INTEGRAL observations of the on-going outburst from the new X-ray transient Swift J1728.9-3613

L Ducci*, V. Grinberg, J. Wilms, L. Sidoli, A. Paizis, J. Chenevez, E. Bozzo, C. Ferrigno, V. Savchenko

*Corresponding author for this work

Research output: Other contributionNet publication - Internet publicationResearch

Abstract

The new X-ray transient source Swift J1728.9-3613 (ATel #12436, ATel #12437, ATel #12443, ATel #12445, ATel #12455, GCN #23800) has been recently detected by INTEGRAL during the monitoring of the Galactic Center (INTEGRAL revolution 2056; PI: J. Wilms).

We extracted the IBIS/ISGRI and JEM-X mosaics combining the available near real time (NRT) INTEGRAL observations (from 2019-02-12 11:55 to 2019-02-12 13:39 UTC; IBIS/ISGRI exposure time: ~5.7ks; JEM-X exposure time: ~2.7ks) and found that the source is detected at a significance of 27 σ in the 20-40 keV energy range and about 12 σ in the 40-80 keV energy range. The corresponding fluxes are 103 ± 4 mCrab and 96 ± 8 mCrab, respectively.

In the JEM-X mosaics, the source is detected at a significance of 60 σ in the 3-10 keV energy range and about 16 σ in the 10-25 keV energy range. The corresponding fluxes are 337 ± 9 mCrab and 154 ± 16 mCrab, respectively.

The average preliminary JEM-X + IBIS/ISGRI spectrum (4-100 keV) can be described (χ2red=1.5, 19 dof) with an absorbed power law with photon index of 2.9 ± 0.1 and exponential rolloff at 50 (+31, -15) keV. We fixed the absorption column density at NH=3.4E22 cm-2, according to the previous measurement in the ATel #12455. The 4-100 keV flux estimated from the spectral fit is (5.3 ± 0.8)*1E-9 erg/cm2/s (all unertainties are given at 68% confidence level). The photon index and flux are consistent with those measured by NICER about two weeks ago (ATel #12455), indicating that during this period the source did not change significantly its spectral state.

A more complete analysis will be carried on the consolidated INTEGRAL data.
Original languageEnglish
Publication date13 Feb 2019
Publication statusPublished - 13 Feb 2019
SeriesThe Astronomer's telegram
NumberATel #12502

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