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Swift/UVOT observations of PSN J11183170+5758372 -- a probable subluminous SN Ia

ATel #3527; Peter J. Brown (University of Utah)
on 3 Aug 2011; 02:28 UT
Credential Certification: Peter J. Brown (grbpeter@yahoo.com)

Subjects: Optical, Ultra-Violet, Request for Observations, Supernovae

The Ultraviolet/Optical Telescope (UVOT) on board the Swift satellite is observing PSN J11183170+5758372 in NGC 3613 as part of the Swift GI program "Improving Standard Candles through Ultraviolet Studies: The Effect of Host Galaxy Environment on Type Ia Supernovae" (PI: Brown). Observations began on 2011-07-22.13 UT and continue approximately every other day. The flux has increased in all filters and peaked about 2011-07-30. The following preliminary UVOT magnitudes were measured for the observation beginning on 2011-07-30.37: v = 15.0 +/-0.1 (164 s exposure time), b = 15.7 +/-0.1 (164 s), u = 16.5 +/-0.1 (164 s), uvw1 [181-321 nm] = 17.9 +/-0.1 (498 s), uvm2 [166-268 nm] = 20.9 +/-0.3 (1426 s), uvw2 [112-264 nm] = 19.4 +/-0.1 (833 s). These magnitudes are on the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) which in the optical is close to Johnson UBV, and have not been corrected for extinction.

Compared to other young SNe observed with Swift, the colors are very red and UV faint (Brown et al. 2009, AJ, 137, 4517). The absolute magnitudes at peak are comparable to the SN1991bg-like SN Ia 2005ke, though the uvm2 measurement of the PSN is about a magnitude fainter than 2005ke was at peak (Brown et al. 2010, ApJ, 721, 1608).

Spectroscopic confirmation is strongly encouraged while the SN is near maximum light.

Preliminary Swift/UVOT Lightcurve