X-ray Upper Limit for PTF11kly in M101 from Historical Chandra Imaging

ATel #3587; N. R. Butler (ASU), E. O. Ofek (Caltech), and J. S. Bloom (UC Berkeley)
on 25 Aug 2011; 17:51 UT
Credential Certification: Nathaniel Butler (natbutler@asu.edu)

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We analyzed Chandra archival observations of M101 which contain the position of the type-Ia supernova PTF11kly (Nugent et al., ATel 3581). Specifically, we considered ObsIDs 4731, 5300, 6114, 6115, 6169, 6170, 6175, representing a total ACIS-I exposure of 328 ksec obtained during 2004 (PI: Kuntz). We do not detect any source in the supernova location. In the 0.3-0.7 keV band, and using 2" radius aperture, we place a 3-sigma upper count rate limit of 1.7e-5 count/s. Assuming a black-body temperature of 67 eV (e.g., Gilfanov & Gilfanov, arXiv 1103.3659; see however Izumi et al. 2010, ApJ 724, 212), a Galactic Hydrogen column density of 1.8e20 cm^-2 (Kalberla 2005), and a distance modulus of 29.05 mag for M101 (Stetson et al. 1998, ApJ 508, 491; Shappee & Stanek 2011, ApJ, 733, 124), this limit corresponds to a time-averaged, unabsorbed luminosity of <1.0e36 erg/s (0.3-0.7 keV).