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X-ray upper limits on the progenitor of the Type Ia supernova 2017cbv

ATel #10237; A. K. H. Kong (NTHU & Oxford)
on 2 Apr 2017; 18:46 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)

Subjects: X-ray, Supernovae

Following the discovery of the Type Ia supernova 2017cbv (ATel #10158), we examined a combined archival Chandra observation of the host galaxy NGC 5643 taken in 2015 May 21 and Dec 26 to search for the X-ray progenitor. The total exposure time of the combined image is 115 ks. Within a circular region with a radius of 2 arcsec, no X-ray source was found at the position of the supernova. The nearest X-ray point source is about 25 arcsec from the supernova. Assuming an absorbed power-law with N_H=8e20 cm^-2 (Galactic value) and a photon index of 1.5, we derived a 3-sigma 0.3-7 keV luminosity upper limit of 4.3e37 erg/s at 16.9 Mpc (ATel #10167). Since some progenitors of Type Ia supernova are expected to be supersoft X-ray sources (see Nielsen et al. 2013, MNRAS, 435, 187 for a review), we also assumed an absorbed blackbody model with N_H=8e20 cm^-2 and kT=100 eV. The resulting 3-sigma 0.3-7 keV luminosity upper limit is 2.7e38 erg/s. Reducing the temperature to 50 eV will yield an upper limit of 2.6e39 erg/s.