Pre-explosion Upper Limit on X-ray Emission from a Progenitor for SN 2014J

ATel #5798; W. P. Maksym (U. Alabama), J. A. Irwin (U. Alabama), W. C. Keel (U. Alabama), D. Burke (CFA-SAO), K. Schawinski (ETH Zurich)
on 23 Jan 2014; 20:50 UT
Credential Certification: Peter Maksym (peter.maksym@gmail.com)

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To identify or set limits on any possible accreting white dwarf progenitor to SN 2014J (CBET #3792, ATel #5786), we examined available pre-explosion archival Chandra data. These data cover multiple observations of M82 dating back to 1999 Sep. 20.

Initial examination by D. Burke (https://twitter.com/doug_burke/status/426065675497381888) cover ~820 ks of mixed ACIS-I and ACIS-S data with non-uniform coverage, and reveals no source at RA,Dec=09:55:42.14, +69:40:26.0 (CBET #3792). The source is also not visible in the longest single exposure.

To minimize effects of off-axis spreading of the Chandra PSF, we examined the archival data using only the sixteen ACIS-S and ACIS-I epochs with off-axis angle < 2 arcmin, totaling ~500 ks in the range of 0.1-8 keV. Within r=0.5 arcsec (~1 Chandra pixel), we find no source with a 1-sigma upper limit of 5.7 counts using the NIRC2 localization by Tendulkar et al. (ATel #5789) RA,Dec=9:55:42.217,+69:40:26.56. In addition, none of the sixteen sub-exposures has any evidence for X-ray flaring at the location of SN 2014J.

Given the likelihood of strong absorption, any upper limit to intrinsic flux will be strongly model-dependent. We assume galactic absorption as determined by http://cxc.harvard.edu/toolkit/colden.jsp . Assuming intrinsic B-V~0.0 (e.g. Foley et al., 2011, ApJ, 742, 89), from the AAVSO light curve generator ( http://www.aavso.org/lcg ) we estimate E(B-V)~1.5. Using the Calzetti (2000, ApJ, 533, 682) reddening law, we convert this to a neutral hydrogen column density nH~1.1x10^22 cm^-2.

Assuming an approximately blackbody spectrum with kT_bb=0.1 keV and weighting ACIS-S and ACIS-I exposures by relative ontime, we use WebPIMMs ( http://heasarc.gsfc.nasa.gov/Tools/w3pimms.html ) to infer an unabsorbed upper limit <1.7x10^-14 erg cm^-1 s^-2, or L_X<2.5x10^37 erg s^-1 at ~3.5 Mpc, F(intrinsic)/F(observed)~400. This corresponds to <0.14 (L/L_Edd) (M/1.4 Msun) assuming steady accretion. Note that this does not account for the time-dependent loss of ACIS effective area due to contaminant build-up, so actual values are likely higher.