XMMU J181227.8-181234: a new ultracompact X-ray binary candidate

Abstract

We report the discovery of Type I (thermonuclear) X-ray bursts from the transient source XMMU J181227.8-181234 = XTE J1812-182. We found 7 X-ray bursts in Rossi X-ray Timing Explorer observations during the 2008 outburst, confirming the source as a neutron star low mass X-ray binary. Based on the measured burst fluence and the average recurrence time of 1.4${}_{-0.5}^{+0.9}$ hr, we deduce that the source is accreting almost pure helium ($X\le 0.1$) fuel. Two bursts occurred just 18 minutes apart; the first short waiting time bursts observed in a source accreting hydrogen-poor fuel. Taking into consideration the effects on the burst and persistent flux due to the inferred system inclination of $30\pm 10$ degrees, we estimate the distance to be $14\pm 2$ kpc, where we report the statistical uncertainty but note that there could be up to $20\%$ variation in the distance due to systematic effects discussed in the paper. The corresponding maximum accretion rate is $0.30\pm 0.05$ times the Eddington limit. Based on the low hydrogen content of the accreted fuel and the short average recurrence time, we classify the source as a transient ultracompact low-mass X-ray binary.

arXiv comment10 pages, 6 figures, 2 tables. Accepted for publication in MNRAS

References in corpus (25)

• Modelling the behaviour of accretion flows in X-ray binaries
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array
• Photospheric radius expansion X-ray bursts as standard candles
• Constraining the Mass and Radius of Neutron Stars in Globular Clusters
• Thermonuclear burst oscillations
• Six new candidate ultracompact X-ray binaries
• When A Standard Candle Flickers
• Evidence for accretion rate change during type I X-ray bursts
• Evidence for enhanced persistent emission during sub-Eddington thermonuclear bursts
• The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
• Multi-Instrument X-ray Observations of Thermonuclear Bursts with Short Recurrence Times
• A bright thermonuclear X-ray burst simultaneously observed with Chandra and RXTE
• Superburst Models for Neutron Stars with Hydrogen and Helium-Rich Atmospheres
• Anisotropy of X-ray bursts from neutron stars with concave accretion disks
• Discovery of X-ray burst triplets in EXO 0748-676
• The influence of accretion rate and metallicity on thermonuclear bursts: predictions from KEPLER models
• Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Advances in the RXTE Proportional Counter Array Calibration: Nearing the Statistical Limit
• Long-term luminosity behavior of 14 ultracompact X-ray binaries
• Deviations from the Flux-Recurrence Time Relationship in GS 1826-238: Potential Transient Spectral Changes
• Neutrino Losses in Type I Thermonuclear X-ray Bursts: An Improved Nuclear Energy Generation Approximation
• X-ray softening during the 2008 outburst of XTE J1810-189
• XMM-Newton Discovery of the X-ray Transient XMMU J181227.8-181234 in the Galactic Plane

Cited by in corpus (8)

• The Multi-INstrument Burst ARchive (MINBAR)
• Low-Mass X-ray Binaries
• UltraCompCAT: a comprehensive Catalogue of Ultra-Compact and Short Orbital Period X-ray Binaries
• The Galactic LMXB Population and the Galactic Centre Region
• Catalog of outbursts of neutron star LMXBs
• A Machine Learning Approach For Classifying Low-mass X-ray Binaries Based On Their Compact Object Nature
• Robust inference of neutron-star parameters from thermonuclear burst observations
• SRG/ART-XC all-sky X-ray survey: Catalog of sources detected during the first year