Resolving a Class I Protostar Binary System with Chandra

TL;DR

This study spatially resolved and analyzed X-ray emissions from a Class I protostar binary system IRS 5, revealing distinct flare activities and spectral properties of the individual sources using Chandra data.

Contribution

First X-ray study of individual sources in a close Class I protostar binary system with sub-arcsecond separation, utilizing a novel sub-pixel event repositioning technique.

Findings

IRS 5a exhibited multiple long-lasting X-ray flares.

IRS 5b was mostly quiescent, with one flux enhancement.

Both sources had similar spectra in quiescence, with NH ~4e22 cm-2 and kT ~2 keV.

Abstract

Using a sub-pixel event repositioning technique, we spatially resolved X-ray emission from the infrared double system IRS 5 in the R Corona Australis molecular cloud with ~0.8" separation. As far as we know, this result - obtained from 8 Chandra archival observations between 2000 and 2005 - is the first X-ray study of individual sources in a Class I protostar binary system with a projected separation of less than 200 AU. We extracted light curves and spectra of the individual sources using a two-dimensional image fitting method. IRS 5a at the south, the source which was brighter in the near-infrared, showed three X-ray flares lasting >20 ksec, reminiscent of X-ray flares from pre-main sequence stars, while the northern source (IRS 5b) was quiescent in X-rays in all the observations except for a 2005 August 9 observation with a factor of ~2 flux enhancement. In quiescence, these sources showed almost identical X-ray spectra, with NH ~4e22 cm-2, kT ~2 keV, and log Lx ~30.2-3 ergs s-1. IRS 5a showed plasma at temperatures up to kT ~5-6 keV during flares, while the column density of IRS 5b increased by a factor of 2 during an observation on 2005 August 9. We discuss the evolutionary stages and variation of the X-ray activity of these sources.