Late Time Swift Observations of the Relativistic TDE candidate AT2022cmc
ATel #15349; C. Han, M. T. Reynolds, J. M. Miller, B. Gediman, Y. Hemrattaphan, M. K. Zak (Univ. Michigan)
on 26 Apr 2022; 00:33 UT
Credential Certification: Mark Reynolds (markrey@umich.edu)
Subjects: Radio, Optical, Ultra-Violet, X-ray, Black Hole, Transient, Tidal Disruption Event
AT2022cmc/ZTF22aaajecp is a fast red optical transient discovered by the Zwicky Transient Factory on Feb. 11, 2022 (Andreoni et al. 2022, GCN #31590), lying at a redshift of z = 1.19 (Tanvir et al. GCN #31602). AT2022cmc was identified as a candidate relativistic tidal disruption event (Pasham et al., ATEL#15232) and has been observed to exhibit variations in the soft and hard X-ray bands (Yao et al, ATEL#15230). To further investigate the late time evolution of this source, we examined observations of AT2022cmc obtained by the Neil Gehrels Swift Observatory, X-Ray Telescope (XRT).
Source counts are extracted from a 20 arcsec radius circle centered on the source position, with background extracted from a neighboring source-free region. In a 12.5 ks observation sequence on March 19th, after rebinning utilizing a bin size of 1ks, the X-ray light curve shows an average count rate of ~ 0.01 ct/s (see table) with significant variability. In the observing sequence, the count rate peaked at 0.0347 +- 0.0076 ct/s, and had a minimum value of 0.0067 +- 0.0038 ct/s. This confirms the continued presence of hourly variations (e.g., Atel #15230). Further observations have revealed continuing flux variability at X-ray energies.
Time [UT] Exposure Time [ks] Count Rate [ct/s (0.5 - 10.0 keV)]
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March 19 23:18 12.46 0.010 +/- 0.0009
March 23 18:56 0.45 0.012 +/- 0.0054
March 27 19:36 1.16 0.013 +/- 0.0034
March 30 06:50 1.96 0.020 +/- 0.0032
April 01 04:48 0.32 0.025 +/- 0.0089
April 01 07:51 0.71 0.018 +/- 0.0049
April 02 03:22 0.16 0.051 +/- 0.018
April 04 10:36 0.36 0.0079 +/- 0.0058
April 07 05:54 1.60 0.0086 +/- 0.0023
April 09 22:43 1.37 0.0064 +/- 0.0022
We also examined the UVOT data obtained simultaneously with the X-ray data above. Utilizing a 5 arcsec extraction region, the source is not detected in individual UV exposures in the M2 filter. We stacked frames of um2 filter together (March 23rd - April 9th) and found statistically significant emission at the source position in the resulting 2.8ks exposure, with um2 AB magnitude of um2 = 22.17 +/- 0.19(stat) +/- 0.03(sys) mag. There is no statistically significant evidence for the evolution of the UV flux at the current time.
