INTEGRAL observations of Terzan 5 X-3

ATel #15921; C. Ferrigno, V. Savchenko, E. Bozzo (ISDC, CH), L. Ducci (IAAT, De), C. Sanchez-Fernandez (ESA), J. Wilms (ECAP, De), F. Coti Zelati (ICE-CSIC, IEEC, Es)
on 1 Mar 2023; 14:04 UT
Credential Certification: Carlo Ferrigno (Carlo.Ferrigno@unige.ch)

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We report on X-ray spectral analysis of the transient source newly reported by MAXI in the direction of the globular cluster Terzan 5: MAXI J1747-249 (ATeL #15917), identified as Swift J174805.3-244637 or Terzan 5 X-3 (ATeL #15919).

The IBIS/ISGRI and JEM-X1 instruments detected, at a significance exceeding 20 σ (IBIS), a transient X-ray source at RA=267.01 and Dec=-24.78, a location compatible with the one of Swift J174805.3-244637.

We exploit the publicly available observations of this target performed between 2023-02-25 at 13:39 UT and 2023-02-27 at 16:18 to obtain a preliminary broad-band spectrum that can be described by an absorbed power law with spectral index Γ=2.77±0.09, n_H=13±7 ×10²² cm^-2 and 20-100 keV flux of ~2×10^-9 erg/s/cm² or about 100 mCrab (uncertainties are at 90% confidence level). The net exposure by IBIS/ISGRI is 30 ks and 19 ks for JEM-X.

With the inclusion of the Swift spectra accumulated on 2023-02-28 between 19:53 and 20:03, the preferred model is a power law with exponential cutoff with parameters n_H=3.9±0.6 ×10²² cm^-2, Γ=1.45(-0.12, +0.22), E_C=6(-2,+3) keV, E_F=34(-5, +8) keV. The relative normalizations have been left to vary between observations and are suggestive of a flux increase with time: the 1-6 keV power-law unabsorbed flux increased from 10^-9 to 2×10^-9 erg/s/cm² from 25 to 28 February 2023.

This analysis made use of the MMODA platform. INTEGRAL products have been posted at this URL (available to registered users).

Further INTEGRAL observations of the region around this source are expected in the coming days.