The chemical composition of the accretion disk and donor star in Ultra Compact X-ray Binaries: A comprehensive X-ray analysis

Abstract

We have analyzed the X-ray spectra of all known Ultra Compact X-ray Binaries (UCXBs), with the purpose of constraining the chemical composition of their accretion disk and donor star. Our investigation was focused on the presence (or absence) of the Fe K$\alpha$ emission line, which was used as the probe of chemical composition of the disk, based on previously established theoretical predictions for the reflection of X-ray radiation off the surface of C/O-rich or He-rich accretion disks in UCXBs. We have contrasted the results of our spectral analysis to the history of type I X-ray bursts from these systems, which can also indicate donor star composition. We found that UCXBs with prominent and persistent iron K$\alpha$ emission also featured repeat bursting activity. On the other hand, the UCXBs for which no iron line was detected, appear to have few or no type I X-ray bursts detected over more than a decade of monitoring. Based on Monte Carlo simulations, demonstrating a strong correlation between the Fe K$\alpha$ line strength and the abundance of C and O in the accretion disk material and given the expected correlation between the H/He abundance and the recurrence rate of type I X-ray bursts, we propose that there is a considerable likelihood that UCXBs with persistent iron emission have He-rich donors, while those that do not, likely have C/O or O/Ne/Mg-rich donors. Our results strongly advocate for the development of more sophisticated simulations of X-ray reflection from hydrogen-poor accretion disks.

arXiv commentAccepted for publication in MNRAS, 16 pages 21 figures

References in corpus (80)

• On the Absorption of X-rays in the Interstellar Medium
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• 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
• Evolutionary Binary Sequences for Low- and Intermediate-Mass X-ray Binaries
• X-ray reflected spectra from accretion disk models. III. A complete grid of ionized reflection calculations
• X-ray reflected spectra from accretion disk models. I. Constant density atmospheres
• The two-hour orbit of a binary millisecond X-ray pulsar
• Origin of the Soft Excess in X-ray Pulsars
• Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305
• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• X-ray Reflection By Photoionized Accretion Discs
• Accretion Disk Boundary Layers Around Neutron Stars: X-ray Production in Low-Mass X-ray Binaries
• Relativistic Lines and Reflection from the Inner Accretion Disks Around Neutron Stars
• Discovery of a High-Latitude Accreting Millisecond Pulsar in an Ultracompact Binary
• Long Type I X-ray Bursts and Neutron Star Interior Physics
• White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of Finite Entropy Objects
• A model for cyclotron resonance scattering features
• Galactic binary science with the new LISA design
• X-ray emission from black-hole binaries
• The Multi-INstrument Burst ARchive (MINBAR)
• Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate
• On the possibility of a helium white dwarf donor in the presumed ultracompact binary 2S 0918-549
• X-ray reflected spectra from accretion disk models.II. Diagnostic tools for X-ray observations
• The chemical composition of donors in AM CVn stars and ultra-compact X-ray binaries: observational tests of their formation
• Models of Type I X-Ray Bursts in 4U 1820-30
• Optical spectra of the carbon-oxygen accretion discs in the ultra-compact X-ray binaries 4U 0614+09, 4U 1543-624 and 2S 0918-549
• Ultracompact X-Ray Binaries with Neon-Rich Degenerate Donors
• High-Speed Optical Photometry of the Ultracompact X-ray Binary 4U 1626-67
• The broad band X-ray/hard X-ray spectra of accreting neutron stars
• Interstellar X-ray Absorption Spectroscopy of Oxygen, Neon, and Iron with the Chandra LETGS Spectrum of X0614+091
• A New Catalog of Globular Clusters in the Milky Way
• Optical spectroscopy of (candidate) ultra-compact X-ray binaries: constraints on the composition of the donor stars
• Mass transfer in white dwarf-neutron star binaries
• A systematic analysis of the broad Fe Kalpha line in neutron star LMXBs with XMM-Newton
• The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9
• Ultra-compact (X-ray) binaries
• Ultracompact Binaries as Bright X-Ray Sources in Elliptical Galaxies
• On the formation of neon-enriched donor stars in ultracompact X-ray binaries
• First superburst from a classical low-mass X-ray binary transient
• An ultracompact X-ray binary in the globular cluster M15 (NGC7078)
• Discovery of X-ray absorption features from the dipping low-mass X-ray binary XB 1916-053 with XMM-Newton
• X-ray emission and absorption features during an energetic thermonuclear X-ray burst from IGR J17062-6143
• Galactic Ultracompact X-ray Binaries: Disk Stability and Evolution
• Arbitrarily Degenerate Helium White Dwarfs as Donors in AM CVn Binaries
• Discovery of a 205.89 Hz accreting-millisecond X-ray pulsar in the globular cluster NGC 6440
• Galactic Populations of Ultracompact Binaries
• X-Ray Spectroscopy of the Low-Mass X-ray Binaries 2S 0918-549 and 4U1543-624: Evidence for Neon-Rich Degenerate Donors
• The Orbital Period of the Ultracompact Low-Mass X-Ray Binary 4U 1543--624
• The long-term evolution of the accreting millisecond X-ray pulsar Swift J1756.9-2508
• On the formation of oxygen-neon white dwarfs in close binary systems
• X-ray Reflection and An Exceptionally Long Thermonuclear Helium Burst from IGR J17062-6143
• Time-resolved optical photometry of the ultra-compact binary 4U0614+091
• An ultracompact X-ray binary in the globular cluster NGC 1851
• Radius-expansion burst spectra from 4U 1728-34: an ultracompact binary?
• VLT spectroscopy and non-LTE modeling of the C/O-dominated accretion disks in two ultracompact X-ray binaries
• NICER Discovers the Ultracompact Orbit of the Accreting Millisecond Pulsar IGR J17062-6143
• Measuring the spin up of the Accreting Millisecond Pulsar XTE J1751-305
• High-resolution X-ray spectroscopy of the ultracompact LMXB pulsar 4U 1626-67
• X-ray Spectroscopy of Candidate Ultracompact X-ray Binaries
• The Likely Orbital Period of the Ultracompact Low-Mass X-Ray Binary 2S 0918-549
• Accreting, highly magnetized neutron stars at the Eddington limit: A study of the 2016 outburst of SMC X-3
• A relativistically broadened O VIII Lyalpha line in the ultra-compact X-ray binary 4U 0614+091
• X-ray reflection in oxygen-rich accretion discs of ultra-compact X-ray binaries
• Discovery of a broad O VIII Ly alpha line in the ultra-compact X-ray binary 4U 1543-624
• Spectral and Timing Analysis of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR
• The UV Spectrum of the Ultra-compact X-ray Binary- 4U 1627-673
• Detection of Highly Ionized Metal Absorption Lines in the Ultracompact X-ray Dipper 4U 1916-05
• Luminosity dependent change of the emission diagram in the X-ray pulsar 4U 1626-67
• Dynamical Ne K Edge and Line Variations in the X-Ray Spectrum of the Ultra-compact Binary 4U 0614+091
• The Fermi-GBM 3-year X-ray Burst Catalog
• Accretion-powered Millisecond Pulsar Outbursts
• The 17 min orbital period in the Ultra Compact X-ray Binary 4U 0513-40
• The Fermi-GBM X-ray burst monitor: thermonuclear bursts from 4U 0614+09
• X-ray properties of 4U 1543-624
• Ignition column depths of helium-rich thermonuclear bursts from 4U 1728-34
• Disappearance of the Fe K$\alpha$ emission line in Ultra Compact X-ray Binaries 4U 1543-624 and Swift J1756.9-2508
• X-ray diagnostics of chemical composition of the accretion disk and donor star in ultra-compact X-ray binaries

Cited by in corpus (14)

• Science objectives of the Einstein Probe mission
• Ultra-compact X-ray binaries with He star companions
• UltraCompCAT: a comprehensive Catalogue of Ultra-Compact and Short Orbital Period X-ray Binaries
• Simultaneous NICER and NuSTAR Observations of the Ultra-compact X-ray Binary 4U 1543-624
• The accretion/ejection link in the neutron star X-ray binary 4U 1820-30 I: A boundary layer-jet coupling?
• Formation and Evolution of Accreting Compact Objects
• Disappearance of the Fe K$\alpha$ emission line in Ultra Compact X-ray Binaries 4U 1543-624 and Swift J1756.9-2508
• Astrophysics with the Laser Interferometer Space Antenna
• Multi-band observations of Swift J0840.7-3516: a new transient ultra-compact X-ray binary candidate
• NICER observations of type-I X-ray bursts from the ultra-compact X-ray binary M15 X-2
• XMM-Newton and NuSTAR discovery of a likely IP candidate XMMU J173029.8-330920 in the Galactic Disk
• The NuSTAR view of Ultra-Compact X-ray Binaries
• Ultra-compact X-ray Binaries: A Review
• Classification of IGR J20084+3221 as an Intermediate Polar using X-ray and Optical Observations