ALBERT

Description: In quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the origin of the thermal X-ray component may be either release of heat from the core of the neutron star, or continuing low-level accretion. In general, heat from the core should be stable on time-scales 〈10 4 yr, while continuing accretion may produce variations on a range of time-scales. While some quiescent neutron stars (e.g. Cen X-4, Aql X-1) have shown variations in their thermal components on a range of time-scales, several others, particularly those in globular clusters with no detectable non-thermal hard X-rays (fit with a power law), have shown no measurable variations. Here, we constrain the spectral variations of 12 low-mass X-ray binaries in three globular clusters over ~10 years. We find no evidence of variations in 10 cases, with limits on temperature variations below 11 per cent for the seven qLMXBs without power-law components, and limits on variations below 20 per cent for three other qLMXBs that do show non-thermal emission. However, in two qLMXBs showing power-law components in their spectra (NGC 6440 CX 1 and Terzan 5 CX 12) we find marginal evidence for a 10 per cent decline in temperature, suggesting the presence of continuing low-level accretion. This work adds to the evidence that the thermal X-ray component in quiescent neutron stars without power-law components can be explained by heat deposited in the core during outbursts. Finally, we also investigate the correlation between hydrogen column density ( N H ) and optical extinction ( A V ) using our sample and current models of interstellar X-ray absorption, finding N H (cm –2 ) = (2.81 ± 0.13)  x  10 21 A V .

Description: Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated gamma-ray emission. Galactic 'microquasars', which are binary systems consisting of a neutron star or stellar-mass black hole accreting gas from a companion star, also produce relativistic jets, generally together with radio flares. Apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar, with the consequence that we are as yet unsure about the mechanism of jet energization. Here we report four gamma-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 (an exceptional X-ray binary that sporadically produces radio jets). There is a clear pattern of temporal correlations between the gamma-ray flares and transitional spectral states of the radio-frequency and X-ray emission. Particle acceleration occurred a few days before radio-jet ejections for two of the four flares, meaning that the process of jet formation implies the production of very energetic particles. In Cygnus X-3, particle energies during the flares can be thousands of times higher than during quiescent states.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tavani, M -- Bulgarelli, A -- Piano, G -- Sabatini, S -- Striani, E -- Evangelista, Y -- Trois, A -- Pooley, G -- Trushkin, S -- Nizhelskij, N A -- McCollough, M -- Koljonen, K I I -- Pucella, G -- Giuliani, A -- Chen, A W -- Costa, E -- Vittorini, V -- Trifoglio, M -- Gianotti, F -- Argan, A -- Barbiellini, G -- Caraveo, P -- Cattaneo, P W -- Cocco, V -- Contessi, T -- D'Ammando, F -- Del Monte, E -- De Paris, G -- Di Cocco, G -- Di Persio, G -- Donnarumma, I -- Feroci, M -- Ferrari, A -- Fuschino, F -- Galli, M -- Labanti, C -- Lapshov, I -- Lazzarotto, F -- Lipari, P -- Longo, F -- Mattaini, E -- Marisaldi, M -- Mastropietro, M -- Mauri, A -- Mereghetti, S -- Morelli, E -- Morselli, A -- Pacciani, L -- Pellizzoni, A -- Perotti, F -- Picozza, P -- Pilia, M -- Prest, M -- Rapisarda, M -- Rappoldi, A -- Rossi, E -- Rubini, A -- Scalise, E -- Soffitta, P -- Vallazza, E -- Vercellone, S -- Zambra, A -- Zanello, D -- Pittori, C -- Verrecchia, F -- Giommi, P -- Colafrancesco, S -- Santolamazza, P -- Antonelli, A -- Salotti, L -- England -- Nature. 2009 Dec 3;462(7273):620-3. doi: 10.1038/nature08578. Epub 2009 Nov 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF-IASF Roma, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy. pi.agile@iasf-roma.inaf.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19935645" target="_blank"〉PubMed〈/a〉

Description: Active galactic nuclei, which are powered by long-term accretion onto central supermassive black holes, produce relativistic jets with lifetimes of at least one million years, and the observation of the birth of such a jet is therefore unlikely. Transient accretion onto a supermassive black hole, for example through the tidal disruption of a stray star, thus offers a rare opportunity to study the birth of a relativistic jet. On 25 March 2011, an unusual transient source (Swift J164449.3+573451) was found, potentially representing such an accretion event. Here we report observations spanning centimetre to millimetre wavelengths and covering the first month of evolution of a luminous radio transient associated with Swift J164449.3+573451. The radio transient coincides with the nucleus of an inactive galaxy. We conclude that we are seeing a newly formed relativistic outflow, launched by transient accretion onto a million-solar-mass black hole. A relativistic outflow is not predicted in this situation, but we show that the tidal disruption of a star naturally explains the observed high-energy properties and radio luminosity and the inferred rate of such events. The weaker beaming in the radio-frequency spectrum relative to gamma-rays or X-rays suggests that radio searches may uncover similar events out to redshifts of z approximately 6.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zauderer, B A -- Berger, E -- Soderberg, A M -- Loeb, A -- Narayan, R -- Frail, D A -- Petitpas, G R -- Brunthaler, A -- Chornock, R -- Carpenter, J M -- Pooley, G G -- Mooley, K -- Kulkarni, S R -- Margutti, R -- Fox, D B -- Nakar, E -- Patel, N A -- Volgenau, N H -- Culverhouse, T L -- Bietenholz, M F -- Rupen, M P -- Max-Moerbeck, W -- Readhead, A C S -- Richards, J -- Shepherd, M -- Storm, S -- Hull, C L H -- England -- Nature. 2011 Aug 24;476(7361):425-8. doi: 10.1038/nature10366.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. bzauderer@cfa.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21866155" target="_blank"〉PubMed〈/a〉

Description: Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Albert, J -- Aliu, E -- Anderhub, H -- Antoranz, P -- Armada, A -- Asensio, M -- Baixeras, C -- Barrio, J A -- Bartelt, M -- Bartko, H -- Bastieri, D -- Bavikadi, S R -- Bednarek, W -- Berger, K -- Bigongiari, C -- Biland, A -- Bisesi, E -- Bock, R K -- Bordas, P -- Bosch-Ramon, V -- Bretz, T -- Britvitch, I -- Camara, M -- Carmona, E -- Chilingarian, A -- Ciprini, S -- Coarasa, J A -- Commichau, S -- Contreras, J L -- Cortina, J -- Curtef, V -- Danielyan, V -- Dazzi, F -- De Angelis, A -- de Los Reyes, R -- De Lotto, B -- Domingo-Santamaria, E -- Dorner, D -- Doro, M -- Errando, M -- Fagiolini, M -- Ferenc, D -- Fernandez, E -- Firpo, R -- Flix, J -- Fonseca, M V -- Font, L -- Fuchs, M -- Galante, N -- Garczarczyk, M -- Gaug, M -- Giller, M -- Goebel, F -- Hakobyan, D -- Hayashida, M -- Hengstebeck, T -- Hohne, D -- Hose, J -- Hsu, C C -- Isar, P G -- Jacon, P -- Kalekin, O -- Kosyra, R -- Kranich, D -- Laatiaoui, M -- Laille, A -- Lenisa, T -- Liebing, P -- Lindfors, E -- Lombardi, S -- Longo, F -- Lopez, J -- Lopez, M -- Lorenz, E -- Lucarelli, F -- Majumdar, P -- Maneva, G -- Mannheim, K -- Mansutti, O -- Mariotti, M -- Martinez, M -- Mase, K -- Mazin, D -- Merck, C -- Meucci, M -- Meyer, M -- Miranda, J M -- Mirzoyan, R -- Mizobuchi, S -- Moralejo, A -- Nilsson, K -- Ona-Wilhelmi, E -- Orduna, R -- Otte, N -- Oya, I -- Paneque, D -- Paoletti, R -- Paredes, J M -- Pasanen, M -- Pascoli, D -- Pauss, F -- Pavel, N -- Pegna, R -- Persic, M -- Peruzzo, L -- Piccioli, A -- Poller, M -- Pooley, G -- Prandini, E -- Raymers, A -- Rhode, W -- Ribo, M -- Rico, J -- Riegel, B -- Rissi, M -- Robert, A -- Romero, G E -- Rugamer, S -- Saggion, A -- Sanchez, A -- Sartori, P -- Scalzotto, V -- Scapin, V -- Schmitt, R -- Schweizer, T -- Shayduk, M -- Shinozaki, K -- Shore, S N -- Sidro, N -- Sillanpaa, A -- Sobczynska, D -- Stamerra, A -- Stark, L S -- Takalo, L -- Temnikov, P -- Tescaro, D -- Teshima, M -- Tonello, N -- Torres, A -- Torres, D F -- Turini, N -- Vankov, H -- Vitale, V -- Wagner, R M -- Wibig, T -- Wittek, W -- Zanin, R -- Zapatero, J -- New York, N.Y. -- Science. 2006 Jun 23;312(5781):1771-3. Epub 2006 May 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universitat Wurzburg, D-97074 Wurzburg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16709745" target="_blank"〉PubMed〈/a〉

Description: Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fermi LAT Collaboration -- Abdo, A A -- Ackermann, M -- Ajello, M -- Axelsson, M -- Baldini, L -- Ballet, J -- Barbiellini, G -- Bastieri, D -- Baughman, B M -- Bechtol, K -- Bellazzini, R -- Berenji, B -- Blandford, R D -- Bloom, E D -- Bonamente, E -- Borgland, A W -- Brez, A -- Brigida, M -- Bruel, P -- Burnett, T H -- Buson, S -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Casandjian, J M -- Cecchi, C -- Celik, O -- Chaty, S -- Cheung, C C -- Chiang, J -- Ciprini, S -- Claus, R -- Cohen-Tanugi, J -- Cominsky, L R -- Conrad, J -- Corbel, S -- Corbet, R -- Dermer, C D -- de Palma, F -- Digel, S W -- do Couto e Silva, E -- Drell, P S -- Dubois, R -- Dubus, G -- Dumora, D -- Farnier, C -- Favuzzi, C -- Fegan, S J -- Focke, W B -- Fortin, P -- Frailis, M -- Fusco, P -- Gargano, F -- Gehrels, N -- Germani, S -- Giavitto, G -- Giebels, B -- Giglietto, N -- Giordano, F -- Glanzman, T -- Godfrey, G -- Grenier, I A -- Grondin, M-H -- Grove, J E -- Guillemot, L -- Guiriec, S -- Hanabata, Y -- Harding, A K -- Hayashida, M -- Hays, E -- Hill, A B -- Hjalmarsdotter, L -- Horan, D -- Hughes, R E -- Jackson, M S -- Johannesson, G -- Johnson, A S -- Johnson, T J -- Johnson, W N -- Kamae, T -- Katagiri, H -- Kawai, N -- Kerr, M -- Knodlseder, J -- Kocian, M L -- Koerding, E -- Kuss, M -- Lande, J -- Latronico, L -- Lemoine-Goumard, M -- Longo, F -- Loparco, F -- Lott, B -- Lovellette, M N -- Lubrano, P -- Madejski, G M -- Makeev, A -- Marchand, L -- Marelli, M -- Max-Moerbeck, W -- Mazziotta, M N -- McColl, N -- McEnery, J E -- Meurer, C -- Michelson, P F -- Migliari, S -- Mitthumsiri, W -- Mizuno, T -- Monte, C -- Monzani, M E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nolan, P L -- Norris, J P -- Nuss, E -- Ohsugi, T -- Omodei, N -- Ong, R A -- Ormes, J F -- Paneque, D -- Parent, D -- Pelassa, V -- Pepe, M -- Pesce-Rollins, M -- Piron, F -- Pooley, G -- Porter, T A -- Pottschmidt, K -- Raino, S -- Rando, R -- Ray, P S -- Razzano, M -- Rea, N -- Readhead, A -- Reimer, A -- Reimer, O -- Richards, J L -- Rochester, L S -- Rodriguez, J -- Rodriguez, A Y -- Romani, R W -- Ryde, F -- Sadrozinski, H F-W -- Sander, A -- Saz Parkinson, P M -- Sgro, C -- Siskind, E J -- Smith, D A -- Smith, P D -- Spinelli, P -- Starck, J-L -- Stevenson, M -- Strickman, M S -- Suson, D J -- Takahashi, H -- Tanaka, T -- Thayer, J B -- Thompson, D J -- Tibaldo, L -- Tomsick, J A -- Torres, D F -- Tosti, G -- Tramacere, A -- Uchiyama, Y -- Usher, T L -- Vasileiou, V -- Vilchez, N -- Vitale, V -- Waite, A P -- Wang, P -- Wilms, J -- Winer, B L -- Wood, K S -- Ylinen, T -- Ziegler, M -- New York, N.Y. -- Science. 2009 Dec 11;326(5959):1512-6. doi: 10.1126/science.1182174. Epub .〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19965378" target="_blank"〉PubMed〈/a〉