# GRO J1655-40: from ASCA and XMM-Newton Observations

## TL;DR

This paper analyzes multiple X-ray observations of GRO J1655-40 in high/soft state, modeling the spectra to estimate black hole spin, spectral hardening factor, and distance, revealing variability across observations.

## Contribution

It applies relativistic disk modeling to multiple datasets to estimate black hole parameters and explores the variability of spectral hardening factor and distance constraints.

## Key findings

- Black hole spin estimated from spectral modeling.
- Spectral hardening factor varies between observations.
- Distance constraints depend on the spectral hardening factor.

## Abstract

We have analysed four ASCA observations (1994--1995, 1996--1997) and three XMM-Newton observations (2005) of this source, in all of which the source is in high/soft state. We modeled the continuum spectra with relativistic disk model kerrbb, estimated the spin of the central black hole, and constrained the spectral hardening factor f_col and the distance. If kerrbb model applies, for normally used value of f_col, the distance cannot be very small, and f_col changes with observations.