ALBERT

Description: We report on the identification of the new Galactic Centre (GC) transient Swift J174540.7–290015 as a likely low-mass X-ray binary located at only 16 arcsec from Sgr A * . This transient was detected on 2016 February 6, during the Swift GC monitoring, and it showed long-term spectral variations compatible with a hard- to soft-state transition. We observed the field with XMM–Newton on February 26 for 35 ks, detecting the source in the soft state, characterized by a low level of variability and a soft X-ray thermal spectrum with a high energy tail (detected by INTEGRAL up to ~50 keV), typical of either accreting neutron stars or black holes. We observed: (i) a high column density of neutral absorbing material, suggesting that Swift J174540.7–290015 is located near or beyond the GC and; (ii) a sub-Solar iron abundance, therefore we argue that iron is depleted into dust grains. The lack of detection of Fe K absorption lines, eclipses or dipping suggests that the accretion disc is observed at a low inclination angle. Radio (Very Large Array) observations did not detect any radio counterpart to Swift J174540.7–290015. No evidence for X-ray or radio periodicity is found. The location of the transient was observed also in the near-infrared (near-IR) with gamma-ray burst optical near-IR detector at MPG/European Southern Observatory La Silla 2.2 m telescope and VLT/ NaCo pre- and post-outburst. Within the Chandra error region, we find multiple objects that display no significant variations.

Description: We present the first very long baseline interferometry (VLBI) detections of Zeeman splitting in another galaxy. We used Arecibo Observatory, the Green Bank Telescope, and the Very Long Baseline Array to perform dual-polarization observations of OH maser lines in the merging galaxy Arp 220. We measured magnetic fields of ~1–5 mG associated with three roughly parsec-sized clouds in the nuclear regions of Arp 220. Our measured magnetic fields have comparable strengths and the same direction as features at the same velocity identified in previous Zeeman observations with Arecibo alone. The agreement between single dish and VLBI results provides critical validation of previous Zeeman splitting observations of OH megamasers that used a single large dish. The measured magnetic field strengths indicate that magnetic energy densities are comparable to gravitational energy in OH maser clouds. We also compare our total intensity results to previously published VLBI observations of OH megamasers in Arp 220. We find evidence for changes in both structure and amplitude of the OH maser lines that are most easily explained by variability intrinsic to the masing region, rather than variability produced by interstellar scintillation. Our results demonstrate the potential for using high-sensitivity VLBI to study magnetic fields on small spatial scales in extragalactic systems.

Description: We present the first very long baseline interferometry (VLBI) detections of Zeeman splitting in another galaxy. We used Arecibo Observatory, the Green Bank Telescope, and the Very Long Baseline Array to perform dual-polarization observations of OH maser lines in the merging galaxy Arp 220. We measured magnetic fields of ~1–5 mG associated with three roughly parsec-sized clouds in the nuclear regions of Arp 220. Our measured magnetic fields have comparable strengths and the same direction as features at the same velocity identified in previous Zeeman observations with Arecibo alone. The agreement between single dish and VLBI results provides critical validation of previous Zeeman splitting observations of OH megamasers that used a single large dish. The measured magnetic field strengths indicate that magnetic energy densities are comparable to gravitational energy in OH maser clouds. We also compare our total intensity results to previously published VLBI observations of OH megamasers in Arp 220. We find evidence for changes in both structure and amplitude of the OH maser lines that are most easily explained by variability intrinsic to the masing region, rather than variability produced by interstellar scintillation. Our results demonstrate the potential for using high-sensitivity VLBI to study magnetic fields on small spatial scales in extragalactic systems.

Description: The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation. Sagittarius A* (Sgr A*), the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black hole mass that is 4,000,000 times that of the Sun. A long-standing astronomical goal is to resolve structures in the innermost accretion flow surrounding Sgr A*, where strong gravitational fields will distort the appearance of radiation emitted near the black hole. Radio observations at wavelengths of 3.5 mm and 7 mm have detected intrinsic structure in Sgr A*, but the spatial resolution of observations at these wavelengths is limited by interstellar scattering. Here we report observations at a wavelength of 1.3 mm that set a size of 37(+16)(-10) microarcseconds on the intrinsic diameter of Sgr A*. This is less than the expected apparent size of the event horizon of the presumed black hole, suggesting that the bulk of Sgr A* emission may not be centred on the black hole, but arises in the surrounding accretion flow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doeleman, Sheperd S -- Weintroub, Jonathan -- Rogers, Alan E E -- Plambeck, Richard -- Freund, Robert -- Tilanus, Remo P J -- Friberg, Per -- Ziurys, Lucy M -- Moran, James M -- Corey, Brian -- Young, Ken H -- Smythe, Daniel L -- Titus, Michael -- Marrone, Daniel P -- Cappallo, Roger J -- Bock, Douglas C-J -- Bower, Geoffrey C -- Chamberlin, Richard -- Davis, Gary R -- Krichbaum, Thomas P -- Lamb, James -- Maness, Holly -- Niell, Arthur E -- Roy, Alan -- Strittmatter, Peter -- Werthimer, Daniel -- Whitney, Alan R -- Woody, David -- England -- Nature. 2008 Sep 4;455(7209):78-80. doi: 10.1038/nature07245.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Massachusetts Institute of Technology (MIT) Haystack Observatory, Off Route 40, Westford, Massachusetts 01886, USA. sdoeleman@haystack.mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18769434" target="_blank"〉PubMed〈/a〉

Description: Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fermi-LAT Collaboration -- Abdo, A A -- Ackermann, M -- Ajello, M -- Atwood, W B -- Baldini, L -- Ballet, J -- Barbiellini, G -- Bastieri, D -- Bechtol, K -- Bellazzini, R -- Berenji, B -- Blandford, R D -- Bloom, E D -- Bonamente, E -- Borgland, A W -- Bouvier, A -- Brandt, T J -- Bregeon, J -- Brez, A -- Brigida, M -- Bruel, P -- Buehler, R -- Burnett, T H -- Buson, S -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Carrigan, S -- Casandjian, J M -- Cecchi, C -- Celik, O -- Charles, E -- Chaty, S -- Chekhtman, A -- Cheung, C C -- Chiang, J -- Ciprini, S -- Claus, R -- Cohen-Tanugi, J -- Conrad, J -- Corbel, S -- Corbet, R -- DeCesar, M E -- den Hartog, P R -- Dermer, C D -- de Palma, F -- Digel, S W -- Donato, D -- do Couto e Silva, E -- Drell, P S -- Dubois, R -- Dubus, G -- Dumora, D -- Favuzzi, C -- Fegan, S J -- Ferrara, E C -- Fortin, P -- Frailis, M -- Fuhrmann, L -- Fukazawa, Y -- Funk, S -- Fusco, P -- Gargano, F -- Gasparrini, D -- Gehrels, N -- Germani, S -- Giglietto, N -- Giordano, F -- Giroletti, M -- Glanzman, T -- Godfrey, G -- Grenier, I A -- Grondin, M-H -- Grove, J E -- Guiriec, S -- Hadasch, D -- Harding, A K -- Hayashida, M -- Hays, E -- Healey, S E -- Hill, A B -- Horan, D -- Hughes, R E -- Itoh, R -- Jean, P -- Johannesson, G -- Johnson, A S -- Johnson, R P -- Johnson, T J -- Johnson, W N -- Kamae, T -- Katagiri, H -- Kataoka, J -- Kerr, M -- Knodlseder, J -- Koerding, E -- Kuss, M -- Lande, J -- Latronico, L -- Lee, S-H -- Lemoine-Goumard, M -- Garde, M Llena -- Longo, F -- Loparco, F -- Lott, B -- Lovellette, M N -- Lubrano, P -- Makeev, A -- Mazziotta, M N -- McConville, W -- McEnery, J E -- Mehault, J -- Michelson, P F -- Mizuno, T -- Moiseev, A A -- Monte, C -- Monzani, M E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nakamori, T -- Naumann-Godo, M -- Nestoras, I -- Nolan, P L -- Norris, J P -- Nuss, E -- Ohno, M -- Ohsugi, T -- Okumura, A -- Omodei, N -- Orlando, E -- Ormes, J F -- Ozaki, M -- Paneque, D -- Panetta, J H -- Parent, D -- Pelassa, V -- Pepe, M -- Pesce-Rollins, M -- Piron, F -- Porter, T A -- Raino, S -- Rando, R -- Ray, P S -- Razzano, M -- Razzaque, S -- Rea, N -- Reimer, A -- Reimer, O -- Reposeur, T -- Ripken, J -- Ritz, S -- Romani, R W -- Roth, M -- Sadrozinski, H F-W -- Sander, A -- Parkinson, P M Saz -- Scargle, J D -- Schinzel, F K -- Sgro, C -- Shaw, M S -- Siskind, E J -- Smith, D A -- Smith, P D -- Sokolovsky, K V -- Spandre, G -- Spinelli, P -- Stawarz, L -- Strickman, M S -- Suson, D J -- Takahashi, H -- Takahashi, T -- Tanaka, T -- Tanaka, Y -- Thayer, J B -- Thayer, J G -- Thompson, D J -- Tibaldo, L -- Torres, D F -- Tosti, G -- Tramacere, A -- Uchiyama, Y -- Usher, T L -- Vandenbroucke, J -- Vasileiou, V -- Vilchez, N -- Vitale, V -- Waite, A P -- Wallace, E -- Wang, P -- Winer, B L -- Wolff, M T -- Wood, K S -- Yang, Z -- Ylinen, T -- Ziegler, M -- Maehara, H -- Nishiyama, K -- Kabashima, F -- Bach, U -- Bower, G C -- Falcone, A -- Forster, J R -- Henden, A -- Kawabata, K S -- Koubsky, P -- Mukai, K -- Nelson, T -- Oates, S R -- Sakimoto, K -- Sasada, M -- Shenavrin, V I -- Shore, S N -- Skinner, G K -- Sokoloski, J -- Stroh, M -- Tatarnikov, A M -- Uemura, M -- Wahlgren, G M -- Yamanaka, M -- New York, N.Y. -- Science. 2010 Aug 13;329(5993):817-21. doi: 10.1126/science.1192537.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20705855" target="_blank"〉PubMed〈/a〉

Description: Variable x-ray and gamma-ray emission is characteristic of the most extreme physical processes in the universe. We present multiwavelength observations of a unique gamma-ray-selected transient detected by the Swift satellite, accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z = 0.3534. Its high-energy emission has lasted much longer than any gamma-ray burst, whereas its peak luminosity was approximately 100 times higher than bright active galactic nuclei. The association of the outburst with the center of its host galaxy suggests that this phenomenon has its origin in a rare mechanism involving the massive black hole in the nucleus of that galaxy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Levan, A J -- Tanvir, N R -- Cenko, S B -- Perley, D A -- Wiersema, K -- Bloom, J S -- Fruchter, A S -- Postigo, A de Ugarte -- O'Brien, P T -- Butler, N -- van der Horst, A J -- Leloudas, G -- Morgan, A N -- Misra, K -- Bower, G C -- Farihi, J -- Tunnicliffe, R L -- Modjaz, M -- Silverman, J M -- Hjorth, J -- Thone, C -- Cucchiara, A -- Ceron, J M Castro -- Castro-Tirado, A J -- Arnold, J A -- Bremer, M -- Brodie, J P -- Carroll, T -- Cooper, M C -- Curran, P A -- Cutri, R M -- Ehle, J -- Forbes, D -- Fynbo, J -- Gorosabel, J -- Graham, J -- Hoffman, D I -- Guziy, S -- Jakobsson, P -- Kamble, A -- Kerr, T -- Kasliwal, M M -- Kouveliotou, C -- Kocevski, D -- Law, N M -- Nugent, P E -- Ofek, E O -- Poznanski, D -- Quimby, R M -- Rol, E -- Romanowsky, A J -- Sanchez-Ramirez, R -- Schulze, S -- Singh, N -- van Spaandonk, L -- Starling, R L C -- Strom, R G -- Tello, J C -- Vaduvescu, O -- Wheatley, P J -- Wijers, R A M J -- Winters, J M -- Xu, D -- New York, N.Y. -- Science. 2011 Jul 8;333(6039):199-202. doi: 10.1126/science.1207143. Epub 2011 Jun 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Warwick, Coventry, UK. a.j.levan@warwick.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21680811" target="_blank"〉PubMed〈/a〉

Description: Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations, at a wavelength of 1.3 millimeters, of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 +/- 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doeleman, Sheperd S -- Fish, Vincent L -- Schenck, David E -- Beaudoin, Christopher -- Blundell, Ray -- Bower, Geoffrey C -- Broderick, Avery E -- Chamberlin, Richard -- Freund, Robert -- Friberg, Per -- Gurwell, Mark A -- Ho, Paul T P -- Honma, Mareki -- Inoue, Makoto -- Krichbaum, Thomas P -- Lamb, James -- Loeb, Abraham -- Lonsdale, Colin -- Marrone, Daniel P -- Moran, James M -- Oyama, Tomoaki -- Plambeck, Richard -- Primiani, Rurik A -- Rogers, Alan E E -- Smythe, Daniel L -- SooHoo, Jason -- Strittmatter, Peter -- Tilanus, Remo P J -- Titus, Michael -- Weintroub, Jonathan -- Wright, Melvyn -- Young, Ken H -- Ziurys, Lucy M -- New York, N.Y. -- Science. 2012 Oct 19;338(6105):355-8. doi: 10.1126/science.1224768. Epub 2012 Sep 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉MIT Haystack Observatory, Off Route 40, Westford, MA 01886, USA. sdoeleman@haystack.mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23019611" target="_blank"〉PubMed〈/a〉

Description: We have detected the intrinsic size of Sagittarius A*, the Galactic center radio source associated with a supermassive black hole, showing that the short-wavelength radio emission arises from very near the event horizon of the black hole. Radio observations with the Very Long Baseline Array show that the source has a size of 24 +/- 2 Schwarzschild radii at 7-millimeter wavelength. In one of eight 7-millimeter epochs, we also detected an increase in the intrinsic size of 60(-17)(+25)%. These observations place a lower limit to the mass density of Sagittarius A* of 1.4 x 10(4) solar masses per cubic astronomical unit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bower, Geoffrey C -- Falcke, Heino -- Herrnstein, Robeson M -- Zhao, Jun-Hui -- Goss, W M -- Backer, Donald C -- New York, N.Y. -- Science. 2004 Apr 30;304(5671):704-8. Epub 2004 Apr 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA. gbower@astro.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15060284" target="_blank"〉PubMed〈/a〉

Description: Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way. Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei. X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed. The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed. Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission--from radio to X-ray wavelengths--from the black hole.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Eatough, R P -- Falcke, H -- Karuppusamy, R -- Lee, K J -- Champion, D J -- Keane, E F -- Desvignes, G -- Schnitzeler, D H F M -- Spitler, L G -- Kramer, M -- Klein, B -- Bassa, C -- Bower, G C -- Brunthaler, A -- Cognard, I -- Deller, A T -- Demorest, P B -- Freire, P C C -- Kraus, A -- Lyne, A G -- Noutsos, A -- Stappers, B -- Wex, N -- England -- Nature. 2013 Sep 19;501(7467):391-4. doi: 10.1038/nature12499. Epub 2013 Aug 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany. reatough@mpifr-bonn.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23945588" target="_blank"〉PubMed〈/a〉

Description: A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of approximately 5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Middleton, Matthew J -- Miller-Jones, James C A -- Markoff, Sera -- Fender, Rob -- Henze, Martin -- Hurley-Walker, Natasha -- Scaife, Anna M M -- Roberts, Timothy P -- Walton, Dominic -- Carpenter, John -- Macquart, Jean-Pierre -- Bower, Geoffrey C -- Gurwell, Mark -- Pietsch, Wolfgang -- Haberl, Frank -- Harris, Jonathan -- Daniel, Michael -- Miah, Junayd -- Done, Chris -- Morgan, John S -- Dickinson, Hugh -- Charles, Phil -- Burwitz, Vadim -- Della Valle, Massimo -- Freyberg, Michael -- Greiner, Jochen -- Hernanz, Margarita -- Hartmann, Dieter H -- Hatzidimitriou, Despina -- Riffeser, Arno -- Sala, Gloria -- Seitz, Stella -- Reig, Pablo -- Rau, Arne -- Orio, Marina -- Titterington, David -- Grainge, Keith -- England -- Nature. 2013 Jan 10;493(7431):187-90. doi: 10.1038/nature11697. Epub 2012 Dec 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Physics Department, University of Durham, Durham DH1 3LE, UK. m.j.middleton@durham.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23235823" target="_blank"〉PubMed〈/a〉