[vsnet-grb-info 15243] Pre-discovery observations of SGR 1935+2154 in Swift archival data

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16535
SUBJECT: Pre-discovery observations of SGR 1935+2154 in Swift archival data
DATE:    14/07/07 13:45:22 GMT
FROM:    Sergio Campana at INAF-OAB  <sergio.campana at brera.inaf.it>

S. Campana (INAF-Brera),  A. de Ugarte Postigo (IAA-CSIC, DARK/NBI),
C. C. Thoene (IAA-CSIC), J. Gorosabel (IAA-CSIC/UPV-EHU),
N. Rea (CSIC-ICE Barcelona) , F. Coti Zelati (Universita` dell'Insubria, 
INAF-Brera)

Swift/XRT observed the new magnetar SGR 1935+2154 (Stamatikos et al. GCN 
16520)
twice before the activation of the source during the monitoring of the 
Galactic plane.

The first observation took place on Dec 30, 2010 for 519 s (obsid 
00045278001).
SGR 1935+2154 is far off-axis and it is barely detected at a rate of
5.4E-03 ± 3.9E-03 cts/s (using sosta within XIMAGE
at the enhanced Swift XRT position, Osborne et al. GCN 16521).

The second observation took place on Aug 28, 2011 for 623 s (obsid 
00045271001).
SGR 1935+2154 is detected at a rate 1.55E-02 ± 0.63E-02 cts/s at
RA(J2000)= 19h34m55.75s
Dec(J2000)= 21:53:49.15
with an error radius of 8.6 arcsec.
This position lies at 1.4 arcsec from the enhanced Swift position.

If the source was in quiescence at that time, the outburst showed only an
increase of the persistent flux of a factor of a few.