ALBERT

Description: Common-envelope events (CEEs), during which two stars temporarily orbit within a shared envelope, are believed to be vital for the formation of a wide range of close binaries. For decades, the only evidence that CEEs actually occur has been indirect, based on the existence of systems that could not be otherwise explained. Here we propose a direct observational signature of CEEs arising from a physical model where emission from matter ejected in a CEE is controlled by a recombination front as the matter cools. The natural range of time scales and energies from this model, as well as the expected colors, light-curve shapes, ejection velocities, and event rate, match those of a recently recognized class of red transient outbursts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ivanova, N -- Justham, S -- Avendano Nandez, J L -- Lombardi, J C Jr -- New York, N.Y. -- Science. 2013 Jan 25;339(6118):433-5. doi: 10.1126/science.1225540.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Alberta, Edmonton, AB T6G 2E7, Canada. nata.ivanova@ualberta.ca〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23349287" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Podsiadlowski, Philipp -- Justham, Stephen -- New York, N.Y. -- Science. 2006 Dec 8;314(5805):1551-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astrophysics, University of Oxford, Oxford, OX1 3RH, UK. podsi@astro.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17158310" target="_blank"〉PubMed〈/a〉

Description: There are two proposed explanations for ultraluminous X-ray sources (ULXs) with luminosities in excess of 10(39) erg s(-1). They could be intermediate-mass black holes (more than 100-1,000 solar masses, M sun symbol) radiating at sub-maximal (sub-Eddington) rates, as in Galactic black-hole X-ray binaries but with larger, cooler accretion disks. Alternatively, they could be stellar-mass black holes radiating at Eddington or super-Eddington rates. On its discovery, M 101 ULX-1 had a luminosity of 3 x 10(39) erg s(-1) and a supersoft thermal disk spectrum with an exceptionally low temperature--uncomplicated by photons energized by a corona of hot electrons--more consistent with the expected appearance of an accreting intermediate-mass black hole. Here we report optical spectroscopic monitoring of M 101 ULX-1. We confirm the previous suggestion that the system contains a Wolf-Rayet star, and reveal that the orbital period is 8.2 days. The black hole has a minimum mass of 5 M sun symbol, and more probably a mass of 20 M sun symbol-30 M sun symbol, but we argue that it is very unlikely to be an intermediate-mass black hole. Therefore, its exceptionally soft spectra at high Eddington ratios violate the expectations for accretion onto stellar-mass black holes. Accretion must occur from captured stellar wind, which has hitherto been thought to be so inefficient that it could not power an ultraluminous source.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Ji-Feng -- Bregman, Joel N -- Bai, Yu -- Justham, Stephen -- Crowther, Paul -- England -- Nature. 2013 Nov 28;503(7477):500-3. doi: 10.1038/nature12762.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, 100012 Beijing, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24284727" target="_blank"〉PubMed〈/a〉

Description: Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. Here we report the spectroscopic detection of circumstellar material in a normal type Ia supernova explosion. The expansion velocities, densities, and dimensions of the circumstellar envelope indicate that this material was ejected from the progenitor system. In particular, the relatively low expansion velocities suggest that the white dwarf was accreting material from a companion star that was in the red-giant phase at the time of the explosion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Patat, F -- Chandra, P -- Chevalier, R -- Justham, S -- Podsiadlowski, Ph -- Wolf, C -- Gal-Yam, A -- Pasquini, L -- Crawford, I A -- Mazzali, P A -- Pauldrach, A W A -- Nomoto, K -- Benetti, S -- Cappellaro, E -- Elias-Rosa, N -- Hillebrandt, W -- Leonard, D C -- Pastorello, A -- Renzini, A -- Sabbadin, F -- Simon, J D -- Turatto, M -- New York, N.Y. -- Science. 2007 Aug 17;317(5840):924-6. Epub 2007 Jul 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉European Southern Observatory (ESO), Karl Schwarzschild Strasse 2, 85748, Garching bei Munchen, Germany. fpatat@eso.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17626848" target="_blank"〉PubMed〈/a〉

Description: Massive stars undergo a violent death when the supply of nuclear fuel in their cores is exhausted, resulting in a catastrophic "core-collapse" supernova. Such events are usually only detected at least a few days after the star has exploded. Observations of the supernova SNLS-04D2dc with the Galaxy Evolution Explorer space telescope reveal a radiative precursor from the supernova shock before the shock reached the surface of the star and show the initial expansion of the star at the beginning of the explosion. Theoretical models of the ultraviolet light curve confirm that the progenitor was a red supergiant, as expected for this type of supernova. These observations provide a way to probe the physics of core-collapse supernovae and the internal structures of their progenitor stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schawinski, Kevin -- Justham, Stephen -- Wolf, Christian -- Podsiadlowski, Philipp -- Sullivan, Mark -- Steenbrugge, Katrien C -- Bell, Tony -- Roser, Hermann-Josef -- Walker, Emma S -- Astier, Pierre -- Balam, Dave -- Balland, Christophe -- Carlberg, Ray -- Conley, Alex -- Fouchez, Dominique -- Guy, Julien -- Hardin, Delphine -- Hook, Isobel -- Howell, D Andrew -- Pain, Reynald -- Perrett, Kathy -- Pritchet, Chris -- Regnault, Nicolas -- Yi, Sukyoung K -- New York, N.Y. -- Science. 2008 Jul 11;321(5886):223-6. doi: 10.1126/science.1160456. Epub 2008 Jun 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Oxford, Oxford OX1 3RH, UK. kevins@astro.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18556514" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Justham, Stephen -- England -- Nature. 2014 Aug 7;512(7512):34-5. doi: 10.1038/512034a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25100478" target="_blank"〉PubMed〈/a〉

Description: The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. Although the theory is poorly understood, observations of relativistic jets from systems known as microquasars (compact binary stars) have led to a well established phenomenology. Relativistic jets are not expected to be produced by sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report the optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1; refs 9, 10). Unexpectedly, the spectra show blueshifted, broad Halpha emission lines, characteristic of baryonic jets with relativistic speeds. These time-variable emission lines have projected velocities of about 17 per cent of the speed of light, and seem to be similar to those from the prototype microquasar SS 433 (refs 11, 12). Such relativistic jets are not expected to be launched from white dwarfs, and an origin from a black hole or a neutron star is hard to reconcile with the persistence of M81 ULS-1's soft X-rays. Thus the unexpected presence of relativistic jets in a ULS challenges canonical theories of jet formation, but might be explained by a long-speculated, supercritically accreting black hole with optically thick outflows.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Ji-Feng -- Bai, Yu -- Wang, Song -- Justham, Stephen -- Lu, You-Jun -- Gu, Wei-Min -- Liu, Qing-Zhong -- Di Stefano, Rosanne -- Guo, Jin-Cheng -- Cabrera-Lavers, Antonio -- Alvarez, Pedro -- Cao, Yi -- Kulkarni, Shri -- England -- Nature. 2015 Dec 3;528(7580):108-10. doi: 10.1038/nature15751. Epub 2015 Nov 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, China. ; College of Astronomy and Space Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China. ; Department of Astronomy, Xiamen University, Xiamen, Fujian Province 361005, China. ; Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, Jiangsu Province 210008, China. ; Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA. ; Instituto de Astrofisica de Canarias, c/Via Lactea s/n, E-38200 La Laguna, Tenerife, Spain. ; Departamento de Astrofisica, Universidad de la Laguna, E-38205 La Laguna, Tenerife, Spain. ; Department of Astronomy, Caltech, Pasadena, California 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26605521" target="_blank"〉PubMed〈/a〉

Description: The potential importance of the angular momentum which is gained by accreting white dwarfs (WDs) has been increasingly recognized in the context of Type Ia supernova (SN Ia) single-degenerate model. The expectation that the spin of the WD can delay the explosion should help the single-degenerate model to be consistent with the observed properties of most SNe Ia, in particular by avoiding hydrogen contamination. In this paper, we attempt to study the most prominent single-degenerate supersoft (WD + MS) channel when the rotation of accreting WDs is considered. We present a detailed binary population synthesis study to examine the predicted population of SNe Ia for this channel. For our standard model, we find that 77 per cent of these SNe Ia explode with WD masses which are low enough to be supported by solid-body rotation ( ≤ 1.5 M ); this is a substantially higher proportion than found by previous work. Only 2 per cent have WD explosion masses ≥2.0 M ; these require the initial WD mass to be larger than 1.0 M . We further discuss the possible origin of the diversity of SNe Ia from the pre- and post-accretion properties of the WDs in this population. We also suggest that some SN Ia progenitors with substantial circumstellar hydrogen, including some apparent Type IIn SNe, might be related to WDs which required support from differential rotation to avoid explosion, since these can still be accreting from hydrogen-rich donors with a relatively high mass-transfer rate at the time of the SN explosion.

Description: The energy budget in common-envelope events (CEEs) is not well understood, with substantial uncertainty even over to what extent the recombination energy stored in ionized hydrogen and helium might be used to help envelope ejection. We investigate the reaction of a red giant envelope to heating which mimics limiting cases of energy input provided by the orbital decay of a binary during a CEE, specifically during the post-plunge-in phase during which the spiral-in has been argued to occur on a time-scale longer than dynamical. We show that the outcome of such a CEE depends less on the total amount of energy by which the envelope is heated than on how rapidly the energy was transferred to the envelope and on where the envelope was heated. The envelope always becomes dynamically unstable before receiving net heat energy equal to the envelope's initial binding energy. We find two types of outcome, both of which likely lead to at least partial envelope ejection: ‘runaway’ solutions in which the expansion of the radius becomes undeniably dynamical, and superficially ‘self-regulated’ solutions, in which the expansion of the stellar radius stops but a significant fraction of the envelope becomes formally dynamically unstable. Almost the entire reservoir of initial helium recombination energy is used for envelope expansion. Hydrogen recombination is less energetically useful, but is nonetheless important for the development of the dynamical instabilities. However, this result requires the companion to have already plunged deep into the envelope; therefore this release of recombination energy does not help to explain wide post-common-envelope orbits.