Detectability of neutron star -- white dwarf coalescences by eROSITA and ART-XC

Abstract

Coalescences of neutron stars and white dwarfs are relatively frequent phenomena, outnumbering other types of compact object mergers (neutron stars and black holes without involving white dwarfs) altogether. Such event potentially can produce not only optical, but also an X-ray burst. Transient source CDF-S XT2 [1] can be an example of this type of events as suggested by [2]. In this note we estimate the rate of these transients in the field of view of X-ray instruments on-board Spectrum-RG satellite. We demonstrate that during four years of the survey program several thousand of events related to neutron star - white dwarf mergers might appear in the field of view of eROSITA. Collimation of X-ray emission can reduce this number. Smaller, but comparable number of transients is expected in the case of ART-XC telescope. However, due to relatively short duration - $\lesssim 10^4$ s, - mostly such transients might be visible just in one scan of telescopes ($\sim 40$ s), and so only a few photons are expected to be detected which makes definite identification without additional information very problematic.

arXiv comment15 pages, 3 figures

References in corpus (10)

• Formation of Double Neutron Star Systems
• Distance measures in cosmology
• Merging stellar-mass binary black holes
• The observed velocity distribution of young pulsars
• The separation distribution and merger rate of double white dwarfs: improved constraints
• Mass transfer in white dwarf-neutron star binaries
• Nuclear Dominated Accretion Flows in Two Dimensions. II. Ejecta dynamics and nucleosynthesis for CO and ONe white dwarfs
• Faint rapid red transients from Neutron star -- CO white-dwarf mergers
• Spins of black holes in coalescing compact binaries
• Fast Extragalactic X-ray Transients From Binary Neutron Star Mergers