An embedded X-ray source shines through the aspherical AT2018cow: revealing the inner workings of the most luminous fast-evolving optical transients
| Autor: | Maria R. Drout, A. Kozlova, Indrek Vurm, Enrico Bozzo, D. Frederiks, Wen-fai Fong, R. Cartier, Brian D. Metzger, Sandro Mereghetti, Brian W. Grefenstette, Giacomo Terreran, P. Laurent, Edo Berger, Nathaniel Roth, James F. Steiner, C. Guidorzi, Lorenzo Ducci, P. K. Blanchard, Carlo Ferrigno, Tanmoy Laskar, Michael Bietenholz, P. Ubertini, Kate D. Alexander, Kerry Paterson, G. Migliori, Ryan Chornock, Dan Milisavljevic, D. Gotz, D. Brethauer, A. Hajela, E. Kuulkers, Kevin Hurley, Tarraneh Eftekhari, Matt Nicholl, Eric R. Coughlin, Ben Margalit, Dmitry S. Svinkin, Igor Chilingarian, V. G. Savchenko, John Banovetz, Raffaella Margutti, Norbert Bartel, Daniel J. Patnaude, Deanne L. Coppejans, Andrew MacFadyen |
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| Přispěvatelé: | Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Margutti, R. and Metzger, B.~D. and Chornock, R. and Vurm, I. and Roth, N. and Grefenstette, B.~W. and Savchenko, V. and Cartier, R. and Steiner, J.~F. and Terreran, G. and Margalit, B. and Migliori, G. and Milisavljevic, D. and Alexander, K.~D. and Bietenholz, M. and Blanchard, P.~K. and Bozzo, E. and Brethauer, D. and Chilingarian, I.~V. and Coppejans, D.~L. and Ducci, L. and Ferrigno, C. and Fong, W. and G |
| Rok vydání: | 2018 |
| Předmět: |
(AT 2018cow)
010504 meteorology & atmospheric sciences Socio-culturale FOS: Physical sciences Astrophysics Compact star Magnetar X-rays: general 01 natural sciences 7. Clean energy Spectral line Luminosity accretion 0103 physical sciences Blue supergiant accretion accretion disks stars: black holes supernovae: individual: AT 2018cow X-rays: general 010303 astronomy & astrophysics supernovae: individual 0105 earth and related environmental sciences Physics High Energy Astrophysical Phenomena (astro-ph.HE) Photosphere supernovae: individual (AT 2018cow) accretion disks Astronomy and Astrophysics accretion accretion disks stars: black holes Supernova Stars 13. Climate action Space and Planetary Science Astrophysics - High Energy Astrophysical Phenomena [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] |
| Zdroj: | Astrophys.J. Astrophys.J., 2019, 872 (1), pp.18. ⟨10.3847/1538-4357/aafa01⟩ |
| DOI: | 10.48550/arxiv.1810.10720 |
| Popis: | We present the first extensive radio to gamma-ray observations of a fast-rising blue optical transient (FBOT), AT2018cow, over its first ~100 days. AT2018cow rose over a few days to a peak luminosity $L_{pk}\sim4\times 10^{44}$ erg/s exceeding those of superluminous supernovae (SNe), before declining as $\propto t^{-2}$. Initial spectra at $\lesssim 15$ days were mostly featureless and indicated large expansion velocities v~0.1c and temperatures reaching 30000 K. Later spectra revealed a persistent optically-thick photosphere and the emergence of H and He emission features with v~sim 4000 km/s with no evidence for ejecta cooling. Our broad-band monitoring revealed a hard X-ray spectral component at $E\ge 10$ keV, in addition to luminous and highly variable soft X-rays, with properties unprecedented among astronomical transients. An abrupt change in the X-ray decay rate and variability appears to accompany the change in optical spectral properties. AT2018cow showed bright radio emission consistent with the interaction of a blastwave with $v_{sh}$~0.1c with a dense environment ($\dot M\sim10^{-3}-10^{-4}\,M_{\odot}yr^{-1}$ for $v_w=1000$ km\s). While these properties exclude Ni-powered transients, our multi-wavelength analysis instead indicates that AT2018cow harbored a "central engine", either a compact object (magnetar or black hole) or an embedded internal shock produced by interaction with a compact, dense circumstellar medium. The engine released $\sim10^{50}-10^{51.5}$ erg over $\sim10^3-10^5$ s and resides within low-mass fast-moving material with equatorial-polar density asymmetry ($M_{ej,fast}\lesssim0.3\,\rm{M_{\odot}}$). Successful SNe from low-mass H-rich stars (like electron-capture SNe) or failed explosions from blue supergiants satisfy these constraints. Intermediate-mass black-holes are disfavored by the large environmental density probed by the radio observations. Comment: 26 pages + tables. Submitted |
| Databáze: | OpenAIRE |
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