Swift J174510.8-262411

Notices:
GCN #13744 Cummings et al. 2012: initial Swift/BAT and XRT results
GCN #13745 Cummings et al. 2012: BAT refined analysis


ATel #4380 Swift J174510.8-262411: GROND discovery of a candidate near-IR counterpart

Arne Rau, Fabian Knust, D. Alexander Kann, Jochen Greiner (all MPE) report:

We observed the new transient Swift J174510.8-262411 / Swift trigger #533836 (Cummings et al. 2012, GCN 13744; Cummings et al. 2012, GCN #13745) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) at the 2.2m MPG/ESO telescope at La Silla Observatory (Chile). Observations were obtained on September 17th 01:40 UT and 03:49 UT for ~20min each and were compared to publicly available deep near-IR images obtained on June 24th 2011 as part of the VISTA Variables in the Via Lactea Survey (Minniti et al. 2010, New Astronomy, 15, 433; Saito et al. 2010, The Messenger, 141, 24).

Within the 5.8" Swift/XRT error circle (Cummings et al. 2012, GCN 13744) we identify a variable source in the GROND images that has brightened by approx. 3 magnitudes with respect to the deeper VISTA J-band image. We suggest this object to be the near-IR counterpart of Swift J174510.8-262411. It's position is

RA(J2000) = 17:45:10.82
Dec(J2000) = -26:24:12.7

with an uncertainty of 0"4 in both coordinates and it has an observed AB magnitude of

J~16.5 +/- 0.5

calibrated against 2MASS field stars. The high stellar density and moderate seeing (~1"9) lead to a rather large uncertainty in the photometry and an further analysis (e.g., multi-band magnitudes and spectral energy distribution) requires future observations under more favorable conditions.



VVV and GROND J-band image
J-band images from VVV (left) and GROND (right). Two error circles, both with radius=5.8", are shown: the red shows the XRT position from GCN #13744, while the green marks the location derived from the source name used in GCN #13745. The blue circle indicates the proposed candidate counterpart.