X-ray emission of SN 2023ixf and its progenitor
ATel #16051; A. K. H. Kong (NTHU)
on 24 May 2023; 08:58 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)
Subjects: X-ray, Supernovae
Following the discovery of the Type II supernova SN 2023ixf in the nearby galaxy in M101 (Itagaki 2023) and its X-ray emission (ATel #16049), we have searched for X-ray emission of the supernova and its progenitor with archival data from the Swift X-ray Telescope and the Chandra X-ray Observatory. Swift TOO observations were triggered shortly after the discovery. Between 2023-05-21 and 2023-05-23, eight Swift/XRT observations were performed. The total Swift/XRT observation time is 10.6 ks. SN 2023ixf is marginally seen in the combined 0.3-10 keV image. There are 13 counts in a circular region of 20 arcsec in radius. With 38 counts in a source-free region covering 2035 pixels, the background is about 0.019 counts per pixel. Using a binomial distribution, the chance probability that all 13 photons or more are background is 0.047%. With 8.8+/-3.7 background subtracted counts and assuming an absorbed power-law with a photon index of 1.3 and N_H of 2e23 cm^-2 (ATel #16049), the 0.03-30keV flux is 7.7e-13 erg/s/cm^2 corresponding to 3.8e39 erg/s assuming a distance of 6.4 Mpc. Taking the uncertainty into account, this is marginally consistent with the NuSTAR detection (ATel #16049).
We also examined archival Chandra images taken before the onset of the SN to look for X-ray emission from the progenitor. Between 2000 and 2017, Chandra observed M101 for 28 times with a total exposure time of 1.1 Msec. We combined all the observations together; at the position of the SN, the effective exposure time is about 781 ks. No source is visible at the SN position. Assuming the same spectral model, we set a 3-sigma 0.3-10 keV luminosity limit of 2.3e37 erg/s. Using a less absorbed (Galactic N_H=8.5e20 cm^-2) and a softer (photon index=2) spectrum, the 3-sigma 0.3-10 keV luminosity limit is 4.3e36 erg/s.
