Swift/XRT observations of the Galactic center detect ongoing X-ray activity of the transient candidate black hole X-ray binary MAXI J1744-294

ATel #17659; N. Degenaar (U. of Amsterdam), M. T. Reynolds (U. of Michigan/Ohio State U.), R. Wijnands (U. of Amsterdam), J. M. Miller (U. of Michigan), J. A. Kennea (PSU), on behalf of a larger collaboration
on 9 Feb 2026; 14:31 UT
Credential Certification: Nathalie Degenaar (degenaar@uva.nl)

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On 2026 February 4, Swift resumed its daily X-ray monitoring of the Galactic center after the region had been Sun-constrained for 3 months (see Degenaar et al. 2015, JHEA, 7, 137 for a description of this program). Within the monitored region of approximately 20x20 arcmin centered on Sgr A*, currently one active transient is seen. It is located close to Sgr A* and consistent with the position of the candidate black hole X-ray binary MAXI J1744-294. This source was seen in outburst from 2025 January onwards (e.g., ATels #16975, #17010, #17087, #17354) and was still detected during the last XRT observation taken before the Sun-constrained window on 2025 October 31. Resumed Swift monitoring thus detects ongoing X-ray activity of MAXI J1744-294.

We utilized the online XRT products tool (Evans et al. 2009) to estimate the current spectral shape and brightness of MAXI J1744-294. In the six XRT PC-mode exposures obtained so far (0.1-1.1 ks, ObsIDs 00098343154-59), the source is detected with a net XRT count rate of 1.8-2.3 c/s. Fitting the obtained spectral data with an absorbed power-law model yields photon indices of 1.4-2.2 and a hydrogen column density of (1.4-2.1)e23 cm-2. The resulting absorbed 0.3-10 keV fluxes are(1.8-3.2)e-10 erg/s/cm2.

We note that the bursting, eclipsing neutron star X-ray binary AX J1745.6-2901, which was also active before the Sun-constrained window, is no longer detected in the 2026 Swift/XRT images. This source has thus returned to quiescence after a long outburst that had persisted since 2023 June (ATels #16436, #16642, #17192).