High density reflection modeling of the transient BH XRB MAXI J1803-298

The newly discovered transient X-ray binary MAXI J1803-298 went into outburst on 1 May 2021, and was initially detected with MAXI/GSC. MAXI J1803-298 brightened in the hard state before undergoing a hard-to-soft state transition beginning on May 12. We report on the results of a NuSTAR Target-of-Opportunity (TOO) observation that began on 14 May, while MAXI J1803-298 was still in its intermediate state and near its peak outburst flux (~200 counts/s/FPM in NuSTAR). We observe clear reflection signatures in the source spectrum and carry out detailed modeling of the full NuSTAR spectrum with high-density reflection models. We are unable to constrain the black hole spin with our best-fitting model, which uses a lamppost geometry