VLA Observations of XTE J1739-285

Michael Rupen, Vivek Dhawan, & Amy Mioduszewski

Last update: 12 September 2005

Please do not use these results without first contacting M. Rupen. These results are preliminary, and provided here primarily to aid other observers.

All error bars are 1sigma unless otherwise noted.

Astronomer's Telegrams

ATel 604: 12sep05
Radio Observations of XTE J1739-285
M.P. Rupen (NRAO/GSFC), A.J. Mioduszewski, V. Dhawan (NRAO)
Posted: 12 Sep 2005; 20:28 UT

Very Large Array (VLA) observations of the X-ray transient XTE J1739-285 (IAUC 7300) during its on-going X-ray outburst (ATel #592, #602) have detected no radio source within the Swift error circle (ATel #602), and no variable source within the INTEGRAL or RXTE error circles (ATel #592; IAUC 7300). For the Swift error circle:
UT Frequency rms noise Min. Max.
27 Aug. 2005, 04.2 hrs 4.86 GHz 0.097 mJy/beam -0.16 mJy/beam +0.07 mJy/beam
29 Aug. 2005, 03.8 hrs 4.86 GHz 0.085 mJy/beam -0.20 mJy/beam +0.12 mJy/beam
4 Sep. 2005, 01.4 hrs 4.86 GHz 0.095 mJy/beam -0.16 mJy/beam +0.19 mJy/beam
4 Sep. 2005, 01.5 hrs 8.46 GHz 0.109 mJy/beam -0.16 mJy/beam +0.21 mJy/beam
In this table, the rms noise is the root-mean-squared noise measured in a source-free region near the Swift error box; the min. and max. are the minimum and maximum flux densities observed within the Swift error box, and are consistent with no detection. Summing up the 4.86 GHz data from all three days gives an rms noise level of 0.053 mJy/beam, and min/max within the Swift error circle of -0.090/+0.048 mJy/beam. A contour plot of this image is available here.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

ATel 602: 3sep05
Swift XRT position for XTE J1739-285
M.A.P.Torres, D.Steeghs (CfA), R.Greimel (ING), T.Augusteijn (NOT)
Posted: 3 Sep 2005; 14:09 UT

Following the recent report of renewed activity in the X-ray transient XTE J1739-285 (ATEL #592, IAUC 7300), we have obtained a Swift TOO observation of the field covering this transient on 2005 Sept 03 05:54:51-06:12:41 UT. The X-ray Telescope (XRT) observation was obtained in Photon Counting mode recording a mean event-rate of 6.4 counts/sec.
A single X-ray source was detected in the field of view of the XRT at the following position: RA(J2000): 17:39:54.2, Dec(J2000): -28:29:44 with an estimated uncertainty of 6 arcseconds. This is 1.3 arcminutes from the INTEGRAL position reported in ATEL #592.
We also acquired three 180s R-band images of the field with the 2.5m Nordic Optical Telescope at La Palma Observatory on 2005 Sep 02 20:59-21:14 UT with seeing conditions close to 0.8 arcsec. An astrometric frame was established using USNO stars. Five point sources were detected within the 6 arcsec SWIFT error circle, two of which have known 2MASS counterparts. Additional observations are planned in order to identify the optical/NIR counterpart to XTE J1739-285.

ATel 592: 26aug05
INTEGRAL detects XTE J1739-285
A. Bodghee, N. Mowlavi (ISDC, Geneva); E. Kuulkers (ESA/ESAC, Spain); R. Wijnands (UvA, Netherlands); S. E. Shaw (Southampton, UK/ISDC, Geneva); T. Courvoisier (ISDC, Geneva); C. Markwardt (NASA/GSFC, USA); T. Oosterbroek, A. Orr (ESA/ESTEC, Netherlands); A. Paizis (ISDC, Geneva/IASF, Milano); K. Ebisawa (NASA/GSFC, USA); P. Kretschmar (ESA/ESAC, Spain)
Posted: 26 Aug 2005; 16:52 UT

The JEM-X telescope on board INTEGRAL detected the X-ray transient XTE J1739-285 while monitoring the Galactic Bulge in revolution 350. The source was detected in three successive pointings of 30 minutes each, starting on 2005-08-25T14:40 UTC. The fluxes in the 3-10 keV band were about 120, 70 and 77 mCrabs, respectively, and about 70, 30 and 40 mCrabs in the 10-20 keV band. The source was not detected above 20 keV by the ISGRI instrument, with an upper limit of 5 mCrabs. The source position (J2000) derived by JEM-X is R.A.=17 40.0 and Dec.=-28 30 (2' accuracy), which is within the 5' accuracy of the position derived by RXTE in 1999 (IAUC 7300). The spectrum can be modeled with a power law with a photon index of 2.9+/-0.1, yielding a flux of 1.8e-9 ergs/cm2/s in the 2-10 keV band. Follow-up observations at other wavelengths are encouraged.

Radio images

This is the central section (+/-2.2 arcmin) of a VLA 4.86 GHz image made by combining the uv-data from Aug. 27, Aug. 29, and Sep. 4, 2005. The rms noise is 0.053 mJy/beam. The error circles from INTEGRAL's JEM-X (ATel #592) and the Swift XRT (ATel #602) are indicated. Neither of the two radio sources visible here (just outside the JEM-X error circle to the upper right, and about halfway down that error circle to the lower left) show signs of variability. The other contours are shown to give a feeling for the map noise.

VLA 4.9 GHz image, 27aug05-4sep05


Please send any questions, comments, or suggestions to Michael Rupen at the e-mail address given below.

Last modified 12 September 2005