Rise and fall of SN 2009ip X-ray emission

ATel #4499; S. Campana (INAF- OA Brera), R. Margutti (Harvard University)
on 18 Oct 2012; 21:27 UT
Credential Certification: Sergio Campana (campana@merate.mi.astro.it)

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We observed the supernova impostor SN2009ip (recently returned to activity, Smith & Mauerhan 2012, Atel # 4412) for a total of ~110 ks with Swift/XRT. A source coincident with the SN position is clearly detected in the summed image, as reported by Margutti & Soderberg (2012, Atel #4457). The close-by source reported by Campana (2012, ATel #4444) at RA(J2000):22 23 09.32 Dec(J2000):-28 56 50.2 (typo in Dec. corrected) is barely visible. The mean 0.3-10 keV count rate of SN 2009ip is (5.5+/-1.1)e-4 cts/s. We split the entire observation into 50 ks pieces deriving a light curve. The source is not detected up to around Sep 25 2012, consistent with Campana's (2012, Atel #4444) and Margutti and Soderberg's (2012, Atel #4457) results. The X-ray light curve shows then a smooth, slow rise until ~ Oct 2. After ~ Oct 14 there is possible evidence for fading. The XRT light curve can be empirically described by a Gaussian centered on Oct 8, 2012 (+/-10 d, 90% c.l.) and with a 6+/-3 d width. The peak rate is ~9e-4 cts/s, within an extraction region of 10 arcsec radius. This corresponds roughly to the Swift XRT Half Energy Width, resulting in a peak flux of ~2e-3 cts/s (PSF corrected). Assuming a power-law spectrum with photon index Gamma=2 and correcting for the Galactic neutral hydrogen column density in the direction of the SN (NH=1.2d20 cm-2, Kalberla et al. 2005), this translates into a peak flux of F~6e-14 erg/s/cm2 and a peak luminosity L~4d39 erg/sec (at the distance of 24 Mpc). The observed X-ray variability almost simultaneous with the steep optical rise (Prieto et al. 2012, Atel #4439), likely indicates a connection of the X-ray source with SN 2009ip.

Swift/XRT image and light curve