INTEGRAL and Swift detection of high energy emission from Swift J1749.4-2807
ATel #2548; L. Pavan (ISDC, Switzerland), J. Chenevez (DTU space, Denmark), E. Bozzo (ISDC, Switzerland), E. Kuulkers (ESA/ESAC, Spain), J. Alfonso-Garzon (LAEX-CAB/INTA-CSIC, Spain), V. Beckmann (APC, France), T. Bird (Southampton, UK), S. Brandt (DTU/NSI, Denmark), T. Courvoisier (ISDC, Switzerland), A. Domingo (LAEX-CAB/INTA-CSIC, Spain), K. Ebisawa (ISAS, Japan), P. Jonker (SRON, The Netherlands), P. Kretschmar (ESAC/ESA, Spain), C. Markwardt (GSFC, USA), T. Oosterbroek (ESTEC/ESA, The Netherlands), A. Paizis (INAF-IASF, Italy), C. Sanchez-Fernandez (ESAC/ESA, Spain), R. Wijnands (UvA, The Netherlands)
on 12 Apr 2010; 21:41 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Nami Mowlavi (Nami.Mowlavi@obs.unige.ch)
Subjects: X-ray, Gamma Ray, Request for Observations, Neutron Star, Transient
During the observations of the Galactic bulge, performed from 2010-04-10 22:00:00
to 2010-04-11 01:41:36 (UTC), INTEGRAL detected high energy emission from a
position coincident with the burst-only source Swift J1749.4−2807 (GRB060602B).
The source is detected at 8 sigma in the IBIS/ISGRI mosaic
in the energy band 20-40 keV.
We used all data of this observation to extract the ISGRI spectrum.
The spectrum could be equally well fitted by using
a power law (photon index 2.5+/-0.9) or a blackbody model
with kT=7.9(+2.6,-1.9) keV. The estimated flux in the
20-40 keV energy band was of 1.3E-10 erg/cm^2/s
(corresponding to 17mCrab, effective exposure time 8.4 ks).
The ISGRI lightcurve did not show any clear evidence for a short burst with a
fast rise and decay time, similar to that observed previously
from this source (Wijnands et al. 2009, MNRAS, 393, 126;
Campana, 2009, ApJ 699 1144).
The source was also detected by both JEMX1 and
JEMX2 at a significance of 4.5 and 3.3 sigma
in the energy bands 3-10 keV and 10-25 keV,
respectively (effective exposure time 6.5 ks).
Given the low significance of the detection,
we roughly estimated a source X-ray flux
of ~10-20 mCrab.
Previous observations of the region of
Swift J1749.4-2807 were performed by INTEGRAL
from 2010-04-07 13:31:59 to 2010-04-07 17:13:34 for
an exposure time of 15 ks (IBIS) and 9 ks (JEM-X).
On that occasion the source was not detected.
We estimated a 5 sigma upper limit on the source X-ray flux
of 10(17) mCrab in the 20-40(40-100) keV energy bands and
5(2) mCrab in the 3-10(11-25) keV energy bands.
The source activity has been confirmed using a Swift ToO observation
performed from 2010-04-11 23:41:10 to 2010-04-12 04:48:48 (UTC).
The Swift lightcurve does not present any evidence for a fast rise and decay.
After clearing of the data for pile-up, the spectrum
is well fitted by a powerlaw model with photon index 2.6+/-0.2
and NH=3.4+/-0.4 10^22 cm-2. The inferred model flux in the 0.5-10 keV band,
not corrected for absorption, is 3.0E-10 erg/cm^2/s.
These values are in agreement with those
reported in Campana, 2009, soon after the burst (powerlaw index 2.7, NH=4.0 10^22 cm-2).
Further INTEGRAL observations of the Galactic
bulge will be performed from 2010-04-13 15:00:00
2010-04-13 18:41:45 (UTC).
We are grateful to the Swift PI, Neil Gehrels, and the Swift mission operations team for their prompt scheduling of the Swift observations.