Anomalous Outbursts of H 1743-322

TL;DR

This study analyzes multiple outbursts of H 1743-322 using RXTE/ASM data, revealing variations in the Keplerian disc size, spectral transition behavior, and identifying the 2008 outburst as anomalous, highlighting the source's enigmatic nature.

Contribution

We introduce a new approach using the dynamic photon index to analyze outburst behavior and identify anomalous events in H 1743-322.

Findings

The Keplerian disc size varies across outbursts, being largest in 2003.

Spectral transitions are governed by the dynamic photon index {}.

The October 2008 outburst was identified as anomalous.

Abstract

Using black body and power-law photon counts of All Sky Monitor (ASM) in Rossi X-ray Timing Explorer (RXTE) satellite it has been established recently by us that there is a significant time lag between the infall timescales of two components in the Two-Component Advective Flow (TCAF) paradigm, where a standard slow moving Keplerian disc is surrounded by a fast moving halo. The time lag is clearly due to the difference in viscosity in the flow components and the size of the Keplerian disc may be considered to be proportional to the arrival time lag. In this paper, using RXTE/ASM (1.5-12 keV) data, we examine eight successive outbursts of the low-mass X-ray binary H 1743-322 since 2003 from a new angle. A dynamic photon index, {\Theta} indicates that the size of the Keplerian disc is biggest during the brightest outburst of 2003. The size diminishes thereafter during subsequent weaker outbursts. These results are corroborated when two energy fluxes corresponding to the two flows are cross-correlated with reference to {\Theta}. Moreover, {\Theta} decides spectral transitions of any outburst. We show from the behaviour of {\Theta} alone that the outburst of October 2008 was an anomalous outburst. In fact, each normal outburst was either preceded or followed by an otherwise premature outburst. This makes H 1743-322 an enigmatic source and a subject of further study.