Swift Observations of SNe 2008hs and 2008hv

ATel #1862; P. J. Brown (Penn State), P. Milne (Steward Observatory), and S. Immler (NASA/CRESST/GSFC) on behalf of the Swift SN team
on 4 Dec 2008; 23:41 UT
Credential Certification: Peter J. Brown (pbrown@astro.psu.edu)

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Swift Ultra-Violet/Optical Telescope (UVOT) has observed SN 2008hs (CBET #1598, #1599 ) to brighten between two epochs beginning 2008-12-03.02 and 2008-12-04.47. The following UVOT magnitudes and 3 sigma upper limits were measured at these two epochs:

2008-12-03.02
uvw2 > 21.4
uvm2 > 20.8
uvw1 = 19.7 +/- 0.1
u = 17.7 +/- 0.1
b = 17.9 +/- 0.1
v = 17.9 +/- 0.1

2008-12-04.47
uvw2 = 20.4 +/- 0.2
uvm2 = 21.2 +/- 0.3
uvw1 = 18.7 +/- 0.1
u = 16.9 +/- 0.1
b = 17.3 +/- 0.1
v = 17.4 +/- 0.1

All magnitudes given are on the UVOT photometric system (Poole et al., 2008, MNRAS, 383, 627) which in the optical is close to Johnson UBV. They have not been corrected for extinction. The red UV-optical colors (see Brown et al. 2008, AJ, submitted, arXiv:0803.1265) and the early type galaxy suggest a type Ia SN (consistent with CBET #1599). The colors best match normal SNe Ia at about 5-10 days before maximum light (B band).

UVOT also observed SN 2008hv (CBET #1601, #1603 ) beginning at 2008-12-04.68 UT. The following UVOT magnitudes and 3 sigma upper limits were measured:

uvw2 > 20.7
uvm2 > 21.3
uvw1 = 19.6 +/- 0.1
u = 17.7 +/- 0.1
b = 17.5 +/- 0.1
v = 17.1 +/- 0.1

The red UV-optical colors and the early type galaxy suggest a type Ia SN. The colors alone leave a degeneracy between an extremely young (~10 days before max) or post-maximum (5-10 days after max) SN. The reported rising (CBET #1601) would favor the young, pre-maximum possibility, consistent with IR spectroscopic observations (CBET #1603).

Swift Supernovae