Swift J123205.1-105602: Swift observations of a short, soft burst source
ATel #6871; J. R. Cummings, M. Gropp (PSU), K. L. Page (U. Leicester), M. Siegel (PSU)
on 3 Jan 2015; 19:22 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Jay R Cummings (jayc@milkyway.gsfc.nasa.gov)
Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, Request for Observations, Neutron Star, Soft Gamma-ray Repeater, Transient
A short burst occurred during a Swift slew at 15:23 on Jan 1, 2015. It
triggered Fermi GBM, trigger number 441818617. A significant source was
found in ground analysis of BAT slew data at RA, Dec 188.044, -10.956,
which is
RA (J2000): 12h 32m 10.5s
Dec (J2000): -10d 57' 21"
with an estimated 90% containment radius of 2.5 arcmin.
The lightcurve shows a single peak with a T90 of 0.018 +- 0.006 seconds.
There appears to be significant spectral lag.
The spectrum seen in BAT is soft. The best fit function is a blackbody
spectrum with kT = 9.6 +- 1.5 keV. A simple powerlaw fit has a photon
index of 3.3 +- 0.5. The blackbody fit gives a fluence between 15-150 keV in
0.1 seconds of (2.3 +- 0.6) x 10^-8 ergs/cm^2. Errors are 90% confidence.
We have analysed 3.3 ks of XRT data from 139.2 ks to 155.5 ks after the burst.
The data are entirely in Photon Counting (PC) mode. An X-ray source is
detected within the BAT error circle, which we designate Swift J123205.1-105602.
Using 2057 s of PC mode data and 3 UVOT images, we find an enhanced XRT position
(using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 188.02119, -10.93389 which is equivalent to:
RA (J2000): 12h 32m 05.09s
Dec(J2000): -10d 56' 02.0"
with an uncertainty of 2.4 arcsec (radius, 90% confidence). This position is
111 arcsec from the BAT position. The source has a mean count rate of
1.4e-02 ct/sec; we cannot determine at the present time whether it is fading.
The spectrum is not well-determined. However, the best fit results from the
data collected so far are: Gamma = 2.5 +- 0.5, with no evidence for NH above
the Galactic value of 3.5e20 cm^-2.
There is an optical source in the DSS consistent with the XRT source. The
source is detected in UVOT with a white magnitude of 18.44 +- 03. It shows no
significant variability over the 15 ks spanned by the observations.
A followup Swift TOO has been requested with the target number 20464, in order
to observe any fading and to refine the spectrum.
XRT automated analysis
