Integral and Rxte/Asm Observations on Igr J17098-3628

TL;DR

This study analyzes long-term X-ray variability of IGR J17098-3628 using RXTE/ASM and INTEGRAL data, revealing outbursts and timing behaviors that suggest it is likely a low-mass X-ray binary (LMXB).

Contribution

It provides the first detailed correlation of soft and hard X-ray outbursts for IGR J17098-3628, supporting its classification as an LMXB.

Findings

Detected a 5-day outburst in March 2005 at >20 keV.

Observed a ~2-day lag between hard and soft X-ray peaks.

Suggested a possible LMXB nature based on outburst behavior.

Abstract

To probe further the possible nature of the unidentified source IGR J17098-3628, we have carried out a detailed analysis of its long-term time variability as monitored by RXTE/ASM, and of its hard X-ray properties as observed by INTEGRAL. INTEGRAL has monitored this sky region over years and significantly detected IGR J17098-3628 only when the source was in this dubbed active state. In particular, at $\ge$ 20 keV, IBIS/ISGRI caught an outburst in March 2005, lasting for $\sim$5 days with detection significance of 73$\sigma$ (20-40 keV) and with the emission at $< $200 keV. The ASM observations reveal that the soft X-ray lightcurve shows a similar outburst to that detected by INTEGRAL, however the peak of the soft X-ray lightcurve either lags, or is preceded by, the hard X-ray ($>$20 keV) outburst by $\sim$2 days. This resembles the behavior of X-ray novae like XN 1124-683, hence it further suggests a LMXB nature for IGR J17098-3628. While the quality of the ASM data prevents us from drawing any definite conclusions, these discoveries are important clues that, coupled with future observations, will help to resolve the as yet unknown nature of IGR J17098-3628.