Observability of HOFNARs with SRG/eROSITA

Abstract

Neutron stars can appear as sources of different nature. In this paper we address observability of a hypothetical class of neutron stars -- HOt and Fast Non Accreting Rotators, HOFNARs. These objects are heated due to the r-mode instability. With surface temperatures $\sim 10^6$~K they are expected to be thermal soft X-ray emitters. We perform a population synthesis modeling of HOFNARs to predict the number of potentially detectable sources in the eROSITA all-sky survey. For surface temperatures $\sim 10^6$~K we obtain $\sim 500$ sources above the detection limit 0.01~cts~s${}^{-1}$ and $\sim 100$ easier identifiable sources with $>0.1$~cts~s${}^{-1}$. Temperatures $\gtrsim 1.2\times 10^6$~K start to be in contradiction with non-detection of HOFNARs by ROSAT. Only for $T\lesssim 5\times 10^5$~K numbers predicted for eROSITA turn out to be so low that identification does not look possible. We conclude that eROSITA has good chances to discover HOFNARs, if they exist. Non-detection will put very stringent limits on the properties of this type of neutron stars.

17 pages, submitted to Universe

References in corpus (21)

• Second ROSAT all-sky survey (2RXS) source catalogue
• The Magnificent Seven: Magnetic fields and surface temperature distributions
• Formation and evolution of compact binaries in globular clusters: II. Binaries with neutron stars
• Magnetic Hydrogen Atmosphere Models and the Neutron Star RX J1856.5-3754
• The distribution of the ISM in the Milky Way A three-dimensional large-scale model
• Thermal luminosities of cooling neutron stars
• Population synthesis of radio and gamma-ray millisecond pulsars from the Galactic disk
• Central Compact Objects in Supernova Remnants
• Ekman layer damping of r-modes revisited
• The Effect of Transient Accretion on the Spin-Up of Millisecond Pulsars
• Chandra studies of the globular cluster 47 Tucanae: A deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars, and new constraints to r-mode instability window
• Bulk viscosity in neutron stars with hyperon cores
• R-modes and neutron star recycling scenario
• New possible class of neutron stars: hot and fast non-accreting rotators
• X-ray bounds on the r-mode amplitude in millisecond pulsars
• Pulse Profiles and Polarization of Terzan 5 Pulsars
• Long-lasting accretion-powered chemical heating of millisecond pulsars
• Candidate isolated neutron stars in the 4XMM-DR10 catalog of X-ray sources
• Resonance suppression of the r-mode instability in superfluid neutron stars: Accounting for muons and entrainment
• Radiation driven instability of rapidly rotating relativistic stars: criterion and evolution equations via multipolar expansion of gravitational waves
• Bulk viscosity, r-modes, and the early evolution of neutron stars

Cited by in corpus (1)

• XMM-Newton and SRG/eROSITA observations of the isolated neutron star candidate 4XMM J022141.5-735632