ATel #13474: INTEGRAL detects a rebrightening of the accreting neutron star XTE J1739-285

C. Sanchez-Fernandez*, C. Ferrigno, E. Bozzo, V. Savchenko, J. Chenevez, L. Sidoli, A. Paizis, E. Kuulkers, J. J. E. Kajava, L. Ducci

*Corresponding author for this work

Research output: Other contributionNet publication - Internet publicationResearch


During observations of the Galactic Center region, INTEGRAL has detected renewed activity of the neutron star X-ray binary XTE J1739-285, which was suggested to have the fastest spin rate, based on burst oscillations (Kaaret et al., 2007, ApJL 657, 2, L97-L100). The most recent outburst from this system was reported in September 2019 (ATel #13138 ). The source was observed by INTEGRAL from February 8 at 9:23 to Feb 9 at 00:07 (UT), and from February 12 at 14:42 to Feb 13 at 5:25 (UT). Between these two observations the source flux as seen by IBIS/ISGRI in the 28-40 keV energy band increased from 15+/-2 mCrab to 20+/-2 mCrab, which suggests we are observing the onset of a new outburst of this system. Fitting the combined source spectrum in the 20-100 keV energy with a power law model, we derive a photon index = 4.2 (-1.2/+1.6) and a 20-100 keV flux =2.0 ± 0.4 1e-10 erg/s/cm2 (net exposure of 54 ks). The source was detected at the edge of the JEM-X field of view of two science windows (3 ks total) during these observations, from which we derive a preliminary 3-sigma upper limit of about 10 mCrab in the 3-20 keV energy range. No Type-I X-ray bursts have been detected by JEM-X. Additional observations of the Galactic Center region by INTEGRAL will be performed in the coming days. We encourage follow up of this source at all wavelengths.
Original languageEnglish
Publication date13 Feb 2020
VolumeATel #13474
Number of pages1
Publication statusPublished - 13 Feb 2020
SeriesThe Astronomer's telegram


  • X-ray
  • Gamma Ray
  • Binary

Cite this

Sanchez-Fernandez, C., Ferrigno, C., Bozzo, E., Savchenko, V., Chenevez, J., Sidoli, L., Paizis, A., Kuulkers, E., Kajava, J. J. E., & Ducci, L. (2020, Feb 13). ATel #13474: INTEGRAL detects a rebrightening of the accreting neutron star XTE J1739-285. The Astronomer's telegram