[vsnet-grb-info 5521] Swift UVOT Monitoring of the SN 2008D Brightening (Transient in NGC 2770)

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7185
SUBJECT: Swift UVOT Monitoring of the SN 2008D Brightening (Transient in NGC 2770)
DATE:    08/01/15 18:08:04 GMT
FROM:    Stefan Immler at NASA/GSFC  <immler at milkyway.gsfc.nasa.gov>

S. Immler (NASA/UMCP/GSFC) reports on behalf of the Swift team:

Regular Swift UVOT monitoring of the optical counterpart to the X-ray
transient in NGC 2770, SN 2008D (Atel 1353), shows a brightening in
the v and b filters by 0.4 mag and 0.2 mag, respectively, over a 3-day
period (2008-01-13 01:24:08 UT to 2008-01-15 01:25:19 UT).
This rise confirms the onset of a supernova component (GCN 7183).
The following magnitudes are measured for observations starting on
2008-01-15 01:26:24 UT:

v = 18.3+/-0.1 (496 s exposure time),
b = 19.1+/-0.1 (496 s)
u = 19.6+/-0.2 (496 s),
uvw1 > 20.5 (3-sigma upper limit, 989 s),
uvm2 > 20.3 (3-sigma upper limit, 1247 s), and
uvw2 > 20.9 (3-sigma upper limit, 1983 s).

We further observe a decline of the optical counterpart in the v, b, and
u filters by 0.1 mag, 0.4 mag, and 0.6 mag, respectively, prior to the
rise (2008-01-11 02:40:44 UT to 2008-01-13 01:12:58 UT).

These magnitudes are on the UVOT photometric system (see Poole et al.,
2007, MNRAS, 383, 627) which in the optical is close to the Johnson
UBV system. They have not been corrected for Galactic extinction of
E(B-V) = 0.023 mag (Schlegel et al. 1998, ApJ 500, 525).

A full report on the complete Swift BAT, XRT, and UVOT data will be
released shortly.