Exploring the Small Magellanic Cloud to the Faintest X-ray Fluxes: Source Catalog, Timing and Spectral Analysis

TL;DR

This study uses deep Chandra X-ray observations of the Small Magellanic Cloud to catalog faint X-ray sources, analyze their timing and spectral properties, and identify new pulsars and high-mass X-ray binary candidates, revealing a dense HMXB population.

Contribution

It provides the first comprehensive catalog of faint X-ray sources in the SMC with timing and spectral analysis, discovering new pulsars and HMXB candidates, and compares results with previous surveys.

Findings

Discovered two new pulsars in outburst.

Detected 13 of 15 known Be-pulsars, with pulsations in 9.

Found quiescent X-ray emission is common among pulsars.

Abstract

We present the results of a pair of 100 ksec Chandra observations in the Small Magellanic Cloud to survey high mass X-ray binaries (HMXBs), stars and LMXBs/CVs down to Lx = 4.3 x 10^32 erg/s The two SMC Deep Fields are located in the most active star forming region of the bar, with Deep Field-1 positioned at the most pulsar-rich location identified from previous surveys. Two new pulsars were discovered in outburst: CXOU J004929.7-731058 (P=892s), CXOU J005252.2-721715 (P=326s), and 3 new HMXB candidates were identified. Of 15 Be-pulsars now known in the field, 13 were detected, with pulsations seen in 9 of them. Ephemerides demonstrate that 6 of the 10 pulsars known to exhibit regular outbursts were seen outside their periastron phase, and quiescent X-ray emission at Lx=10^33 - 10^34 is shown to be common. Comparison with ROSAT, ASCA, XMM-Newton catalogs resulted in positive identification of several previously ambiguous sources. Bright optical counterparts exist for 40 of the X-ray sources, of which 33 are consistent with early-type stars Mv<-2, B-V<0.2), and are the subject of a companion paper. The results point to an underlying HMXB population-density up to double that of active systems. The full catalog of 394 point-sources is presented along with detailed analyses of timing and spectral properties.