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PAIRITEL Monitoring of SN 2007sr

ATel #1343; J. S. Bloom, D. Poznanski , M. Modjaz (UC Berkeley), M. Wood-Vasey, A. Friedman, R. P. Kirshner (Harvard/CfA)
on 24 Dec 2007; 23:47 UT
Credential Certification: J. S. Bloom (jbloom@cfa.harvard.edu)

Subjects: Infra-Red, Supernovae, Transient

We observed Transient CSS-071218 = SN2007sr (Drake et al. CBET 1172) with the Peters Automated Infrared Imaging Telescope (PAIRITEL; http://pairitel.org ) on 3 nights starting 21 Dec 2007 UT. The source is well detected in J, H, and Ks bands. Aperture photometry relative to the 2MASS catalog, reveals a slowly variable source with a color comparable to the stellar locus. At time MJD = 54455.482894, we find J= 13.99 +/- 0.03 mag, H - Ks = 0.15, J - H = 0.29. From Dec 21 to Dec 23 UT, the source dimmed by 0.29 +/- 0.05 mag in the J-band. At the distance of 13.8 Mpc, as measured by Saviane et al. (2004, AJ, 127, 660), the source is about 1.5 to 2 mag fainter than the average peak brightness of a SN Ia in those bands, as compiled by Krisciunas et al. (2004, ApJ, 602, L81), despite its early phase (cf. Umbriaco et al. CBET 1174). In addition, the colors appear somewhat redder than those derived using synthetic photometry on the Type-Ia "Nugent templates" (www.lbl.gov/~nugent/nugent_templates.html), at a similar phase (J - H ~ 0, H - Ks ~ 0.1), and redder than the colors at peak from Krisciunas et al. (J - H ~ -0.3 , H - K ~ 0.2). While a significant amount of dust along the line of sight might explain the color mismatch, the brightness discrepancy probably favors a greater distance to the Antennae galaxies, as much as 30 Mpc, consistent with a distance derived using Hubble's law. We acknowledge helpful discussions with A. Drake (Caltech) as well as support from the NSF-DDDAS/TMRP ("Real-Time Astronomy with a Rapid-Response Telescope Grid," PI Williams, R.).