[vsnet-grb-info 5510] XRB 080109/SN 2008D:PAIRITEL NIR observations and t_0 from Swift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7175
SUBJECT: XRB 080109/SN 2008D:PAIRITEL NIR observations and t_0 from Swift
DATE:    08/01/13 03:42:47 GMT
FROM:    Maryam Modjaz at UC Berkeley  <mmodjaz at astro.berkeley.edu>

M. Modjaz, J. S. Bloom, N. R. Butler, D. Starr (UC Berkeley), R. P. 
Kirshner, A. Friedman (Harvard/CfA) report on behalf of a larger 
collaboration:

"From our analysis of the Swift XRT data we find an explosion time for the 
start of XRB 080109 (Berger & Soderberg, GCN 7159; Kong & Marcone, ATEL 
1355) as viewed by Swift of:

      t_0 = 2008-01-09 13:32:49 UT (+/- 5 sec).

We observed the field of SN 2007uy (Nakano et al. IAUC 8908; Blondin et 
al. CBET 1191) with the 1.3m PAIRITEL on Mt. Hopkins on 2008-01-09 08:45 
UT, i.e. 4.5 hours before t_0. We started observing again on 2008-01-10 
06:23:06 UT, i.e. 17 hours after the burst and for the following nights.

The SN 2008D (Li & Filippenko, IAUC 1202; Soderberg et al., GCN 7165; 
Malesani et al., GCN 7169; Valenti et al., GCN 7171; Blondin et al., CBET 
1205, see also GCN 7160-7168) associated with XRB 080109 is clearly 
detected in mosaic-stacks of each ~1100-sec integration time. From 
preliminary reductions of multi-epoch observations on Jan 11 and Jan 12, 
using ~15-20 2MASS stars in the field for the zeropoint, we derive the 
following error-weighted aperture magnitudes:

Filter  midtime (UTC)           Magnitude       MagError
 J     2008-01-11 8.4           16.63           0.13
 H     2008-01-11 8.4           16.33           0.17
 K_s   2008-01-11 8.3           16.11           0.18

 J     2008-01-12 8.0           16.51           0.06
 H     2008-01-12 7.9           16.15           0.14
 K_s   2008-01-12 7.9           16.22           0.29

No strong variability is detected over those 2 nights but the source was 
clearly not visible at these magnitudes on Jan 9 UT. Further data 
reduction and observations are in progress.  SN 2007uy was measured to be
~1 mag brighter in the J, H, K_s filters on Jan 11 and 12 UT."

A comparison of the 9 Jan, 12 Jan and historical 2MASS imaging can be 
found at:"

       http://pairitel.org/2sne-fig4.tiff