{
  "email": "weidong@astron.berkeley.edu",
  "submitter": "Weidong Li at UC Berkeley KAIT/LOSS  <weidong@astron.berkeley.edu>",
  "createdOn": 1200220898000,
  "subject": "XRB 080109/SN 2008D: Early decline in brightness and change in colors",
  "body": "Weidong Li, Ryan Chornock, Ryan J. Foley, Alexei V. Filippenko, \nMaryam Modjaz, Dovi Poznanski, and Joshua S. Bloom (UC Berkeley) \nreport: \n\nWe analyzed the Swift/UVOT images of XRB 080109/SN 2008D in the \nU, B, and V filters taken on Jan 11 and 12 UT. We constructed \ntemplate images for the field from follow-up data taken for \nSN 2007uy, and attempted image subtraction to remove the heavy\ngalaxy contamination at the site of SN 2008D. We were able to\nobtain clean subtracted images as demonstrated at\nhttp://astro.berkeley.edu/~bait/sn2008d.uvot-sub.gif\n\nUsing the calibration and photometry recipe of the UVOT \nU, B, V filters as described by Li et al. (2006, PASP 118, 37), \nwe obtained the following photometry for SN 2008D. We used\nt_0 as determined by Modjaz et al. (GCN 7175). \n\nUT date       t(days)   Total exp. time       Mag and err \n\nJan 11.569     2.0047      2771.32s           U = 18.65 +/- 0.04   \nJan 11.591     2.0265      2579.13s           B = 19.05 +/- 0.04   \nJan 11.585     2.0203      2349.89s           V = 18.38 +/- 0.05   \n\nJan 12.408     2.9434       730.82s           U = 19.02 +/- 0.07  \nJan 12.409     2.8443       668.02s           B = 19.34 +/- 0.07  \nJan 12.445     2.8802       605.26s           V = 18.56 +/- 0.08  \n\nThe SN is seen to decline in the U (by 0.37 mag), B (by 0.29 mag),\nand V (by 0.18 mag) filters between t = 2.0-2.9 d after the XRB. \nAs the SN declined faster in U than in V, it became progressively\nredder during this period. \n\nPossible explanations for the decline in the brightness at such early \ntimes for SN 2008D in the context of a SN Ib/c include the following.\n(a) The SN had a bright initial optical flash from shock breakout,\nand is now declining due to adiabatic expansion, similar to what\nwas observed for SN 1999ex (Stritzinger et al. 2002, AJ 124, 2100).\nIf this is the case, the SN will brighten again when the energy\ninput from radioactive decay starts becoming visible.\n(b) The object is still dominated by the afterglow emission\nfrom the XRB, similar to SN 2003dh/GRB 030329. However, spectroscopy\nby Malesani et al. (GCN 7169), Blondin et al. and Valenti et al. (CBET \n1205) indicate rather strong SN features with no prominent power-law \ncontinuum.\n(c) The SN has a similar behavior to the peculiar SN 2005bf\n(Folatelli et al. 2006, ApJ 641, 1039), with two broad peaks in \nthe light curves. However, the first peak of SN 2005bf was reached\nmore than 20 d after its discovery, and SN 2008D may have a \nvery early and sharp first peak at t < 2 d. \n\n[GCN OPS NOTE(14jan08): Per author's request, the Malesani reference\nwas added to the \"(b)\" paragraph.]",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>",
  "eventId": "SN 2008D",
  "bibcode": "2008GCN..7176....1L",
  "version": 2,
  "circularId": 7176,
  "editedOn": 1777053110462
}