DRAFT
2022-12-23 14:36:12
Type: Object/s-Data/Analysis
Discovery of Minute-timescale Optical Flares with Supernova-like Luminosities at the Position of the Luminous Fast Blue Optical Transient AT2022tsd (the "Tasmanian Devil")
Authors: Anna Y. Q. Ho (Cornell), Daniel A. Perley (LJMU), Ping Chen (Weizmann), Steve Schulze (OKC), Jesper Sollerman (OKC), Avishay Gal-Yam (Weizmann)
Source Group: ZTF
Abstract:
We report the detection of several minute-timescale optical flares with vLv~10^43 erg/s at the position of the luminous fast blue optical transient (LFBOT) AT2022tsd (the "Tasmanian Devil"), occurring 30-100 days after the original LFBOT event.

AT2022tsd (the “Tasmanian Devil,” internal name ZTF22abftjko) was a luminous fast blue optical transient (LFBOT) at z=0.256 (AstroNote #2022-199) first detected on 6 September 2022 (AstroNote #2022-208) with luminous radio (AstroNote #2022-205) and X-ray (AstroNote #2022-207, #2022-218) counterparts. 

In a photometric optical imaging sequence starting at 2022-12-15T04:29:57 UT, a hundred days (observer frame) after the initial transient event, we detected a minute-timescale optical flare at the position of AT2022tsd across five three-minute Magellan/IMACS g-band images. The peak flare magnitude was g = 20.45 +/- 0.02 mag, which was nearly as bright as the original LFBOT, and implies a luminosity of vLv ~ 10^43 erg/s at the redshift of AT2022tsd. In an exposure five minutes later the magnitude was g = 21.55 +/- 0.05 mag, and five minutes after that the magnitude was g = 23.53 +/- 0.30 mag.

Forced photometry on ZTF survey images at the position of the transient revealed three additional detections out of 67 individual 30s exposures obtained after the initial LFBOT: i = 19.45 +/- 0.10 mag (10-sigma) in an image starting at 2022-10-05T08:10:04 UT (~30 days post-explosion), r = 20.65 +/- 0.14 (8-sigma) in an image starting at 2022-10-04T09:53:38, and r = 20.91 +/- 0.30 (4-sigma) in an image starting at 2022-10-29T04:45:28 (~60 days post-explosion).

Flaring behavior from a foreground star is unlikely: the position of the optical flare is within 0.5 arcseconds of the VLA radio position, and only one 3.2-sigma detection was recovered in the 600 ZTF exposures obtained prior to the transient event, which is consistent with statistical fluctuations. No historical activity was observed by Pan-STARRS (AstroNote #2022-206).

Since the IMACS flare detection, we have obtained a total of ~200 minutes of 120s exposures on six different nights, using the Liverpool Telescope. The duration of each sequence ranged from 10-20 minutes. In a sequence beginning at 2022-12-16T20:33:52.70 UT, we detected an additional flare in a sequence of six g-band images spanning 12 minutes total. The flare was detected in each image at 21.3-22 mag, and exhibited significant variability from one image to the next. 

To our knowledge, the only precedent in the literature for long-lasting minute-timescale optical variability at supernova-like luminosities is blazars (e.g., Dai et al. 2001, AJ 122 2901). In this analogy, we would be observing an on-axis relativistic jet powered by a stellar- or intermediate-mass black hole, due to the fast timescale of the LFBOT itself and its apparent projection of 1.5’’ (8 kpc) from the nucleus of its host galaxy. 

Given the very likely association between the flaring behavior and AT2022tsd, additional multiwavelength follow-up observations are highly encouraged. 

Show current TNS values
Catalog Name Reported RA Reported DEC Reported Obj-Type Reported Redshift Host Name Host Redshift Remarks TNS RA TNS DEC TNS Obj-Type TNS Redshift
TNS 2022tsd 03:20:10.863 +08:44:55.63 03:20:10.863 +08:44:55.63

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