English

A multiwavelength study of the Galactic center black hole candidate MAXI J1744-294

High Energy Astrophysical Phenomena 2026-02-10 v3

Abstract

For the first time in nearly a decade, a bright transient was detected in the central parsec (pc) of the Galaxy. MAXI J1744-294, or -- as it was known in its previous life -- Swift J174540.2-290037, was discovered in outburst by the MAXI telescope in January 2025. We present the results of a broadband, multi-wavelength study of MAXI J1744-294, including data from the NuSTAR, Chandra, XMM-Newton, Swift, and NICER X-ray telescopes, as well as complementary radio and near-infrared observations. We analyze the changing X-ray emission as the outburst evolved from the high/soft to the low/hard state. Using relativistic reflection features in the data, we estimate a spin of a>0.92a>0.92 and viewing inclination θ=284+3\theta=28^{+3}_{-4} deg, consistent with the parameters measured for Swift J174540.2-290037. Based on the spectral and temporal characteristics of MAXI J1744-294, we reaffirm its classification as a candidate black hole (BH) low-mass X-ray binary (LMXB) -- the third candidate BH transient discovered within 20 arcsec of the Galactic supermassive black hole Sgr~A*. This work provides further evidence for a cusp of BH-LMXBs in the central pc of our Galaxy, as argued for in previous observational studies and suggested by analytical and theoretical work. Our ongoing multi-wavelength study, involving a complementary range of observatories and spanning different outburst states, can serve as a model for future time domain astrophysics research.

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Cite

@article{arxiv.2509.14465,
  title  = {A multiwavelength study of the Galactic center black hole candidate MAXI J1744-294},
  author = {Shifra Mandel and Kaya Mori and Paul A. Draghis and Mark Reynolds and Chichuan Jin and Maxime Parra and Benjamin Levin and Eric Miao and Noa Grollimund and Anna Ciurlo and Sean A. Granados and Gaurava K. Jaisawal and Lorenzo Marra and Matteo Bachetti and Fiamma Capitanio and Nathalie Degenaar and Charles J. Hailey and JaeSub Hong and Sara Motta and Gabriele Ponti and Michael M. Shara and Megumi Shidatsu and John A. Tomsick and Randall Campbell and Stéphane Corbel and Rob Fender and Andrea Ghez and Jonathan Grindlay and Daryl Haggard and Matthew W. Hosek and Ziqian Hua and Ole König and Kai Matsunaga and Romana Mikušincová and Melania Nynka and Grace Sanger-Johnson and Giovanni Stel and Antonella Tarana and Rudy Wijnands and Shuo Zhang},
  journal= {arXiv preprint arXiv:2509.14465},
  year   = {2026}
}