Swift/XRT position of MAXI J1744-294 near Sgr A*
ATel #17010; C. O. Heinke (U. Alberta), M. Nakajima, Y. Kudo, H. Negoro (Nihon U.), A. Bahramian, J. Miller-Jones (Curtin U.), N. Degenaar (U. Amsterdam), T. Maccarone (Texas Tech), F. Yusef-Zadeh (Northwestern U.), G. R. Sivakoff, M. Ridder (U. Alberta)
on 2 Feb 2025; 06:10 UT
Credential Certification: Craig Heinke (cheinke@virginia.edu)
Subjects: X-ray, Black Hole, Transient
MAXI reported a new X-ray transient near the Galactic Center from Jan. 2, 2025, tentatively named MAXI J1744-294 (Atels #16975, #16983, #17009). Its average MAXI 4-10 keV flux was estimated at 252 mCrab on Jan. 13-15. Swift/BAT data also detected emission from the Galactic Center at 0.2 Crab from Jan. 14-16, though it has not been detectable in Swift/BAT since then.
We requested Swift/XRT tiling of the MAXI error circle (target IDs 19509, 19512, 19513), which were executed with observation lengths of 350, 290, and 300 seconds respectively, on Feb. 1, 2025. Two sources are visible in the last image, close to Sgr A*. A fainter source is consistent within 10" of the position of AX J1745.6-2901 (with countrate of order 0.2 counts/s), while a brighter source (countrate 6 counts/s) appears centered 25" southeast of Sgr A*. The Swift online tool (Evans et al. 2009) gives an enhanced position for the bright source of 17:45:41.93, -29:00:35, with 6.4" uncertainty. As the source is piled up, and Swift astrometric refinement is not easy in this field, the astrometric uncertainty may be larger. As this bright source appears uncataloged and previously undetected, we deem it is the likely counterpart to MAXI J1744-294.
We extracted a spectrum using the Swift online tool, which attempts to correct for pileup (though this can be difficult due to crowding in this region). Fits to an absorbed power-law gave a curiously high photon index of 5.5+-0.8, and N_H of 2.1*10^23 cm^-2. Alternatively, fits to an absorbed disk-blackbody gave a temperature of 0.8+-0.1 keV, and N_H=1.3+-0.2*10^23 cm^-2. The absorbed 2-10 keV flux for either model is 1.0*10^-9 ergs/cm^2/s, while the unabsorbed 2-10 keV flux varies from 3.3*10^-9 for the diskbb model to 1.0*10^-8 ergs/cm^2/s for the power-law model. At an 8 kpc distance (implied by its location near Sgr A*), this gives luminosity estimates of 2-8*10^37 erg/s. We consider that MAXI J1744-294 is likely in the soft state now, as suggested by Atel #16983. Further observations will soon become possible with other pointed X-ray instruments, as it emerges from Sun constraints.
We thank the Swift team for their rapid response.