.; Miller, J.; Mineo, T.;
Minuti, M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.;
Mitchell, A.; Mizuno, T.; Moderski, R.; Mognet, I.; Mohammed, M.;
Moharana, R.; Mohrmann, L.; Molinari, E.; Molyneux, P.; Monmarthe,
E.; Monnier, G.; Montaruli, T.; Monte, C.; Monteiro, I.; Mooney, D.;
Moore, P.; Moralejo, A.; Morello, C.; Moretti, E.; Mori, K.; Morris,
P.; Morselli, A.; Moscato, F.; Motohashi, D.; Mottez, F.; Moudden,
Y.; Moulin, E.; Mueller, S.; Mukherjee, R.; Munar, P.; Munari, M.;
Mundell, C.; Mundet, J.; Muraishi, H.; Murase, K.; Muronga, A.; Murphy,
A.; Nagar, N.; Nagataki, S.; Nagayoshi, T.; Nagesh, B. K.; Naito,
T.; Nakajima, D.; Nakajima, D.; Nakamori, T.; Nakayama, K.; Nanni,
J.; Naumann, D.; Nayman, P.; Nellen, L.; Nemmen, R.; Neronov, A.;
Neyroud, N.; Nguyen, T.; Nguyen, T. T.; Nguyen Trung, T.; Nicastro, L.;
Nicolau-Kukliński, J.; Niederwanger, F.; Niedźwiecki, A.; Niemiec,
J.; Nieto, D.; Nievas-Rosillo, M.; Nikolaidis, A.; Nikołajuk, M.;
Nishijima, K.; Nishikawa, K. -I.; Nishiyama, G.; Noda, K.; Noda,
K.; Nogues, L.; Nolan, S.; Northrop, R.; Nosek, D.; Nöthe, M.;
Novosyadlyj, B.; Nozka, L.; Nunio, F.; Oakes, L.; O'Brien, P.; Ocampo,
C.; Occhipinti, G.; Ochoa, J. P.; OFaolain de Bhroithe, A.; Oger, R.;
Ohira, Y.; Ohishi, M.; Ohm, S.; Ohoka, H.; Okazaki, N.; Okumura, A.;
Olive, J. -F.; Olszowski, D.; Ong, R. A.; Ono, S.; Orienti, M.; Orito,
R.; Orlati, A.; Osborne, J.; Ostrowski, M.; Ottaway, D.; Otte, N.;
Öttl, S.; Ovcharov, E.; Oya, I.; Ozieblo, A.; Padovani, M.; Pagano,
I.; Paiano, S.; Paizis, A.; Palacio, J.; Palatka, M.; Pallotta, J.;
Panagiotidis, K.; Panazol, J. -L.; Paneque, D.; Panter, M.; Panzera,
M. R.; Paoletti, R.; Paolillo, M.; Papayannis, A.; Papyan, G.; Paravac,
A.; Paredes, J. M.; Pareschi, G.; Park, N.; Parsons, D.; Paśko, P.;
Pavy, S.; Pech, M.; Peck, A.; Pedaletti, G.; Pe'er, A.; Peet, S.;
Pelat, D.; Pepato, A.; Perez, M. d. C.; Perri, L.; Perri, M.; Persic,
M.; Persic, M.; Petrashyk, A.; Petrucci, P. -O.; Petruk, O.; Peyaud,
B.; Pfeifer, M.; Pfeiffer, G.; Piano, G.; Pieloth, D.; Pierre, E.;
Pinto de Pinho, F.; García, C. Pio; Piret, Y.; Pisarski, A.; Pita,
S.; Platos, Ł.; Platzer, R.; Podkladkin, S.; Pogosyan, L.; Pohl,
M.; Poinsignon, P.; Pollo, A.; Porcelli, A.; Porthault, J.; Potter,
W.; Poulios, S.; Poutanen, J.; Prandini, E.; Prandini, E.; Prast, J.;
Pressard, K.; Principe, G.; Profeti, F.; Prokhorov, D.; Prokoph, H.;
Prouza, M.; Pruchniewicz, R.; Pruteanu, G.; Pueschel, E.; Pühlhofer,
G.; Puljak, I.; Punch, M.; Pürckhauer, S.; Pyzioł, R.; Queiroz,
F.; Quel, E. J.; Quinn, J.; Quirrenbach, A.; Rafighi, I.; Rainò, S.;
Rajda, P. J.; Rameez, M.; Rando, R.; Rannot, R. C.; Rataj, M.; Ravel,
T.; Razzaque, S.; Reardon, P.; Reichardt, I.; Reimann, O.; Reimer,
A.; Reimer, O.; Reisenegger, A.; Renaud, M.; Renner, S.; Reposeur,
T.; Reville, B.; Rezaeian, A.; Rhode, W.; Ribeiro, D.; Ribeiro Prado,
R.; Ribó, M.; Richards, G.; Richer, M. G.; Richtler, T.; Rico, J.;
Ridky, J.; Rieger, F.; Riquelme, M.; Ristori, P. R.; Rivoire, S.; Rizi,
V.; Roache, E.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodríguez
Vázquez, J. J.; Rojas, G.; Romano, P.; Romeo, G.; Roncadelli, M.;
Rosado, J.; Rose, J.; Rosen, S.; Rosier Lees, S.; Ross, D.; Rouaix,
G.; Rousselle, J.; Rovero, A. C.; Rowell, G.; Roy, F.; Royer, S.;
Rubini, A.; Rudak, B.; Rugliancich, A.; Rujopakarn, W.; Rulten,
C.; Rupiński, M.; Russo, F.; Russo, F.; Rutkowski, K.; Saavedra,
O.; Sabatini, S.; Sacco, B.; Sadeh, I.; Saemann, E. O.; Safi-Harb,
S.; Saggion, A.; Sahakian, V.; Saito, T.; Sakaki, N.; Sakurai, S.;
Salamon, A.; Salega, M.; Salek, D.; Salesa Greus, F.; Salgado, J.;
Salina, G.; Salinas, L.; Salini, A.; Sanchez, D.; Sanchez-Conde, M.;
Sandaker, H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.;
Santander, M.; Santangelo, A.; Santos, E. M.; Santos-Lima, R.; Sanuy,
A.; Sapozhnikov, L.; Sarkar, S.; Satalecka, K.; Satalecka, K.; Sato,
Y.; Savalle, R.; Sawada, M.; Sayède, F.; Schanne, S.; Schanz, T.;
Schioppa, E. J.; Schlenstedt, S.; Schmid, J.; Schmidt, T.; Schmoll,
J.; Schneider, M.; Schoorlemmer, H.; Schovanek, P.; Schubert, A.;
Schullian, E. -M.; Schultze, J.; Schulz, A.; Schulz, S.; Schure, K.;
Schussler, F.; Schwab, T.; Schwanke, U.; Schwarz, J.; Schweizer, T.;
Schwemmer, S.; Schwendicke, U.; Schwerdt, C.; Sciacca, E.; Scuderi,
S.; Segreto, A.; Seiradakis, J. -H.; Sembroski, G. H.; Semikoz, D.;
Sergijenko, O.; Serre, N.; Servillat, M.; Seweryn, K.; Shafi, N.;
Shalchi, A.; Sharma, M.; Shayduk, M.; Shellard, R. C.; Shibata, T.;
Shigenaka, A.; Shilon, I.; Shum, E.; Sidoli, L.; Sidz, M.; Sieiro, J.;
Siejkowski, H.; Silk, J.; Sillanpää, A.; Simone, D.; Simpson, H.;
Singh, B. B.; Sinha, A.; Sironi, G.; Sitarek, J.; Sizun, P.; Sliusar,
V.; Sliusar, V.; Smith, A.; Sobczyńska, D.; Sol, H.; Sottile, G.;
Sowiński, M.; Spanier, F.; Spengler, G.; Spiga, R.; Stadler, R.;
Stahl, O.; Stamerra, A.; Stanič, S.; Starling, R.; Staszak, D.;
Stawarz, Ł.; Steenkamp, R.; Stefanik, S.; Stegmann, C.; Steiner, S.;
Stella, C.; Stephan, M.; Stergioulas, N.; Sternberger, R.; Sterzel, M.;
Stevenson, B.; Stinzing, F.; Stodulska, M.; Stodulski, M.; Stolarczyk,
T.; Stratta, G.; Straumann, U.; Stringhetti, L.; Strzys, M.; Stuik,
R.; Sulanke, K. -H.; Suomijärvi, T.; Supanitsky, A. D.; Suric, T.;
Sushch, I.; Sutcliffe, P.; Sykes, J.; Szanecki, M.; Szepieniec, T.;
Szwarnog, P.; Tacchini, A.; Tachihara, K.; Tagliaferri, G.; Tajima,
H.; Takahashi, H.; Takahashi, K.; Takahashi, M.; Takalo, L.; Takami,
S.; Takata, J.; Takeda, J.; Talbot, G.; Tam, T.; Tanaka, M.; Tanaka,
S.; Tanaka, T.; Tanaka, Y.; Tanci, C.; Tanigawa, S.; Tavani, M.;
Tavecchio, F.; Tavernet, J. -P.; Tayabaly, K.; Taylor, A.; Tejedor,
L. A.; Telezhinsky, I.; Temme, F.; Temnikov, P.; Tenzer, C.; Terada,
Y.; Terrazas, J. C.; Terrier, R.; Terront, D.; Terzic, T.; Tescaro,
D.; Teshima, M.; Teshima, M.; Testa, V.; Tezier, D.; Thayer, J.;
Thornhill, J.; Thoudam, S.; Thuermann, D.; Tibaldo, L.; Tiengo,
A.; Timpanaro, M. C.; Tiziani, D.; Tluczykont, M.; Todero Peixoto,
C. J.; Tokanai, F.; Tokarz, M.; Toma, K.; Tomastik, J.; Tomono, Y.;
Tonachini, A.; Tonev, D.; Torii, K.; Tornikoski, M.; Torres, D. F.;
Torres, M.; Torresi, E.; Toso, G.; Tosti, G.; Totani, T.; Tothill, N.;
Toussenel, F.; Tovmassian, G.; Toyama, T.; Travnicek, P.; Trichard,
C.; Trifoglio, M.; Troyano Pujadas, I.; Trzeciak, M.; Tsinganos, K.;
Tsujimoto, S.; Tsuru, T.; Uchiyama, Y.; Umana, G.; Umetsu, Y.; Upadhya,
S. S.; Uslenghi, M.; Vagelli, V.; Vagnetti, F.; Valdes-Galicia, J.;
Valentino, M.; Vallania, P.; Valore, L.; van Driel, W.; van Eldik,
C.; van Soelen, B.; Vandenbroucke, J.; Vanderwalt, J.; Vasileiadis,
G.; Vassiliev, V.; Vázquez, J. R.; Vázquez Acosta, M. L.; Vecchi,
M.; Vega, A.; Vegas, I.; Veitch, P.; Venault, P.; Venema, L.; Venter,
C.; Vercellone, S.; Vergani, S.; Verma, K.; Verzi, V.; Vettolani,
G. P.; Veyssiere, C.; Viana, A.; Viaux, N.; Vicha, J.; Vigorito,
C.; Vincent, P.; Vincent, S.; Vink, J.; Vittorini, V.; Vlahakis, N.;
Vlahos, L.; Voelk, H.; Voisin, V.; Vollhardt, A.; Volpicelli, A.; von
Brand, H.; Vorobiov, S.; Vovk, I.; Vrastil, M.; Vu, L. V.; Vuillaume,
T.; Wagner, R.; Wagner, R.; Wagner, S. J.; Wakely, S. P.; Walstra, T.;
Walter, R.; Walther, T.; Ward, J. E.; Ward, M.; Warda, K.; Warren,
D.; Wassberg, S.; Watson, J. J.; Wawer, P.; Wawrzaszek, R.; Webb,
N.; Wegner, P.; Weiner, O.; Weinstein, A.; Wells, R.; Werner, F.;
Wetteskind, H.; White, M.; White, R.; Więcek, M.; Wierzcholska, A.;
Wiesand, S.; Wijers, R.; Wilcox, P.; Wild, N.; Wilhelm, A.; Wilkinson,
M.; Will, M.; Will, M.; Williams, D. A.; Williams, J. T.; Willingale,
R.; Wilson, N.; Winde, M.; Winiarski, K.; Winkler, H.; Winter, M.;
Wischnewski, R.; Witt, E.; Wojcik, P.; Wolf, D.; Wood, M.; Wörnlein,
A.; Wu, E.; Wu, T.; Yadav, K. K.; Yamamoto, H.; Yamamoto, T.; Yamane,
N.; Yamazaki, R.; Yanagita, S.; Yang, L.; Yelos, D.; Yoshida, A.;
Yoshida, M.; Yoshida, T.; Yoshiike, S.; Yoshikoshi, T.; Yu, P.;
Zabalza, V.; Zaborov, D.; Zacharias, M.; Zaharijas, G.; Zajczyk,
A.; Zampieri, L.; Zandanel, F.; Zanmar Sanchez, R.; Zaric, D.;
Zavrtanik, D.; Zavrtanik, M.; Zdziarski, A.; Zech, A.; Zechlin, H.;
Zhao, A.; Zhdanov, V.; Ziegler, A.; Ziemann, J.; Ziętara, K.; Zink,
A.; Ziółkowski, J.; Zitelli, V.; Zoli, A.; Zorn, J.; Żychowski, P.
2016arXiv161005151C Altcode:
List of contributions from the Cherenkov Telescope Array (CTA)
Consortium presented at the 6th International Symposium on High-Energy
Gamma-Ray Astronomy (Gamma 2016), July 11-15, 2016, in Heidelberg,
Germany.
---------------------------------------------------------
Title: Exoplanet Transits Enable High-Resolution Spectroscopy Across
Spatially Resolved Stellar Surfaces
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Dahlén, Erik;
Pazira, Hiva
2016csss.confE..66D Altcode: 2016arXiv160703489D
Observations of stellar surfaces ndash; except for the Sun ndash;
are hampered by their tiny angular extent, while observed spectral
lines are smeared by averaging over the stellar surface, and by stellar
rotation. Exoplanet transits can be used to analyze stellar atmospheric
structure, yielding high-resolution spectra across spatially highly
resolved stellar surfaces, free from effects of spatial smearing and the
rotational wavelength broadening present in full-disk spectra. During
a transit, stellar surface portions successively become hidden, and
differential spectroscopy between various transit phases provides
spectra of those surface segments then hidden behind the planet. The
small area subtended by even a large planet (about 1% of a main-sequence
star) offers high spatial resolution but demands very precise
observations. We demonstrate the reconstruction of photospheric Fe I
line profilesnbsp;at a spectral resolution R=80,000 across the surface
of the solar-type star HD 209458. Any detailed understanding of stellar
atmospheres requires modeling with 3-dimensional hydrodynamics. The
properties predicted by such models are mapped onto the precise
spectral-line shapes, asymmetries and wavelength shifts, and their
variation from the center to the limb across any stellar disk. This
method provides a tool for testing and verifying such models. The
method will soon become applicable to more diverse types of stars,
thanks to new spectrometers on very large telescopes, and since ongoing
photometric searches are expected to discover additional bright host
stars of transiting exoplanets.>
---------------------------------------------------------
Title: Intensity interferometry: optical imaging with kilometer
baselines
Authors: Dravins, Dainis
2016SPIE.9907E..0MD Altcode: 2016arXiv160703490D
Optical imaging with microarcsecond resolution will reveal details
across and outside stellar surfaces but requires kilometer-scale
interferometers, challenging to realize either on the ground or in
space. Intensity interferometry, electronically connecting independent
telescopes, has a noise budget that relates to the electronic time
resolution, circumventing issues of atmospheric turbulence. Extents up
to a few km are becoming realistic with arrays of optical air Cherenkov
telescopes (primarily erected for gamma-ray studies), enabling an
optical equivalent of radio interferometer arrays. Pioneered by
Hanbury Brown and Twiss, digital versions of the technique have now
been demonstrated, reconstructing diffraction-limited images from
laboratory measurements over hundreds of optical baselines. This review
outlines the method from its beginnings, describes current experiments,
and sketches prospects for future observations.
---------------------------------------------------------
Title: Spatially Resolved Spectroscopy Across HD189733 (K1V) Using
Exoplanet Transits
Authors: Gustavsson, Martin; Dravins, Dainis; Ludwig, Hans-Günter
2016csss.confE..53G Altcode:
For testing 3-dimensional models of stellar atmospheres, spectroscopy
across spatially resolved stellar surfaces would be desired with
a spectral resolution of(R = 100,000) or more. Hydrodynamic models
predict variations in line profile shapes, strengths, wavelength
positions and asymmetries. These variations vary systematically between
disk center and limb and as a function of line strength, excitation
potential and wavelength region. However, except for a few supergiants
and the Sun, current telescopes are not yet capable of resolving
any stellar surfaces. One alternative method to resolve distant
stellar surfaces, feasible already now, is differential spectroscopy
of transiting exoplanet systems. By subtracting in-transit spectra
from the spectrum outside of transit, the spectra from stellar surface
portions temporarily hidden behind the planet can be disentangled. Since
transiting planets cover only a small portion of the stellar surface,
the method requires a very high signal-to-noise ratio, obtainable by
averaging numerous similar spectral lines. We apply such differential
spectroscopy on the 7.7 mag K1V star HD 189733 ('Alopex'*); its
transiting planet covers ∼ 3% of its host star's surface, which
is the deepest known transit among the brighter systems. Archival
data from the ESO HARPS spectrometerare used to construct averaged
profiles of photospheric Fe I lines, with the aim of comparing spatially
resolved profiles to analogous synthetic line profiles computed from the
3-dimensional hydrodynamic CO<SUP>5</SUP>BOLD model.<BR /> * We refer
to HD 189733 as 'Alopex' (from the Greek 'αλɛπού'), denoting a
fox related to the one that gave name to its constellation of Vulpecula.
---------------------------------------------------------
Title: Stellar Intensity Interferometry over Kilometer Baselines:
Optical aperture synthesis with electronically connected telescopes
Authors: Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.
2015IAUGA..2233727D Altcode:
Diffraction-limited optical imaging over kilometer baselines will reveal
stellar surfaces, perhaps even resolving the silhouettes of transiting
exoplanets. An opportunity is opening up with arrays of air Cherenkov
telescopes used for intensity interferometry, a technique once pioneered
by Hanbury Brown and Twiss. Being essentially insensitive to atmospheric
turbulence, this permits both very long baselines and observing at
short optical wavelengths.System verifications have been made in a
large optics laboratory. Artificial stars were observed by a group of
small telescopes equipped with nanosecond-resolving photon-counting
detectors, their outputs processed in a digital correlator. Numerous
telescope pairs at different baseline lengths and orientations build
up a two-dimensional map of the second-order spatial coherence of the
source, from which its image can be extracted.From up to 180 baselines
thus measured, full two-dimensional images were reconstructed. As far as
we are aware, these are the first diffraction-limited images produced
by an array of optical telescopes connected only electronically
in software, with no optical connections between them. Since the
electronic signal from any telescope can be freely copied without
loss of signal, very many baselines can be built up between dispersed
telescopes. Using arrays of air Cherenkov telescopes, this should enable
the optical equivalent of interferometric aperture synthesis arrays
currently operating at radio wavelengths. arxiv.org/abs/1407.5993,
Nature Commun., in press (2015)
---------------------------------------------------------
Title: CTA Contributions to the 34th International Cosmic Ray
Conference (ICRC2015)
Authors: CTA Consortium, The; :; Abchiche, A.; Abeysekara, U.; Abril,
Ó.; Acero, F.; Acharya, B. S.; Actis, M.; Agnetta, G.; Aguilar,
J. A.; Aharonian, F.; Akhperjanian, A.; Albert, A.; Alcubierre,
M.; Alfaro, R.; Aliu, E.; Allafort, A. J.; Allan, D.; Allekotte,
I.; Aloisio, R.; Amans, J. -P.; Amato, E.; Ambrogi, L.; Ambrosi, G.;
Ambrosio, M.; Anderson, J.; Anduze, M.; Angüner, E. O.; Antolini, E.;
Antonelli, L. A.; Antonucci, M.; Antonuccio, V.; Antoranz, P.; Aramo,
C.; Aravantinos, A.; Argan, A.; Armstrong, T.; Arnaldi, H.; Arnold, L.;
Arrabito, L.; Arrieta, M.; Arrieta, M.; Asano, K.; Asorey, H. G.; Aune,
T.; Singh, C. B.; Babic, A.; Backes, M.; Bais, A.; Bajtlik, S.; Balazs,
C.; Balbo, M.; Balis, D.; Balkowski, C.; Ballester, O.; Ballet, J.;
Balzer, A.; Bamba, A.; Bandiera, R.; Barber, A.; Barbier, C.; Barceló,
M.; Barnacka, A.; Barres de Almeida, U.; Barrio, J. A.; Basso, S.;
Bastieri, D.; Bauer, C.; Baushev, A.; Becciani, U.; Becherini, Y.;
Becker Tjus, J.; Beckmann, V.; Bednarek, W.; Benbow, W.; Benedico
Ventura, D.; Berdugo, J.; Berge, D.; Bernardini, E.; Bernhard, S.;
Bernlöhr, K.; Bertucci, B.; Besel, M. -A.; Bhatt, N.; Bhattacharjee,
P.; Bhattachryya, S.; Biasuzzi, B.; Bicknell, G.; Bigongiari, C.;
Biland, A.; Billotta, S.; Bilnik, W.; Biondo, B.; Bird, T.; Birsin,
E.; Bissaldi, E.; Biteau, J.; Bitossi, M.; Blanch Bigas, O.; Blasi,
P.; Boehm, C.; Bogacz, L.; Bogdan, M.; Bohacova, M.; Boisson, C.;
Boix Gargallo, J.; Bolmont, J.; Bonanno, G.; Bonardi, A.; Bonifacio,
P.; Bonnoli, G.; Borkowski, J.; Bose, R.; Bosnjak, Z.; Bottani, A.;
Böttcher, M.; Bousquet, J. -J.; Boutonnet, C.; Bouyjou, F.; Braiding,
C.; Brandt, L.; Brau-Nogué, S.; Bregeon, J.; Bretz, T.; Briggs,
M.; Brigida, M.; Bringmann, T.; Brisken, W.; Brocato, E.; Brook, P.;
Brown, A. M.; Brun, P.; Brunetti, G.; Brunetti, L.; Bruno, P.; Bryan,
M.; Buanes, T.; Bucciantini, N.; Buchholtz, G.; Buckley, J.; Bugaev,
V.; Bühler, R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.;
Busetto, G.; Buson, S.; Buss, J.; Byrum, K.; Cameron, R.; Camprecios,
J.; Canelli, F.; Canestrari, R.; Cantu, S.; Capalbi, M.; Capasso, M.;
Capobianco, G.; Caraveo, P.; Cardenzana, J.; Carius, S.; Carlile, C.;
Carmona, E.; Carosi, A.; Carosi, R.; Carr, J.; Carroll, M.; Carter,
J.; Carton, P. -H.; Caruso, R.; Casandjian, J. -M.; Casanova, S.;
Cascone, E.; Casiraghi, M.; Castellina, A.; Catalano, O.; Catalanotti,
S.; Cavazzani, S.; Cazaux, S.; Cefalà, M.; Cerchiara, P.; Cereda,
M.; Cerruti, M.; Chabanne, E.; Chadwick, P.; Champion, C.; Chaty,
S.; Chaves, R.; Cheimets, P.; Chen, A.; Chen, X.; Chernyakova, M.;
Chiappetti, L.; Chikawa, M.; Chinn, D.; Chitnis, V. R.; Cho, N.;
Christov, A.; Chudoba, J.; Cieślar, M.; Cillis, A.; Ciocci, M. A.;
Clay, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Colin, P.; Colombo,
E.; Colome, J.; Colonges, S.; Compin, M.; Conforti, V.; Connaughton,
V.; Connell, S.; Conrad, J.; Contreras, J. L.; Coppi, P.; Corbel, S.;
Coridian, J.; Corona, P.; Corti, D.; Cortina, J.; Cossio, L.; Costa,
A.; Costantini, H.; Cotter, G.; Courty, B.; Covino, S.; Covone, G.;
Crimi, G.; Criswell, S. J.; Crocker, R.; Croston, J.; Cusumano, G.;
Da Vela, P.; Dale, Ø.; D'Ammando, F.; Dang, D.; Daniel, M.; Davids,
I.; Dawson, B.; Dazzi, F.; de Aguiar Costa, B.; De Angelis, A.; de
Araujo Cardoso, R. F.; De Caprio, V.; De Cesare, G.; De Franco, A.;
De Frondat, F.; de Gouveia Dal Pino, E. M.; de la Calle, I.; De La
Vega, G. A.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de
Mello Neto, J. R. T.; de Naurois, M.; de Oña Wilhelmi, E.; De Palma,
F.; de Souza, V.; Decock, G.; Deil, C.; Del Santo, M.; Delagnes, E.;
Deleglise, G.; Delgado, C.; della Volpe, D.; Deloye, P.; Depaola, G.;
Detournay, M.; Dettlaff, A.; Di Girolamo, T.; Di Giulio, C.; Di Paola,
A.; Di Pierro, F.; Di Sciascio, G.; Díaz, C.; Dick, J.; Dickinson, H.;
Diebold, S.; Diez, V.; Digel, S.; Dipold, J.; Disset, G.; Distefano,
A.; Djannati-Ataï, A.; Doert, M.; Dohmke, M.; Domainko, W.; Dominik,
N.; Dominis Prester, D.; Donat, A.; Donnarumma, I.; Dorner, D.; Doro,
M.; Dournaux, J. -L.; Doyle, K.; Drake, G.; Dravins, D.; Drury, L.;
Dubus, G.; Dumas, D.; Dumm, J.; Durand, D.; D'Urso, D.; Dwarkadas,
V.; Dyks, J.; Dyrda, M.; Ebr, J.; Echaniz, J. C.; Edy, E.; Egberts,
K.; Egberts, K.; Eger, P.; Einecke, S.; Eisch, J.; Eisenkolb, F.;
Eleftheriadis, C.; Elsässer, D.; Emmanoulopoulos, D.; Engelbrecht,
C.; Engelhaupt, D.; Ernenwein, J. -P.; Errando, M.; Eschbach, S.;
Etchegoyen, A.; Evans, P.; Fairbairn, M.; Falcone, A.; Fantinel, D.;
Farakos, K.; Farnier, C.; Farrell, E.; Farrell, S.; Fasola, G.; Fegan,
S.; Feinstein, F.; Ferenc, D.; Fernandez, A.; Fernandez-Alonso, M.;
Ferreira, O.; Fesquet, M.; Fetfatzis, P.; Fiasson, A.; Filipčič, A.;
Filipovic, M.; Fink, D.; Finley, C.; Finley, J. P.; Finoguenov, A.;
Fioretti, V.; Fiorini, M.; Firpo Curcoll, R.; Fleischhack, H.; Flores,
H.; Florin, D.; Föhr, C.; Fokitis, E.; Font, L.; Fontaine, G.; Fontes,
B.; Forest, F.; Fornasa, M.; Förster, A.; Fortin, P.; Fortson, L.;
Fouque, N.; Franckowiak, A.; Franco, F. J.; Frankowski, A.; Frega,
N.; Freire Mota Albuquerque, I.; Freixas Coromina, L.; Fresnillo,
L.; Fruck, C.; Fuessling, M.; Fugazza, D.; Fujita, Y.; Fukami, S.;
Fukazawa, Y.; Fukuda, T.; Fukui, Y.; Funk, S.; Gäbele, W.; Gabici,
S.; Gadola, A.; Galante, N.; Gall, D. D.; Gallant, Y.; Galloway, D.;
Gallozzi, S.; Gao, S.; Garcia, B.; García Gil, R.; Garcia López,
R.; Garczarczyk, M.; Gardiol, D.; Gargano, C.; Gargano, F.; Garozzo,
S.; Garrecht, F.; Garrido, D.; Garrido, L.; Gascon, D.; Gaskins,
J.; Gaudemard, J.; Gaug, M.; Gaweda, J.; Geffroy, N.; Gérard, L.;
Ghalumyan, A.; Ghedina, A.; Ghigo, M.; Ghislain, P.; Giannakaki, E.;
Gianotti, F.; Giarrusso, S.; Giavitto, G.; Giebels, B.; Giglietto,
N.; Gika, V.; Gimenes, R.; Giomi, M.; Giommi, P.; Giordano, F.;
Giovannini, G.; Giro, E.; Giroletti, M.; Giuliani, A.; Glicenstein,
J. -F.; Godinovic, N.; Goldoni, P.; Gomez Berisso, M.; Gomez Vargas,
G. A.; Gonzalez, M. M.; González, A.; González, F.; González
Muñoz, A.; Gothe, K. S.; Gotz, D.; Grabarczyk, T.; Graciani, R.;
Grandi, P.; Grañena, F.; Granot, J.; Grasseau, G.; Gredig, R.;
Green, A. J.; Green, A. M.; Greenshaw, T.; Grenier, I.; Grillo, A.;
Grondin, M. -H.; Grube, J.; Grudzinska, M.; Grygorczuk, J.; Guarino,
V.; Guberman, D.; Gunji, S.; Gyuk, G.; Hadasch, D.; Hagedorn, A.;
Hahn, J.; Hakansson, N.; Hamer Heras, N.; Hanabata, Y.; Hara, S.;
Hardcastle, M. J.; Harris, J.; Hassan, T.; Hatanaka, K.; Haubold,
T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, M.; Heller, R.;
Henault, F.; Henri, G.; Hermann, G.; Hermel, R.; Herrera Llorente, J.;
Herrero, A.; Hervet, O.; Hidaka, N.; Hinton, J.; Hirai, W.; Hirotani,
K.; Hoard, D.; Hoffmann, D.; Hofmann, W.; Hofverberg, P.; Holch, T.;
Holder, J.; Hooper, S.; Horan, D.; Hörandel, J. R.; Hormigos, S.;
Horns, D.; Hose, J.; Houles, J.; Hovatta, T.; Hrabovsky, M.; Hrupec,
D.; Huet, J. -M.; Hütten, M.; Humensky, T. B.; Huovelin, J.; Huppert,
J. -F.; Iacovacci, M.; Ibarra, A.; Idźkowski, B.; Ikawa, D.; Illa,
J. M.; Impiombato, D.; Incorvaia, S.; Inome, Y.; Inoue, S.; Inoue,
T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.; Ishio, K.; Israel,
G. L.; Jablonski, C.; Jacholkowska, A.; Jacquemier, J.; Jamrozy,
M.; Janecek, P.; Janiak, M.; Jankowsky, F.; Jean, P.; Jeanney, C.;
Jegouzo, I.; Jenke, P.; Jimenez, J. J.; Jingo, M.; Jingo, M.; Jocou,
L.; Jogler, T.; Johnson, C. A.; Journet, L.; Juffroy, C.; Jung,
I.; Kaaret, P. E.; Kagaya, M.; Kakuwa, J.; Kalekin, O.; Kalkuhl, C.;
Kankanyan, R.; Karastergiou, A.; Kärcher, K.; Karczewski, M.; Karkar,
S.; Karn, P.; Kasperek, J.; Katagiri, H.; Kataoka, J.; Katarzyński,
K.; Katz, U.; Kaufmann, S.; Kawanaka, N.; Kawashima, T.; Kazanas,
D.; Kelley-Hoskins, N.; Kellner-Leidel, B.; Kendziorra, E.; Kersten,
J.; Khélifi, B.; Kieda, D. B.; Kihm, T.; Kisaka, S.; Kissmann, R.;
Klepser, S.; Kluźniak, W.; Knapen, J.; Knapp, J.; Knödlseder, J.;
Köck, F.; Kocot, J.; Kodakkadan, A.; Kodani, K.; Kohri, K.; Kojima,
T.; Kokkotas, K.; Kolitzus, D.; Komin, N.; Kominis, I.; Konno, Y.;
Kosack, K.; Koss, G.; Koul, R.; Kowal, G.; Koyama, S.; Kozioł,
J.; Kraus, M.; Krause, J.; Krause, M.; Krawzcynski, H.; Krennrich,
F.; Kretzschmann, A.; Kruger, P.; Kubo, H.; Kudryavtsev, V.; Kukec
Mezek, G.; Kushida, J.; Kuznetsov, A.; La Barbera, A.; La Palombara,
N.; La Parola, V.; La Rosa, G.; Laffon, H.; Lagadec, T.; Lahmann,
R.; Lalik, K.; Lamanna, G.; Landriu, D.; Landt, H.; Lang, R. G.;
Languignon, D.; Lapington, J.; Laporte, P.; Latovski, N.; Law-Green,
D.; Le Fèvre, J. -P.; Le Flour, T.; Le Sidaner, P.; Lee, S. -H.; Lee,
W. H.; Leffhalm, K.; Leich, H.; Leigui de Oliveira, M. A.; Lelas,
D.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.; Leonard, R.;
Leoni, R.; Lessio, L.; Leto, G.; Leveque, A.; Lieunard, B.; Limon,
M.; Lindemann, R.; Lindfors, E.; Liolios, A.; Lipniacka, A.; Lockart,
H.; Lohse, T.; Loiseau, D.; Łokas, E.; Lombardi, S.; Longo, F.;
Longo, G.; Lopatin, A.; Lopez, M.; López-Coto, R.; López-Oramas,
A.; Loreggia, D.; Louge, T.; Louis, F.; Lu, C. -C.; Lucarelli, F.;
Lucchesi, D.; Lüdecke, H.; Luque-Escamilla, P. L.; Luz, O.; Lyard,
E.; Maccarone, M. C.; Maccarone, T. J.; Mach, E.; Madejski, G. M.;
Madonna, A.; Mahabir, M.; Maier, G.; Majumdar, P.; Makariev, M.;
Malaguti, G.; Malaspina, G.; Mallot, A. K.; Maltezos, S.; Mancilla,
A.; Mandat, D.; Maneva, G.; Manigot, P.; Mankushiyil, N.; Mannheim,
K.; Maragos, N.; Marano, D.; Marchegiani, P.; Marcomini, J. A.;
Marcowith, A.; Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek,
A.; Martens, C.; Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.;
Martínez, M.; Martínez, O.; Marx, R.; Massimino, P.; Mastichiadis,
A.; Mastroianni, S.; Mastropietro, M.; Masuda, S.; Matsumoto, H.;
Matsuoka, S.; Mattiazzo, S.; Maurin, G.; Maxted, N.; Maya, J.; Mayer,
M.; Mazin, D.; Mazureau, E.; Mazziotta, M. N.; Mc Comb, L.; McCann,
A.; McCubbin, N.; McHardy, I.; McKay, R.; McKinney, K.; Meagher, K.;
Medina, C.; Mehrez, F.; Melioli, C.; Melkumyan, D.; Melo, D.; Melse,
T.; Mereghetti, S.; Mertsch, P.; Meyer, M.; Meyrelles, J. L., jr;
Miccichè, A.; Michałowski, J.; Micolon, P.; Mientjes, P.; Mignot,
S.; Mihailidis, A.; Mineo, T.; Minuti, M.; Mirabal, N.; Mirabel, F.;
Miranda, J. M.; Mirzoyan, R.; Mistò, A.; Mitchell, A.; Mizuno, T.;
Moderski, R.; Mognet, I.; Mohammed, M.; Moharana, R.; Molinari, E.;
Monmarthe, E.; Monnier, G.; Montaruli, T.; Monte, C.; Monteiro, I.;
Moore, P.; Moralejo Olaizola, A.; Morello, C.; Moretti, E.; Mori,
K.; Morlino, G.; Morselli, A.; Mottez, F.; Moudden, Y.; Moulin, E.;
Mrusek, I.; Mueller, S.; Mukherjee, R.; Munar-Adrover, P.; Mundell,
C.; Muraishi, H.; Murase, K.; Muronga, A.; Murphy, A.; Nagataki,
S.; Nagayoshi, T.; Nagesh, B. K.; Naito, T.; Nakajima, D.; Nakamori,
T.; Nakayama, K.; Naumann, D.; Nayman, P.; Nellen, L.; Nemmen, R.;
Neronov, A.; Neustroev, V.; Neyroud, N.; Nguyen, T.; Nicastro,
L.; Nicolau-Kukliński, J.; Niederwanger, F.; Niedźwiecki, A.;
Niemiec, J.; Nieto, D.; Nievas, M.; Nikolaidis, A.; Nishijima, K.;
Nishikawa, K. -I.; Noda, K.; Nogues, L.; Nolan, S.; Northrop, R.;
Nosek, D.; Nozka, L.; Nunio, F.; Oakes, L.; O'Brien, P.; Occhipinti,
G.; O'Faolain de Bhroithe, A.; Ogino, M.; Ohira, Y.; Ohishi, M.; Ohm,
S.; Ohoka, H.; Okumura, A.; Olive, J. -F.; Olszowski, D.; Ong, R. A.;
Ono, S.; Orienti, M.; Orito, R.; Orlati, A.; Orlati, A.; Osborne, J.;
Ostrowski, M.; Otero, L. A.; Ottaway, D.; Otte, N.; Oya, I.; Ozieblo,
A.; Padovani, M.; Pagano, I.; Paiano, S.; Paizis, A.; Palacio, J.;
Palatka, M.; Pallotta, J.; Panagiotidis, K.; Panazol, J. -L.; Paneque,
D.; Panter, M.; Panzera, M. R.; Paoletti, R.; Paolillo, M.; Papayannis,
A.; Papyan, G.; Paravac, A.; Paredes, J. M.; Pareschi, G.; Park, N.;
Parsons, D.; Paśko, P.; Pavy, S.; Arribas, M. Paz; Pech, M.; Peck,
A.; Pedaletti, G.; Peet, S.; Pelassa, V.; Pelat, D.; Peres, C.;
Perez, M. d. C.; Perri, L.; Persic, M.; Petrashyk, A.; Petrucci,
P. -O.; Peyaud, B.; Pfeifer, M.; Pfeiffer, G.; Piano, G.; Pichel,
A.; Pieloth, D.; Pierbattista, M.; Pierre, E.; Pinto de Pinho, F.;
García, C. Pio; Piret, Y.; Pita, S.; Planes, A.; Platino, M.; Platos,
Ł.; Platzer, R.; Podkladkin, S.; Pogosyan, L.; Pohl, M.; Poinsignon,
P.; Ponz, J. D.; Porcelli, A.; Potter, W.; Poulios, S.; Poutanen,
J.; Prandini, E.; Prast, J.; Preece, R.; Profeti, F.; Prokhorov, D.;
Prokoph, H.; Prouza, M.; Proyetti, M.; Pruchniewicz, R.; Pueschel,
E.; Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł, R.; Queiroz,
F.; Quel, E. J.; Quinn, J.; Quirrenbach, A.; Racero, E.; Räck,
T.; Rafalski, J.; Rafighi, I.; Rainò, S.; Rajda, P. J.; Rameez, M.;
Rando, R.; Rannot, R. C.; Rataj, M.; Rateau, S.; Ravel, T.; Ravignani,
D.; Razzaque, S.; Reardon, P.; Reimann, O.; Reimer, A.; Reimer, O.;
Reitberger, K.; Renaud, M.; Renner, S.; Reposeur, T.; Rettig, R.;
Reville, B.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richards, G.; Richer,
M. G.; Rico, J.; Ridky, J.; Rieger, F.; Ringegni, P.; Ristori, P. R.;
Rivière, A.; Rivoire, S.; Roache, E.; Rodeghiero, G.; Rodriguez,
J.; Rodriguez Fernandez, G.; Rodríguez Vázquez, J. J.; Rogers, T.;
Rojas, G.; Romano, P.; Romay Rodriguez, M. P.; Romeo, G.; Romero,
G. E.; Roncadelli, M.; Rose, J.; Rosen, S.; Rosier Lees, S.; Ross,
D.; Rossiter, P.; Rouaix, G.; Rousselle, J.; Rovero, A. C.; Rowell,
G.; Roy, F.; Royer, S.; Różańska, A.; Rudak, B.; Rugliancich,
A.; Rulten, C.; Rupiński, M.; Russo, F.; Rutkowski, K.; Saavedra,
O.; Sabatini, S.; Sacco, B.; Saemann, E. O.; Saggion, A.; Saha, L.;
Sahakian, V.; Saito, K.; Saito, T.; Sakaki, N.; Salega, M.; Salek, D.;
Salgado, J.; Salini, A.; Sanchez, D.; Sanchez, F.; Sanchez-Conde, M.;
Sandaker, H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.;
Santander, M.; Santangelo, A.; Santos, E. M.; Santos-Lima, R.; Sanuy,
A.; Sapozhnikov, L.; Sarkar, S.; Satalecka, K.; Savalle, R.; Sawada,
M.; Sayède, F.; Schafer, J.; Schanne, S.; Schanz, T.; Schioppa, E. J.;
Schlenstedt, S.; Schlickeiser, R.; Schmidt, T.; Schmoll, J.; Schneider,
M.; Schovanek, P.; Schubert, A.; Schultz, C.; Schultze, J.; Schulz,
A.; Schulz, S.; Schure, K.; Schussler, F.; Schwab, T.; Schwanke, U.;
Schwarz, J.; Schweizer, T.; Schwemmer, S.; Schwendicke, U.; Schwerdt,
C.; Segreto, A.; Seiradakis, J. -H.; Sembroski, G. H.; Semikoz, D.;
Serre, N.; Servillat, M.; Seweryn, K.; Shafi, N.; Sharma, M.; Shayduk,
M.; Shellard, R. C.; Shibata, T.; Shiningayamwe Pandeni, K.; Shukla,
A.; Shum, E.; Sidoli, L.; Sidz, M.; Sieiro, J.; Siejkowski, H.; Silk,
J.; Sillanpää, A.; Simone, D.; Singh, B. B.; Sinha, A.; Sironi, G.;
Sitarek, J.; Sizun, P.; Slyusar, V.; Smith, A.; Smith, J.; Sobczyńska,
D.; Sol, H.; Sottile, G.; Sowiński, M.; Spanier, F.; Spengler, G.;
Spiga, D.; Stadler, R.; Stahl, O.; Stamatescu, V.; Stamerra, A.;
Stanič, S.; Starling, R.; Stawarz, Ł.; Steenkamp, R.; Stefanik, S.;
Stegmann, C.; Steiner, S.; Stella, C.; Stergioulas, N.; Sternberger,
R.; Sterzel, M.; Stevenson, B.; Stinzing, F.; Stodulska, M.; Stodulski,
M.; Stolarczyk, T.; Straumann, U.; Strazzeri, E.; Stringhetti, L.;
Strzys, M.; Stuik, R.; Sulanke, K. -H.; Supanitsky, A. D.; Suric, T.;
Sushch, I.; Sutcliffe, P.; Sykes, J.; Szanecki, M.; Szepieniec, T.;
Szwarnog, P.; Tacchini, A.; Tachihara, K.; Tagliaferri, G.; Tajima, H.;
Takahashi, H.; Takahashi, K.; Takahashi, M.; Takalo, L.; Takami, H.;
Talbot, G.; Tammi, J.; Tanaka, M.; Tanaka, S.; Tanaka, T.; Tanaka, Y.;
Tanci, C.; Tarantino, E.; Tavani, M.; Tavecchio, F.; Tavernet, J. -P.;
Tayabaly, K.; Tejedor, L. A.; Telezhinsky, I.; Temme, F.; Temnikov, P.;
Tenzer, C.; Terada, Y.; Terrier, R.; Tescaro, D.; Teshima, M.; Testa,
V.; Tezier, D.; Thayer, J.; Thomas, V.; Thornhill, J.; Thuermann,
D.; Tibaldo, L.; Tibolla, O.; Tiengo, A.; Tijsseling, G.; Timpanaro,
M. C.; Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tokarz, M.;
Toma, K.; Toma, K.; Tomastik, J.; Tomono, Y.; Tonachini, A.; Tonev,
D.; Torii, K.; Tornikoski, M.; Torres, D. F.; Torres, M.; Torresi, E.;
Toscano, S.; Toso, G.; Tosti, G.; Totani, T.; Tothill, N.; Toussenel,
F.; Tovmassian, G.; Townsley, C.; Toyama, T.; Travnicek, P.; Trifoglio,
M.; Troyano Pujadas, I.; Troyano Pujadas, I.; Trzeciak, M.; Tsinganos,
K.; Tsubone, Y.; Tsuchiya, Y.; Tsujimoto, S.; Tsuru, T.; Uchiyama, Y.;
Umana, G.; Umetsu, Y.; Underwood, C.; Upadhya, S. S.; Uslenghi, M.;
Vagnetti, F.; Valdes-Galicia, J.; Vallania, P.; Vallejo, G.; Valore,
L.; van Driel, W.; van Eldik, C.; van Soelen, B.; Vandenbroucke, J.;
Vanderwalt, J.; Vasileiadis, G.; Vassiliev, V.; Vázquez Acosta,
M. L.; Vecchi, M.; Vegas, I.; Veitch, P.; Venema, L.; Venter, C.;
Vercellone, S.; Vergani, S.; Verma, K.; Verzi, V.; Vettolani, G. P.;
Viana, A.; Vicha, J.; Videla, M.; Vigorito, C.; Vincent, P.; Vincent,
S.; Vink, J.; Vittorini, V.; Vlahakis, N.; Vlahos, L.; Voelk, H.;
Vogler, P.; Voisin, V.; Vollhardt, A.; Volpicelli, A.; Vorobiov,
S.; Vovk, I.; Vu, L. V.; Wagner, R.; Wagner, R. M.; Wagner, R. G.;
Wagner, S. J.; Wakely, S. P.; Walter, R.; Walther, T.; Ward, J. E.;
Ward, M.; Warda, K.; Warwick, R.; Wassberg, S.; Watson, J.; Wawer,
P.; Wawrzaszek, R.; Webb, N.; Wegner, P.; Weinstein, A.; Weitzel, Q.;
Wells, R.; Werner, F.; Werner, M.; Wetteskind, H.; White, M.; White,
R.; Więcek, M.; Wierzcholska, A.; Wiesand, S.; Wijers, R.; Wild, N.;
Wilhelm, A.; Wilkinson, M.; Will, M.; Williams, D. A.; Williams, J. T.;
Willingale, R.; Winde, M.; Winiarski, K.; Winkler, H.; Wischnewski,
R.; Wojcik, P.; Wolf, D.; Wood, M.; Wörnlein, A.; Wu, E.; Wu, T.;
Yadav, K. K.; Yamamoto, H.; Yamamoto, T.; Yamazaki, R.; Yanagita, S.;
Yang, L.; Yebras, J. M.; Yelos, D.; Yeung, W.; Yoshida, A.; Yoshida,
T.; Yoshiike, S.; Yoshikoshi, T.; Yu, P.; Zabalza, V.; Zabalza, V.;
Zacharias, M.; Zaharijas, G.; Zajczyk, A.; Zampieri, L.; Zandanel,
F.; Zanin, R.; Zanmar Sanchez, R.; Zavrtanik, D.; Zavrtanik, M.;
Zdziarski, A.; Zech, A.; Zechlin, H.; Zhao, A.; Ziegler, A.; Ziemann,
J.; Ziętara, K.; Ziółkowski, J.; Zitelli, V.; Zoli, A.; Zurbach,
C.; Żychowski, P.
2015arXiv150805894C Altcode:
List of contributions from the CTA Consortium presented at the 34th
International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague,
The Netherlands.
---------------------------------------------------------
Title: Long-baseline optical intensity interferometry. Laboratory
demonstration of diffraction-limited imaging
Authors: Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.
2015A&A...580A..99D Altcode: 2015arXiv150605804D
Context. A long-held vision has been to realize diffraction-limited
optical aperture synthesis over kilometer baselines. This will
enable imaging of stellar surfaces and their environments, and reveal
interacting gas flows in binary systems. An opportunity is now opening
up with the large telescope arrays primarily erected for measuring
Cherenkov light in air induced by gamma rays. With suitable software,
such telescopes could be electronically connected and also used for
intensity interferometry. Second-order spatial coherence of light
is obtained by cross correlating intensity fluctuations measured in
different pairs of telescopes. With no optical links between them,
the error budget is set by the electronic time resolution of a few
nanoseconds. Corresponding light-travel distances are approximately
one meter, making the method practically immune to atmospheric
turbulence or optical imperfections, permitting both very long
baselines and observing at short optical wavelengths. <BR /> Aims:
Previous theoretical modeling has shown that full images should be
possible to retrieve from observations with such telescope arrays. This
project aims at verifying diffraction-limited imaging experimentally
with groups of detached and independent optical telescopes. <BR />
Methods: In a large optics laboratory, artificial stars (single
and double, round and elliptic) were observed by an array of small
telescopes. Using high-speed photon-counting solid-state detectors and
real-time electronics, intensity fluctuations were cross-correlated over
up to 180 baselines between pairs of telescopes, producing coherence
maps across the interferometric Fourier-transform plane. <BR /> Results:
These interferometric measurements were used to extract parameters about
the simulated stars, and to reconstruct their two-dimensional images. As
far as we are aware, these are the first diffraction-limited images
obtained from an optical array only linked by electronic software, with
no optical connections between the telescopes. <BR /> Conclusions: These
experiments serve to verify the concepts for long-baseline aperture
synthesis in the optical, somewhat analogous to radio interferometry.
---------------------------------------------------------
Title: Stellar Spectroscopy during Exoplanet Transits: Revealing
structures across stellar surfaces
Authors: Dravins, Dainis; Ludwig, Hans-Günter; Dahlén, Erik
2015IAUGA..2233688D Altcode:
Exoplanet transits permit to study stellar surface portions that
successively become hidden behind the planet. Differential spectroscopy
between various transit phases reveals spectra of those stellar
surface segments that were hidden. The deduced center-to-limb behavior
of stellar spectral line shapes, asymmetries and wavelength shifts
enables detailed tests of 3-dimensional hydrodynamic models of stellar
atmospheres, such that are required for any precise determination
of abundances or seismic properties. Such models can now be computed
for widely different classes of stars (including metal-poor ones and
white dwarfs), but have been feasible to test and verify only for the
Sun with its resolved surface structure. Exoplanet transits may also
occur across features such as starspots, whose magnetic signatures will
be retrieved from spectra of sufficient fidelity.Knowing the precise
background stellar spectra, also properties of exoplanet atmospheres
are better constrained: e.g., the Rossiter-McLaughlin effect becomes
resolved as not only a simple change of stellar wavelength, but as a
variation of the full line profiles and their asymmetries.Such studies
are challenging since exoplanets cover only a tiny fraction of the
stellar disk. Current work, analyzing sequences of high-fidelity ESO
UVES spectra, demonstrate that such spatially resolved stellar spectra
can already be (marginally) retrieved in a few cases with the brightest
host stars. Already in a near future, ongoing exoplanet surveys are
likely to find further bright hosts that will enable such studies for
various stellar types. http://arxiv.org/abs/1408.1402
---------------------------------------------------------
Title: Optical aperture synthesis with electronically connected
telescopes
Authors: Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.
2015NatCo...6.6852D Altcode: 2015NatCo...6E6852D; 2015arXiv150404619D
Highest resolution imaging in astronomy is achieved by interferometry,
connecting telescopes over increasingly longer distances and
at successively shorter wavelengths. Here, we present the first
diffraction-limited images in visual light, produced by an array of
independent optical telescopes, connected electronically only, with
no optical links between them. With an array of small telescopes,
second-order optical coherence of the sources is measured through
intensity interferometry over 180 baselines between pairs of telescopes,
and two-dimensional images reconstructed. The technique aims at
diffraction-limited optical aperture synthesis over kilometre-long
baselines to reach resolutions showing details on stellar surfaces
and perhaps even the silhouettes of transiting exoplanets. Intensity
interferometry circumvents problems of atmospheric turbulence that
constrain ordinary interferometry. Since the electronic signal can be
copied, many baselines can be built up between dispersed telescopes,
and over long distances. Using arrays of air Cherenkov telescopes,
this should enable the optical equivalent of interferometric arrays
currently operating at radio wavelengths.
---------------------------------------------------------
Title: Stellar Spectroscopy During Exoplanet Transits: Dissecting
Fine Structure Across Stellar Surfaces
Authors: Dravins, Dainis; Ludwig, Hans-Gunter; Dahlen, Erik; Pazira,
Hiva
2015csss...18..853D Altcode: 2014arXiv1408.1402D
Differential spectroscopy during exoplanet transits permits to
reconstruct spectra of small stellar surface portions that successively
become hidden behind the planet. The center-to-limb behavior of stellar
line shapes, asymmetries and wavelength shifts will enable detailed
tests of 3-dimensional hydrodynamic models of stellar atmospheres,
such that are required for any precise determination of abundances or
seismic properties. Such models can now be computed for widely different
stars but have been feasible to test in detail only for the Sun with
its resolved surface structure. Although very high quality spectra are
required, already current data permit reconstructions of line profiles
in the brightest transit host stars such as HD 209458 (G0 V).
---------------------------------------------------------
Title: Stellar intensity interferometry over kilometer baselines:
laboratory simulation of observations with the Cherenkov Telescope
Array
Authors: Dravins, Dainis; Lagadec, Tiphaine
2014SPIE.9146E..0ZD Altcode: 2014arXiv1407.5993D
A long-held astronomical vision is to realize diffraction-limited
optical aperture synthesis over kilometer baselines. This will enable
imaging of stellar surfaces and their environments, show their evolution
over time, and reveal interactions of stellar winds and gas flows in
binary star systems. An opportunity is now opening up with the large
telescope arrays primarily erected for measuring Cherenkov light in
air induced by gamma rays. With suitable software, such telescopes
could be electronically connected and used also for intensity
interferometry. With no optical connection between the telescopes,
the error budget is set by the electronic time resolution of a few
nanoseconds. Corresponding light-travel distances are on the order of
one meter, making the method practically insensitive to atmospheric
turbulence or optical imperfections, permitting both very long baselines
and observing at short optical wavelengths. Theoretical modeling has
shown how stellar surface images can be retrieved from such observations
and here we report on experimental simulations. In an optical
laboratory, artificial stars (single and double, round and elliptic)
are observed by an array of telescopes. Using high-speed photon-counting
solid-state detectors and real-time electronics, intensity fluctuations
are cross correlated between up to a hundred baselines between pairs
of telescopes, producing maps of the second-order spatial coherence
across the interferometric Fourier-transform plane. These experiments
serve to verify the concepts and to optimize the instrumentation and
observing procedures for future observations with (in particular) CTA,
the Cherenkov Telescope Array, aiming at order-of-magnitude improvements
of the angular resolution in optical astronomy.
---------------------------------------------------------
Title: Intensity Interferometry with Cherenkov Telescope Arrays:
Prospects for submilliarcsecond optical imaging
Authors: Dravins, D.
2014ipco.conf...19D Altcode:
Intensity interferometry measures the second-order coherence
of light. Very rapid (nanosecond) fluctuations are correlated
between separate telescopes, without any optical connection. This
makes the method insensitive to atmospheric turbulence and optical
imperfections, permitting observations over long baselines, and at
short wavelengths. The required large telescopes are becoming available
as those primarily erected to study gamma rays: the planned Cherenkov
Telescope Array (https://www.cta-observatory.org/) envisions many tens
of telescopes distributed over a few square km. Digital signal handling
enables very many baselines to be simultaneously synthesized between
many pairs of telescopes, while stars may be tracked across the sky
with electronic time delays, synthesizing an optical interferometer
in software. Simulations indicate limiting magnitudes around m(v)=8,
reaching a resolution of 30 microarcseconds in the violet. Since
intensity interferometry provides only the modulus (not phase) of any
spatial frequency component of the source image, image reconstruction
requires phase retrieval techniques. As shown in simulations, full
two-dimensional images can be retrieved, provided there is an extensive
coverage of the (u,v)-plane, such as will be available once the number
of telescopes reaches numbers on the order of ten.
---------------------------------------------------------
Title: A Community Science Case for E-ELT HIRES
Authors: Maiolino, R.; Haehnelt, M.; Murphy, M. T.; Queloz, D.;
Origlia, L.; Alcala, J.; Alibert, Y.; Amado, P. J.; Allende Prieto, C.;
Ammler-von Eiff, M.; Asplund, M.; Barstow, M.; Becker, G.; Bonfils, X.;
Bouchy, F.; Bragaglia, A.; Burleigh, M. R.; Chiavassa, A.; Cimatti,
D. A.; Cirasuolo, M.; Cristiani, S.; D'Odorico, V.; Dravins, D.;
Emsellem, E.; Farihi, J.; Figueira, P.; Fynbo, J.; Gansicke, B. T.;
Gillon, M.; Gustafsson, B.; Hill, V.; Israelyan, G.; Korn, A.; Larsen,
S.; De Laverny, P.; Liske, J.; Lovis, C.; Marconi, A.; Martins, C.;
Molaro, P.; Nisini, B.; Oliva, E.; Petitjean, P.; Pettini, M.; Recio
Blanco, A.; Rebolo, R.; Reiners, A.; Rodriguez-Lopez, C.; Ryde, N.;
Santos, N. C.; Savaglio, S.; Snellen, I.; Strassmeier, K.; Tanvir, N.;
Testi, L.; Tolstoy, E.; Triaud, A.; Vanzi, L.; Viel, M.; Volonteri, M.
2013arXiv1310.3163M Altcode:
Building on the experience of the high-resolution community with the
suite of VLT high-resolution spectrographs, which has been tremendously
successful, we outline here the (science) case for a high-fidelity,
high-resolution spectrograph with wide wavelength coverage at the
E-ELT. Flagship science drivers include: the study of exo-planetary
atmospheres with the prospect of the detection of signatures of life
on rocky planets; the chemical composition of planetary debris on the
surface of white dwarfs; the spectroscopic study of protoplanetary and
proto-stellar disks; the extension of Galactic archaeology to the Local
Group and beyond; spectroscopic studies of the evolution of galaxies
with samples that, unlike now, are no longer restricted to strongly
star forming and/or very massive galaxies; the unraveling of the
complex roles of stellar and AGN feedback; the study of the chemical
signatures imprinted by population III stars on the IGM during the
epoch of reionization; the exciting possibility of paradigm-changing
contributions to fundamental physics. The requirements of these science
cases can be met by a stable instrument with a spectral resolution
of R~100,000 and broad, simultaneous spectral coverage extending
from 370nm to 2500nm. Most science cases do not require spatially
resolved information, and can be pursued in seeing-limited mode,
although some of them would benefit by the E-ELT diffraction limited
resolution. Some multiplexing would also be beneficial for some of
the science cases. (Abridged)
---------------------------------------------------------
Title: CTA contributions to the 33rd International Cosmic Ray
Conference (ICRC2013)
Authors: CTA Consortium, The; :; Abril, O.; Acharya, B. S.; Actis, M.;
Agnetta, G.; Aguilar, J. A.; Aharonian, F.; Ajello, M.; Akhperjanian,
A.; Alcubierre, M.; Aleksic, J.; Alfaro, R.; Aliu, E.; Allafort,
A. J.; Allan, D.; Allekotte, I.; Aloisio, R.; Amato, E.; Ambrosi,
G.; Ambrosio, M.; Anderson, J.; Angüner, E. O.; Antonelli, L. A.;
Antonuccio, V.; Antonucci, M.; Antoranz, P.; Aravantinos, A.; Argan,
A.; Arlen, T.; Aramo, C.; Armstrong, T.; Arnaldi, H.; Arrabito, L.;
Asano, K.; Ashton, T.; Asorey, H. G.; Aune, T.; Awane, Y.; Baba, H.;
Babic, A.; Baby, N.; Bähr, J.; Bais, A.; Baixeras, C.; Bajtlik, S.;
Balbo, M.; Balis, D.; Balkowski, C.; Ballet, J.; Bamba, A.; Bandiera,
R.; Barber, A.; Barbier, C.; Barceló, M.; Barnacka, A.; Barnstedt,
J.; Barres de Almeida, U.; Barrio, J. A.; Basili, A.; Basso, S.;
Bastieri, D.; Bauer, C.; Baushev, A.; Becciani, U.; Becerra, J.;
Becerra, J.; Becherini, Y.; Bechtol, K. C.; Becker Tjus, J.; Beckmann,
V.; Bednarek, W.; Behera, B.; Belluso, M.; Benbow, W.; Berdugo, J.;
Berge, D.; Berger, K.; Bernard, F.; Bernardino, T.; Bernlöhr, K.;
Bertucci, B.; Bhat, N.; Bhattacharyya, S.; Biasuzzi, B.; Bigongiari,
C.; Biland, A.; Billotta, S.; Bird, T.; Birsin, E.; Bissaldi, E.;
Biteau, J.; Bitossi, M.; Blake, S.; Blanch Bigas, O.; Blasi, P.;
Bobkov, A.; Boccone, V.; Böttcher, M.; Bogacz, L.; Bogart, J.;
Bogdan, M.; Boisson, C.; Boix Gargallo, J.; Bolmont, J.; Bonanno,
G.; Bonardi, A.; Bonev, T.; Bonifacio, P.; Bonnoli, G.; Bordas,
P.; Borgland, A.; Borkowski, J.; Bose, R.; Botner, O.; Bottani, A.;
Bouchet, L.; Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.;
Braun, I.; Bretz, T.; Briggs, M.; Brigida, M.; Bringmann, T.; Britto,
R.; Brook, P.; Brun, P.; Brunetti, L.; Bruno, P.; Bucciantini, N.;
Buanes, T.; Buckley, J.; Bühler, R.; Bugaev, V.; Bulgarelli, A.;
Bulik, T.; Busetto, G.; Buson, S.; Byrum, K.; Cailles, M.; Cameron,
R.; Camprecios, J.; Canestrari, R.; Cantu, S.; Capalbi, M.; Caraveo,
P.; Carmona, E.; Carosi, A.; Carosi, R.; Carr, J.; Carter, J.;
Carton, P. -H.; Caruso, R.; Casanova, S.; Cascone, E.; Casiraghi, M.;
Castellina, A.; Catalano, O.; Cavazzani, S.; Cazaux, S.; Cerchiara,
P.; Cerruti, M.; Chabanne, E.; Chadwick, P.; Champion, C.; Chaves,
R.; Cheimets, P.; Chen, A.; Chiang, J.; Chiappetti, L.; Chikawa, M.;
Chitnis, V. R.; Chollet, F.; Christof, A.; Chudoba, J.; Cieślar, M.;
Cillis, A.; Cilmo, M.; Codino, A.; Cohen-Tanugi, J.; Colafrancesco,
S.; Colin, P.; Colome, J.; Colonges, S.; Compin, M.; Conconi, P.;
Conforti, V.; Connaughton, V.; Conrad, J.; Contreras, J. L.; Coppi,
P.; Coridian, J.; Corona, P.; Corti, D.; Cortina, J.; Cossio, L.;
Costa, A.; Costantini, H.; Cotter, G.; Courty, B.; Couturier, S.;
Covino, S.; Crimi, G.; Criswell, S. J.; Croston, J.; Cusumano, G.;
Dafonseca, M.; Dale, O.; Daniel, M.; Darling, J.; Davids, I.; Dazzi,
F.; de Angelis, A.; De Caprio, V.; De Frondat, F.; de Gouveia Dal Pino,
E. M.; de la Calle, I.; De La Vega, G. A.; de los Reyes Lopez, R.;
de Lotto, B.; De Luca, A.; de Naurois, M.; de Oliveira, Y.; de Oña
Wilhelmi, E.; de Palma, F.; de Souza, V.; Decerprit, G.; Decock, G.;
Deil, C.; Delagnes, E.; Deleglise, G.; Delgado, C.; della Volpe, D.;
Demange, P.; Depaola, G.; Dettlaff, A.; Di Girolamo, T.; Di Giulio,
C.; Di Paola, A.; Di Pierro, F.; di Sciascio, G.; Díaz, C.; Dick, J.;
Dickherber, R.; Dickinson, H.; Diez-Blanco, V.; Digel, S.; Dimitrov,
D.; Disset, G.; Djannati-Ataï, A.; Doert, M.; Dohmke, M.; Domainko,
W.; Dominis Prester, D.; Donat, A.; Dorner, D.; Doro, M.; Dournaux,
J. -L.; Drake, G.; Dravins, D.; Drury, L.; Dubois, F.; Dubois, R.;
Dubus, G.; Dufour, C.; Dumas, D.; Dumm, J.; Durand, D.; Dwarkadas, V.;
Dyks, J.; Dyrda, M.; Ebr, J.; Edy, E.; Egberts, K.; Eger, P.; Einecke,
S.; Eleftheriadis, C.; Elles, S.; Emmanoulopoulos, D.; Engelhaupt,
D.; Enomoto, R.; Ernenwein, J. -P.; Errando, M.; Etchegoyen, A.;
Evans, P. A.; Falcone, A.; Faltenbacher, A.; Fantinel, D.; Farakos,
K.; Farnier, C.; Farrell, E.; Fasola, G.; Favill, B. W.; Fede,
E.; Federici, S.; Fegan, S.; Feinstein, F.; Ferenc, D.; Ferrando,
P.; Fesquet, M.; Fetfatzis, P.; Fiasson, A.; Fillin-Martino, E.;
Fink, D.; Finley, C.; Finley, J. P.; Fiorini, M.; Firpo Curcoll,
R.; Flandrini, E.; Fleischhack, H.; Flores, H.; Florin, D.; Focke,
W.; Föhr, C.; Fokitis, E.; Font, L.; Fontaine, G.; Fornasa, M.;
Förster, A.; Fortson, L.; Fouque, N.; Franckowiak, A.; Franco, F. J.;
Frankowski, A.; Fransson, C.; Fraser, G. W.; Frei, R.; Fresnillo, L.;
Fruck, C.; Fugazza, D.; Fujita, Y.; Fukazawa, Y.; Fukui, Y.; Funk,
S.; Gäbele, W.; Gabici, S.; Gabriele, R.; Gadola, A.; Galante, N.;
Gall, D.; Gallant, Y.; Gámez-García, J.; Garczarczyk, M.; García,
B.; Garcia López, R.; Gardiol, D.; Gargano, F.; Garrido, D.; Garrido,
L.; Gascon, D.; Gaug, M.; Gaweda, J.; Gebremedhin, L.; Geffroy, N.;
Gerard, L.; Ghedina, A.; Ghigo, M.; Ghislain, P.; Giannakaki, E.;
Gianotti, F.; Giarrusso, S.; Giavitto, G.; Giebels, B.; Giglietto,
N.; Gika, V.; Giomi, M.; Giommi, P.; Giordano, F.; Girard, N.; Giro,
E.; Giuliani, A.; Glanzman, T.; Glicenstein, J. -F.; Godinovic, N.;
Golev, V.; Gomez Berisso, M.; Gómez-Ortega, J.; Gonzalez, M. M.;
González, A.; González, F.; González Muñoz, A.; Gothe, K. S.;
Grabarczyk, T.; Gougerot, M.; Graciani, R.; Grandi, P.; Grañena,
F.; Granot, J.; Grasseau, G.; Gredig, R.; Green, A.; Greenshaw, T.;
Grégoire, T.; Grillo, A.; Grimm, O.; Grondin, M. -H.; Grube, J.;
Grudzinska, M.; Gruev, V.; Grünewald, S.; Grygorczuk, J.; Guarino,
V.; Gunji, S.; Gyuk, G.; Hadasch, D.; Hagedorn, A.; Hagiwara, R.;
Hahn, J.; Hakansson, N.; Hallgren, A.; Hamer Heras, N.; Hara, S.;
Hardcastle, M. J.; Harezlak, D.; Harris, J.; Hassan, T.; Hatanaka,
K.; Haubold, T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, R.;
Henault, F.; Henri, G.; Hermann, G.; Hermel, R.; Herrero, A.; Hervet,
O.; Hidaka, N.; Hinton, J. A.; Hirotani, K.; Hoffmann, D.; Hofmann,
W.; Hofverberg, P.; Holder, J.; Hörandel, J. R.; Horns, D.; Horville,
D.; Houles, J.; Hrabovsky, M.; Hrupec, D.; Huan, H.; Huber, B.; Huet,
J. -M.; Hughes, G.; Humensky, T. B.; Huovelin, J.; Huppert, J. -F.;
Ibarra, A.; Ikawa, D.; Illa, J. M.; Impiombato, D.; Incorvaia, S.;
Inoue, S.; Inoue, Y.; Iocco, F.; Ioka, K.; Israel, G. L.; Jablonski,
C.; Jacholkowska, A.; Jacquemier, J.; Jamrozy, M.; Janiak, M.; Jean,
P.; Jeanney, C.; Jimenez, J. J.; Jogler, T.; Johnson, C.; Johnson,
T.; Journet, L.; Juffroy, C.; Jung, I.; Kaaret, P.; Kabuki, S.;
Kagaya, M.; Kakuwa, J.; Kalkuhl, C.; Kankanyan, R.; Karastergiou,
A.; Kärcher, K.; Karczewski, M.; Karkar, S.; Kasperek, J.; Kastana,
D.; Katagiri, H.; Kataoka, J.; Katarzyński, K.; Katz, U.; Kawanaka,
N.; Kazanas, D.; Kelley-Hoskins, N.; Kellner-Leidel, B.; Kelly, H.;
Kendziorra, E.; Khélifi, B.; Kieda, D. B.; Kifune, T.; Kihm, T.;
Kishimoto, T.; Kitamoto, K.; Kluźniak, W.; Knapic, C.; Knapp, J.;
Knödlseder, J.; Köck, F.; Kocot, J.; Kodani, K.; Köhne, J. -H.;
Kohri, K.; Kokkotas, K.; Kolitzus, D.; Komin, N.; Kominis, I.; Konno,
Y.; Köppel, H.; Korohoda, P.; Kosack, K.; Koss, G.; Kossakowski,
R.; Koul, R.; Kowal, G.; Koyama, S.; Kozioł, J.; Krähenbühl, T.;
Krause, J.; Krawzcynski, H.; Krennrich, F.; Krepps, A.; Kretzschmann,
A.; Krobot, R.; Krueger, P.; Kubo, H.; Kudryavtsev, V. A.; Kushida,
J.; Kuznetsov, A.; La Barbera, A.; La Palombara, N.; La Parola, V.;
La Rosa, G.; Lacombe, K.; Lamanna, G.; Lande, J.; Languignon, D.;
Lapington, J. S.; Laporte, P.; Laurent, B.; Lavalley, C.; Le Flour,
T.; Le Padellec, A.; Lee, S. -H.; Lee, W. H.; Lefèvre, J. -P.; Leich,
H.; Leigui de Oliveira, M. A.; Lelas, D.; Lenain, J. -P.; Leoni,
R.; Leopold, D. J.; Lerch, T.; Lessio, L.; Leto, G.; Lieunard, B.;
Lieunard, S.; Lindemann, R.; Lindfors, E.; Liolios, A.; Lipniacka,
A.; Lockart, H.; Lohse, T.; Lombardi, S.; Longo, F.; Lopatin, A.;
Lopez, M.; López-Coto, R.; López-Oramas, A.; Lorca, A.; Lorenz,
E.; Louis, F.; Lubinski, P.; Lucarelli, F.; Lüdecke, H.; Ludwin, J.;
Luque-Escamilla, P. L.; Lustermann, W.; Luz, O.; Lyard, E.; Maccarone,
M. C.; Maccarone, T. J.; Madejski, G. M.; Madhavan, A.; Mahabir, M.;
Maier, G.; Majumdar, P.; Malaguti, G.; Malaspina, G.; Maltezos, S.;
Manalaysay, A.; Mancilla, A.; Mandat, D.; Maneva, G.; Mangano, A.;
Manigot, P.; Mannheim, K.; Manthos, I.; Maragos, N.; Marcowith, A.;
Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek, A.; Martens,
C.; Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.; Martínez,
F.; Martínez, M.; Massaro, F.; Masserot, A.; Mastichiadis, A.;
Mathieu, A.; Matsumoto, H.; Mattana, F.; Mattiazzo, S.; Maurer, A.;
Maurin, G.; Maxfield, S.; Maya, J.; Mazin, D.; Mc Comb, L.; McCann,
A.; McCubbin, N.; McHardy, I.; McKay, R.; Meagher, K.; Medina, C.;
Melioli, C.; Melkumyan, D.; Melo, D.; Mereghetti, S.; Mertsch, P.;
Meucci, M.; Meyer, M.; Michałowski, J.; Micolon, P.; Mihailidis,
A.; Mineo, T.; Minuti, M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.;
Mirzoyan, R.; Mistò, A.; Mizuno, T.; Moal, B.; Moderski, R.; Mognet,
I.; Molinari, E.; Molinaro, M.; Montaruli, T.; Monte, C.; Monteiro, I.;
Moore, P.; Moralejo Olaizola, A.; Mordalska, M.; Morello, C.; Mori,
K.; Morlino, G.; Morselli, A.; Mottez, F.; Moudden, Y.; Moulin, E.;
Mrusek, I.; Mukherjee, R.; Munar-Adrover, P.; Muraishi, H.; Murase, K.;
StJ. Murphy, A.; Nagataki, S.; Naito, T.; Nakajima, D.; Nakamori, T.;
Nakayama, K.; Naumann, C.; Naumann, D.; Naumann-Godo, M.; Nayman, P.;
Nedbal, D.; Neise, D.; Nellen, L.; Neronov, A.; Neustroev, V.; Neyroud,
N.; Nicastro, L.; Nicolau-Kukliński, J.; Niedźwiecki, A.; Niemiec,
J.; Nieto, D.; Nikolaidis, A.; Nishijima, K.; Nishikawa, K. -I.;
Noda, K.; Nolan, S.; Northrop, R.; Nosek, D.; Nowak, N.; Nozato, A.;
Oakes, L.; O'Brien, P. T.; Ohira, Y.; Ohishi, M.; Ohm, S.; Ohoka, H.;
Okuda, T.; Okumura, A.; Olive, J. -F.; Ong, R. A.; Orito, R.; Orr, M.;
Osborne, J. P.; Ostrowski, M.; Otero, L. A.; Otte, N.; Ovcharov, E.;
Oya, I.; Ozieblo, A.; Padilla, L.; Pagano, I.; Paiano, S.; Paillot, D.;
Paizis, A.; Palanque, S.; Palatka, M.; Pallota, J.; Palatiello, M.;
Panagiotidis, K.; Panazol, J. -L.; Paneque, D.; Panter, M.; Panzera,
M. R.; Paoletti, R.; Papayannis, A.; Papyan, G.; Paredes, J. M.;
Pareschi, G.; Parraud, J. -M.; Parsons, D.; Pauletta, G.; Paz Arribas,
M.; Pech, M.; Pedaletti, G.; Pelassa, V.; Pelat, D.; Perez, M. d. C.;
Persic, M.; Petrucci, P. -O.; Peyaud, B.; Pichel, A.; Pieloth, D.;
Pierre, E.; Pita, S.; Pivato, G.; Pizzolato, F.; Platino, M.; Platos,
Ł.; Platzer, R.; Podkladkin, S.; Pogosyan, L.; Pohl, M.; Pojmanski,
G.; Ponz, J. D.; Potter, W.; Poutanen, J.; Prandini, E.; Prast,
J.; Preece, R.; Profeti, F.; Prokoph, H.; Prouza, M.; Proyetti, M.;
Puerto-Giménez, I.; Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł,
R.; Quel, E. J.; Quesada, J.; Quinn, J.; Quirrenbach, A.; Racero, E.;
Rainò, S.; Rajda, P. J.; Rameez, M.; Ramon, P.; Rando, R.; Rannot,
R. C.; Rataj, M.; Raue, M.; Ravignani, D.; Reardon, P.; Reimann,
O.; Reimer, A.; Reimer, O.; Reitberger, K.; Renaud, M.; Renner,
S.; Reville, B.; Rhode, W.; Ribó, M.; Ribordy, M.; Richards, G.;
Richer, M. G.; Rico, J.; Ridky, J.; Rieger, F.; Ringegni, P.; Ripken,
J.; Ristori, P. R.; Rivière, A.; Rivoire, S.; Rob, L.; Rodeghiero,
G.; Roeser, U.; Rohlfs, R.; Rojas, G.; Romano, P.; Romaszkan, W.;
Romero, G. E.; Rosen, S. R.; Rosier Lees, S.; Ross, D.; Rouaix, G.;
Rousselle, J.; Rousselle, S.; Rovero, A. C.; Roy, F.; Royer, S.;
Rudak, B.; Rulten, C.; Rupiński, M.; Russo, F.; Ryde, F.; Saavedra,
O.; Sacco, B.; Saemann, E. O.; Saggion, A.; Sahakian, V.; Saito, K.;
Saito, T.; Saito, Y.; Sakaki, N.; Sakonaka, R.; Salini, A.; Sanchez,
F.; Sanchez-Conde, M.; Sandoval, A.; Sandaker, H.; Sant'Ambrogio, E.;
Santangelo, A.; Santos, E. M.; Sanuy, A.; Sapozhnikov, L.; Sarkar,
S.; Sartore, N.; Sasaki, H.; Satalecka, K.; Sawada, M.; Scalzotto, V.;
Scapin, V.; Scarcioffolo, M.; Schafer, J.; Schanz, T.; Schlenstedt,
S.; Schlickeiser, R.; Schmidt, T.; Schmoll, J.; Schovanek, P.;
Schroedter, M.; Schubert, A.; Schultz, C.; Schultze, J.; Schulz,
A.; Schure, K.; Schussler, F.; Schwab, T.; Schwanke, U.; Schwarz,
J.; Schwarzburg, S.; Schweizer, T.; Schwemmer, S.; Schwendicke, U.;
Schwerdt, C.; Segreto, A.; Seiradakis, J. -H.; Sembroski, G. H.;
Servillat, M.; Seweryn, K.; Sharma, M.; Shayduk, M.; Shellard,
R. C.; Shi, J.; Shibata, T.; Shibuya, A.; Shore, S.; Shum, E.;
Sideras-Haddad, E.; Sidoli, L.; Sidz, M.; Sieiro, J.; Sikora, M.;
Silk, J.; Sillanpää, A.; Singh, B. B.; Sironi, G.; Sitarek, J.;
Skole, C.; Smareglia, R.; Smith, A.; Smith, D.; Smith, J.; Smith,
N.; Sobczyńska, D.; Sol, H.; Sottile, G.; Sowiński, M.; Spanier,
F.; Spiga, D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.; Starling,
R. L. C.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steiner, S.;
Stella, C.; Stergioulas, N.; Sternberger, R.; Sterzel, M.; Stinzing,
F.; Stodulski, M.; Stolarczyk, Th.; Straumann, U.; Strazzeri, E.;
Stringhetti, L.; Suarez, A.; Suchenek, M.; Sugawara, R.; Sulanke,
K. -H.; Sun, S.; Supanitsky, A. D.; Suric, T.; Sutcliffe, P.; Sykes,
J. M.; Szanecki, M.; Szepieniec, T.; Szostek, A.; Tagliaferri, G.;
Tajima, H.; Takahashi, H.; Takahashi, K.; Takalo, L.; Takami, H.;
Talbot, G.; Tammi, J.; Tanaka, M.; Tanaka, S.; Tasan, J.; Tavani,
M.; Tavernet, J. -P.; Tejedor, L. A.; Telezhinsky, I.; Temnikov, P.;
Tenzer, C.; Terada, Y.; Terrier, R.; Teshima, M.; Testa, V.; Tezier,
D.; Thayer, J.; Thuermann, D.; Tibaldo, L.; Tibaldo, L.; Tibolla,
O.; Tiengo, A.; Timpanaro, M. C.; Tluczykont, M.; Todero Peixoto,
C. J.; Tokanai, F.; Tokarz, M.; Toma, K.; Tonachini, A.; Torii, K.;
Tornikoski, M.; Torres, D. F.; Torres, M.; Toscano, S.; Toso, G.;
Tosti, G.; Totani, T.; Toussenel, F.; Tovmassian, G.; Travnicek, P.;
Treves, A.; Trifoglio, M.; Troyano, I.; Tsinganos, K.; Ueno, H.; Umana,
G.; Umehara, K.; Upadhya, S. S.; Usher, T.; Uslenghi, M.; Vagnetti, F.;
Valdes-Galicia, J. F.; Vallania, P.; Vallejo, G.; van Driel, W.; van
Eldik, C.; Vandenbrouke, J.; Vanderwalt, J.; Vankov, H.; Vasileiadis,
G.; Vassiliev, V.; Veberic, D.; Vegas, I.; Vercellone, S.; Vergani,
S.; Verzi, V.; Vettolani, G. P.; Veyssière, C.; Vialle, J. P.;
Viana, A.; Videla, M.; Vigorito, C.; Vincent, P.; Vincent, S.; Vink,
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R.; Wagner, R. G.; Wagner, S.; Wakely, S. P.; Walter, R.; Walther,
T.; Warda, K.; Warwick, R. S.; Wawer, P.; Wawrzaszek, R.; Webb, N.;
Wegner, P.; Weinstein, A.; Weitzel, Q.; Welsing, R.; Werner, M.;
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A.; Zhou, X.; Zietara, K.; Ziolkowski, J.; Ziółkowski, P.; Zitelli,
V.; Zurbach, C.; Zychowski, P.
2013arXiv1307.2232C Altcode:
Compilation of CTA contributions to the proceedings of the 33rd
International Cosmic Ray Conference (ICRC2013), which took place in
2-9 July, 2013, in Rio de Janeiro, Brazil
---------------------------------------------------------
Title: Introducing the CTA concept
Authors: Acharya, B. S.; Actis, M.; Aghajani, T.; Agnetta, G.;
Aguilar, J.; Aharonian, F.; Ajello, M.; Akhperjanian, A.; Alcubierre,
M.; Aleksić, J.; Alfaro, R.; Aliu, E.; Allafort, A. J.; Allan, D.;
Allekotte, I.; Amato, E.; Anderson, J.; Angüner, E. O.; Antonelli,
L. A.; Antoranz, P.; Aravantinos, A.; Arlen, T.; Armstrong, T.;
Arnaldi, H.; Arrabito, L.; Asano, K.; Ashton, T.; Asorey, H. G.; Awane,
Y.; Baba, H.; Babic, A.; Baby, N.; Bähr, J.; Bais, A.; Baixeras, C.;
Bajtlik, S.; Balbo, M.; Balis, D.; Balkowski, C.; Bamba, A.; Bandiera,
R.; Barber, A.; Barbier, C.; Barceló, M.; Barnacka, A.; Barnstedt, J.;
Barres de Almeida, U.; Barrio, J. A.; Basili, A.; Basso, S.; Bastieri,
D.; Bauer, C.; Baushev, A.; Becerra, J.; Becherini, Y.; Bechtol, K. C.;
Becker Tjus, J.; Beckmann, V.; Bednarek, W.; Behera, B.; Belluso,
M.; Benbow, W.; Berdugo, J.; Berger, K.; Bernard, F.; Bernardino, T.;
Bernlöhr, K.; Bhat, N.; Bhattacharyya, S.; Bigongiari, C.; Biland,
A.; Billotta, S.; Bird, T.; Birsin, E.; Bissaldi, E.; Biteau, J.;
Bitossi, M.; Blake, S.; Blanch Bigas, O.; Blasi, P.; Bobkov, A.;
Boccone, V.; Boettcher, M.; Bogacz, L.; Bogart, J.; Bogdan, M.;
Boisson, C.; Boix Gargallo, J.; Bolmont, J.; Bonanno, G.; Bonardi,
A.; Bonev, T.; Bonifacio, P.; Bonnoli, G.; Bordas, P.; Borgland,
A.; Borkowski, J.; Bose, R.; Botner, O.; Bottani, A.; Bouchet, L.;
Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.; Braun, I.;
Bretz, T.; Briggs, M.; Bringmann, T.; Brook, P.; Brun, P.; Brunetti,
L.; Buanes, T.; Buckley, J.; Buehler, R.; Bugaev, V.; Bulgarelli, A.;
Bulik, T.; Busetto, G.; Buson, S.; Byrum, K.; Cailles, M.; Cameron,
R.; Camprecios, J.; Canestrari, R.; Cantu, S.; Capalbi, M.; Caraveo,
P.; Carmona, E.; Carosi, A.; Carr, J.; Carton, P. -H.; Casanova,
S.; Casiraghi, M.; Catalano, O.; Cavazzani, S.; Cazaux, S.; Cerruti,
M.; Chabanne, E.; Chadwick, P.; Champion, C.; Chen, A.; Chiang, J.;
Chiappetti, L.; Chikawa, M.; Chitnis, V. R.; Chollet, F.; Chudoba, J.;
Cieślar, M.; Cillis, A.; Cohen-Tanugi, J.; Colafrancesco, S.; Colin,
P.; Colome, J.; Colonges, S.; Compin, M.; Conconi, P.; Conforti, V.;
Connaughton, V.; Conrad, J.; Contreras, J. L.; Coppi, P.; Corona, P.;
Corti, D.; Cortina, J.; Cossio, L.; Costantini, H.; Cotter, G.; Courty,
B.; Couturier, S.; Covino, S.; Crimi, G.; Criswell, S. J.; Croston,
J.; Cusumano, G.; Dafonseca, M.; Dale, O.; Daniel, M.; Darling, J.;
Davids, I.; Dazzi, F.; De Angelis, A.; De Caprio, V.; De Frondat,
F.; de Gouveia Dal Pino, E. M.; de la Calle, I.; De La Vega, G. A.;
de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de Mello Neto,
J. R. T.; de Naurois, M.; de Oliveira, Y.; de Oña Wilhelmi, E.;
de Souza, V.; Decerprit, G.; Decock, G.; Deil, C.; Delagnes, E.;
Deleglise, G.; Delgado, C.; Della Volpe, D.; Demange, P.; Depaola,
G.; Dettlaff, A.; Di Paola, A.; Di Pierro, F.; Díaz, C.; Dick, J.;
Dickherber, R.; Dickinson, H.; Diez-Blanco, V.; Digel, S.; Dimitrov,
D.; Disset, G.; Djannati-Ataï, A.; Doert, M.; Dohmke, M.; Domainko,
W.; Dominis Prester, D.; Donat, A.; Dorner, D.; Doro, M.; Dournaux,
J. -L.; Drake, G.; Dravins, D.; Drury, L.; Dubois, F.; Dubois, R.;
Dubus, G.; Dufour, C.; Dumas, D.; Dumm, J.; Durand, D.; Dyks, J.;
Dyrda, M.; Ebr, J.; Edy, E.; Egberts, K.; Eger, P.; Einecke, S.;
Eleftheriadis, C.; Elles, S.; Emmanoulopoulos, D.; Engelhaupt, D.;
Enomoto, R.; Ernenwein, J. -P.; Errando, M.; Etchegoyen, A.; Evans,
P.; Falcone, A.; Fantinel, D.; Farakos, K.; Farnier, C.; Fasola,
G.; Favill, B.; Fede, E.; Federici, S.; Fegan, S.; Feinstein, F.;
Ferenc, D.; Ferrando, P.; Fesquet, M.; Fiasson, A.; Fillin-Martino,
E.; Fink, D.; Finley, C.; Finley, J. P.; Fiorini, M.; Firpo Curcoll,
R.; Flores, H.; Florin, D.; Focke, W.; Föhr, C.; Fokitis, E.; Font,
L.; Fontaine, G.; Fornasa, M.; Förster, A.; Fortson, L.; Fouque,
N.; Franckowiak, A.; Fransson, C.; Fraser, G.; Frei, R.; Albuquerque,
I. F. M.; Fresnillo, L.; Fruck, C.; Fujita, Y.; Fukazawa, Y.; Fukui,
Y.; Funk, S.; Gäbele, W.; Gabici, S.; Gabriele, R.; Gadola, A.;
Galante, N.; Gall, D.; Gallant, Y.; Gámez-García, J.; García, B.;
Garcia López, R.; Gardiol, D.; Garrido, D.; Garrido, L.; Gascon,
D.; Gaug, M.; Gaweda, J.; Gebremedhin, L.; Geffroy, N.; Gerard, L.;
Ghedina, A.; Ghigo, M.; Giannakaki, E.; Gianotti, F.; Giarrusso, S.;
Giavitto, G.; Giebels, B.; Gika, V.; Giommi, P.; Girard, N.; Giro,
E.; Giuliani, A.; Glanzman, T.; Glicenstein, J. -F.; Godinovic, N.;
Golev, V.; Gomez Berisso, M.; Gómez-Ortega, J.; Gonzalez, M. M.;
González, A.; González, F.; González Muñoz, A.; Gothe, K. S.;
Gougerot, M.; Graciani, R.; Grandi, P.; Grañena, F.; Granot, J.;
Grasseau, G.; Gredig, R.; Green, A.; Greenshaw, T.; Grégoire,
T.; Grimm, O.; Grube, J.; Grudzinska, M.; Gruev, V.; Grünewald,
S.; Grygorczuk, J.; Guarino, V.; Gunji, S.; Gyuk, G.; Hadasch, D.;
Hagiwara, R.; Hahn, J.; Hakansson, N.; Hallgren, A.; Hamer Heras,
N.; Hara, S.; Hardcastle, M. J.; Harris, J.; Hassan, T.; Hatanaka,
K.; Haubold, T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, R.;
Henault, F.; Henri, G.; Hermann, G.; Hermel, R.; Herrero, A.; Hidaka,
N.; Hinton, J.; Hoffmann, D.; Hofmann, W.; Hofverberg, P.; Holder, J.;
Horns, D.; Horville, D.; Houles, J.; Hrabovsky, M.; Hrupec, D.; Huan,
H.; Huber, B.; Huet, J. -M.; Hughes, G.; Humensky, T. B.; Huovelin,
J.; Ibarra, A.; Illa, J. M.; Impiombato, D.; Incorvaia, S.; Inoue,
S.; Inoue, Y.; Ioka, K.; Ismailova, E.; Jablonski, C.; Jacholkowska,
A.; Jamrozy, M.; Janiak, M.; Jean, P.; Jeanney, C.; Jimenez, J. J.;
Jogler, T.; Johnson, T.; Journet, L.; Juffroy, C.; Jung, I.; Kaaret,
P.; Kabuki, S.; Kagaya, M.; Kakuwa, J.; Kalkuhl, C.; Kankanyan, R.;
Karastergiou, A.; Kärcher, K.; Karczewski, M.; Karkar, S.; Kasperek,
J.; Kastana, D.; Katagiri, H.; Kataoka, J.; Katarzyński, K.; Katz,
U.; Kawanaka, N.; Kellner-Leidel, B.; Kelly, H.; Kendziorra, E.;
Khélifi, B.; Kieda, D. B.; Kifune, T.; Kihm, T.; Kishimoto, T.;
Kitamoto, K.; Kluźniak, W.; Knapic, C.; Knapp, J.; Knödlseder, J.;
Köck, F.; Kocot, J.; Kodani, K.; Köhne, J. -H.; Kohri, K.; Kokkotas,
K.; Kolitzus, D.; Komin, N.; Kominis, I.; Konno, Y.; Köppel, H.;
Korohoda, P.; Kosack, K.; Koss, G.; Kossakowski, R.; Kostka, P.;
Koul, R.; Kowal, G.; Koyama, S.; Kozioł, J.; Krähenbühl, T.;
Krause, J.; Krawzcynski, H.; Krennrich, F.; Krepps, A.; Kretzschmann,
A.; Krobot, R.; Krueger, P.; Kubo, H.; Kudryavtsev, V. A.; Kushida,
J.; Kuznetsov, A.; La Barbera, A.; La Palombara, N.; La Parola, V.;
La Rosa, G.; Lacombe, K.; Lamanna, G.; Lande, J.; Languignon, D.;
Lapington, J.; Laporte, P.; Lavalley, C.; Le Flour, T.; Le Padellec,
A.; Lee, S. -H.; Lee, W. H.; Leigui de Oliveira, M. A.; Lelas, D.;
Lenain, J. -P.; Leopold, D. J.; Lerch, T.; Lessio, L.; Lieunard, B.;
Lindfors, E.; Liolios, A.; Lipniacka, A.; Lockart, H.; Lohse, T.;
Lombardi, S.; Lopatin, A.; Lopez, M.; López-Coto, R.; López-Oramas,
A.; Lorca, A.; Lorenz, E.; Lubinski, P.; Lucarelli, F.; Lüdecke, H.;
Ludwin, J.; Luque-Escamilla, P. L.; Lustermann, W.; Luz, O.; Lyard,
E.; Maccarone, M. C.; Maccarone, T. J.; Madejski, G. M.; Madhavan,
A.; Mahabir, M.; Maier, G.; Majumdar, P.; Malaguti, G.; Maltezos, S.;
Manalaysay, A.; Mancilla, A.; Mandat, D.; Maneva, G.; Mangano, A.;
Manigot, P.; Mannheim, K.; Manthos, I.; Maragos, N.; Marcowith, A.;
Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek, A.; Martens, C.;
Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.; Martínez, F.;
Martínez, M.; Masserot, A.; Mastichiadis, A.; Mathieu, A.; Matsumoto,
H.; Mattana, F.; Mattiazzo, S.; Maurin, G.; Maxfield, S.; Maya, J.;
Mazin, D.; Mc Comb, L.; McCubbin, N.; McHardy, I.; McKay, R.; Medina,
C.; Melioli, C.; Melkumyan, D.; Mereghetti, S.; Mertsch, P.; Meucci,
M.; Michałowski, J.; Micolon, P.; Mihailidis, A.; Mineo, T.; Minuti,
M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.; Mizuno,
T.; Moal, B.; Moderski, R.; Mognet, I.; Molinari, E.; Molinaro,
M.; Montaruli, T.; Monteiro, I.; Moore, P.; Moralejo Olaizola,
A.; Mordalska, M.; Morello, C.; Mori, K.; Mottez, F.; Moudden, Y.;
Moulin, E.; Mrusek, I.; Mukherjee, R.; Munar-Adrover, P.; Muraishi,
H.; Murase, K.; Murphy, A.; Nagataki, S.; Naito, T.; Nakajima, D.;
Nakamori, T.; Nakayama, K.; Naumann, C.; Naumann, D.; Naumann-Godo,
M.; Nayman, P.; Nedbal, D.; Neise, D.; Nellen, L.; Neustroev, V.;
Neyroud, N.; Nicastro, L.; Nicolau-Kukliński, J.; Niedźwiecki, A.;
Niemiec, J.; Nieto, D.; Nikolaidis, A.; Nishijima, K.; Nolan, S.;
Northrop, R.; Nosek, D.; Nowak, N.; Nozato, A.; O'Brien, P.; Ohira,
Y.; Ohishi, M.; Ohm, S.; Ohoka, H.; Okuda, T.; Okumura, A.; Olive,
J. -F.; Ong, R. A.; Orito, R.; Orr, M.; Osborne, J.; Ostrowski, M.;
Otero, L. A.; Otte, N.; Ovcharov, E.; Oya, I.; Ozieblo, A.; Padilla,
L.; Paiano, S.; Paillot, D.; Paizis, A.; Palanque, S.; Palatka, M.;
Pallota, J.; Panagiotidis, K.; Panazol, J. -L.; Paneque, D.; Panter,
M.; Paoletti, R.; Papayannis, A.; Papyan, G.; Paredes, J. M.; Pareschi,
G.; Parks, G.; Parraud, J. -M.; Parsons, D.; Paz Arribas, M.; Pech,
M.; Pedaletti, G.; Pelassa, V.; Pelat, D.; Perez, M. d. C.; Persic,
M.; Petrucci, P. -O.; Peyaud, B.; Pichel, A.; Pita, S.; Pizzolato, F.;
Platos, Ł.; Platzer, R.; Pogosyan, L.; Pohl, M.; Pojmanski, G.; Ponz,
J. D.; Potter, W.; Poutanen, J.; Prandini, E.; Prast, J.; Preece, R.;
Profeti, F.; Prokoph, H.; Prouza, M.; Proyetti, M.; Puerto-Gimenez, I.;
Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł, R.; Quel, E. J.; Quinn,
J.; Quirrenbach, A.; Racero, E.; Rajda, P. J.; Ramon, P.; Rando, R.;
Rannot, R. C.; Rataj, M.; Raue, M.; Reardon, P.; Reimann, O.; Reimer,
A.; Reimer, O.; Reitberger, K.; Renaud, M.; Renner, S.; Reville, B.;
Rhode, W.; Ribó, M.; Ribordy, M.; Richer, M. G.; Rico, J.; Ridky,
J.; Rieger, F.; Ringegni, P.; Ripken, J.; Ristori, P. R.; Riviére,
A.; Rivoire, S.; Rob, L.; Roeser, U.; Rohlfs, R.; Rojas, G.; Romano,
P.; Romaszkan, W.; Romero, G. E.; Rosen, S.; Rosier Lees, S.; Ross,
D.; Rouaix, G.; Rousselle, J.; Rousselle, S.; Rovero, A. C.; Roy,
F.; Royer, S.; Rudak, B.; Rulten, C.; Rupiński, M.; Russo, F.; Ryde,
F.; Sacco, B.; Saemann, E. O.; Saggion, A.; Sahakian, V.; Saito, K.;
Saito, T.; Saito, Y.; Sakaki, N.; Sakonaka, R.; Salini, A.; Sanchez,
F.; Sanchez-Conde, M.; Sandoval, A.; Sandaker, H.; Sant'Ambrogio,
E.; Santangelo, A.; Santos, E. M.; Sanuy, A.; Sapozhnikov, L.;
Sarkar, S.; Sartore, N.; Sasaki, H.; Satalecka, K.; Sawada, M.;
Scalzotto, V.; Scapin, V.; Scarcioffolo, M.; Schafer, J.; Schanz,
T.; Schlenstedt, S.; Schlickeiser, R.; Schmidt, T.; Schmoll, J.;
Schovanek, P.; Schroedter, M.; Schultz, C.; Schultze, J.; Schulz,
A.; Schure, K.; Schwab, T.; Schwanke, U.; Schwarz, J.; Schwarzburg,
S.; Schweizer, T.; Schwemmer, S.; Segreto, A.; Seiradakis, J. -H.;
Sembroski, G. H.; Seweryn, K.; Sharma, M.; Shayduk, M.; Shellard,
R. C.; Shi, J.; Shibata, T.; Shibuya, A.; Shum, E.; Sidoli, L.; Sidz,
M.; Sieiro, J.; Sikora, M.; Silk, J.; Sillanpää, A.; Singh, B. B.;
Sitarek, J.; Skole, C.; Smareglia, R.; Smith, A.; Smith, D.; Smith,
J.; Smith, N.; Sobczyńska, D.; Sol, H.; Sottile, G.; Sowiński, M.;
Spanier, F.; Spiga, D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.;
Starling, R.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steiner,
S.; Stergioulas, N.; Sternberger, R.; Sterzel, M.; Stinzing, F.;
Stodulski, M.; Straumann, U.; Strazzeri, E.; Stringhetti, L.;
Suarez, A.; Suchenek, M.; Sugawara, R.; Sulanke, K. -H.; Sun, S.;
Supanitsky, A. D.; Suric, T.; Sutcliffe, P.; Sykes, J.; Szanecki, M.;
Szepieniec, T.; Szostek, A.; Tagliaferri, G.; Tajima, H.; Takahashi,
H.; Takahashi, K.; Takalo, L.; Takami, H.; Talbot, G.; Tammi, J.;
Tanaka, M.; Tanaka, S.; Tasan, J.; Tavani, M.; Tavernet, J. -P.;
Tejedor, L. A.; Telezhinsky, I.; Temnikov, P.; Tenzer, C.; Terada,
Y.; Terrier, R.; Teshima, M.; Testa, V.; Tezier, D.; Thuermann, D.;
Tibaldo, L.; Tibolla, O.; Tiengo, A.; Tluczykont, M.; Todero Peixoto,
C. J.; Tokanai, F.; Tokarz, M.; Toma, K.; Torii, K.; Tornikoski,
M.; Torres, D. F.; Torres, M.; Tosti, G.; Totani, T.; Toussenel, F.;
Tovmassian, G.; Travnicek, P.; Trifoglio, M.; Troyano, I.; Tsinganos,
K.; Ueno, H.; Umehara, K.; Upadhya, S. S.; Usher, T.; Uslenghi, M.;
Valdes-Galicia, J. F.; Vallania, P.; Vallejo, G.; van Driel, W.; van
Eldik, C.; Vandenbrouke, J.; Vanderwalt, J.; Vankov, H.; Vasileiadis,
G.; Vassiliev, V.; Veberic, D.; Vegas, I.; Vercellone, S.; Vergani,
S.; Veyssiére, C.; Vialle, J. P.; Viana, A.; Videla, M.; Vincent, P.;
Vincent, S.; Vink, J.; Vlahakis, N.; Vlahos, L.; Vogler, P.; Vollhardt,
A.; von Gunten, H. -P.; Vorobiov, S.; Vuerli, C.; Waegebaert, V.;
Wagner, R.; Wagner, R. G.; Wagner, S.; Wakely, S. P.; Walter, R.;
Walther, T.; Warda, K.; Warwick, R.; Wawer, P.; Wawrzaszek, R.; Webb,
N.; Wegner, P.; Weinstein, A.; Weitzel, Q.; Welsing, R.; Werner, M.;
Wetteskind, H.; White, R.; Wierzcholska, A.; Wiesand, S.; Wilkinson,
M.; Williams, D. A.; Willingale, R.; Winiarski, K.; Wischnewski, R.;
Wiśniewski, Ł.; Wood, M.; Wörnlein, A.; Xiong, Q.; Yadav, K. K.;
Yamamoto, H.; Yamamoto, T.; Yamazaki, R.; Yanagita, S.; Yebras,
J. M.; Yelos, D.; Yoshida, A.; Yoshida, T.; Yoshikoshi, T.; Zabalza,
V.; Zacharias, M.; Zajczyk, A.; Zanin, R.; Zdziarski, A.; Zech, A.;
Zhao, A.; Zhou, X.; Ziętara, K.; Ziolkowski, J.; Ziółkowski, P.;
Zitelli, V.; Zurbach, C.; Żychowski, P.; CTA Consortium
2013APh....43....3A Altcode: 2013APh....43....3C
The Cherenkov Telescope Array (CTA) is a new observatory for very
high-energy (VHE) gamma rays. CTA has ambitions science goals, for which
it is necessary to achieve full-sky coverage, to improve the sensitivity
by about an order of magnitude, to span about four decades of energy,
from a few tens of GeV to above 100 TeV with enhanced angular and energy
resolutions over existing VHE gamma-ray observatories. An international
collaboration has formed with more than 1000 members from 27 countries
in Europe, Asia, Africa and North and South America. In 2010 the CTA
Consortium completed a Design Study and started a three-year Preparatory
Phase which leads to production readiness of CTA in 2014. In this paper
we introduce the science goals and the concept of CTA, and provide an
overview of the project.
---------------------------------------------------------
Title: Optical intensity interferometry with the Cherenkov Telescope
Array
Authors: Dravins, Dainis; LeBohec, Stephan; Jensen, Hannes; Nuñez,
Paul D.; CTA Consortium
2013APh....43..331D Altcode: 2012arXiv1204.3624D
With its unprecedented light-collecting area for night-sky observations,
the Cherenkov Telescope Array (CTA) holds great potential for also
optical stellar astronomy, in particular as a multi-element intensity
interferometer for realizing imaging with sub-milliarcsecond angular
resolution. Such an order-of-magnitude increase of the spatial
resolution achieved in optical astronomy will reveal the surfaces of
rotationally flattened stars with structures in their circumstellar
disks and winds, or the gas flows between close binaries. Image
reconstruction is feasible from the second-order coherence of light,
measured as the temporal correlations of arrival times between photons
recorded in different telescopes. This technique (once pioneered by
Hanbury Brown and Twiss) connects telescopes only with electronic
signals and is practically insensitive to atmospheric turbulence
and to imperfections in telescope optics. Detector and telescope
requirements are very similar to those for imaging air Cherenkov
observatories, the main difference being the signal processing
(calculating cross correlations between single camera pixels
in pairs of telescopes). Observations of brighter stars are not
limited by sky brightness, permitting efficient CTA use during also
bright-Moon periods. While other concepts have been proposed to realize
kilometer-scale optical interferometers of conventional amplitude
(phase-) type, both in space and on the ground, their complexity places
them much further into the future than CTA, which thus could become
the first kilometer-scale optical imager in astronomy.
---------------------------------------------------------
Title: Stellar intensity interferometry: Prospects for
sub-milliarcsecond optical imaging
Authors: Dravins, Dainis; LeBohec, Stephan; Jensen, Hannes; Nuñez,
Paul D.
2012NewAR..56..143D Altcode: 2012arXiv1207.0808D
Using kilometric arrays of air Cherenkov telescopes at short
wavelengths, intensity interferometry may increase the spatial
resolution achieved in optical astronomy by an order of magnitude,
enabling images of rapidly rotating hot stars with structures in
their circumstellar disks and winds, or mapping out patterns of
nonradial pulsations across stellar surfaces. Intensity interferometry
(once pioneered by Hanbury Brown and Twiss) connects telescopes only
electronically, and is practically insensitive to atmospheric turbulence
and optical imperfections, permitting observations over long baselines
and through large airmasses, also at short optical wavelengths. The
required large telescopes (∼10 m) with very fast detectors (∼ns)
are becoming available as the arrays primarily erected to measure
Cherenkov light emitted in air by particle cascades initiated by
energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope
Array) envision many tens of telescopes distributed over a few square
km. Digital signal handling enables very many baselines (from tens of
meters to over a kilometer) to be simultaneously synthesized between
many pairs of telescopes, while stars may be tracked across the sky with
electronic time delays, in effect synthesizing an optical interferometer
in software. Simulated observations indicate limiting magnitudes around
m<SUB>V</SUB> = 8, reaching angular resolutions ∼30 μarcsec in the
violet. The signal-to-noise ratio favors high-temperature sources and
emission-line structures, and is independent of the optical passband,
be it a single spectral line or the broad spectral continuum. Intensity
interferometry directly provides the modulus (but not phase) of any
spatial frequency component of the source image; for this reason a
full image reconstruction requires phase retrieval techniques. This is
feasible if sufficient coverage of the interferometric (u, v)-plane is
available, as was verified through numerical simulations. Laboratory and
field experiments are in progress; test telescopes have been erected,
intensity interferometry has been achieved in the laboratory, and first
full-scale tests of connecting large Cherenkov telescopes have been
carried out. This paper reviews this interferometric method in view of
the new possibilities offered by arrays of air Cherenkov telescopes,
and outlines observational programs that should become realistic
already in the rather near future.
---------------------------------------------------------
Title: Design concepts for the Cherenkov Telescope Array CTA: an
advanced facility for ground-based high-energy gamma-ray astronomy
Authors: Actis, M.; Agnetta, G.; Aharonian, F.; Akhperjanian,
A.; Aleksić, J.; Aliu, E.; Allan, D.; Allekotte, I.; Antico, F.;
Antonelli, L. A.; Antoranz, P.; Aravantinos, A.; Arlen, T.; Arnaldi,
H.; Artmann, S.; Asano, K.; Asorey, H.; Bähr, J.; Bais, A.; Baixeras,
C.; Bajtlik, S.; Balis, D.; Bamba, A.; Barbier, C.; Barceló, M.;
Barnacka, A.; Barnstedt, J.; Barres de Almeida, U.; Barrio, J. A.;
Basso, S.; Bastieri, D.; Bauer, C.; Becerra, J.; Becherini, Y.;
Bechtol, K.; Becker, J.; Beckmann, V.; Bednarek, W.; Behera, B.;
Beilicke, M.; Belluso, M.; Benallou, M.; Benbow, W.; Berdugo, J.;
Berger, K.; Bernardino, T.; Bernlöhr, K.; Biland, A.; Billotta, S.;
Bird, T.; Birsin, E.; Bissaldi, E.; Blake, S.; Blanch, O.; Bobkov,
A. A.; Bogacz, L.; Bogdan, M.; Boisson, C.; Boix, J.; Bolmont,
J.; Bonanno, G.; Bonardi, A.; Bonev, T.; Borkowski, J.; Botner, O.;
Bottani, A.; Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.;
Braun, I.; Bretz, T.; Briggs, M. S.; Brun, P.; Brunetti, L.; Buckley,
J. H.; Bugaev, V.; Bühler, R.; Bulik, T.; Busetto, G.; Buson, S.;
Byrum, K.; Cailles, M.; Cameron, R.; Canestrari, R.; Cantu, S.;
Carmona, E.; Carosi, A.; Carr, J.; Carton, P. H.; Casiraghi, M.;
Castarede, H.; Catalano, O.; Cavazzani, S.; Cazaux, S.; Cerruti,
B.; Cerruti, M.; Chadwick, P. M.; Chiang, J.; Chikawa, M.; Cieślar,
M.; Ciesielska, M.; Cillis, A.; Clerc, C.; Colin, P.; Colomé, J.;
Compin, M.; Conconi, P.; Connaughton, V.; Conrad, J.; Contreras, J. L.;
Coppi, P.; Corlier, M.; Corona, P.; Corpace, O.; Corti, D.; Cortina,
J.; Costantini, H.; Cotter, G.; Courty, B.; Couturier, S.; Covino,
S.; Croston, J.; Cusumano, G.; Daniel, M. K.; Dazzi, F.; de Angelis,
A.; de Cea Del Pozo, E.; de Gouveia Dal Pino, E. M.; de Jager, O.;
de La Calle Pérez, I.; de La Vega, G.; de Lotto, B.; de Naurois,
M.; de Oña Wilhelmi, E.; de Souza, V.; Decerprit, B.; Deil, C.;
Delagnes, E.; Deleglise, G.; Delgado, C.; Dettlaff, T.; di Paolo,
A.; di Pierro, F.; Díaz, C.; Dick, J.; Dickinson, H.; Digel, S. W.;
Dimitrov, D.; Disset, G.; Djannati-Ataï, A.; Doert, M.; Domainko,
W.; Dorner, D.; Doro, M.; Dournaux, J. -L.; Dravins, D.; Drury, L.;
Dubois, F.; Dubois, R.; Dubus, G.; Dufour, C.; Durand, D.; Dyks,
J.; Dyrda, M.; Edy, E.; Egberts, K.; Eleftheriadis, C.; Elles, S.;
Emmanoulopoulos, D.; Enomoto, R.; Ernenwein, J. -P.; Errando, M.;
Etchegoyen, A.; Falcone, A. D.; Farakos, K.; Farnier, C.; Federici,
S.; Feinstein, F.; Ferenc, D.; Fillin-Martino, E.; Fink, D.; Finley,
C.; Finley, J. P.; Firpo, R.; Florin, D.; Föhr, C.; Fokitis, E.;
Font, Ll.; Fontaine, G.; Fontana, A.; Förster, A.; Fortson, L.;
Fouque, N.; Fransson, C.; Fraser, G. W.; Fresnillo, L.; Fruck, C.;
Fujita, Y.; Fukazawa, Y.; Funk, S.; Gäbele, W.; Gabici, S.; Gadola,
A.; Galante, N.; Gallant, Y.; García, B.; García López, R. J.;
Garrido, D.; Garrido, L.; Gascón, D.; Gasq, C.; Gaug, M.; Gaweda,
J.; Geffroy, N.; Ghag, C.; Ghedina, A.; Ghigo, M.; Gianakaki, E.;
Giarrusso, S.; Giavitto, G.; Giebels, B.; Giro, E.; Giubilato, P.;
Glanzman, T.; Glicenstein, J. -F.; Gochna, M.; Golev, V.; Gómez
Berisso, M.; González, A.; González, F.; Grañena, F.; Graciani,
R.; Granot, J.; Gredig, R.; Green, A.; Greenshaw, T.; Grimm, O.;
Grube, J.; Grudzińska, M.; Grygorczuk, J.; Guarino, V.; Guglielmi,
L.; Guilloux, F.; Gunji, S.; Gyuk, G.; Hadasch, D.; Haefner, D.;
Hagiwara, R.; Hahn, J.; Hallgren, A.; Hara, S.; Hardcastle, M. J.;
Hassan, T.; Haubold, T.; Hauser, M.; Hayashida, M.; Heller, R.; Henri,
G.; Hermann, G.; Herrero, A.; Hinton, J. A.; Hoffmann, D.; Hofmann,
W.; Hofverberg, P.; Horns, D.; Hrupec, D.; Huan, H.; Huber, B.; Huet,
J. -M.; Hughes, G.; Hultquist, K.; Humensky, T. B.; Huppert, J. -F.;
Ibarra, A.; Illa, J. M.; Ingjald, J.; Inoue, Y.; Inoue, S.; Ioka, K.;
Jablonski, C.; Jacholkowska, A.; Janiak, M.; Jean, P.; Jensen, H.;
Jogler, T.; Jung, I.; Kaaret, P.; Kabuki, S.; Kakuwa, J.; Kalkuhl,
C.; Kankanyan, R.; Kapala, M.; Karastergiou, A.; Karczewski, M.;
Karkar, S.; Karlsson, N.; Kasperek, J.; Katagiri, H.; Katarzyński, K.;
Kawanaka, N.; Kȩdziora, B.; Kendziorra, E.; Khélifi, B.; Kieda, D.;
Kifune, T.; Kihm, T.; Klepser, S.; Kluźniak, W.; Knapp, J.; Knappy,
A. R.; Kneiske, T.; Knödlseder, J.; Köck, F.; Kodani, K.; Kohri,
K.; Kokkotas, K.; Komin, N.; Konopelko, A.; Kosack, K.; Kossakowski,
R.; Kostka, P.; Kotuła, J.; Kowal, G.; Kozioł, J.; Krähenbühl,
T.; Krause, J.; Krawczynski, H.; Krennrich, F.; Kretzschmann, A.;
Kubo, H.; Kudryavtsev, V. A.; Kushida, J.; La Barbera, N.; La Parola,
V.; La Rosa, G.; López, A.; Lamanna, G.; Laporte, P.; Lavalley, C.;
Le Flour, T.; Le Padellec, A.; Lenain, J. -P.; Lessio, L.; Lieunard,
B.; Lindfors, E.; Liolios, A.; Lohse, T.; Lombardi, S.; Lopatin,
A.; Lorenz, E.; Lubiński, P.; Luz, O.; Lyard, E.; Maccarone, M. C.;
Maccarone, T.; Maier, G.; Majumdar, P.; Maltezos, S.; Małkiewicz,
P.; Mañá, C.; Manalaysay, A.; Maneva, G.; Mangano, A.; Manigot,
P.; Marín, J.; Mariotti, M.; Markoff, S.; Martínez, G.; Martínez,
M.; Mastichiadis, A.; Matsumoto, H.; Mattiazzo, S.; Mazin, D.; McComb,
T. J. L.; McCubbin, N.; McHardy, I.; Medina, C.; Melkumyan, D.; Mendes,
A.; Mertsch, P.; Meucci, M.; Michałowski, J.; Micolon, P.; Mineo,
T.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.; Mizuno,
T.; Moal, B.; Moderski, R.; Molinari, E.; Monteiro, I.; Moralejo, A.;
Morello, C.; Mori, K.; Motta, G.; Mottez, F.; Moulin, E.; Mukherjee,
R.; Munar, P.; Muraishi, H.; Murase, K.; Murphy, A. Stj.; Nagataki,
S.; Naito, T.; Nakamori, T.; Nakayama, K.; Naumann, C.; Naumann, D.;
Nayman, P.; Nedbal, D.; Niedźwiecki, A.; Niemiec, J.; Nikolaidis,
A.; Nishijima, K.; Nolan, S. J.; Nowak, N.; O'Brien, P. T.; Ochoa,
I.; Ohira, Y.; Ohishi, M.; Ohka, H.; Okumura, A.; Olivetto, C.; Ong,
R. A.; Orito, R.; Orr, M.; Osborne, J. P.; Ostrowski, M.; Otero, L.;
Otte, A. N.; Ovcharov, E.; Oya, I.; Oziȩbło, A.; Paiano, S.; Pallota,
J.; Panazol, J. L.; Paneque, D.; Panter, M.; Paoletti, R.; Papyan,
G.; Paredes, J. M.; Pareschi, G.; Parsons, R. D.; Paz Arribas, M.;
Pedaletti, G.; Pepato, A.; Persic, M.; Petrucci, P. O.; Peyaud,
B.; Piechocki, W.; Pita, S.; Pivato, G.; Płatos, Ł.; Platzer,
R.; Pogosyan, L.; Pohl, M.; Pojmański, G.; Ponz, J. D.; Potter,
W.; Prandini, E.; Preece, R.; Prokoph, H.; Pühlhofer, G.; Punch,
M.; Quel, E.; Quirrenbach, A.; Rajda, P.; Rando, R.; Rataj, M.;
Raue, M.; Reimann, C.; Reimann, O.; Reimer, A.; Reimer, O.; Renaud,
M.; Renner, S.; Reymond, J. -M.; Rhode, W.; Ribó, M.; Ribordy,
M.; Rico, J.; Rieger, F.; Ringegni, P.; Ripken, J.; Ristori, P.;
Rivoire, S.; Rob, L.; Rodriguez, S.; Roeser, U.; Romano, P.; Romero,
G. E.; Rosier-Lees, S.; Rovero, A. C.; Roy, F.; Royer, S.; Rudak, B.;
Rulten, C. B.; Ruppel, J.; Russo, F.; Ryde, F.; Sacco, B.; Saggion, A.;
Sahakian, V.; Saito, K.; Saito, T.; Sakaki, N.; Salazar, E.; Salini,
A.; Sánchez, F.; Sánchez Conde, M. Á.; Santangelo, A.; Santos,
E. M.; Sanuy, A.; Sapozhnikov, L.; Sarkar, S.; Scalzotto, V.; Scapin,
V.; Scarcioffolo, M.; Schanz, T.; Schlenstedt, S.; Schlickeiser, R.;
Schmidt, T.; Schmoll, J.; Schroedter, M.; Schultz, C.; Schultze, J.;
Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schweizer, T.; Seiradakis,
J.; Selmane, S.; Seweryn, K.; Shayduk, M.; Shellard, R. C.; Shibata,
T.; Sikora, M.; Silk, J.; Sillanpää, A.; Sitarek, J.; Skole, C.;
Smith, N.; Sobczyńska, D.; Sofo Haro, M.; Sol, H.; Spanier, F.; Spiga,
D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.; Starling, R. L. C.;
Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steiner, S.; Stergioulas,
N.; Sternberger, R.; Stinzing, F.; Stodulski, M.; Straumann, U.;
Suárez, A.; Suchenek, M.; Sugawara, R.; Sulanke, K. H.; Sun, S.;
Supanitsky, A. D.; Sutcliffe, P.; Szanecki, M.; Szepieniec, T.;
Szostek, A.; Szymkowiak, A.; Tagliaferri, G.; Tajima, H.; Takahashi,
H.; Takahashi, K.; Takalo, L.; Takami, H.; Talbot, R. G.; Tam, P. H.;
Tanaka, M.; Tanimori, T.; Tavani, M.; Tavernet, J. -P.; Tchernin, C.;
Tejedor, L. A.; Telezhinsky, I.; Temnikov, P.; Tenzer, C.; Terada,
Y.; Terrier, R.; Teshima, M.; Testa, V.; Tibaldo, L.; Tibolla, O.;
Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tokarz, M.; Toma,
K.; Torres, D. F.; Tosti, G.; Totani, T.; Toussenel, F.; Vallania,
P.; Vallejo, G.; van der Walt, J.; van Eldik, C.; Vandenbroucke, J.;
Vankov, H.; Vasileiadis, G.; Vassiliev, V. V.; Vegas, I.; Venter, L.;
Vercellone, S.; Veyssiere, C.; Vialle, J. P.; Videla, M.; Vincent,
P.; Vink, J.; Vlahakis, N.; Vlahos, L.; Vogler, P.; Vollhardt, A.;
Volpe, F.; von Gunten, H. P.; Vorobiov, S.; Wagner, S.; Wagner,
R. M.; Wagner, B.; Wakely, S. P.; Walter, P.; Walter, R.; Warwick,
R.; Wawer, P.; Wawrzaszek, R.; Webb, N.; Wegner, P.; Weinstein, A.;
Weitzel, Q.; Welsing, R.; Wetteskind, H.; White, R.; Wierzcholska,
A.; Wilkinson, M. I.; Williams, D. A.; Winde, M.; Wischnewski, R.;
Wiśniewski, Ł.; Wolczko, A.; Wood, M.; Xiong, Q.; Yamamoto, T.;
Yamaoka, K.; Yamazaki, R.; Yanagita, S.; Yoffo, B.; Yonetani, M.;
Yoshida, A.; Yoshida, T.; Yoshikoshi, T.; Zabalza, V.; Zagdański,
A.; Zajczyk, A.; Zdziarski, A.; Zech, A.; Ziȩtara, K.; Ziółkowski,
P.; Zitelli, V.; Zychowski, P.
2011ExA....32..193A Altcode: 2011ExA...tmp..121A; 2010arXiv1008.3703C
Ground-based gamma-ray astronomy has had a major breakthrough with
the impressive results obtained using systems of imaging atmospheric
Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge
potential in astrophysics, particle physics and cosmology. CTA is
an international initiative to build the next generation instrument,
with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV
range and the extension to energies well below 100 GeV and above 100
TeV. CTA will consist of two arrays (one in the north, one in the south)
for full sky coverage and will be operated as open observatory. The
design of CTA is based on currently available technology. This document
reports on the status and presents the major design concepts of CTA.
---------------------------------------------------------
Title: Gravitational redshifts in main-sequence and giant stars
Authors: Pasquini, L.; Melo, C.; Chavero, C.; Dravins, D.; Ludwig,
H. -G.; Bonifacio, P.; de La Reza, R.
2011A&A...526A.127P Altcode: 2010arXiv1011.4635P
Context. Precise analyses of stellar radial velocities is able to
reveal intrinsic causes of the wavelength shifts of spectral lines
(other than Doppler shifts due to radial motion), such as gravitational
redshifts and convective blueshifts. <BR /> Aims: Gravitational
redshifts in solar-type main-sequence stars are expected to be some
500 m s<SUP>-1</SUP> greater than those in giants. We search for this
difference in redshifts among groups of open-cluster stars that share
the same average space motion and thus have the same average Doppler
shift. <BR /> Methods: We observed 144 main-sequence stars and cool
giants in the M 67 open cluster using the ESO FEROS spectrograph and
obtained radial velocities by means of cross-correlation with a spectral
template. Binaries and doubtful members were not analyzed, and average
spectra were created for different classes of stars. <BR /> Results:
The M 67 dwarf and giant radial-velocity distributions are each well
represented by Gaussian functions, which share the same apparent average
radial velocity to within ≃100 m s<SUP>-1</SUP>. In addition, dwarfs
in M 67 appear to be dynamically hotter (σ = 0.90 km s<SUP>-1</SUP>)
than giants (σ = 0.68 km s<SUP>-1</SUP>). <BR /> Conclusions: We fail
to detect any difference in the gravitational redshifts of giants and
MS stars. This is probably because of the differential wavelength
shifts produced by the different hydrodynamics of dwarf and giant
atmospheres. Radial-velocity differences measured between unblended
lines in averaged spectra vary with line-strength: stronger lines
are more blueshifted in dwarfs than in giants, apparently removing
any effect of the gravitational redshift. Synthetic high-resolution
spectra are computed from three dimensional (3D) hydrodynamic model
atmospheres for both giants and dwarfs, and synthetic wavelength
shifts obtained. In agreement with observations, 3D models predict
substantially smaller wavelength-shift differences than expected from
gravitational redshifts only. The procedures developed could be used
to test 3D models for different classes of stars, but will ultimately
require high-fidelity spectra for measurements of wavelength shifts in
individual spectral lines. <P />Based on observations collected at ESO,
La Silla, Chile, during the agreement between the Observatorio Nacional
at Rio de Janeiro and ESO.Table 1 is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A> and also at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A127">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A127</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Velocities of M67 main-sequence
and giant stars (Pasquini+, 2011)
Authors: Pasquini, L.; Melo, C.; Chavero, C.; Dravins, D.; Ludwig,
H. -G.; Bonifacio, P.; de La, Reza R.
2011yCat..35260127P Altcode: 2011yCat..35269127P
We observed 144 main-sequence stars and cool giants in the M67 open
cluster using the ESO FEROS spectrograph and obtained radial velocities
by means of cross-correlation with a spectral template. Binaries and
doubtful members were not analyzed, and average spectra were created
for different classes of stars. <P />(1 data file).
---------------------------------------------------------
Title: Stellar intensity interferometry: experimental steps toward
long-baseline observations
Authors: LeBohec, Stephan; Adams, Ben; Bond, Isobel; Bradbury, Stella;
Dravins, Dainis; Jensen, Hannes; Kieda, David B.; Kress, Derrick;
Munford, Edward; Nuñez, Paul D.; Price, Ryan; Ribak, Erez; Rose,
Joachim; Simpson, Harold; Smith, Jeremy
2010SPIE.7734E..1DL Altcode: 2010arXiv1009.5585L; 2010SPIE.7734E..40L
Experiments are in progress to prepare for intensity interferometry with
arrays of air Cherenkov telescopes. At the Bonneville Seabase site, near
Salt Lake City, a testbed observatory has been set up with two 3-m air
Cherenkov telescopes on a 23-m baseline. Cameras are being constructed,
with control electronics for either off- or online analysis of the
data. At the Lund Observatory (Sweden) and in Technion (Israel) and
at the University of Utah (USA), laboratory intensity interferometers
simulating stellar observations have been set up and experiments are in
progress, using various analog and digital correlators, reaching 1.4 ns
time resolution, to analyze signals from pairs of laboratory telescopes.
---------------------------------------------------------
Title: Stellar intensity interferometry: astrophysical targets for
sub-milliarcsecond imaging
Authors: Dravins, Dainis; Jensen, Hannes; LeBohec, Stephan; Nuñez,
Paul D.
2010SPIE.7734E..0AD Altcode: 2010arXiv1009.5815D; 2010SPIE.7734E...9D
Intensity interferometry permits very long optical baselines and
the observation of sub-milliarcsecond structures. Using planned
kilometric arrays of air Cherenkov telescopes at short wavelengths,
intensity interferometry may increase the spatial resolution achieved
in optical astronomy by an order of magnitude, inviting detailed
studies of the shapes of rapidly rotating hot stars with structures
in their circumstellar disks and winds, or mapping out patterns
of nonradial pulsations across stellar surfaces. Signal-to-noise
in intensity interferometry favors high-temperature sources and
emission-line structures, and is independent of the optical passband,
be it a single spectral line or the broad spectral continuum. Prime
candidate sources have been identified among classes of bright and
hot stars. Observations are simulated for telescope configurations
envisioned for large Cherenkov facilities, synthesizing numerous
optical baselines in software, confirming that resolutions of tens of
microarcseconds are feasible for numerous astrophysical targets.
---------------------------------------------------------
Title: Stellar intensity interferometry: optimizing air Cherenkov
telescope array layouts
Authors: Jensen, Hannes; Dravins, Dainis; LeBohec, Stephan; Nuñez,
Paul D.
2010SPIE.7734E..1TJ Altcode: 2010SPIE.7734E..54J; 2010arXiv1009.5828J
Kilometric-scale optical imagers seem feasible to realize by intensity
interferometry, using telescopes primarily erected for measuring
Cherenkov light induced by gamma rays. Planned arrays envision 50-100
telescopes, distributed over some 1-4 km<SUP>2</SUP>. Although
array layouts and telescope sizes will primarily be chosen for
gamma-ray observations, also their interferometric performance may be
optimized. Observations of stellar objects were numerically simulated
for different array geometries, yielding signal-to-noise ratios for
different Fourier components of the source images in the interferometric
(u, v)-plane. Simulations were made for layouts actually proposed for
future Cherenkov telescope arrays, and for subsets with only a fraction
of the telescopes. All large arrays provide dense sampling of the (u,
v)-plane due to the sheer number of telescopes, irrespective of their
geographic orientation or stellar coordinates. However, for improved
coverage of the (u, v)-plane and a wider variety of baselines (enabling
better image reconstruction), an exact east-west grid should be avoided
for the numerous smaller telescopes, and repetitive geometric patterns
avoided for the few large ones. Sparse arrays become severely limited
by a lack of short baselines, and to cover astrophysically relevant
dimensions between 0.1-3 milliarcseconds in visible wavelengths,
baselines between pairs of telescopes should cover the whole interval
30-2000 m.
---------------------------------------------------------
Title: Stellar intensity interferometry: imaging capabilities of
air Cherenkov telescope arrays
Authors: Nuñez, Paul D.; LeBohec, Stephan; Kieda, David; Holmes,
Richard; Jensen, Hannes; Dravins, Dainis
2010SPIE.7734E..1CN Altcode: 2010arXiv1009.5599N; 2010SPIE.7734E..39N
Sub milli-arcsecond imaging in the visible band will provide a new
perspective in stellar astrophysics. Even though stellar intensity
interferometry was abandoned more than 40 years ago, it is capable of
imaging and thus accomplishing more than the measurement of stellar
diameters as was previously thought. Various phase retrieval techniques
can be used to reconstruct actual images provided a sufficient coverage
of the interferometric plane is available. Planned large arrays of Air
Cherenkov telescopes will provide thousands of simultaneously available
baselines ranging from a few tens of meters to over a kilometer, thus
making imaging possible with unprecedented angular resolution. Here we
investigate the imaging capabilities of arrays such as CTA or AGIS used
as Stellar Intensity Interferometry receivers. The study makes use of
simulated data as could realistically be obtained from these arrays. A
Cauchy-Riemann based phase recovery allows the reconstruction of images
which can be compared to the pristine image for which the data were
simulated. This is first done for uniform disk stars with different
radii and corresponding to various exposure times, and we find that
the uncertainty in reconstructing radii is a few percent after a few
hours of exposure time. Finally, more complex images are considered,
showing that imaging at the sub-milli-arc-second scale is possible.
---------------------------------------------------------
Title: High-fidelity spectroscopy at the highest resolutions
Authors: Dravins, D.
2010AN....331..535D Altcode: 2010arXiv1002.1190D
High-fidelity spectroscopy presents challenges for both observations
and in designing instruments. High-resolution and high-accuracy
spectra are required for verifying hydrodynamic stellar atmospheres
and for resolving intergalactic absorption-line structures in
quasars. Even with great photon fluxes from large telescopes with
matching spectrometers, precise measurements of line profiles and
wavelength positions encounter various physical, observational, and
instrumental limits. The analysis may be limited by astrophysical
and telluric blends, lack of suitable lines, imprecise laboratory
wavelengths, or instrumental imperfections. To some extent, such limits
can be pushed by forming averages over many similar spectral lines,
thus averaging away small random blends and wavelength errors. In
situations where theoretical predictions of lineshapes and shifts can
be accurately made (e.g., hydrodynamic models of solar-type stars),
the consistency between noisy observations and theoretical predictions
may be verified; however this is not feasible for, e.g., the complex
of intergalactic metal lines in spectra of distant quasars, where
the primary data must come from observations. To more fully resolve
lineshapes and interpret wavelength shifts in stars and quasars alike,
spectral resolutions on order R=300 000 or more are required; a level
that is becoming (but is not yet) available. A grand challenge remains
to design efficient spectrometers with resolutions approaching R=1
000 000 for the forthcoming generation of extremely large telescopes.
---------------------------------------------------------
Title: Division Iv: Stars
Authors: Spite, Monique; Corbally, Christopher; Dravins, Dainis; Allen,
Christine; d'Antona, Francesca; Giridhar, Sunetra; Landstreet, John;
Parthasarathy, Mudumba
2010IAUTB..27..188S Altcode:
During the General Assembly in Rio de Janeiro the Division IV meeting,
and the meetings of the participating working groups and commissions,
were held on thursday 6th (session 1 and 2) and friday 7th (sessions 1,
2, 3, 4).
---------------------------------------------------------
Title: Towards a Square-Kilometer Optical Telescope: The Potential
of Intensity Interferometry
Authors: Dravins, D.
2010RMxAC..38...17D Altcode:
Kilometric-scale optical baselines are required for imaging features
across stellar disks. Ground-based intensity interferometry is
insensitive to both atmospheric turbulence and to imperfections
in telescope optics, permitting long-baseline observations even at
short optical wavelengths. Its required large flux collectors are
becoming available as arrays of atmospheric Cherenkov telescopes
set up for studying energetic gamma rays. High-speed detectors and
digital signal handling enable very many baselines to be synthesized
in software between numerous pairs of telescopes in a digital revival
of a technique once pioneered by Hanbury Brown & Twiss.
---------------------------------------------------------
Title: High Time Resolution Astrophysics in the Extremely Large
Telescope Era : White Paper
Authors: Shearer, A.; Kanbach, G.; Slowikowska, A.; Barbieri, C.;
Marsh, T.; Dhillon, V.; Mignani, R.; Dravins, D.; Gouiffes, c.;
MacKay, C.; Bonanno, G.; Collins, S.
2010htra.confE..54S Altcode: 2010PoS...108E..54S; 2010arXiv1008.0605S
High Time Resolution Astrophysics (HTRA) concerns itself with
observations on short scales normally defined as being lower than
the conventional read-out time of a CCD. As such it is concerned with
condensed objects such as neutron stars, black holes and white dwarfs,
surfaces with extreme magnetic reconnection phenomena, as well as
with planetary scale objects through transits and occultations. HTRA
is the only way to make a major step forward in our understanding of
several important astrophysical and physical processes; these include
the extreme gravity conditions around neutron stars and stable orbits
around stellar mass black holes. Transits, involving fast timing,
can give vital information on the size of, and satellites around
exoplanets. In the realm of fundamental physics very interesting
applications lie in the regime of ultra-high time resolution, where
quantum-physical phenomena, currently studied in laboratory physics,
may be explored. HTRA science covers the full gamut of observational
optical/IR astronomy from asteroids to {\gamma}-rays bursts,
contributing to four out of six of AstroNet's fundamental challenges
described in their Science Vision for European Astronomy. Giving
the European-Extremely Large Telescope (E-ELT) an HTRA capability is
therefore importance. We suggest that there are three possibilities
for HTRA and E-ELT. These are, firstly giving the E-ELT first light
engineering camera an HTRA science capability. Secondly, to include
a small HTRA instrument within another instrument. Finally, to have
separate fibre feeds to a dedicated HTRA instrument. In this case a
small number of fibres could be positioned and would provide a flexible
and low cost means to have an HTRA capability. By the time of E-ELT
first light, there should be a number of significant developments in
fast detector arrays, in particular in the infra-red (IR) region.
---------------------------------------------------------
Title: High-Fidelity Spectroscopy at the Highest Resolution
Authors: Dravins, Dainis
2010RvMA...22..191D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Towards the Intensity Interferometry Stellar Imaging System
Authors: Daniel, M.; de Wit, W. J.; Dravins, D.; Kieda, D.; LeBohec,
S.; Nunez, P.; Ribak, E.
2009arXiv0906.3276D Altcode:
The imminent availability of large arrays of large light collectors
deployed to exploit atmospheric Cherenkov radiation for gamma-ray
astronomy at more than 100GeV, motivates the growing interest in
application of intensity interferometry in astronomy. Indeed, planned
arrays numbering up to one hundred telescopes will offer close to 5,000
baselines, ranging from less than 50m to more than 1000m. Recent and
continuing signal processing technology developments reinforce this
interest. Revisiting Stellar Intensity Interferometry for imaging
is well motivated scientifically. It will fill the short wavelength
(B/V bands) and high angular resolution (< 0.1mas) gap left open
by amplitude interferometers. It would also constitute a first and
important step toward exploiting quantum optics for astronomical
observations, thus leading the way for future observatories. In this
paper we outline science cases, technical approaches and schedule
for an intensity interferometer to be constructed and operated in the
visible using gamma-ray astronomy Air Cherenkov Telescopes as receivers.
---------------------------------------------------------
Title: New Astrophysical Opportunities Exploiting Spatio-Temporal
Optical Correlations
Authors: Barbieri, C.; Daniel, M. K.; de Wit, W. J.; Dravins, D.;
Jensen, H.; Kervella, P.; Le Bohec, S.; Malbet, F.; Nunex, P.; Ralston,
J. P.; Ribak, E. N.
2009astro2010S..61B Altcode: 2009arXiv0903.0062B; 2009astro2010S..61D
The space-time correlations of streams of photons can provide
fundamentally new channels of information about the Universe. Today's
astronomical observations essentially measure certain amplitude
coherence functions produced by a source. The spatial correlations
of wave fields has traditionally been exploited in Michelson-style
amplitude interferometry. However the technology of the past was
largely incapable of fine timing resolution and recording multiple
beams. When time and space correlations are combined it is possible
to achieve spectacular measurements that are impossible by any other
means. Stellar intensity interferometry is ripe for development
and is one of the few unexploited mechanisms to obtain potentially
revolutionary new information in astronomy. As we discuss below, the
modern use of stellar intensity interferometry can yield unprecedented
measures of stellar diameters, binary stars, distance measures including
Cepheids, rapidly rotating stars, pulsating stars, and short-time
scale fluctuations that have never been measured before.
---------------------------------------------------------
Title: Highest-resolution spectroscopy at the largest telescopes?
Authors: Dravins, Dainis
2009MmSAI..80..614D Altcode:
3-D models of stellar atmospheres predict spectral-line shapes
with asymmetries and wavelength shifts, but the confrontation with
observations is limited by blends, lack of suitable lines, imprecise
laboratory wavelengths, and instrumental imperfections. Limits
can be pushed by averaging many similar lines, thus averaging small
random blends and wavelength errors. In non-solar cases, any detailed
verification of 3-D hydrodynamics requires spectra of resolutions R =
lambda /Delta lambda ≈ 300,000, soon to become available. An issue
is the optical interface of high-resolution spectrometers to [very]
large telescopes with their [very] large image scales, possibly
requiring adaptive optics. The next observational frontier may be
spectroscopy across spatially resolved stellar disks, utilizing optical
interferometers and extremely large telescopes.
---------------------------------------------------------
Title: Division IV: Stars
Authors: Spite, Monique; Corbally, Christopher J.; Dravins, Dainis;
Allen, Christine; d'Antona, Francesca; Giridhar, Sunetra; Landstreet,
John D.; Parthasarathy, Mudumba
2009IAUTA..27..193S Altcode:
IAU Division IV organizes astronomers studying the characteristics,
interior and atmospheric structure, and evolution of stars of all
masses, ages, and chemical compositions.
---------------------------------------------------------
Title: “Ultimate” information content in solar and stellar
spectra. Photospheric line asymmetries and wavelength shifts
Authors: Dravins, Dainis
2008A&A...492..199D Altcode: 2008arXiv0810.2533D
Context: Spectral-line asymmetries (displayed as bisectors) and
wavelength shifts are signatures of the hydrodynamics in solar and
stellar atmospheres. Theory may precisely predict idealized lines,
but accuracies in real observed spectra are limited by blends, few
suitable lines, imprecise laboratory wavelengths, and instrumental
imperfections. <BR />Aims: We extract bisectors and shifts until
the “ultimate” accuracy limits in highest-quality solar and
stellar spectra, so as to understand the various limits set by
(i) stellar physics (number of relevant spectral lines, effects of
blends, rotational line broadening); by (ii) observational techniques
(spectral resolution, photometric noise); and by (iii) limitations
in laboratory data. <BR />Methods: Several spectral atlases of the
Sun and bright solar-type stars were examined for those thousands of
“unblended” lines with the most accurate laboratory wavelengths,
yielding bisectors and shifts as averages over groups of similar
lines. Representative data were obtained as averages over groups
of similar lines, thus minimizing the effects of photometric noise
and of random blends. <BR />Results: For the solar-disk center and
integrated sunlight, the bisector shapes and shifts were extracted
for previously little-studied species (Fe II, Ti I, Ti II, Cr II,
Ca I, C I), using recently determined and very accurate laboratory
wavelengths. In Procyon and other F-type stars, a sharp blueward bend
in the bisector near the spectral continuum is confirmed, revealing
line saturation and damping wings in upward-moving photospheric
granules. Accuracy limits are discussed: “astrophysical” noise due
to few measurable lines, finite instrumental resolution, superposed
telluric absorption, inaccurate laboratory wavelengths, and calibration
noise in spectrometers, together limiting absolute lineshift studies
to ≈50-100 m s<SUP>-1</SUP>. <BR />Conclusions: Spectroscopy with
resolutions λ/Δλ ≈ 300 000 and accurate wavelength calibration
will enable bisector studies for many stars. Circumventing remaining
limits of astrophysical noise in line-blends and rotationally smeared
profiles may ultimately require spectroscopy across spatially resolved
stellar disks, utilizing optical interferometers and extremely large
telescopes of the future. <P />Tables are only available in electronic
form at http://www.aanda.org
---------------------------------------------------------
Title: Toward a revival of stellar intensity interferometry
Authors: LeBohec, Stephan; Barbieri, Cesare; de Wit, Willem-Jan;
Dravins, Dainis; Feautrier, Philippe; Foellmi, Cédric; Glindemann,
Andreas; Hall, Jeter; Holder, Jamie; Holmes, Richard; Kervella,
Pierre; Kieda, David; Le Coarer, Etienne; Lipson, Stephan; Malbet,
Fabien; Morel, Sébastien; Nuñez, Paul; Ofir, Aviv; Ribak, Erez;
Saha, Swapan; Schoeller, Markus; Zhilyaev, Boriz; Zinnecker, Hans
2008SPIE.7013E..2EL Altcode: 2008SPIE.7013E..72L
Building on technological developments over the last 35 years,
intensity interferometry now appears a feasible option by which to
achieve diffraction-limited imaging over a square-kilometer synthetic
aperture. Upcoming Atmospheric Cherenkov Telescope projects will
consist of up to 100 telescopes, each with ~100m<SUP>2</SUP> of light
gathering area, and distributed over ~1km<SUP>2</SUP>. These large
facilities will offer thousands of baselines from 50m to more than 1km
and an unprecedented (u,v) plane coverage. The revival of interest
in Intensity Interferometry has recently led to the formation of a
IAU working group. Here we report on various ongoing efforts towards
implementing modern Stellar Intensity Interferometry.
---------------------------------------------------------
Title: Toward a diffraction-limited square-kilometer optical
telescope: digital revival of intensity interferometry
Authors: Dravins, Dainis; LeBohec, Stephan
2008SPIE.6986E..09D Altcode: 2008SPIE.6986E...9D
Much of the progress in astronomy follows imaging with improved
resolution. In observing stars, current capabilities are only
marginal in beginning to image the disks of a few, although many
stars will appear as surface objects for baselines of hundreds
of meters. Since atmospheric turbulence makes ground-based phase
interferometry challenging for such long baselines, kilometric
space telescope clusters have been proposed for imaging stellar
surface details. The realization of such projects remains uncertain,
but comparable imaging could be realized by ground-based intensity
interferometry. While insensitive to atmospheric turbulence and
imperfections in telescope optics, the method requires large flux
collectors, such as being set up as arrays of atmospheric Cherenkov
telescopes for studying energetic gamma rays. High-speed detectors and
digital signal handling enable very many baselines to be synthesized
between pairs of telescopes, while stars may be tracked across the sky
by electronic time delays. First observations with digitally combined
optical instruments have now been made with pairs of 12-meter telescopes
of the VERITAS array in Arizona. Observing at short wavelengths adds no
problems, and similar techniques on an extremely large telescope could
achieve diffraction-limited imaging down to the atmospheric cutoff,
achieving a spatial resolution significantly superior by that feasible
by adaptive optics operating in the red or near-infrared.
---------------------------------------------------------
Title: Photon Correlation Spectroscopy for Observing Natural Lasers
Authors: Dravins, Dainis; Germanà, Claudio
2008AIPC..984..216D Altcode: 2007arXiv0710.1756D
Natural laser emission may be produced whenever suitable atomic
energy levels become overpopulated. Strong evidence for laser emission
exists in astronomical sources such as Eta Carinae, and other luminous
stars. However, the evidence is indirect in that the laser lines have
not yet been spectrally resolved. The lines are theoretically estimated
to be extremely narrow, requiring spectral resolutions very much higher
(R~10<SUP>8</SUP>) than possible with ordinary spectroscopy. Such can be
attained with photon-correlation spectroscopy on nanosecond timescales,
measuring the autocorrelation function of photon arrival times to
obtain the coherence time of light, and thus the spectral linewidth. A
particular advantage is the insensitivity to spectral, spatial, and
temporal shifts of emission-line components due to local velocities
and probable variability of `hot-spots' in the source. A laboratory
experiment has been set up, simulating telescopic observations of
cosmic laser emission. Numerically simulated observations estimate
how laser emission components within realistic spectral and spatial
passbands for various candidate sources carry over to observable
statistical functions.
---------------------------------------------------------
Title: Intrinsic Lineshifts in Astronomical Spectra
Authors: Dravins, Dainis
2008psa..conf..139D Altcode:
Spectral-line displacements away from the wavelengths naively expected
from the Doppler shift due to radial motion may originate as convective
shifts (correlated velocity and brightness patterns), as gravitational
redshifts, or be induced by wave motions. Convective shifts are
important tools for testing 3-dimensional stellar hydrodynamics;
analogous shifts may be expected even in intergalactic absorption lines
(convection driven by AGNs in clusters of galaxies).
---------------------------------------------------------
Title: Photonic Astronomy and Quantum Optics
Authors: Dravins, Dainis
2008ASSL..351...95D Altcode: 2007astro.ph..1220D
Quantum optics potentially offers an information channel from the
Universe beyond the established ones of imaging and spectroscopy. All
existing cameras and all spectrometers measure aspects of the
first-order spatial and/or temporal coherence of light. However,
light has additional degrees of freedom, manifest in the statistics
of photon arrival times, or in the amount of photon orbital angular
momentum. Such quantum-optical measures may carry information on
how the light was created at the source, and whether it reached
the observer directly or via some intermediate process. Astronomical
quantum optics may help to clarify emission processes in natural laser
sources and in the environments of compact objects, while high-speed
photon-counting with digital signal handling enables multi-element
and long-baseline versions of the intensity interferometer. Time
resolutions of nanoseconds are required, as are large photon fluxes,
making photonic astronomy very timely in an era of large telescopes.
---------------------------------------------------------
Title: Division Iv: Stars
Authors: Dravins, Dainis; Spite, Monique; Barbuy, Beatriz; Corbally,
Christopher; Dziembowski, Wojciech; Hartkopf, William I.; Sneden,
Christopher
2007IAUTB..26..145D Altcode:
Division IV organizes astronomers studying the characterization,
interior and atmospheric structure of stars of all masses, ages and
chemical compositions.
---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres
Authors: Spite, Monique; Landstreet, John D.; Asplund, Martin; Ayres,
Thomas R.; Balachandran, Suchitra C.; Dravins, Dainis; Hauschildt,
Peter H.; Kiselman, Dan; Nagendra, K. N.; Sneden, Christopher;
Tautvaišiené, Grazina; Werner, Klaus
2007IAUTB..26..160S Altcode:
The business meeting of Commission 36 was held during the General
Assembly in Prague on 16 August. It was attended by about 15
members. The issues presented included a review of the work made
by members of Commission 36, and the election of the new Organising
Committee. We note that a comprehensive report on the activities of
the commission during the last triennium has been published in Reports
on Astronomy, Transactions IAU Volume XXVIA. The scientific activity
of the members of the commission has been very intense, and has led
to the publication of a large number of papers.
---------------------------------------------------------
Title: Commission 30: Radial Velocities
Authors: Nordström, Birgitta; Udry, Stéphane; Tokovinin, Andrei A.;
Dravins, Dainis; Fekel, Francis C.; Glushkova, Elena V.; Levato, Hugo;
Pourbaix, Dimitri; Smith, Myron A.; Szabados, Laszlo; Torres, Guillermo
2007IAUTB..26..197N Altcode:
The president welcomed all the participants of the Business Meeting
and remarked that several of the major ongoing and planned Radial
Velocity projects were well represented.
---------------------------------------------------------
Title: Wolfe Creek Crater in Western Australia
Authors: Dravins, Dainis
2007S&T...114d.102D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Searching for Optical Lasers in Emission-Line Stars
Authors: Dravins, Dainis; Germano, Claudio
2007jena.confE..26D Altcode:
Natural laser emission may be produced whenever radiative mechanisms
overpopulate suitable atomic energy levels. Well-studied cases
are optical emission lines from gas ejecta around the extremely
luminous star Eta Carinae. Theoretically expected linewidths are
very narrow, requiring spectral resolution around 100 million,
far beyond classical spectroscopy. Such resolutions are feasible
with nanosecond-resolution photon-correlation spectroscopy, a
quantum-optical method of analyzing the autocorrelation function of
photon arrival times. Observations with large telescopes are simulated
both numerically, and in a laboratory experiment measuring narrow
emission lines with photon-counting avalanche photodiodes. Further
discussion: http://www.astro.lu.se/~dainis/
---------------------------------------------------------
Title: Very fast photon counting photometers for astronomical
applications: from QuantEYE to AquEYE
Authors: Naletto, Giampiero; Barbieri, Cesare; Occhipinti, Tommaso;
Tamburini, Fabrizio; Billotta, Sergio; Cocuzza, Silvio; Dravins, Dainis
2007SPIE.6583E..0BN Altcode: 2007SPIE.6583E...9N
In the great majority of the cases, present astronomical observations
are realized analyzing only first order spatial or temporal
coherence properties of the collected photon stream. However, a lot
of information is "hidden" in the second and higher order coherence
terms, as details about a possible stimulated emission mechanism
or about photon scattering along the travel from the emitter to the
telescope. The Extremely Large Telescopes of the future could provide
the high photon flux needed to extract this information. To this aim
we have recently studied a possible focal plane instrument, named
QuantEYE, for the 100 m OverWhelmingly Large Telescope of the European
Southern Observatory. This instrument is the fastest photon counting
photometer ever conceived, with an array of 100 parallel channels
operating simultaneously, to push the time tagging capabilities toward
the pico-second region. To acquire some experience with this novel
type of instrumentation, we are now in the process of realizing a
small instrument prototype (AquEYE) for the Asiago 182 cm telescope,
for then building a larger instrument for one of the existing 8-10
m class telescopes. We hope that the results we will obtain by these
instruments will open a new frontier in the astronomical observations.
---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres
Authors: Spite, Monique; Landstreet, John; Asplund, M.; Ayres, T.;
Balachandran, S.; Dravins, D.; Hauschildt, P.; Kiselman, D.; Nagendra,
K. N.; Sneden, C.; Tautvaišiené, G.; Werner, K.
2007IAUTA..26..215S Altcode:
Commission 36 covers all the physics of stellar atmospheres. The
scientific activity in this large field has been very intense during
the last triennium and led to the publication of a large number of
papers which makes an exhaustive report practically not feasible. As
a consequence we decided to keep the format of the preceding report:
first a list of areas of current research, then web links for obtaining
further information.
---------------------------------------------------------
Title: Commission 12: Solar Radiation & Structure
Authors: Bogdan, Thomas. J.; Martínez Pillet, Valentin; Asplund,
M.; Christensen-Dalsgaard, J.; Cauzzi, G.; Cram, L. E.; Dravins, D.;
Gan, W.; Henzl, P.; Kosovichev, A.; Mariska, J. T.; Rovira, M. G.;
Venkatakrishnan, P.
2007IAUTA..26...89B Altcode:
Commission 12 covers research on the internal structure and dynamics
of the Sun, the "quiet" solar atmosphere, solar radiation and its
variability, and the nature of relatively stable magnetic structures
like sunspots, faculae and the magnetic network. There is considerable
productive overlap with the other Commissions of Division II as
investigations move progressively toward the fertile intellectual
boundaries between traditional research disciplines. In large part,
the solar magnetic field provides the linkage that connects these
diverse themes. The same magnetic field that produces the more subtle
variations of solar structure and radiative output over the 11 yr
activity cycle is also implicated in rapid and often violent phenomena
such as flares, coronal mass ejections, prominence eruptions, and
episodes of sporadic magnetic reconnection.The last three years have
again brought significant progress in nearly all the research endeavors
touched upon by the interests of Commission 12. The underlying causes
for this success remain the same: sustained advances in computing
capabilities coupled with diverse observations with increasing levels
of spatial, temporal and spectral resolution. It is all but impossible
to deal with these many advances here in anything except a cursory and
selective fashion. Thankfully, the Living Reviews in Solar Physics; has
published several extensive reviews over the last two years that deal
explicitly with issues relevant to the purview of Commission 12. The
reader who is eager for a deeper and more complete understanding of
some of these advances is directed to http://www.livingreviews.org
for access to these articles.
---------------------------------------------------------
Title: Division IV: Stars
Authors: Dravins, Dainis; Barbuy, Beatriz; Corbally, Christopher;
Dziembowski, Wojciech; Hartkopf, William; Sneden, Christopher;
Spite, Monique
2007IAUTA..26..191D Altcode:
The IAU Division IV (`Stars') organizes astronomers studying the
characteristics, interior and atmospheric structure, and evolution of
stars of all masses, ages, and chemical compositions.
---------------------------------------------------------
Title: COMMISSION 30: Radial Velocities*
Authors: Nordström, Birgitta; Udry, Stephane; Dravins, D.; Fekel,
F.; Glushkova, E.; Levato, H.; Pourbaix, D.; Smith, M. A.; Szabados,
L.; Torres, G.
2007IAUTA..26E...1N Altcode:
This report from Commission 30 covers the salient areas in which
major progress has been made in the triennium covered by the
present volume. The principal scientific areas are: The Milky Way,
star clusters, spectroscopic binaries, extrasolar planets, pulsating
stars and stellar oscillations. Following these, an account is given
of the progress in techniques and methodology for radial velocity
determinations. Finally, a summary is given of the progress made
by the working groups of the Commission, followed by a list of key
papers in the triennium. A more extensive report also covering
extragalactic work, which due to unforeseen circumstances could
not be included here, can be found at the web page of Commission 30
(http://www.iau.org/IAU/Organization/divcom/).
---------------------------------------------------------
Title: Astronomical applications of quantum optics for extremely
large telescopes
Authors: Barbieri, C.; Dravins, D.; Occhipinti, T.; Tamburini, F.;
Naletto, G.; da Deppo, V.; Fornasier, S.; D'Onofrio, M.; Fosbury,
R. A. E.; Nilsson, R.; Uthas, H.
2007JMOp...54..191B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: QuantEYE: a quantum optics instrument for extremely large
telescopes
Authors: Naletto, Giampiero; Barbieri, Cesare; Dravins, Dainis;
Occhipinti, Tommaso; Tamburini, Fabrizio; Da Deppo, Vania; Fornasier,
Sonia; D'Onofrio, Mauro; Fosbury, Robert A. E.; Nilsson, Ricky; Uthas,
Helena; Zampieri, Luca
2006SPIE.6269E..1WN Altcode: 2006SPIE.6269E..62N
We have carried out a conceptual study for an instrument (QuantEYE)
capable to detect and measure photon-stream statistics, e.g. power
spectra or autocorrelation functions. Such functions increase with
the square of the detected signal, implying an enormously increased
sensitivity at the future Extremely Large Telescopes, such as
the OverWhelmingly Large (OWL) telescope of the European Southern
Observatory (ESO). Furthermore, QuantEYE will have the capability
of exploring astrophysical variability on microsecond and nanosecond
scales, down to the quantum-optical limit. Expected observable phenomena
include instabilities of photon-gas bubbles in accretion flows, p-mode
oscillations in neutron stars, and quantum-optical photon bunching in
time. This paper describes QuantEYE, an instrument aimed to realize
the just described science, proposed for installation at the ESO OWL
telescope focal plane. The adopted optical solution is relatively
simple and possible with actual technologies, the main constraint
essentially being the present limited availability of very fast photon
counting detector arrays. Also some possible alternative designs are
described, assuming a future technology development of fast photon
counting detector arrays.
---------------------------------------------------------
Title: Astronomical quantum optics with Extremely Large Telescopes
Authors: Dravins, D.; Barbieri, C.; Fosbury, R. A. E.; Naletto, G.;
Nilsson, R.; Occhipinti, T.; Tamburini, F.; Uthas, H.; Zampieri, L.
2006IAUS..232..502D Altcode:
Modern optics focuses on photonics and quantum optics, studying
individual photons and statistics of photon streams. Those can be
complex and carry information beyond that recorded by imaging,
spectroscopy, polarimetry or interferometry. Since [almost] all
astronomy is based upon the interpretation of subtleties in the light
from astronomical sources, quantum optics has the potential of becoming
another information channel from the Universe. The observability
of quantum statistics increases rapidly with telescope size making
photonic astronomy very timely in an era of very large telescopes.
---------------------------------------------------------
Title: QuantEYE, the quantum optics instrument for OWL
Authors: Barbieri, C.; da Deppo, V.; D'Onofrio, M.; Dravins, D.;
Fornasier, S.; Fosbury, R. A. E.; Naletto, G.; Nilsson, R.; Occhipinti,
T.; Tamburini, F.; Uthas, H.; Zampieri, L.
2006IAUS..232..506B Altcode:
A brief description of the QuantEYE instrument proposed as a focal
plane instrument for OWL is given. This instrument is dedicated to the
very high speed observation of many active phenomena with a photon
counting capability of up to 1GHz. The system samples the beam in
10×10 subpupils, each focused on a fast photon counting detector.
---------------------------------------------------------
Title: QuantEYE: The Quantum Optics Instrument for OWL
Authors: Dravins, D.; Barbieri, C.; Fosbury, R. A. E.; Naletto, G.;
Nilsson, R.; Occhipinti, T.; Tamburini, F.; Uthas, H.; Zampieri, L.
2005astro.ph.11027D Altcode:
QuantEYE is designed to be the highest time-resolution instrument
on ESO:s planned Overwhelmingly Large Telescope, devised to explore
astrophysical variability on microsecond and nanosecond scales, down to
the quantum-optical limit. Expected phenomena include instabilities of
photon-gas bubbles in accretion flows, p-mode oscillations in neutron
stars, and quantum-optical photon bunching in time. Precise timescales
are both variable and unknown, and studies must be of photon-stream
statistics, e.g., their power spectra or autocorrelations. Such
functions increase with the square of the intensity, implying an
enormously increased sensitivity at the largest telescopes. QuantEYE
covers the optical, and its design involves an array of photon-counting
avalanche-diode detectors, each viewing one segment of the OWL entrance
pupil. QuantEYE will work already with a partially filled OWL main
mirror, and also without [full] adaptive optics.
---------------------------------------------------------
Title: Report by the ESA-ESO Working Group on Extra-Solar Planets
Authors: Perryman, M.; Hainaut, O.; Dravins, D.; Leger, A.;
Quirrenbach, A.; Rauer, H.; Kerber, F.; Fosbury, R.; Bouchy, F.;
Favata, F.; Fridlund, M.; Gilmozzi, R.; Lagrange, A. -M.; Mazeh, T.;
Rouan, D.; Udry, S.; Wambsganss, J.
2005astro.ph..6163P Altcode:
Various techniques are being used to search for extra-solar planetary
signatures, including accurate measurement of radial velocity and
positional (astrometric) displacements, gravitational microlensing,
and photometric transits. Planned space experiments promise a
considerable increase in the detections and statistical knowledge
arising especially from transit and astrometric measurements over the
years 2005-15, with some hundreds of terrestrial-type planets expected
from transit measurements, and many thousands of Jupiter-mass planets
expected from astrometric measurements. Beyond 2015, very ambitious
space (Darwin/TPF) and ground (OWL) experiments are targeting direct
detection of nearby Earth-mass planets in the habitable zone and the
measurement of their spectral characteristics. Beyond these, `Life
Finder' (aiming to produce confirmatory evidence of the presence of
life) and `Earth Imager' (some massive interferometric array providing
resolved images of a distant Earth) appear as distant visions. This
report, to ESA and ESO, summarises the direction of exo-planet research
that can be expected over the next 10 years or so, identifies the
roles of the major facilities of the two organisations in the field,
and concludes with some recommendations which may assist development
of the field. The report has been compiled by the Working Group members
and experts over the period June-December 2004.
---------------------------------------------------------
Title: ESA-ESO Working Group on "Extra-solar Planets"
Authors: Perryman, M.; Hainaut, O.; Dravins, D.; Leger, A.;
Quirrenbach, A.; Rauer, H.; Kerber, F.; Fosbury, R.; Bouchy, F.;
Favata, F.; Fridlund, M.; Gilmozzi, R.; Lagrange, A. -M.; Mazeh, T.;
Rouan, D.; Udry, S.; Wambsganss, J.
2005ewg1.rept.....P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Wavelength shifts in solar-type spectra
Authors: Dravins, D.; Lindegren, L.; Ludwig, H. -G.; Madsen, S.
2005ESASP.560..113D Altcode: 2004astro.ph..9212D; 2005csss...13..113D
Spectral-line displacements away from the wavelengths naively expected
from the Doppler shift caused by stellar radial motion may originate as
convective shifts (correlated velocity and brightness patterns in the
photosphere), as gravitational redshifts, or perhaps be induced by wave
motions. Absolute lineshifts, in the past studied only for the Sun, are
now accessible also for other stars thanks to astrometric determination
of stellar radial motion, and spectrometers with accurate wavelength
calibration. Comparisons between spectroscopic apparent radial
velocities and astrometrically determined radial motions reveal greater
spectral blueshifts in F-type stars than in the Sun (as theoretically
expected from their more vigorous convection), further increasing in
A-type stars (possibly due to atmospheric shockwaves). An important
near-future development to enable a further analysis of stellar surface
structure will be the study of wavelength variations across spatially
resolved stellar disks, e.g., the center-to-limb wavelength changes
along a stellar diameter, and their spatially resolved time variability.
---------------------------------------------------------
Title: Intrinsic Wavelength Shifts in Stellar Spectra
Authors: Dravins, D.; Lindegren, L.; Ludwig, H. -G.; Madsen, S.
2004AAS...20517004D Altcode: 2004BAAS...36.1624D
Wavelengths of stellar spectral lines do not have the precise values
`naively' expected from laboratory wavelengths merely Doppler-shifted
by stellar radial motion. Slight displacements may originate as
convective shifts (correlated velocity and brightness patterns in the
photosphere), as gravitational redshifts, or perhaps be induced by wave
motions. Intrinsic lineshifts thus reveal stellar surface structure,
while possible periodic changes (during a stellar activity cycle,
say) need to be segregated from variability induced by orbiting
exoplanets. <P />Absolute lineshifts can now be studied also in some
stars other than the Sun, thanks to astrometric determinations of
stellar radial motion. Comparisons between spectroscopic apparent radial
velocities and astrometrically determined radial motions reveal greater
spectral blueshifts in F-type stars than in the Sun (as theoretically
expected from their more vigorous convection), further increasing
in A-type stars (possibly due to atmospheric shockwaves). <P />Solar
spectral atlases, and high-resolution spectra (from UVES on ESO VLT) of
a dozen solar-type stars are being surveyed for `unblended' photospheric
lines of most atomic species with accurate laboratory wavelengths
available. One aim is to understand the ultimate information content
of stellar spectra, and in what detail it will be feasible to verify
models of stellar atmospheric hydrodynamics. These may predict line
asymmetries (bisectors) and shifts for widely different classes of
lines, but there will not result any comparison with observations if
such lines do not exist in real spectra. <P />An expected near-future
development in stellar physics is spatially resolved spectroscopy across
stellar disks, enabled by optical interferometry and adaptive optics
on very large telescopes. Stellar surface structure manifests itself
in the center-to-limb wavelength changes along a stellar diameter,
and their spatially resolved time variability, diagnostics which
already now can be theoretically modeled.
---------------------------------------------------------
Title: Absolute Wavelength Shifts- A New Diagnostic for Rapidly
Rotating Stars
Authors: Dravins, D.
2004IAUS..215...27D Altcode: 2003astro.ph..2592D
Accuracies reached in space astrometry now permit the accurate
determination of astrometric radial velocities, without any use of
spectroscopy. Knowing this true stellar motion, spectral shifts
intrinsic to stellar atmospheres can be identified, for instance
gravitational redshifts and those caused by velocity fields on
stellar surfaces. The astrometric accuracy is independent of any
spectral complexity, such as the smeared-out line profiles of rapidly
rotating stars. Besides a better determination of stellar velocities,
this permits more precise studies of atmospheric dynamics, such as
possible modifications of stellar surface convection (granulation)
by rotation-induced forces, as well as a potential for observing
meridional flows across stellar surfaces.
---------------------------------------------------------
Title: Intrinsic spectral blueshifts in rapidly rotating stars?
Authors: Madsen, Søren; Dravins, Dainis; Ludwig, Hans-Günter;
Lindegren, Lennart
2003A&A...411..581M Altcode: 2003astro.ph..9346M
Spectroscopic radial velocities for several nearby open clusters
suggest that spectra of (especially earlier-type) rapidly rotating
stars are systematically blueshifted by 3 km s<SUP>-1</SUP> or more,
relative to the spectra of slowly rotating ones. Comparisons with
astrometrically determined radial motions in the Hyades suggests this
to be an absolute blueshift, relative to wavelengths naively expected
from stellar radial motion and gravitational redshift. Analogous
trends are seen also in most other clusters studied (Pleiades,
Coma Berenices, Praesepe, alpha Persei, IC 2391, NGC 6475, IC 4665,
NGC 1976 and NGC 2516). Possible mechanisms are discussed, including
photospheric convection, stellar pulsation, meridional circulation,
and shock-wave propagation, as well as effects caused by template
mismatch in determining wavelength displacements. For early-type
stars, a plausible mechanism is shock-wave propagation upward through
the photospheric line-forming regions. Such wavelength shifts thus
permit studies of certain types of stellar atmospheric dynamics and
- irrespective of their cause - may influence deduced open-cluster
membership (when selected from common velocity) and deduced cluster
dynamics (some types of stars might show fortuitous velocity patterns).
---------------------------------------------------------
Title: The fundamental definition of “radial velocity”
Authors: Lindegren, Lennart; Dravins, Dainis
2003A&A...401.1185L Altcode: 2003astro.ph..2522L
Accuracy levels of metres per second require the fundamental concept of
“radial velocity” for stars and other distant objects to be examined,
both as a physical velocity, and as measured by spectroscopic and
astrometric techniques. Already in a classical (non-relativistic)
framework the line-of-sight velocity component is an ambiguous concept,
depending on whether, e.g., the time of light emission (at the object)
or that of light detection (by the observer) is used for recording
the time coordinate. Relativistic velocity effects and spectroscopic
measurements made inside gravitational fields add further complications,
causing wavelength shifts to depend, e.g., on the transverse velocity
of the object and the gravitational potential at the source. Aiming
at definitions that are unambiguous at accuracy levels of 1 m
s<SUP>-1</SUP>, we analyse different concepts of radial velocity and
their interrelations. At this accuracy level, a strict separation must
be made between the purely geometric concepts on one hand, and the
spectroscopic measurement on the other. Among the geometric concepts
we define kinematic radial velocity, which corresponds most closely to
the “textbook definition” of radial velocity as the line-of-sight
component of space velocity; and astrometric radial velocity, which
can be derived from astrometric observations. Consistent with these
definitions, we propose strict definitions also of the complementary
kinematic and astrometric quantities, namely transverse velocity and
proper motion. The kinematic and astrometric radial velocities depend
on the chosen spacetime metric, and are accurately related by simple
coordinate transformations. On the other hand, the observational
quantity that should result from accurate spectroscopic measurements
is the barycentric radial-velocity measure. This is independent of the
metric, and to first order equals the line-of-sight velocity. However,
it is not a physical velocity, and cannot be accurately transformed
to a kinematic or astrometric radial velocity without additional
assumptions and data in modelling the process of light emission from
the source, the transmission of the signal through space, and its
recording by the observer. For historic and practical reasons, the
spectroscopic radial-velocity measure is expressed in velocity units
as cz<SUB>B</SUB>, where c is the speed of light and z<SUB>B</SUB> is
the observed relative wavelength shift reduced to the solar-system
barycentre, at an epoch equal to the barycentric time of light
arrival. The barycentric radial-velocity measure and the astrometric
radial velocity are defined by recent resolutions adopted by the
International Astronomical Union (IAU), the motives and consequences
of which are explained in this paper.
---------------------------------------------------------
Title: Absolute Lineshifts - a New Diagnostic for Stellar
Hydrodynamics
Authors: Dravins, D.
2003IAUS..210P..E4D Altcode: 2003astro.ph..2591D
For hydrodynamic model atmospheres, absolute lineshifts are becoming an
observable diagnostic tool beyond the classical ones of line-strength,
-width, -shape, and -asymmetry. This is the wavelength displacement
of different types of spectral lines away from the positions naively
expected from the Doppler shift caused by stellar radial motion. Caused
mainly by correlated velocity and brightness patterns in granular
convection, such absolute lineshifts could in the past be studied
only for the Sun (since the relative Sun-Earth motion, and the ensuing
Doppler shift is known). For other stars, this is now becoming possible
thanks to three separate developments: (a) Astrometric determination of
stellar radial motion; (b) High-resolution spectrometers with accurate
wavelength calibration, and (c) Accurate laboratory wavelengths for
several atomic species. Absolute lineshifts offer a tool to segregate
various 2- and 3-dimensional models, and to identify non-LTE effects
in line formation.
---------------------------------------------------------
Title: Commission 36: Theory of stellar atmospheres (Théorie des
atmosphères stellaires)
Authors: Dravins, Dainis
2003IAUTA..25..242D Altcode: 2003IAUTr..25A.242D
No abstract at ADS
---------------------------------------------------------
Title: Critical science for the largest telescopes: science drivers
for a 100m ground-based optical-IR telescope
Authors: Hawarden, Timothy G.; Dravins, Dainis; Gilmore, Gerard F.;
Gilmozzi, Roberto; Hainaut, Olivier; Kuijken, K.; Leibindgut, Bruno;
Merrifield, Michael; Queloz, Didier; Wyse, Rosie
2003SPIE.4840..299H Altcode:
Extremely large filled-aperture ground-based optical-IR telescopes, or
ELTs, ranging from 20 to 100m in diameter, are now being proposed. The
all-important choice of the aperture must clearly be driven by the
potential science offered. We here highlight science goals from the
Leiden Workshop in May 2001 suggesting that for certain critical
observations the largest possible aperture - assumed to be 100m
(the proposed European OverWhelmingly Large telescope (OWL) - is
strongly to be desired. Examples from a long list include: COSMOLOGY:
* Identifying the first sources of ionisation in the universe, out to
z >=14 * Identifying and stufdying the first generation of dusty
galaxies * More speculatively, observing the formation of the laws
of physics, via the evolution of the fundamental physical contants
in the very early Universe, by high-resolution spectroscopy of very
distant quasars. NEARER GALAXIES: *Determining detailed star-formation
histories of galaxies out to the Virtgo Cluster, and hence for all
major galaxy types (not just those available close to the Local Group
of galaxies). THE SOLAR SYSTEM: A 100-m telescope would do the work of
a flotilla of fly-by space probes for investigations ranging from the
evolution of planetary sutfaces and atmospheres to detailed surface
spectroscopy of Kuiper Belt Objects. (Such studies could easily occupy
it full-time.) EARTHLIKE PLANETS OF NEARBY STARS: A propsect so exciting
as perhaps to justify the 100-m telescope on its own, is that of the
direct detection of earthlike planets of solar-type stars by imaging,
out to at least 25 parsecs (80 light years) from the sun, followed by
spectroscopic and photometric searches for the signature of life on
the surfaces of nearer examples.
---------------------------------------------------------
Title: HARPS: ESO's coming planet searcher. Chasing exoplanets with
the La Silla 3.6-m telescope
Authors: Pepe, F.; Mayor, M.; Rupprecht, G.; Avila, G.; Ballester,
P.; Beckers, J. -L.; Benz, W.; Bertaux, J. -L.; Bouchy, F.; Buzzoni,
B.; Cavadore, C.; Deiries, S.; Dekker, H.; Delabre, B.; D'Odorico,
S.; Eckert, W.; Fischer, J.; Fleury, M.; George, M.; Gilliotte, A.;
Gojak, D.; Guzman, J. -C.; Koch, F.; Kohler, D.; Kotzlowski, H.;
Lacroix, D.; Le Merrer, J.; Lizon, J. -L.; Lo Curto, G.; Longinotti,
A.; Megevand, D.; Pasquini, L.; Petitpas, P.; Pichard, M.; Queloz,
D.; Reyes, J.; Richaud, P.; Sivan, J. -P.; Sosnowska, D.; Soto, R.;
Udry, S.; Ureta, E.; van Kesteren, A.; Weber, L.; Weilenmann, U.;
Wicenec, A.; Wieland, G.; Christensen-Dalsgaard, J.; Dravins, D.;
Hatzes, A.; Kürster, M.; Paresce, F.; Penny, A.
2002Msngr.110....9P Altcode:
An extensive review of past, present and future research on extrasolar
planets is given in the article “Extrasolar Planets” by N. Santos
et al. in the present issue of The Messenger. Here we want to mention
only that the search for extrasolar planets and the interpretation of
the scientific results have evolved in recent years into one of the
most exciting and dynamic research topics in modern astronomy.
---------------------------------------------------------
Title: Astrometric radial velocities. III. Hipparcos measurements
of nearby star clusters and associations
Authors: Madsen, Søren; Dravins, Dainis; Lindegren, Lennart
2002A&A...381..446M Altcode: 2001astro.ph.10617M
Radial motions of stars in nearby moving clusters are determined
from accurate proper motions and trigonometric parallaxes, without
any use of spectroscopy. Assuming that cluster members share the
same velocity vector (apart from a random dispersion), we apply a
maximum-likelihood method on astrometric data from Hipparcos to compute
radial and space velocities (and their dispersions) in the Ursa Major,
Hyades, Coma Berenices, Pleiades, and Praesepe clusters, and for the
Scorpius-Centaurus, alpha Persei, and “HIP 98321” associations. The
radial motion of the Hyades cluster is determined to within 0.4 km
s<SUP>-1</SUP> (standard error), and that of its individual stars
to within 0.6 km s<SUP>-1</SUP>. For other clusters, Hipparcos data
yield astrometric radial velocities with typical accuracies of a
few km s<SUP>-1</SUP>. A comparison of these astrometric values with
spectroscopic radial velocities in the literature shows a good general
agreement and, in the case of the best-determined Hyades cluster,
also permits searches for subtle astrophysical differences, such as
evidence for enhanced convective blueshifts of F-dwarf spectra, and
decreased gravitational redshifts in giants. Similar comparisons for
the Scorpius OB2 complex indicate some expansion of its associations,
albeit slower than expected from their ages. As a by-product from
the radial-velocity solutions, kinematically improved parallaxes
for individual stars are obtained, enabling Hertzsprung-Russell
diagrams with unprecedented accuracy in luminosity. For the Hyades
(parallax accuracy 0.3 mas), its main sequence resembles a thin
line, possibly with wiggles in it. Although this main sequence has
underpopulated regions at certain colours (previously suggested to be
“Böhm-Vitense gaps”), such are not visible for other clusters,
and are probably spurious. Future space astrometry missions carry
a great potential for absolute radial-velocity determinations,
insensitive to the complexities of stellar spectra. Based on
observations by the ESA Hipparcos satellite. Extended versions of
Tables \ref{tab1} and \ref{tab2} are available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.125.8)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/446
---------------------------------------------------------
Title: VizieR Online Data Catalog: Astrometric Radial
Velocities. III. (Madsen+, 2002)
Authors: Madsen, S.; Dravins, D.; Lindegren, L.
2001yCat..33810446M Altcode:
Astrometrically determined kinematic data are given for nearby
clusters and associations, including astrometric radial velocities and
kinematically improved parallaxes for individual stars. The astrometric
radial velocities are determined independent of spectroscopy. Table 1
gives the space velocities and internal velocity dispersions of the
clusters and associations. The electronic Table1 (Table1.dat) is an
extended version of Table 1 in the journal paper, now including the
full covariances of the space velocity components as well as the space
motion in spherical coordinates. Table 2 gives the astrometric radial
velocities and kinematically improved parallaxes for the individual
stars. The electronic Table 2 is an extended version of Table 2 in the
journal paper, now including all clusters and associations studied;
results using data from both the Hipparcos and Tycho-2catalogues, as
well as the standard errors for all deduced quantities. The electronic
Table 2 is divided into 10 sub-tables (table1a.dat through table2j.dat),
one for each cluster or association. (11 data files).
---------------------------------------------------------
Title: The Velocity Dispersion of the Hyades as a Function of Mass
and Radius
Authors: Madsen, S.; Lindegren, L.; Dravins, D.
2001ASPC..228..506M Altcode: 2001dscm.conf..506M
No abstract at ADS
---------------------------------------------------------
Title: Quantum-Optical Signatures of Stimulated Emission
Authors: Dravins, D.
2001ASPC..242..339D Altcode: 2001ecom.conf..339D
No abstract at ADS
---------------------------------------------------------
Title: Division IV: Stars
Authors: Barbuy, Beatriz; Cram, L.; Dravins, D.; Evans, T. L.; Mathys,
G.; Scarfe, C.; VandenBerg, D.
2001IAUTB..24..157B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Lineshifts as Signatures of Stellar Surface Convection
(CD-ROM Directory: contribs/dravins)
Authors: Dravins, D.
2001ASPC..223..778D Altcode: 2001csss...11..778D
No abstract at ADS
---------------------------------------------------------
Title: Avalanche diodes as photon-counting detectors in astronomical
photometry
Authors: Dravins, Dainis; Faria, Daniel; Nilsson, Bo
2000SPIE.4008..298D Altcode:
Photon-counting silicon avalanche photo-diodes (APDs) offer very
high quantum efficiency, and might eventually replace photocathode
detectors in high-speed photometry of astronomical objects. Laboratory
studies have been performed on both passively and actively quenched
APDs. Peculiarities of APDs include that the dark signal may
exhibit bistability, with the count rate jumping between discrete
levels. Following any photon detection, the detector itself emits some
light, which might be confusing under certain conditions. Deadtimes and
after pulsing properties appear favorable, but the small physical size
of APDs causes challenges in optically matching them to the entrance
pupils of large telescopes.
---------------------------------------------------------
Title: Astrometric radial velocities. II. Maximum-likelihood
estimation of radial velocities in moving clusters
Authors: Lindegren, Lennart; Madsen, Søren; Dravins, Dainis
2000A&A...356.1119L Altcode:
Accurate proper motions and trigonometric parallaxes of stars in
nearby open clusters or associations permit to determine their space
motions relative to the Sun, without using spectroscopy for their
radial-velocity component. This assumes that the member stars share
the same mean velocity vector, apart from a (small) random velocity
dispersion. We present a maximum-likelihood formulation of this problem
and derive an algorithm for estimating the space velocity and internal
velocity dispersion of a cluster using astrometric data only. As
a by-product, kinematically improved parallaxes and distances are
obtained for the individual cluster stars. The accuracy of the method,
its robustness, and its sensitivity to internal velocity fields, are
studied through Monte Carlo simulations, using the Hyades as a test
case. From Hipparcos data we derive the centroid velocity and internal
velocity dispersion of the Hyades cluster. The astrometric radial
velocities are obtained with a standard error of 0.47 km s<SUP>-1</SUP>
for the cluster centroid, increasing to about 0.68 km s<SUP>-1</SUP>
for the individual stars due to their peculiar velocities. If known
binaries are removed, this improves to 0.60 km s<SUP>-1</SUP>. Based
(in part) on observations by the ESA Hipparcos satellite
---------------------------------------------------------
Title: Magnetic deformation of the white dwarf surface structure
Authors: Fendt, C.; Dravins, D.
2000AN....321..193F Altcode: 2000astro.ph..7387F
The influence of strong, large-scale magnetic fields on the
structure and temperature distribution in white dwarf atmospheres is
investigated. Magnetic fields may provide an additional component
of pressure support, thus possibly inflating the atmosphere
compared to the non-magnetic case. Since the magnetic forces are
not isotropic, atmospheric properties may significantly deviate from
spherical symmetry. In this paper the magnetohydrostatic equilibrium
is calculated numerically in the radial direction for either for
small deviations from different assumptions for the poloidal current
distribution. We generally find indication that the scale height of the
magnetic white dwarf atmosphere enlarges with magnetic field strength
and/or poloidal current strength. This is in qualitative agreement
with recent spectropolarimetric observations of Grw+10<SUP>o</SUP>
-8247. Quantitatively, we find for e.g. a mean surface poloidal
field strength of 100 MG and a toroidal field strength of 2-10 MG
an increase of scale height by a factor of 10. This is indicating
that already a small deviation from the initial force-free dipolar
magnetic field may lead to observable effects. We further propose
the method of finite elements for the solution of the two-dimensional
magnetohydrostatic equilibrium including radiation transport in the
diffusive approximation. We present and discuss preliminary solutions,
again indicating on an expansion of the magnetized atmosphere.
---------------------------------------------------------
Title: Main sequences of nearby open clusters and OB associations
from kinematic modelling of Hipparcos data
Authors: Madsen, S.; Lindegren, L.; Dravins, D.
2000ASPC..198..137M Altcode: 2000scac.conf..137M
No abstract at ADS
---------------------------------------------------------
Title: Commission 12: Solar Radiation and Structure (Radiation et
Structure Solaires)
Authors: Foukal, Peter; Solanki, Sami; Mariska, J.; Baliunas, S.;
Dravins, D.; Duvall, T.; Fang, C.; Gaizauskas, V.; Heinzel, P.;
Kononovich, E.; Koutchmy, S.; Melrose, D.; Stix, M.; Suematsu, Y.;
Deubner, F.
2000IAUTA..24...73F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres: (Theorie des
Atmospheres Stellaires)
Authors: Pallavicini, R.; Dravins, D.; Barbuy, B.; Cram, L.; Hubeny,
I.; Owocki, S.; Saio, H.; Sasselov, D.; Spite, M.; Stepien, K.;
Wehrse, R.
2000IAUTA..24..219P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Beyond imaging, spectroscopy and interferometry: Quantum
optics at the largest telescopes
Authors: Dravins, D.
2000ESOC...57...36D Altcode: 2000elt..conf...36D
No abstract at ADS
---------------------------------------------------------
Title: Astrometric radial velocities. I. Non-spectroscopic methods
for measuring stellar radial velocity
Authors: Dravins, Dainis; Lindegren, Lennart; Madsen, Søren
1999A&A...348.1040D Altcode: 1999astro.ph..7145D
High-accuracy astrometry permits the determination of not only stellar
tangential motion, but also the component along the line-of-sight. Such
non-spectroscopic (i.e. astrometric) radial velocities are independent
of stellar atmospheric dynamics, spectral complexity and variability,
as well as of gravitational redshift. Three methods are analysed: (1)
changing annual parallax, (2) changing proper motion and (3) changing
angular extent of a moving group of stars. All three have significant
potential in planned astrometric projects. Current accuracies are still
inadequate for the first method, while the second is marginally feasible
and is here applied to 16 stars. The third method reaches high accuracy
(<1 km s(-1) ) already with present data, although for some clusters
an accuracy limit is set by uncertainties in the cluster expansion
rate. Based (in part) on observations by the ESA Hipparcos satellite
---------------------------------------------------------
Title: Exactly What Is Stellar 'Radial Velocity'?
Authors: Lindegren, L.; Dravins, D.; Madsen, S.
1999ASPC..185...73L Altcode: 1999IAUCo.170...73L; 1999psrv.conf...73L
Accuracy levels of metres per second require the fundamental
concept of 'radial velocity' to be examined, in particular due to
relativistic velocity effects, and spectroscopic measurements made
inside gravitational fields. Naively, 'radial velocity' equals the
line-of-sight component of the stellar velocity vector, measured by
the Doppler shifts of stellar spectral lines. Although many physical
effects in stellar atmospheres contribute to the line shifts, those
could in principle be corrected for, leaving the 'true' (centre-of-mass)
velocity. However, also this concept becomes ambiguous at accuracy
levels around 10-100 m/s. Radial velocity is the change in distance
with respect to 'time'. But is this the time of light emission (at
the star) or light reception (at the observer)? The former seems
natural if radial velocity is considered a 'property' of the star,
while the latter is more natural for the observer. The difference is
of second order in velocity (v*v/c), exceeding 100 m/s for v >
173 km/s. Similar differences exist between the classical and the
relativistic Doppler formulae, and depend on how the transverse
Doppler effect is treated. Thus, the determination of the radial
velocity component cannot be separated from the determination of the
transverse one, requiring knowledge also of the stellar proper motion,
and distance. Gravitational redshift caused by the Sun diminishes
with distance as 1/r. At the solar surface (r = R<SUB>o</SUB>),
it is 636 m/s, diminishing to 3 m/s at the Earth's distance (215
R<SUB>o</SUB>). Thus, in principle, all stars will have such a blueshift
component, if measured near the Earth. A general-relativistic treatment
introduces additional complications, e.g. that the numerical velocities
depend on the chosen metric. Also, variable relativistic delay along
the light path would introduce line shifts, e.g. during microlensing
events. Among the effects influencing the measurement of accurate line
shifts, only local ones can be reliably calculated. These depend on
the motion and gravitational potential of the observer relative to
the desired reference frame, usually the solar system barycentre. We
argue that the barycentric fractional wavelength shift z is therefore
the proper observational quantity to be derived from spectroscopic
measurements. However, this barycentric shift cannot be uniquely
interpreted as a radial motion of the object. If velocity units are
desired, this shift can be expressed as cz, analogous to the case
in cosmology.
---------------------------------------------------------
Title: Radial Velocities without Spectroscopy
Authors: Madsen, S.; Lindegren, L.; Dravins, D.
1999ASPC..185...77M Altcode: 1999IAUCo.170...77M; 1999psrv.conf...77M
Accuracies in space astrometry now permit accurate determination of
stellar radial velocity without using spectroscopy or invoking the
Doppler principle. Already Hipparcos data permit accuracies of 100 m/s
in some cases, while future space astrometry missions will enable such
determinations for a broad range of stars. Fundamental radial-velocity
standards have hitherto been limited to solar-system objects, in
particular asteroids, whose space motions can be derived with very
high accuracy without the use of spectroscopic data. Astrometric
techniques are now extending the realm of such geometrically determined
radial velocities to many nearby stars. Among astrometric measures
for radial-velocity determination, the most direct is the secular
change in trigonometric parallax due to the radial displacement
of a star. Although this requires extremely accurate measurements
over years or decades, it should become feasible with planned space
missions. For Barnard's star (parallax 549 mas, V_<SUB>r</SUB> = -110
km/s), the expected parallax change is 34 microarcsec/year. Assuming
that a star moves uniformly through space, its velocity can also be
derived from the secular change in its proper motion (which varies
due to the observer). For astrometric missions now being planned, this
method should yield space velocities to better than 100 m/s for several
nearby high-velocity stars. A third astrometric method that already
has been applied using data from the Hipparcos mission, concerns the
secular change of the angular extent of moving star clusters. Since all
cluster stars share the same (average) velocity vector, the cluster's
apparent size changes as it moves in the radial direction. This relative
change (revealed by the proper-motion vectors towards the cluster apex)
corresponds to the relative change in distance. Since the individual
stellar distances are known from parallaxes, their radial velocities
follow. Applying this moving-cluster method to Hipparcos data, radial
velocities have now been derived for many stars in the Hyades and in
the Ursa Major clusters, reaching accuracies between 100-400 m/s. The
comparison of these values with precise spectroscopic measurements
reveals wavelength shifts not caused by stellar motion, as discussed
elsewhere in this colloquium.
---------------------------------------------------------
Title: Astrometric versus Spectroscopic Radial Velocities
Authors: Dravins, D.; Gullberg, D.; Lindegren, L.; Madsen, S.
1999ASPC..185...41D Altcode: 1999IAUCo.170...41D; 1999psrv.conf...41D
The radial velocity of a star, as deduced from wavelength shifts, does
not merely contain the true velocity of the stellar center of mass
but also components arising from dynamics in the star's atmosphere,
gravitational redshifts, and other effects. For the Sun, the segregation
of such effects has been possible because the relative Sun-Earth motion
is accurately known from planetary system dynamics, and does not have to
be deduced from asymmetric and shifted line profiles. For other stars,
accurate determinations of their true radial motion have only recently
become feasible with space astrometry. Data from Hipparcos permit
accurate such determinations for stars in nearby moving clusters such as
Ursa Major and the Hyades (Dravins et al., in Proc. Hipparcos - Venice
'97, ESA SP-402, p.733, 1997). When a star cluster (whose stars share
the same velocity vector) moves in the radial direction, its angular
size changes, as measured by stellar proper-motion vectors. This
rate of change equals the time derivative of the [known] distance,
i.e. the radial velocity. Future astrometric missions will extend
astrometric radial-velocity determinations also to individual field
stars with measurable changes in parallax and proper motion. For these
stars with astrometric radial-velocity determinations, a parallel
spectroscopic program has recently been completed at Haute-Provence
Observatory, using its ELODIE radial-velocity spectrometer. Almost
100 program stars of many different spectral types were observed
under very good signal-to-noise conditions. Work is in progress to
compare the spectroscopic radial velocities with the astrometric
values, and to search for systematic line shift differences between
groups of different spectral lines (with respect to line-strength,
excitation potential, or wavelength region). The overall stability of
ELODIE spectra reaches 10 m/s; the expected spectroscopic precision
for groups of 100 selected lines in any one star is about 50 m/s;
the accuracy in astrometric radial velocity reaches 200 m/s, while
hydrodynamic models of stellar atmospheres predict differences
on the order of 1 km/s in convective line shifts between different
stars. Gravitational redshifts are of comparable magnitude. This program
thus aims at identifying signatures of stellar surface structure from
line shift patterns, at finding differences in gravitational redshift
between different spectral types, and at improving the absolute
calibration of velocity values for stars of different rotational
velocity and spectral complexity. The program includes not only
Hyades and Ursa Major stars, but also IAU radial-velocity standards,
metal-deficient stars, and others. For a further discussion, see:
<A HREF="http://www.astro.lu.se/dainis/HTML/ASTROMET.html">
Discussion </A>
---------------------------------------------------------
Title: Stellar Surface Convection, Line Asymmetries, and Wavelength
Shifts
Authors: Dravins, D.
1999ASPC..185..268D Altcode: 1999IAUCo.170..268D; 1999psrv.conf..268D
When observed under sufficient resolution, practically all stellar
spectral lines prove to be slightly asymmetric. Absorption lines in
cooler stars form in inhomogeneous atmospheres, affected by surface
convection (stellar granulation). Asymmetries and wavelength shifts
originate from correlated velocity and brightness patterns: rising (
= blueshifted) elements are hot (=bright), and convective blueshifts
result from a larger contribution of such blueshifted photons than
of redshifted ones from the sinking and cooler (=darker) gas. For
the Sun, the effect is around 300 m/s. High-excitation lines form
predominantly in the hottest elements and show a more pronounced
blueshift. The effects are predicted to be greater in F-type stars,
and in giants. In the presence of magnetic fields, convection is
disturbed and granules do not develop to equally large size or
velocity amplitude, resulting in smaller blueshifts (by perhaps 10%
or 30 m/s) during the years around activity maximum in the 11-year
solar cycle. Such activity-cycle induced lineshift variations must
of course be segregated from stellar velocity signals in searches for
exoplanets with comparable periods. While line asymmetries and shifts
may appear as a noise source in determining stellar motions, they are
an important observational signature for constraining three-dimensional
(magneto-) hydrodynamic models of stellar atmospheres. These are capable
of predicting not only line-widths and shapes, but also second-order
quantities such as asymmetries and shifts. A high measuring precision
reveals properties of the stellar surface structure also through the
temporal variability of stellar line wavelengths. On the visible solar
disk, there are on the order of 10**6 granules, each with a velocity
amplitude of some 2 km/s, evolving over some 10 min. In integrated
sunlight, this amplitude is reduced by a factor of about sqrt(10**6)
to perhaps 2 m/s. Stars with larger velocity amplitudes and/or fewer
granules will show correspondingly greater fluctuations, observable
already with current techniques. Until the present, wavelength-shift
observations have generally been for unresolved (i.e. spatially
averaged) stellar disks. A major future development will be the study
of wavelength variations across spatially resolved stars, e.g. the
center-to-limb changes along the equatorial and polar diameters, and
their spatially resolved time variability. Adaptive optics on very
large telescopes, long-baseline optical interferometry, and optical
aperture synthesis will soon open up new vistas of stellar atmospheric
physics through radial-velocity observations.
---------------------------------------------------------
Title: Atmospheric Intensity Scintillation of Stars (PASP, 110, 610
[1998]).
Authors: Dravins, Dainis; Lindegren, Lennart; Mezey, Eva; Young,
Andrew T.
1998PASP..110.1118D Altcode:
In the paper “Atmospheric Intensity Scintillation of
Stars. III. Effects for Different Telescope Apertures” by Dainis
Dravins, Lennart Lindegren, Eva Mezey, and Andrew T. Young (PASP, 110,
610 [1998]), there is a typographical error on page 625, column (2), 17
lines from bottom. The expression giving the frequencies for which the
previous equation (10) is valid has the superfluous characters “3D”
on its right-hand side, which thus should read only “1 Hz.” The error
was caused in proof stage from inconsistencies in e-mail sending and
receiving “standards.”
---------------------------------------------------------
Title: Atmospheric Intensity Scintillation of Stars. III. Effects
for Different Telescope Apertures
Authors: Dravins, Dainis; Lindegren, Lennart; Mezey, Eva; Young,
Andrew T.
1998PASP..110..610D Altcode:
Stellar intensity scintillation in the optical was extensively
studied at the astronomical observatory on La Palma (Canary
Islands). Atmospheric turbulence causes “flying shadows” on the
ground, and intensity fluctuations occur both because this pattern is
carried by winds and is intrinsically changing. Temporal statistics and
time changes were treated in Paper I, and the dependence on optical
wavelength in Paper II. This paper discusses the structure of these
flying shadows and analyzes the scintillation signals recorded in
telescopes of different size and with different (secondary-mirror)
obscurations. Using scintillation theory, a sequence of power spectra
measured for smaller apertures is extrapolated up to very large (8 m)
telescopes. Apodized apertures (with a gradual transmission falloff
near the edges) are experimentally tested and modeled for suppressing
the most rapid scintillation components. Double apertures determine
the speed and direction of the flying shadows. Challenging photometry
tasks (e.g., stellar microvariability) require methods for decreasing
the scintillation “noise.” The true source intensity I(lambda) may
be segregated from the scintillation component DeltaI(t,lambda,x,y)
in postdetection computation, using physical modeling of the temporal,
chromatic, and spatial properties of scintillation, rather than treating
it as mere “noise.” Such a scheme ideally requires multicolor
high-speed (<~10 ms) photometry on the flying shadows over the
spatially resolved (<~10 cm) telescope entrance pupil. Adaptive
correction in real time of the two-dimensional intensity excursions
across the telescope pupil also appears feasible, but would probably
not offer photometric precision. However, such “second-order”
adaptive optics, correcting not only the wavefront phase but also
scintillation effects, is required for other critical tasks such as the
direct imaging of extrasolar planets with large ground-based telescopes.
---------------------------------------------------------
Title: Beta Hydri (G2 IV): a revised age for the closest subgiant
Authors: Dravins, D.; Lindegren, L.; Vandenberg, D. A.
1998A&A...330.1077D Altcode:
The secular evolution of solar-type atmospheres may be studied through
comparisons of the current Sun with old solar-type stars of known
age. Among the few such stars in the solar Galactic neighborhood,
beta Hydri (G2 IV) stands out as a normal single star with an advanced
age. Previous age determinations ( =~ 9.5 Gy) were based on the old
ground-based parallax of 153 mas. The new Hipparcos value of 133.78+/-
0.51 mas implies an absolute magnitude M_V=3.43 +/- 0.01, 0.3 mag
brighter than previously believed. New evolutionary calculations produce
best-fit models with ages around 6.7 Gy. Although the Hipparcos data
thus lead to a significant reduction of its estimated age, beta Hyi
remains an old star. Based on observations made with the ESA Hipparcos
astrometry satellite
---------------------------------------------------------
Title: Astrometric Radial Velocities from HIPPARCOS
Authors: Dravins, D.; Lindegren, L.; Madsen, S.; Holmberg, J.
1998HiA....11..564D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic Radial Velocities: Photospheric Lineshifts
Calibrated by HIPPARCOS
Authors: Gullberg, D.; Dravins, D.
1998HiA....11..564G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Beta Hydri (G2 IV): A Revised Age for the Closest Subgiant
Authors: Dravins, D.; Lindegren, L.; Vandenberg, D. A.
1997ESASP.402..397D Altcode: 1997hipp.conf..397D
The secular evolution of solar-type atmospheres may be studied through
comparisons of the current Sun with old solar-type stars of known
age. Among the few such stars in the solar Galactic neighborhood,
beta Hydri (G2 IV) stands out as a normal single star with an advanced
age. Previous age determinations (~= 9.5 Gy) were based on the old
ground-based parallax of 153 mas. The new Hipparcos value of 133.78
+/- 0.51 mas implies an absolute magnitude M_V=3.43 +/- 0.01, 0.3 mag
brighter than previously believed. New evolutionary calculations produce
best-fit models with ages around 6.7 Gy. Although the Hipparcos data
thus lead to a significant reduction of its age, beta Hyi remains an
old star.
---------------------------------------------------------
Title: Astrometric Radial Velocities from HIPPARCOS
Authors: Dravins, D.; Lindegren, L.; Madsen, S.; Holmberg, J.
1997ESASP.402..733D Altcode: 1997hipp.conf..733D
Space astrometry now permits accurate determinations of stellar
radial motion, without using spectroscopy. Using Hipparcos data,
this is possible for stars in nearby moving clusters, where all stars
share nearly the same space velocity. A maximum-likelihood method
has been developed to yield kinematic cluster parameters (including
the internal velocity dispersion) purely from parallaxes and proper
motions. The deduced astrometric radial velocities of the Ursa Major
open cluster and the Hyades have inaccuracies of 0.3 and 0.4 km/s,
respectively, and the internal cluster velocity dispersions are
found to be 0.66 +/- 0.10 and 0.25 +/- 0.04 km/s (consistent with
random stellar motions). Remaining errors arise from uncertainties
in excluding binary stars. The errors get worse for the more distant
Coma Berenices cluster. The fitting of cluster parameters includes
all individual stellar distances. The constraint of a uniform average
cluster velocity markedly improves the parallax precisions (roughly by
a factor two), compared with Hipparcos data for individual stars. The
HR diagram for the Hyades now reveals a very narrow main sequence line
(not band), even suggesting some wiggles in it. Discrepancies between
astrometric and spectroscopic radial velocities reveal effects (other
than stellar motion) that affect wavelength positions of spectral
lines. Such are caused by stellar pulsation, surface convection,
and by gravitational redshifts. A parallel programme is obtaining and
analysing high-precision spectroscopic radial velocities for different
classes of spectral lines in these programme stars.
---------------------------------------------------------
Title: Atmospheric Intensity Scintillation of Stars. II. Dependence
on Optical Wavelength
Authors: Dravins, D.; Lindegren, L.; Mezey, E.; Young, A. T.
1997PASP..109..725D Altcode:
Atmospheric intensity scintillation of stars on milli- and microsecond
time scales was extensively measured at the astronomical observatory on
La Palma (Canary Island). Scintillation statistics and temporal changes
were discussed in Paper I, while this paper shows how scintillation
depends on optical wavelength. Such effects originate from the
changing refractive index of air, and from wavelength-dependent
diffraction in atmospheric inhomogeneities. The intensity variance
\sigma2/I increases for shorter wavelengths, at small zenith distances
approximately consistent with a theoretical \lambda $^{-7/6}$ slope,
but with a tendency for a somewhat weaker dependence. Scintillation
in the blue is more rapid than in the red. The increase with
wavelength of autocorrelation time scales (roughly proportional to
$sqrt{\lambda}$ is most pronounced in very small apertures, but was
measured up to \o 20 cm. Scintillation at different wavelengths
is not simultaneous: atmospheric chromatic dispersion stretches
the atmospherically induced 'flying shadows' into 'flying spectra'
on the ground. As the 'shadows' fly past the telescope aperture,
a time delay appears between fluctuations at different wavelengths
whenever the turbulence-carrying winds have components parallel to the
direction of dispersion. These effects increase with zenith distance
(reaching \approx 100 ms cross-correlation delay between blue and red
at Z = 60°), and also with increased wavelength difference. This time
delay between scintillation in different colors is a property of the
atmospheric flying shadows, and thus a property that remains unchanged
even in very large telescopes. However, the wavelength dependence of
scintillation amplitude and time scale is 'fully' developed only in
small telescope apertures (less than about 5 cm), the scales where
the 'flying shadows' on the Earth's surface become resolved. Although
these dependences rapidly vanish after averaging in larger apertures,
an understanding of chromatic effects may still be needed for the
most accurate photometric measurements. These will probably require
a sampling of the [stellar] signal with full spatial, temporal and
chromatic resolution to segregate the scintillation signatures from
those of astrophysical variability. (SECTION: Atmospheric Phenomena
and Seeing)
---------------------------------------------------------
Title: Atmospheric Intensity Scintillation of Stars, I. Statistical
Distributions and Temporal Properties
Authors: Dravins, Dainis; Lindegren, Lennart; Mezey, Eva; Young,
Andrew T.
1997PASP..109..173D Altcode:
Stellar intensity scintillation in the optical was extensively
studies at the astronomical observatory on La Palma (Canary
Islands). Photon-counting detectors and digital signal processors
recorded temporal auto-and cross-correlation functions, power spectra,
and probability distributions. This first paper of a series treats
the temporal properties of scintillation, ranging from microseconds
to seasons of year. Previous studies, and the mechanisms producing
scintillation are reviewed. Atmospheric turbulence causes 'flying
shadows' on the ground, and intensity fluctuations occur both because
this pattern is carried by winds, and is intrinsically changing. On
very short timescales, a break in the correlation functions around
300 mus may be a signature of an inner scale (approx. 3 mm in the
shadow pattern at windspeeds of ms -1). On millisecond timescales,
the autocorrelation decreases for smaller telescope apertures until
approx. 5 cm, when the 'flying shadows' become resolved. During
any night, timescales and amplitudes evolve on scales of tens of
minutes. In good summer conditions, the flying-shadow patterns are
sufficiently regular and long-lived to show anti-correlation dips
in autocorrelation functions, which in winter are smeared out by
apparent wind shear. Recordings of intensity variance together with
stellar speckle images suggest some correlation between good [angular]
seeing and large scintillation. Near zenith, the temporal statistics
(with up to 12:th order moments measured)is best fitted by a Beta
distribution of the second kind (F-distribution), although it is well
approximated by log-normal functions, evolving with time. (SECTION:
Atmospheric Phenomena and Seeing)
---------------------------------------------------------
Title: Astrometric Radial Velocities from HIPPARCOS
Authors: Dravins, D.; Lindegren, L.; Madsen, S.; Holmberg, J.
1997IAUJD..14E..33D Altcode:
Space astrometry now permits accurate determinations of stellar radial
motion, without using spectroscopy. Although the feasibility of deducing
astrometric radial velocities from geometric projection effects was
realized already by Schlesinger (1917), only with Hipparcos has it
become practical. Such a program has now been carried out for the
moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized
inaccuracies reach 500 m/s, or slightly better (Dravins et
al. 1997). Discrepancies between astrometric and spectroscopic radial
velocities reveal effects (other than stellar motion) that affect
wavelength positions of spectral lines. Such are caused by stellar
surface convection, and by gravitational redshifts. A parallel program
(Gullberg & Dravins 1997) is analyzing high-precision spectroscopic
radial velocities for different spectral lines in these stars, using
the ELODIE radial-velocity instrument at Haute-Provence.
---------------------------------------------------------
Title: Spectroscopic Radial Velocities: Photospheric Lineshifts
Calibrated by HIPPARCOS
Authors: Gullberg, D.; Dravins, D.
1997IAUJD..14E..32G Altcode:
Stellar wavelengths depend not only on the star's motion. Until
recently, accurate studies of shifts not caused by radial motion
were feasible only for the Sun. Solar lineshifts are interpreted as
gravitational redshift (636 m/s) and convective blueshifts (~400
m/s; caused by velocity-brightness correlations). In other stars,
such effects may be greater (Dravins & Nordlund 1990). Accurate
astrometric radial velocities are now available from Hipparcos
(Dravins et al. 1997a; 1997b), permitting studies of such shifts
also in some other stars. For such stars in the open clusters of
Hyades, Ursa Major and Coma Berenices, a spectroscopic program is
in progress, analyzing wavelength shifts in groups of lines with
different strengths, excitation potentials, etc., using the ELODIE
high-precision radial-velocity instrument (Baranne et al., 1996) at
Haute-Provence. Baranne, A. et al., 1996, A&AS 119, 373 Dravins,
D., Nordlund, AA., 1990, A&A 228, 203 Dravins, D., Lindegren, L.,
Madsen, S., Holmberg, J., 1997a, in ESA SP-402, Hipparcos Symposium,
Venice Dravins, D., Lindegren, L., Madsen, S., Holmberg, J., 1997b,
IAU General Assembly, Kyoto
---------------------------------------------------------
Title: Observed and computed spectral line profiles
Authors: Dravins, D.
1996IAUS..176..519D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Optical Observations on Milli-, Micro-, and Nanosecond
Timescales
Authors: Dravins, D.; Lindegren, L.; Mezey, E.
1995LNP...454..129D Altcode: 1995flfl.conf..129D
Instrumentation and observing methods are developed for optical
high-speed astrophysics, aiming at exploring milli-, micro-, and
nanosecond variability. Such rapid fluctuations can be expected from
instabilities in accretion flows, and in the fine structure of photon
emission. For the optical, we have constructed a dedicated instrument,
whose first version was tested on La Palma to study atmospheric
scintillation on very short timescales. A second version is now under
development, using photon-counting avalanche photodiodes as detectors.
---------------------------------------------------------
Title: Observational Astrophysics on Milli-, Micro-, and Nanosecond
Timescales
Authors: Dravins, D.; Lindegren, L.; Mezey, E.
1995svlt.conf..139D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic measurements of stellar rotation
Authors: Dravins, D.
1995HiA....10..403D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Astrophysics on its shortest timescales.
Authors: Dravins, D.
1994Msngr..78....9D Altcode:
The VLT will permit enormously more sensitive searches for high-speed
phenomena in astrophysics.
---------------------------------------------------------
Title: Optical astronomy on milli-, micro-, and nanosecond timescales
Authors: Dravins, Dainis; Hagerbo, Hans O.; Lindegren, Lennart; Mezey,
Eva; Nilsson, Bo
1994SPIE.2198..289D Altcode:
Instrumentation and observing methods are being developed for a program
in optical high-speed astrophysics, an exploratory project entering the
domains of milli-, micro-, and nanosecond variability. Current studies
include accretion flows around compact objects, stellar scintillation,
and astronomical quantum optics. To study such rapid phenomena is not
possible everywhere in the spectrum (e.g., X-ray studies are constrained
by the photon count rates feasible with current spacecraft). The ground-
based optical is a promising region, for which we have constructed a
dedicated instrument, QVANTOS ('Quantum-Optical Spectrometer'). It
was designed for real-time handling of large amounts of data, for
observing also faint sources, and with a time resolution that can be
extended to reveal quantum properties of light, such as the bunching
of photons in time. Its first version was used to study atmospheric
scintillation on timescales between 100 milli- and 100 nsec, utilizing
some 25 full nights at a telescope on La Palma (Canary Islands). An
understanding of the atmosphere is required to segregate astrophysical
variability from terrestial effects, and to find optimal observing
strategies. For very high time resolution, light curves are of little
use, and statistical functions of variability have to be measured. The
noise in such functions decreases dramatically with increased light
collecting power, making very large telescopes much more sensitive
for the study of rapid variability than ordinary-sized ones.
---------------------------------------------------------
Title: Instrumental effects in stellar spectroscopy
Authors: Dravins, D.
1994ASIC..436..269D Altcode: 1994iltm.conf..269D
No abstract at ADS
---------------------------------------------------------
Title: The Distant Future of Solar Activity: A Case Study of beta
Hydri. II. Chromospheric Activity and Variability
Authors: Dravins, D.; Linde, P.; Fredga, K.; Gahm, G. F.
1993ApJ...403..396D Altcode:
A detailed comparison of the present sun with the very old star Beta
Hyi (G2 IV) is presented in order to study the secular evolution
of solar-type chromospheres, with emphasis placed on chromospheric
features and their time variability. High-resolution Ca II H and
K profiles show the emission to be about half that for the sun, but
with the same sense of violet-red asymmetry. The emission's wavelength
width is slightly broader, consistent with the Wilson-Bappu relation
for this slightly more luminous star. Mg II h and k profiles also
exhibit an emission weaker than the sun, but with the opposite sense
of asymmetry, probably altered by absorption in a nearby interstellar
cloud. The emission variations are small and are characterized by
smooth and systematic change in the line profiles from year to year,
suggesting continuous changes in the chromospheric structure, rather
than the sudden emergence of growth of active regions.
---------------------------------------------------------
Title: Atmospheric Intensity Scintillation of Stars on Millisecond
and Microsecond Time Scales
Authors: Dravins, D.; Lindegren, L.; Mezey, E.
1993spct.conf..113D Altcode: 1993IAUCo.136..113D
No abstract at ADS
---------------------------------------------------------
Title: The Distant Future of Solar Activity: A Case Study of beta
Hydri. I. Stellar Evolution, Lithium Abundance, and Photospheric
Structure
Authors: Dravins, D.; Lindegren, L.; Nordlund, A.; Vandenberg, D. A.
1993ApJ...403..385D Altcode:
A detailed comparison of the current sun (G2 V) with the very old
solar-type star Beta Hyi (G2 IV) is presented in order to study the
postmain-sequence evolution of stellar activity and of nonthermal
processes in solar-type atmospheres. Special attention is given to
general stellar properties and the deeper atmosphere of Beta Hyi. A
critical review of data from various sources is presented, and the
age of Beta Hyi is determined from evolutionary models to 9.5 +/-
0.8 Gyr. The relatively high lithium abundance may be a signature of
the early subgiant stage, when lithium that once diffused to beneath
the main-sequence convection zone is dredged up to the surface as the
convection zone deepens. Numerical simulations of the 3D photospheric
hydrodynamics show typical granules to be significantly larger (a
factor of about 5) than solar ones.
---------------------------------------------------------
Title: The Distant Future of Solar Activity: A Case Study of beta
Hydri. III. Transition Region, Corona, and Stellar Wind
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Linsky, J. L.;
Monsignori-Fossi, B.; Simon, T.; Wallinder, F.
1993ApJ...403..412D Altcode:
The paper investigates the secular decay of solar-type activity
through a detailed comparison of the present sun with the very old
solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses
of successive atmospheric layers are presented, with emphasis of the
outermost parts. The FUV emission lines for the transition zone are
among the faintest so far seen in any solar-type star. The coronal soft
X-ray spectrum was measured through different filters on EXOSAT and
compared to simulated X-ray observations of the sun seen as a star. The
flux from Beta Hyi is weaker than that from the solar corona and has
a different spectrum. It is inferred that a thermally driven stellar
wind can no longer be supported, which removes the mechanism from
further rotational braking of the star through a magnetic stellar wind.
---------------------------------------------------------
Title: High Resolution Spectroscopy of Stellar Velocity Signatures
Authors: Dravins, D.
1992ESOC...40...55D Altcode: 1992hrsw.conf...55D
No abstract at ADS
---------------------------------------------------------
Title: The distant future of solar activity: a case study of beta
Hydri (abstract)
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, Å.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1992sccw.conf..105D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The rotationally broadened line profiles of Sirius.
Authors: Dravins, D.; Lindegren, L.; Torkelsson, U.
1990A&A...237..137D Altcode:
Photospheric Fe I and Fe II absorption line profiles in Sirius
are analyzed. The Fourier transforms of the line profiles reveal
several sidelobes consistent with line broadening from rigid stellar
rotation at V sin i = 15.3 + or - 0.3 km/s. The Fourier transforms
are fitted, leading to deduced parameters of line profiles and stellar
rotation. These profiles are remarkably similar to Gaussians with FWHM
at about 8 km/s and resemble synthetic line profiles computed from
hydrodynamic model atmospheres by Gigas (1989). The 'superposition' of
neighboring absorption lines occasionally produces spectral features
that are much narrower than the widths of individual rotationally
broadened profiles. The widths of such 'subrotational' features may
approach these of the 'intrinsic' line profiles, illustrating the need
for very high spectral resolution to fully resolve the spectra also
of rapidly rotating stars.
---------------------------------------------------------
Title: Stellar activity cycles
Authors: Dravins, D.
1990ESASP.310...61D Altcode: 1990eaia.conf...61D
No abstract at ADS
---------------------------------------------------------
Title: Enhancing IUE spectrophotometry: a case study of Beta Hydri
Authors: Linde, P.; Dravins, D.
1990ESASP.310..605L Altcode: 1990eaia.conf..605L
No abstract at ADS
---------------------------------------------------------
Title: The distant future of solar activity - A case study of
Beta Hydri
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, A.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1990ESASP.310..323D Altcode: 1990eaia.conf..323D
No abstract at ADS
---------------------------------------------------------
Title: The archival reprocessing of IUE data: I. An accurate
registration technique for distorted images
Authors: de La Pena, M. D.; Shaw, R. A.; Linde, P.; Dravins, D.
1990ESASP.310..617D Altcode: 1990eaia.conf..617D
No abstract at ADS
---------------------------------------------------------
Title: Stellar granulation. IV. Line formation in inhomogeneous
stellar photospheres.
Authors: Dravins, D.; Nordlund, A.
1990A&A...228..184D Altcode:
Synthetic images of stellar granulation and photospheric Fe line
profiles are computed in model atmospheres obtained from detailed
numerical simulations of stellar surface convection. Models
corresponding to Procyon (F5 IV-V), α Cen A (G2V), β Hyi (G2IV),
and β Cen B (K1V) are studied (5200 ≤T<SUB>eff</SUB>≤6600 K). The
broadening, wavelength shift and asymmetry of spatially and temporally
resolved line profiles follows from radiative transfer in explicitly
computed three- dimensional and time-variable velocity fields, and
no adjustable - fitting parameters (such as e. g. "turbulence") are
used. Synthetic white-light and monochromatic images illustrate the
intensity contrast on stellar surfaces, its center-to-limb variation
and the morphology of line formation. Spatially resolved and spatially
averaged profiles illustrate line broadening through the Doppler
effect in photospheric velocity fields. An increase in the velocity
spread of spatially resolved lines near the stellar limbs reflects the
larger amplitudes of horizontal velocities in line-forming layers. Time
variability of spatially averaged line profiles and of their continuum
flux levels reflects time evolution of convective patterns larger than
individual granules. Spatially and temporally averaged data identify
how different shapes, asymmetries and shifts among lines of different
strength, excitation potential, ionization level, and wavelength region,
map the detailed physical properties throughout the photo sphere. The
properties of averaged profiles (in particular their asymmetries)
are not at all typical for individual points on the stellar surface,
but rather reflect the statistical distribution of photospheric
inhomogeneities. Only very strong lines have sufficiently extended
depths of formation for their asymmetry to be significantly influenced
also by the depth-variation of photospheric flow velocities. Effects of
the (non-LTE) radiative ionization of iron are not large but visible
as a weakening of blueshifted Fe I line components above especially
hot and bright granules. Convective blueshifts, originating from
correlations between local brightness and local Doppler shift, vary
between ∼=200 and 1000 ms<SUP>-1</SUP> at disk center in different
stars. Since such correlations change throughout the atmosphere, already
small differences in line formation conditions for lines of different
strength or excitation potential may result in different asymmetries
and wavelength shifts. For example, the lower surface gravity on the
solar near-twin α Cen A permits larger velocity amplitudes in the
high photosphere, causing noticeable differences to the Sun in the
asymmetries of its stronger photospheric lines.
---------------------------------------------------------
Title: Stellar granulation. V. Synthetic spectral lines in
disk-integrated starlight.
Authors: Dravins, D.; Nordlund, A.
1990A&A...228..203D Altcode:
Numerical simulations of stellar photo spheric structure have provided
line profiles at different positions across stellar disks. Using
these data, synthetic Fe line profiles in disk-integrated flux are
computed (including their asymmetries and wavelength shifts) for
models corresponding to Procyon (F 5 IV-V), α Cen A (G2V), β Hyi
(G2IV) and α Cen B (K1V). The line profiles are computed without
any adjustable physical parameters besides that of stellar rotation,
and the model atmospheres contain no classical parameters such as
"mixing-length" nor "turbulence". Since line strength, width, asymmetry,
rotational broadening, and limb darkening change with disk position,
the disk-integrated profiles reflect these properties in a complex
manner. This intercoupling might allow determinations of not only
stellar rotation, but also line profile variations across stellar disks,
using observations of similar stars with different rotation. Grids of
"observed" synthetic line profiles and bisectors illustrate effects
of finite spectral resolution. Comparisons with observations show good
agreement, and the stellar rotation can be independently determined from
the symmetric line broadening, and from the bisector patterns. For the
well observed stars Procyon and α Cen A, we estimate V sin i≃2.9
and 1.8 km s<SUP>-1</SUP>, respectively. For the solar near-twin α
Cen A, the profile and bisector fits are almost perfect, and permit
the identification of subtle differences against the Sun, apparently
reflecting changes in solar-type granulation during some billion years
of stellar evolution. The bisector fit for Procyon is excellent, but
some absorption is missing in the flanks of the intensity profiles
outside about ±5 km s<SUP>-1</SUP>. This, and a similar effect in the
subgiant β Hyi, is believed to be an artifact of the hydrodynamically
anelastic atmospheric model, which excludes sound waves and absorption
by features moving at near-sonic speeds. Different stars have different
line asymmetries, and in each star there is a systematic dependence
on line-strength. The excitation-potential and wavelength-region
dependences are smaller. The convective blueshift of spectral lines
ranges between ≃200 km s<SUP>-1</SUP> in K dwarfs to ≃1000 m
s<SUP>-1</SUP> in F stars. Such effects may limit the accuracies
possible in spectroscopic determinations of stellar radial velocities.
---------------------------------------------------------
Title: Stellar granulation. VI. Four-component models and
non-solar-type stars.
Authors: Dravins, Dainis
1990A&A...228..218D Altcode:
A series of relatively simple empirical models of inhomogeneous stellar
surfaces that allow granulation properties to be estimated also in
stars for which detailed hydrodynamic models cannot yet be computed
(e.g., the stars of spectral types A,F,G and K, reproducing observed
line asymmetries) are presented. In these models, the stellar surface
is divided into four components of different brightness and velocity,
and the integrated stellar line profile is obtained as a summation
of profiles from different components. By matching the synthetic and
observed bisector patterns, estimates of the velocity and brightness
amplitudes of stellar granulation can be obtained without a major
computational effort.
---------------------------------------------------------
Title: Stellar granulation. III. Hydrodynamic model atmospheres.
Authors: Nordlund, A.; Dravins, D.
1990A&A...228..155N Altcode:
Detailed models for the three-dimensional, time-dependent and
radiation-coupled hydrodynamics of solar granular convection have been
adapted to stellar conditions, and extensive numerical simulations have
been carried out to model four different stars in the vicinity of the
sun in the H-R diagram. The results from the simulations, showing the
three-dimensional structure and time evolution of temperature, velocity,
and pressure features in stellar photospheres, are presented. They are
then used as sets of temporally and spatially varying model atmospheres
in which radiative transfer computations are made of the continuum and
line radiation leaving the stars. Synthetic images show the optical
appearance of stellar surface structure at different positions across
stellar disks. Synthetic spectral line profiles are computed for
different locations and times, and the buildup of average line profiles
is examined for lines of different strength, excitation potential,
ionization level, and wavelength region. The average line profiles
are then used as an input to synthesize the disk-integrated flux of
photospheric Fe lines for stars of different rotational velocities
in order to predict observable spectral line shapes, asymmetries,
and wavelength shifts.
---------------------------------------------------------
Title: Stellar Granulation
Authors: Dravins, Dainis
1990ASPC....9...27D Altcode: 1990csss....6...27D
Numerical simulations of the three-dimensional structure and time
evolution of stellar surface convection are now feasible. Using the
output from such simulations as sets of spatially and temporally
varying model atmospheres, synthetic images of the stellar surface
structure (granulation) as well as photospheric line profiles can
be computed, and compared to observations. Such models are free
from the classical ad hoc parameters of 'mixing-length', 'micro-' or
'macro-turbulence'. Challenges for the future include detailed modeling
of early-type, giant, and other nonsolar type stars. Signatures
of stellar granulation are primarily observed as asymmetries and
wavelength shifts in photospheric absorption lines. Observational
challenges include identifying such asymmetries and shifts throughout
the HR-diagram, monitoring lineshift variations during stellar activity
cycles, and ultimately achieving spectroscopy across spatially resolved
stellar disks.
---------------------------------------------------------
Title: Observing, Modeling, and Understanding Stellar Granulation
Authors: Dravins, D.
1990IAUS..138..397D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The rotationally broadened line profiles of Sirius.
Authors: Dravins, D.; Lindegren, L.; Torkelsson, U.
1990apsu.conf...19D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Enhancing IUE spectrophotometry: a case study of Beta Hydri.
Authors: Linde, P.; Dravins, D.
1990apsu.conf...45L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The distant future of solar activity - a case study of
Beta Hydri.
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, Å.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1990apsu.conf...17D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Enhancing IUE spectrophotometry: a case study of Beta Hydri.
Authors: Linde, P.; Dravins, D.
1990nba..meet..181L Altcode: 1990taco.conf..181L
A technique for improved processing of data from the IUE satellite has
been developed. A correlation scheme is used to directly measure the
geometric displacement of the raw image, which enables the necessary
geometric transformation to be carried out with subpixel accuracy. The
resulting improvement in photometric calibration allows the subsequent
data extraction to give spectra with significantly lower noise than with
standard reduction methods. In an on-going search for chromospheric
variability in the solar-type star β Hydri, nearly 100 IUE exposures
have been reduced with the new method.
---------------------------------------------------------
Title: Atmospheric intensity scintillation of stars on milli- and
microsecond time scales.
Authors: Dravins, D.; Lindegren, L.; Mezey, E.
1990apsu.conf...18D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar granulation.
Authors: Dravins, Dainis
1990MmSAI..61..513D Altcode:
The spectroscopic features that can be interpreted as signatures
of stellar granulation are described. Special attention is given to
theoretical models of stellar granulation and synthetic photospheric
line profiles in solar-type stars. Problems involved in observing
subtle photospheric line asymmetries caused by stellar granulation
are illustrated, and indirect methods that can be used for imaging
stellar surfaces are discussed.
---------------------------------------------------------
Title: A Cross Correlation Technique for Improved IUE Image
Registration
Authors: de La Peña, M. D.; Shaw, R. A.; Linde, P.; Dravins, D.
1989BAAS...21.1073D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute flux calibration of the H and K lines of CA II :
chromospheric radiative losses in F and G-type stars.
Authors: Pasquini, L.; Pallavicini, R.; Dravins, D.
1989A&A...213..261P Altcode:
Ca II H and K spectra of 81 (mainly Southern) F and G stars are
analyzed using two different calibration methods. It is shown that, for
spectra of sufficiently high resolution, and for stars of relatively
low rotation rates, the calibrations of Linsky et al. (1979) and
of Pasquini et al. (1988) give essentially the same results. These
calibrations are used to derive absolute surface fluxes in the H and
K lines of Ca II for 64 stars. It is shown that several late-F and
early-G giants and supergiants have Ca II H and K fluxes in excess
of about 10 to the 6th erg/sq cm s, much larger than those typically
observed for normal giants of later spectral types.
---------------------------------------------------------
Title: Stellar Granulation: Modeling of Stellar Surfaces and
Photospheric Line Asymmetries
Authors: Dravins, D.
1989ASIC..263..493D Altcode: 1989ssg..conf..493D
No abstract at ADS
---------------------------------------------------------
Title: Challenges and Opportunities in Stellar Granulation
Observations
Authors: Dravins, D.
1989ASIC..263..153D Altcode: 1989ssg..conf..153D
No abstract at ADS
---------------------------------------------------------
Title: The Lunde observatory method for IUE spectral image processing
Authors: Linde, Peter; Dravins, Dainis
1988ESASP.281b.345L Altcode: 1988uvai....2..345L; 1988IUE88...2..345L
A method for IUE data processing and spectrum extraction is
described. The geometric transformation of the raw image is made
by identifying fixed patterns in the background outside spectral
orders. By correlating these with patterns in the flat-field
calibration exposures, geometric correction to within a fraction of
one pixel appears possible. The photometric calibration thus avoids
the pixel-to-pixel fixed-pattern noise ordinarily present, and the
subsequent spectrum extraction may give spectra with significantly
lower noise than ordinary reduction methods.
---------------------------------------------------------
Title: Stellar Granulation and Photospheric Line Asymmetries
Authors: Dravins, D.
1988IAUS..132..239D Altcode:
Numerical simulations of stellar surface convection in different stars
have now been carried out, and such three-dimensional and time-dependent
models predict the detailed stellar line profiles (including asymmetries
and wavelength shifts), thus enabling a direct confrontation between
observations and theory.
---------------------------------------------------------
Title: The Lund Observatory method for IUE spectral image processing.
Authors: Linde, P.; Dravins, D.
1988EIUEN..29....9L Altcode:
Since 1978 the authors have used the International Ultraviolet Explorer
(IUE) satellite to monitor the solar-type star β Hydri (G2 IV) in order
to detect long-term variations in chromospheric activity. The indicators
they use are the Mg II h and k emission lines near 280 nm. β Hydri is
estimated to be about twice as old as the sun. Current astrophysical
theory predicts that this should result in a lowered overall magnetic-
and chromospheric activity. This also implies that any variations of the
Mg II emission line intensities are expected to be small. Preliminary
data reductions, basically using the standard IUE software package,
have shown this to be correct.
---------------------------------------------------------
Title: The Lund Observatory method for IUE spectral image processing.
Authors: Linde, P.; Dravins, D.
1988IUEEN..29....1L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar Granulation
Authors: Dravins, D.
1987MitAG..70...64D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar granulation. I - The observability of stellar
photospheric convection
Authors: Dravins, Dainis
1987A&A...172..200D Altcode:
The application of astrophysical techniques, data analysis methods,
and theoretical tools to investigate the stellar equivalent of solar
granulation is considered. The aim is to study stellar photospheric
convection patterns, the ensuing atmospheric inhomogeneities, and
their effects on other observable parameters. Through experimental
observations of sunlight, the ESO coude echelle spectrometer (in the
special double-pass scanner mode) has been shown to be adequate for
this task. The spectrometer, its performance, and its mode of operation
are described. The selection of spectral lines is discussed for seven
program stars (Sirius, Canopus, Procyon, Beta Hydri, Alpha Cen A,
Alpha Cen B, and Arcturus). Examples are shown of observed stellar line
profiles and the asymmetry of these line profiles is described by the
computed line bisectors. The stellar bisector patterns for differently
strong lines turn out to constitute a characteristic signature for
each spectral type.
---------------------------------------------------------
Title: Stellar granulation. II. Stellar photospheric line asymmetries.
Authors: Dravins, D.
1987A&A...172..211D Altcode:
A search for a spectral signature of stellar granulation is made
in seven stars of spectral types A, F, G, and K. Very high quality
absorption line profiles have been obtained for Fe lines, using the
ESO coude echelle spectrometer double-pass photoelectric scanner
at a resolution λ/Δλ ≃ 200,000. Intrinsic line asymmetries are
seen in all stars, with marked differences among different spectral
types. The asymmetries are described by average bisectors for groups of
similar spectral lines. A typical bisector amplitude is ≃ 300 m/s,
a few percent of the line width. The characteristic solar granulation
signature of progressively changing bisector slopes with changing
line-strength is clearly indicated, in particular in the best-studied
stars αCen A and Procyon. A survey of the Procyon spectral atlas is
also made, and the asymmetries of 233 unblended Fe lines analyzed. This
larger sample agrees very well with the photoelectric measurements
and also shows additional trends, such as decreased bisector slope
for lines at longer wavelengths.
---------------------------------------------------------
Title: Photospheric Structure in Solar-Type Stars (Abstract)
Authors: Dravins, D.
1987LNP...292...72D Altcode: 1987ssp..conf...72D
No abstract at ADS
---------------------------------------------------------
Title: Stellar Granulation: Photospheric Line Asymmetries and
Hydrodynamic Model Atmospheres
Authors: Dravins, D.; Nordlund, A.
1986BAAS...18.1002D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Fe II line asymmetries and wavelength shifts.
Authors: Dravins, D.; Larsson, B.; Nordlund, A.
1986A&A...158...83D Altcode:
Convective motions of solar granulation are manifest in the spatially
unresolved spectrum as slight asymmetries and wavelength shifts of
photospheric spectral lines. In a previous paper (Dravins et al.,
1981) that dependence for Fe I lines with line strength, excitation
potential and wavelength region was analyzed. This paper extends that
work to Fe II lines, examining bisector shapes and wavelength shifts
of "unblended" Fe II lines both at disk center and in integrated
sunlight. Fe II lines form predominantly in the hotter and denser
regions of the deep photosphere, and these different line formation
conditions for Fe II manifest themselves in well-defined differences
from Fe I: the average Fe II bisectors show a more articulated curvature
and a larger convective blueshift. Synthetic spectral lines, computed
from a three-dimensional time-dependent hydrodynamic simulation of
solar photospheric convection confirm the observed behavior.
---------------------------------------------------------
Title: Stellar Activity Cycle in Beta Hydri
Authors: Dravins, D.
1986iue..prop.2585D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar activity cycles
Authors: Dravins, D.
1986HiA.....7..393D Altcode:
Stellar activity cycles in the corona, chromosphere, photosphere,
and deeper layers are examined. Observational problems related to the
study of magnetic flux variations during solar cycle, of changes in
the deeper layer and convective zone, and of ancient sun activity are
described. Chromospheric activity cycles in ordinary stars, irradiance
cycles in spotted stars, and flare frequency cycles in flare stars are
considered. The need for the analysis of magnetic cycles in stellar
activity and of cyclic activity in ordinary stars, and direct imaging
of stellar surfaces is discussed.
---------------------------------------------------------
Title: Stellat Activity Cycle in Beta Hydri
Authors: Dravins, D.
1986iue..prop.2574D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar Activity Cycle in Beta Hydri
Authors: Dravins, D.
1985iue..prop.2301D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar Lineshifts Induced by Photospheric Convection
Authors: Dravins, Dainis
1985srv..conf..311D Altcode: 1985IAUCo..88..311D; 1985srv..proc..311D; 1985LDP.....5..311D
Effects of stellar atmospheres on measured radial velocities are
examined. Surface convection ("stellar granulation") causes photospheric
line asymmetries and wavelength shifts of ≅ 100 - 500 m/s. Cyclic
changes in the convection patterns, such as observed during the solar
11-year cycle, may mimic radial velocity variations of perhaps 30
m/s. The study of stellar atmospheres would benefit from accurate
(< 100 m/s) differential radial velocity measurements among lines
of different parameters (strength, excitation potential, wavelength
region) in the same star.
---------------------------------------------------------
Title: High resolution spectroscopy of alpha Centauri. I. Lithium
depletion near one solar mass.
Authors: Soderblom, D. R.; Dravins, D.
1984A&A...140..427S Altcode:
The lithium (Li) abundance of Alpha-Centauri A was measured and an
upper limit was found for Li in Alpha Centauri B using the ESO Coude
Echelle Spectrometer. The measurements were made in the 670.7 nm
region in single-pass mode. The signal to noise ratio was not less
than about 300 and was limited by the properties of the recorder. For
Alpha-Centauri A the measured abundance was log N(Li) = 1.28, on a
scale where log N(H) = 12.00. The upper limit for Li abundance in Alpha
Centauri B was 0.7. It is shown that these abundances are consistent
with the probable evolutionary age of the stars, given a mass of 1.1
solar mass for Alpha Centauri A. The lithium depletion e-folding time
for that mass is therefore about 1.4 Gyr, compared to 1.1 Gyr at 1.0
solar mass. It is shown that the accuracy of estimates of the ages of
individual stars based on Li abundances is limited when the masses are
not precisely known. The age-related properties of solar-type stars
that depend on Li abundances are discussed.
---------------------------------------------------------
Title: Solar Fe II Line Asymmetries and Wavelength Shifts
Authors: Dravins, D.; Larsson, Birgitta
1984ssdp.conf..306D Altcode:
Asymmetries are studied for 32 apparently unblended Fe II photospheric
absorption lines in the solar disk center spectrum, and in the spectrum
of integrated sunlight. Average bisectors have been computed for groups
of similar lines, and the bisector variation is shown as function
of line-strength and of excitation potential. The same trends as
previously known from Fe I are present, although Fe II line shapes
show subtle differences.
---------------------------------------------------------
Title: Observing Stellar Granulation (Keynote)
Authors: Dravins, D.; Lind, J.
1984ssdp.conf..414D Altcode:
Granulation-induced photospheric spectrum line asymmetries can be
detected with high-resolution stellar spectrometers. Such stellar line
asymmetries are well respresented by bisectors which show changing
shapes for lines of different strengths. The solar near-twin α Cen A
shows a bisector pattern very similar to that of the Sun. F- and K-type
main-sequence stars have line asymmetries reminiscent of solar ones,
but very different from those of F- and K-type giants. Stellar bisector
patterns are presented from very high-resolution (λ/Δλ ≅ 200,000)
observations made with the ESO double-pass coudé echelle spectrometer,
and the observability of stellar bisectors also at moderate resolutions
(≅ 100,000) is shown.
---------------------------------------------------------
Title: Stellar granulation: evidence for stellar surface convection
from photospheric line asymmetries.
Authors: Dravins, D.; Lind, J.
1983PASP...95R.588D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar Granulation and the Structure of Stellar Surfaces
Authors: Dravins, D.
1983Msngr..32...15D Altcode:
Convection in Stars Stellar convection is a central but poorly
understood parameter In the construction of stellar models and
the determination of stellar ages, influencing both the energy
transport through the atmosPh.ere and the replenishment 01 nuclear
fuels in the core. The motlons in stellar convection zones probably
supply the energy for generating magnetic fields, heating stellar
chromospheres and coronae, driving stellar winds, and for many other
nonthermal phenomena. The inhomogeneous structure of velocity fields
on stellar surfaces complicates the accurate determination of stellar
radial velocities. Further, the temperature inhomogeneities on stellar
surfaces induce molecular abundance inhomogeneities and entangle the
accurate determination of chemical abundances.
---------------------------------------------------------
Title: High Resolution Spectroscopy - the Need for Larger Telescopes
Authors: Dravins, D.
1983ESOC...17..107D Altcode: 1983vlt..work..107D
No abstract at ADS
---------------------------------------------------------
Title: Solar Activity 5 Billion Years in the Future - A Case Study
of Beta Hydri
Authors: Dravins, D.; Linde, P.; Fredga, K.; Gahm, G.
1983BAAS...15..698D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrograph Instrumental Profiles - Dependence on Dispersion
Authors: Andersen, J.; Dravins, D.
1982PASP...94..390A Altcode:
Spectrograph instrumental profiles (including stray light far away
from the central peak) have been measured in blue and red light for
the three cameras in the coudé spectrograph of the 1.52-m telescope
at Observatoire de Haute-Provence. The different dispersions 0.7,
1.2, and 2.0 nm mm<SUP>-1</SUP> are obtained using the same ruled
diffraction grating. On a linear distance scale in the focal plane
the profiles are rather similar down to a 10<SUP>-3</SUP> intensity
level, but on a wavelength scale the profiles improve with increasing
dispersion, indicating the presence of a stray light component other
than that caused by diffraction by grating irregularities. The effects
of these instrumental profiles on observed spectra are illustrated by
numerical convolutions with the solar spectrum.
---------------------------------------------------------
Title: Convection in stellar atmospheres.
Authors: Dravins, D.; Lind, J.
1982ROLun..18..109D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements of Photon Statistics with Nanosecond Resolution
Authors: Dravins, D.
1982ASSL...92..229D Altcode: 1982IAUCo..67..229D; 1982ialo.coll..229D
No abstract at ADS
---------------------------------------------------------
Title: Photospheric spectrum line asymmetries and wavelength shifts
Authors: Dravins, D.
1982ARA&A..20...61D Altcode:
Results of studies on the asymmetries of spectral lines that have
hitherto been regarded as symmetric are discussed. The discrepancy
between solar and laboratory wavelengths is summarized, including
the limb effect. Solar line profiles have been accurately measured,
revealing intrinsic asymmetries in the lines. The causes of asymmetries
and shifts can be traced back to photospheric inhomogeneities, so that
high spatial resolution images and spectra of the solar granulation are
needed to understand their origins. Recent theoretical developments in
time-dependent and hydrodynamic solar and stellar model atmospheres
incorporating convection permit predictions and interpretations of
observed asymmetries and shifts. The asymmetries are also visible in
integrated sunlight and the corresponding phenomena have been seen
for a few bright stars.
---------------------------------------------------------
Title: CA II and K chromospheric emission in F-and G-type stars.
Authors: Dravins, D.
1981A&A....98..367D Altcode:
A survey of representative Ca II H and K line profiles (the most
pronounced chromospheric indicators observable from the ground) is
presented to illustrate the chromospheric emission of different types
of F and G stars. Of the 90 stars observed, a typical one is selected
for each spectral type, leaving a sample of 47. The spectral types are
taken from Jaschek (1978), except when superseded by Keenan and Pitts
(1980). For BS 3591 the Bright Star Catalog classification of F 8
III is retained, and data for the sun (G 2 V) refer to observations
of skylight, which is almost equal to integrated sunlight. General
trends in the changing appearance of chromospheric emission, as well
as the physical scatter of chromospheric activity levels among stars
of similar photospheric properties, are presented. It is shown that
the sun's level of chromospheric activity does not deviate much from
what is typical for field stars of a similar spectral class.
---------------------------------------------------------
Title: Nanosecond Resolution Observations: Quantum-Optical
Spectroscopy and Intensity Interferometry
Authors: Dravins, D.
1981siwn.conf..253D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Search for chromospheres in A-type stars.
Authors: Dravins, D.
1981A&A....96...64D Altcode:
A search for chromospheric emission in the Ca II H and K lines was
made for eight main-sequence A-stars in the young clusters C 0838-528
(IC 2391) and in the Hyades, where (at least later-type) stars have
generally enhanced chromospheric activity, making possible emission
easier to detect. No evidence for emission was found in these stars
and nor in Sirius (A 1 V).
---------------------------------------------------------
Title: Solar granulation - Influence of convection on spectral line
asymmetries and wavelength shifts
Authors: Dravins, D.; Lindegren, L.; Nordlund, A.
1981A&A....96..345D Altcode:
The observed shapes and shifts of 311 Fe I lines in the spectrum of
solar disk center and also of integrated sunlight are investigated. Line
shapes are described using bisectors, and the dependence of
these on line strength, excitation potential, and wavelength
region is analyzed. A theoretical model atmosphere incorporating
radiation-coupled, time-dependent hydrodymamics of solar convection
is used to compute synthetic photospheric spectral lines. These lines
exhibit asymmetries and wavelength shifts, and the observed bisector
behavior can be closely reproduced. The detailed properties of, for
example, convective motions and changing granulation constrast with
wavelength manifest themselves in the detailed bisector shapes. It is
confirmed that convection is the principal cause of solar line shifts,
and errors in other suggested explanations are pointed out. It is
concluded that the study of line shapes and shifts is a powerful tool
for the analysis of solar photospheric convection.
---------------------------------------------------------
Title: Possible applications of long-baseline intensity
interferometry.
Authors: Dravins, D.
1981siha.conf..295D Altcode:
Atmospheric phase distortions presently limit ground-based optical
phase interferometers to baselines of the order of 100 m. Intensity
interferometry, however, avoids both atmospheric and instrumental
phase distortion problems and permits the operation of optical
interferometers with baselines of more than 10 km between existing large
telescopes. Such baselines may make feasible the search for stellar
surface inhomogeneities, and although only very bright objects could be
observed, the angular resolution of about 0.000001 arcsec obtained would
permit the study of fine structure on the surfaces of nearby stars.
---------------------------------------------------------
Title: Photometric Properties of the IUE Flat-Field Calibration
Exposures
Authors: Dravins, D.; Linde, P.
1980idr..conf...85D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Methods for accurate photographic stellar spectrophotometry
using the solar spectrum as calibration
Authors: Lind, J.; Dravins, D.
1980A&A....90..151L Altcode:
Methods for photographic spectrophotometry using single-pass
spectrographs are developed with the purpose of obtaining stellar
spectra of sufficiently high quality to allow detailed spectral line
studies over extended wavelength regions. The spectrograph instrumental
profile and photographic development effects are investigated, and
the corresponding MTFs are determined by measuring the modulation
experienced by a calibration spectrum of skylight and moonlight
which is exposed side by side with the stellar spectrum on each
plate. Either of these calibration spectra is very similar to the
accurately known spectrum of integrated sunlight, whose modulation in
the observing/recording/measuring process is then determined.
---------------------------------------------------------
Title: Search for Spectral Line Polarization in the Solar Vacuum
Ultraviolet
Authors: Stenflo, J. O.; Dravins, D.; Wihlborg, N.; Bruns, A.;
Prokofev, V. K.; Zhitnik, I. A.; Biverot, H.; Stenmark, L.
1980SoPh...66...13S Altcode:
An instrument designed to record polarization in the region 120-150 nm
of the solar spectrum was launched on the satellite Intercosmos-16,
July 27, 1976. The aim was to search for resonance-line polarization
that is caused by coherent scattering. Oblique reflections at gold-
and aluminium-coated mirrors in the instrument were used to analyze
the polarization. The average polarization of the Lα solar limb was
found to be less than 1%. It is indicated how future improved VUV
polarization measurements may be a diagnostic tool for chromospheric
and coronal magnetic fields and for the three-dimensional geometry of
the emitting structures.
---------------------------------------------------------
Title: Observed Solar Spectral Line Asymmetries and Wavelength Shifts
due to Convection
Authors: Dravins, D.
1980LNP...114...51D Altcode: 1980IAUCo..51...51D; 1980sttu.coll...51D
No abstract at ADS
---------------------------------------------------------
Title: Comments on solar chromospheric activity compared to that
of other stars (These comments were intended to be presented during
the discussion but it was not possible for shortage of time.)
Authors: Dravins, D.
1980fsoo.conf..266D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The far-UV spectrum of the T Tauri star RU Lupi.
Authors: Gahm, G. F.; Fredga, K.; Liseau, R.; Dravins, D.
1979A&A....73L...4G Altcode:
The spectrum of the T Tauri star RU Lupi from 1150 to 3100 A has
been observed from the IUE satellite. It is rich in emission lines,
seen superimposed on a background continuum and traceable from
Ly-alpha to 3100 A. The region from 2000 to 3100 A is dominated by
metal line emission of the same nature as previously observed in
the optical region. The resonance lines of Mg II at 2795 and 2780 A
are exceedingly strong. In the region from 1150 to 2000 A the most
conspicuous features are the very strong emission lines of C IV,
Si IV and Si III, indicating that regions of very high temperature
(50,000 to 100,000 K) exist around the star.
---------------------------------------------------------
Title: Comments on solar chromospheric activity compared to that of
other stars.
Authors: Dravins, D.
1979MmArc.106..266D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Holography at the telescope - an interferometric method for
recording stellar spectra in thick photographic emulsions.
Authors: Lindegren, L.; Dravins, D.
1978A&A....67..241L Altcode:
Low-resolution spectra (resolving power of no more than about 100) are
recorded without any dispersive optics by direct focal-plane Lippmann
photography using thick holographic emulsions. These record the Fourier
transforms of the spectra, enabling spectrum reconstruction by reflected
light and analysis with a microspectrophotometer. Since the spectral
information is stored inside the emulsion and perpendicular to the
holographic plate surface, problems with overlapping spectrograms in
dense star fields are eliminated. Spectral resolution is set by emulsion
thickness and is independent of seeing and telescope guiding. The
holographic storage format appears suitable for automated spectral
searches, and the future feasibility of a holographic spectral
sky survey with Schmidt telescopes is suggested. Theoretical and
experimental work is presented, and practical and theoretical
limitations discussed.
---------------------------------------------------------
Title: High-dispersion astronomical spectroscopy with holographic
and rules diffraction gratings.
Authors: Dravins, D.
1978ApOpt..17..404D Altcode:
Holographic gratings cause much less stray light and spectral
degradation than classically ruled gratings. Their high groove
densities enable high dispersion in first diffraction order and a
high spectrograph throughput comparable to the best echelles. Their
lower reflective efficiency is compensated by the avoidance of
cross dispersers, enabling efficient high-fidelity spectroscopy with
single-pass spectrographs. Instrumental profiles of the ESO coude
spectrograph with large holographic and ruled gratings have been
studied in detail, and their effects on astronomical spectra are
discussed and compared to those of other instruments.
---------------------------------------------------------
Title: Holographic gratings for astronomical spectroscopy.
Authors: Dravins, D.
1978sss..meet...E5D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Diffraction Gratings - Holographic and Ruled
Authors: Dravins, D.
1978hrs..conf..221D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comments on solar chromospheric activity compared to that of
other stars
Authors: Dravins, D.
1978fsoo.conf..266D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Beryllium in Alpha Centauri A and constraints on beryllium
formation.
Authors: Dravins, D.; Hultqvist, L.
1977A&A....55..463D Altcode:
The equivalent width of the Be II 313.1-nm line in Alpha Cen A (G2 V)
is determined to be 1.25 times the solar value, leading to a Be/H
abundance ratio of 2.5 by 10 to the -11th power. The age of Alpha
Cen A is estimated to 8 billion years. This, together with observed
Be in the old stars Delta Eri (K0 IV) and Mu Her A (G5 IV), indicates
that beryllium existed in significant amounts relatively early in the
history of the Galaxy.
---------------------------------------------------------
Title: Observations of resonance-line polarization in the solar EUV.
Authors: Stenflo, J. O.; Dravins, D.; Öhman, Y.; Wihlborg, N.;
Bruns, A.; Prokof'ev, V. K.; Severnyj, A.; Severny, A.; Zhitnik,
I. A.; Biverot, H.; Stenmark, L.
1977ROLun..12..147S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric activity and atmospheric dynamics in Rho Puppis
and other Delta-Scuti stars.
Authors: Dravins, D.; Lind, J.; Sarg, K.
1977A&A....54..381D Altcode:
Summary. The Scuti pulsating variable Pup (P = 0d 14) is studied using
simultaneous spectrographic and photometric observations. A transient
Ca ii K chromospheric emission is seen at a phase near maximum outward
acceleration, shock waves are identified from radial velocity behavior
at different atmospheric levels, a secondary minimum is seen in radial
velocity and phase- shifts are detected between light-curves for
different wavelengths. The latter permit a stellar radius determination
through a phase-matching method. In addition, four other a Scuti
stars have been studied for K emission. Key words: variable stars -
stellar chromospheres shock waves - stellar radii uvby photometry
---------------------------------------------------------
Title: Spectrograph Instrumental Profiles--A Comparison between
Holographic and Ruled Gratings.
Authors: Dravins, D.
1976BAAS....8..517D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric Activity in f- and G-Stars
Authors: Dravins, D.
1976IAUS...71..469D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observation of convection in stellar atmospheres
Authors: Dravins, D.
1976pmas.conf..459D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: a Self-Scanned Silicon Diode Array for Astronomical Photometry
Authors: Dravins, D.
1975ASSL...54...97D Altcode: 1975ipta.proc...97D
No abstract at ADS
---------------------------------------------------------
Title: Physical limits to attainable accuracies in stellar radial
velocities.
Authors: Dravins, D.
1975A&A....43...45D Altcode:
It is shown that true stellar radial velocities cannot be obtained
from spectral lines with a precision of better than 0.5 km/sec unless
detailed knowledge of small-scale inhomogeneities in the line-formation
region is available. Two models are calculated which demonstrate
that convection-cell velocity patterns in particular cause line
asymmetries and average wavelength shifts that depend critically on
many unknown parameters and are likely to vary from star to star. It
is suggested that more accurate radial velocities might be obtained
from strong lines that form in layers above both the convection zone
and the region of convective overshoot. The Na I D(1) line at 5896 A
is recommended as the best line to use for this purpose, although it
may be contaminated by chromospheric emission as well as circumstellar
and interstellar absorption.
---------------------------------------------------------
Title: Height Dependence of Horizontal Velocities in the Photosphere
Authors: Dravins, D.
1975BAAS....7..363D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Horizontal Velocities in the Solar Photosphere
Authors: Dravins, D.
1975SoPh...40...53D Altcode:
Horizontal macroscopic velocities V<SUB>hor</SUB> in the photosphere
are studied. High-resolution spectrograms of quiet regions are
analyzed for center-limb variation of rms Doppler shifts. The data
are treated to assure that the observed velocities refer to constant
size volumes on the Sun (800 × × 3000 × 250 km), independent of
μ. Using known height variation of vertical velocities and calculated
line formation heights, the height dependence of «V<SUB>hor</SUB>»
is obtained. From a value around 450 m s<SUP>−1</SUP> it decreases
rapidly with increasing height. To study also small-scale velocities,
the time evolution of subarcsecond size elements in the photospheric
network (solar filigree) is studied on filtergrams. It is concluded
that they show proper motions implying «V<SUB>hor</SUB>» about 1
km s<SUP>−1</SUP>.
---------------------------------------------------------
Title: Instrument profiles in stellar spectrography.
Authors: Dravins, D.
1975ROLun...5..241D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements in stellar spectra: Lectures at the Lund
Observatory Nordic Summer School 1975
Authors: Ardeberg, A.; Larsson-Leander, G.; Lynga, G.; Dravins, D.;
Andersen, J.
1975STIN...7634081A Altcode:
Transcripts of five lecture series given during the 1975 summer
are given. These deal with the following subjects: measurement of
stellar continuous spectra, measurement of spectral lines, automatic
evaluation methods, instrument profiles in stellar spectrographs,
and modern spectrograph design.
---------------------------------------------------------
Title: Convection in the photosphere of Arcturus
Authors: Dravins, D.
1974A&A....36..143D Altcode:
Convective motions in stellar atmospheres involve hot gases that
rise, cool off and then sink back. High-excitation spectral lines are
preferentially formed in the hot, rising and thus locally blue-shifted
elements while low-excitation lines are preferentially formed in
the cooler, sinking and red-shifted elements. By comparing accurate
wavelengths for spectral lines in Arcturus with laboratory values, a
relation is found, such that high-excitation lines are systematically
blue-shifted relative to low-excitation lines. This relation is very
similar to the one previously known for the sun and is interpreted as
the existence of convection cells, similar to the solar granulation,
in the photosphere of Arcturus.
---------------------------------------------------------
Title: Magnetic Field and Electric Current Structure in the
Chromosphere
Authors: Dravins, D.
1974SoPh...37..323D Altcode:
Three dimensional vector magnetic field structure throughout the
chromosphere above an active region is deduced by combining high
resolution Hα filtergrams with a simultaneous digital magnetogram. An
analog model of the field is made with 400 metal wires representing
fieldlines which are assumed to outline the Hα structure. The
height extent of the field is determined from vertical field gradient
observations around sunspots, from observed fibril heights and from an
assumption that the sources of the field should be largely local. After
digitization the magnetic field H matrix is retrieved. Electric current
densities j are computed from j=curl H. The currents (typically 10 mA
m<SUP>−2</SUP>) flow in patterns not similar to observed features
and not parallel to magnetic fields. Lorentz forces are computed
from {ie0323-01}. The force structures correspond to observed
solar features and a series of observed dynamics may be expected:
downward motion in bipolar areas in lower chromosphere, an outflow
of the outer chromosphere into the corona with radially outward flow
above bipolar plage regions (where coronal streamers are observed)
and motions of arch filament systems. Observed current structure and
magnitude agree well with previous vector magnetograph observations
but disagree with theoretical current-free or force-free concepts. A
dynamic chromosphere with electromagnetic forces in action is thus
inferred from observations.
---------------------------------------------------------
Title: Evolution of Structures in the Bright Hα Network
Authors: Dravins, D.
1974IAUS...56..257D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Possible Solar Electrograph
Authors: Dravins, Dainis
1973ApL....13..243D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solen sedd i väteljus.
Authors: Dravins, D.
1973ATi.....6..100D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Fields, Electric Currents and Lorentz Forces in
the Chromosphere.
Authors: Dravins, D.
1972BAAS....4Q.309D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ballongastronomi.
Authors: Dravins, D.
1970ATi.....3...53D Altcode:
No abstract at ADS
