| Autor: |
Perley, Daniel A, Mazzali, Paolo A, Yan, Lin, Cenko, S Bradley, Gezari, Suvi, Taggart, Kirsty, Blagorodnova, Nadia, Fremling, Christoffer, Mockler, Brenna, Singh, Avinash, Tominaga, Nozomu, Tanaka, Masaomi, Watson, Alan M, Ahumada, Tomás, Anupama, G C, Ashall, Chris, Becerra, Rosa L, Bersier, David, Bhalerao, Varun, Bloom, Joshua S |
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| Zdroj: |
Monthly Notices of the Royal Astronomical Society; Mar2019, Vol. 484 Issue 1, p1031-1049, 19p |
| Abstrakt: |
Wide-field optical surveys have begun to uncover large samples of fast (t rise ≲ 5 d), luminous (M peak < −18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the transients of this class found so far have hampered detailed investigation of their properties. We present photometry and spectroscopy from a comprehensive worldwide campaign to observe AT 2018cow (ATLAS 18qqn), the first fast-luminous optical transient to be found in real time at low redshift. Our first spectra (<2 days after discovery) are entirely featureless. A very broad absorption feature suggestive of near-relativistic velocities develops between 3 and 8 days, then disappears. Broad emission features of H and He develop after >10 days. The spectrum remains extremely hot throughout its evolution, and the photospheric radius contracts with time (receding below R < 1014 cm after 1 month). This behaviour does not match that of any known supernova, although a relativistic jet within a fallback supernova could explain some of the observed features. Alternatively, the transient could originate from the disruption of a star by an intermediate-mass black hole, although this would require long-lasting emission of highly super-Eddington thermal radiation. In either case, AT 2018cow suggests that the population of fast luminous transients represents a new class of astrophysical event. Intensive follow-up of this event in its late phases, and of any future events found at comparable distance, will be essential to better constrain their origins. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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