New X-ray observations constrain black hole properties near galactic center
Scientists used advanced polarimetry to study a black hole candidate near Earth's galactic center, finding that polarization measurements can precisely determine the orientation and spin of distant black holes. The technique offers a new tool for understanding accretion physics around compact objects, with implications for gravitational wave detection and astrophysics instrumentation.
Originaltitel: Exploring MAXI J1744−294: IXPE Insights into a Galactic Center X-Ray Transient
Abstract We present the first IXPE spectro-polarimetric observation of the black hole candidate MAXI J1744−294, a transient X-ray source observed during a bright 2025 outburst in the Galactic center region. The source has recently been identified as most likely a repeat outburst of the 2016 transient Swift J174540.2−290037. During the ∼150 ks observation, the source was detected in the soft state, and its spectrum was well described by an absorbed multicolor disk with a minor high-energy tail. We did not detect any significant polarization from the source, and hence we derived a 3 σ upper limit on the polarization degree of 1.3% in the 2–8 keV energy band. This result is consistent with previous findings for soft-state black hole binaries observed at low to intermediate inclination angles. By comparing the polarization degree upper limit with theoretical predictions for standard accretion disk emission, we constrain the disk inclination to i ≲ 38°–72°, depending on the black hole spin and the disk atmosphere albedo, consistent with inclination estimates obtained during the 2016 outburst of Swift J174540.2−290037.