XMM observation of 1RXS J180431.1-273932: a new M-type X-ray binary with a 494 s-pulse period neutron star?

Abstract

Low-mass X-ray binaries are binary systems composed of a compact object and a low-mass star. Recently, a new class of these systems, known as symbiotic $X$-ray binaries (with a neutron star with a M-type giant companion), has been discovered. Here, we present long-duration $XMM$ observations of the source 1RXS J180431.1-273932. Temporal and spectral analysis of the source was performed along with a search for an optical counterpart. We used a Lomb-Scargle periodogram analysis for the period search and evaluated the confidence level using Monte-Carlo simulations. The source is characterized by regular pulses so that it is most likely a neutron star. A modulation of $494.1\pm 0.2$ s (3$\sigma$ error) was found with a confidence level of $>$99%. Evidence of variability is also present, since the data show a rate of change in the signal of $\sim -7.7\times 10^{-4}$ counts s${}^{-1}$ hr${}^{-1}$. A longer observation will be necessary in order to determine if the source shows any periodic behavior. The spectrum can be described by a power law with photon index $\Gamma \sim 1$ and a Gaussian line at 6.6 keV. The X-ray flux in the 0.2--10 keV energy band is $5.4\times 10^{-12}$ erg s${}^{-1}$ cm${}^{-2}$. The identification of an optical counterpart (possibly an M6III red-giant star with an apparent visual magnitude of $\simeq 17.6$) allows a conservative distance of $\sim 10$ kpc to be estimated. Other possibilities are also discussed. Once the distance was estimated, we got an $X$-ray luminosity of $L_X\ut<6\times 10^{34}$ erg s${}^{-1}$, which is consistent with the typical $X$-ray luminosity of a symbiotic LMXB system.

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References in corpus (2)

• M-type giants as optical counterparts of X-ray sources 4U 1700+24 and 4U 1954+319
• A 33 hour period for the Wolf-Rayet/black hole X-ray binary candidate NGC 300 X-1

Cited by in corpus (8)

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• XRBcats: Galactic Low Mass X-ray Binary Catalogue
• A Comparison of the Variability of the Symbiotic X-ray Binaries GX 1+4, 4U 1954+31, and 4U 1700+24 from Swift/BAT and RXTE/ASM Observations
• Low-Mass X-ray Binaries
• INTEGRAL/IBIS 17-yr hard X-ray all-sky survey
• Revealing a new symbiotic X-ray binary with Gemini NIFS
• The Symbiotic X-ray binaries Sct X-1, 4U 1700+24 and IGR J17329-2731
• XMM-Newton observation of MACHO 104.20906.960: a dwarf nova candidate with a 2 h period