Minutes-duration optical flares with supernova luminosities.

Ho, Anna Y Q; Perley, Daniel A; Chen, Ping; Schulze, Steve; Dhillon, Vik; Kumar, Harsh; Suresh, Aswin; Swain, Vishwajeet et al. · Nature · 2023

basic_science · Level V

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Abstract

In recent years, certain luminous extragalactic optical transients have been observed to last only a few days<sup>1</sup>. Their short observed duration implies a different powering mechanism from the most common luminous extragalactic transients (supernovae), whose timescale is weeks<sup>2</sup>. Some short-duration transients, most notably AT2018cow (ref. <sup>3</sup>), show blue optical colours and bright radio and X-ray emission<sup>4</sup>. Several AT2018cow-like transients have shown hints of a long-lived embedded energy source<sup>5</sup>, such as X-ray variability<sup>6,7</sup>, prolonged ultraviolet emission<sup>8</sup>, a tentative X-ray quasiperiodic oscillation<sup>9,10</sup> and large energies coupled to fast (but subrelativistic) radio-emitting ejecta<sup>11,12</sup>. Here we report observations of minutes-duration optical flares in the aftermath of an AT2018cow-like transient, AT2022tsd (the 'Tasmanian Devil'). The flares occur over a period of months, are highly energetic and are probably nonthermal, implying that they arise from a near-relativistic outflow or jet. Our observations confirm that, in some AT2018cow-like transients, the embedded energy source is a compact object, either a magnetar or an accreting black hole.