An X-Ray-dim “Isolated” Neutron Star in a Binary?

Abstract

We report the discovery of a dark companion to 2MASS J15274848+3536572 with an orbital period of 6.14 hr. Combining the radial velocity from LAMOST observations and modeling of the multiband light curve, one obtains a mass function of ≃0.131 M ⊙, an inclination of 45 .° 20 − 0 .° 20 + 0 .° 13 , and a mass ratio of 0.631 − 0.003 + 0.014 , which demonstrate the binary nature of the dark companion with a mass of 0.98 ± 0.03M ⊙ and a main-sequence K9-M0 star of 0.62 ± 0.01 M ⊙. LAMOST optical spectra at a range of orbital phases reveal extra-peaked H α emission that suggests the presence of an accretion disk. The dark companion does not seem to be a white dwarf because of the lack of any observed dwarf nova outbursts in the long-term data archive, although a magnetic white dwarf cannot be excluded. Alternatively, we propose a scenario wherein the dark companion is a neutron star, but we have not detected radio pulsations or a single pulse from the system with the FAST (Five-hundred-meter Aperture Spherical radio Telescope), which hints at a radio-quiet compact object. If the dark companion is identified as a neutron star, it will be the nearest (∼118 pc) and lightest neutron star. Furthermore, kinematic analysis of the system’s orbit in the galaxy may suggest its supernova event is associated with the radionuclide 60Fe signal observed from deep-sea crusts. This radio-quiet and X-ray-dim nearby neutron star may resemble an XDINS (X-ray-dim isolated neutron star) but in a binary.

Proposed Lunar Measurements of r-Process Radioisotopes to Distinguish the Origin of Deep-sea 244Pu

“…such events are broad, with consequences for the heliosphere (Fields et al 2008; and possibly for the biosphere (Ruderman 1974;Hartmann et al 2002;Melott et al 2004Melott et al , 2019. Other astrophysical observables include searches for nearby neutron stars whose location and kinematics point to a Local Bubble origin (Tetzlaff et al 2010;Neuhäuser et al 2020;Lin et al 2023;Zheng et al 2022).…”

A light strange star in the remnant HESS J1731−347: Minimal consistency checks

“…It is premature to claim any stronger conclusion, although this is an important case and other detections could add to the whole picture. A recent work by Lin et al (2023) reports another candidate with M = 0.98 ± 0.03 M ⊙ that deserves attention in connection to the XMMU J173203.3-344518 case.…”

The Hidden Companion in J1527: A 0.69 Solar-mass White Dwarf?

“…Hence, it is of great interest to find the potential remnants, e.g., nearby NSs, of these events. Recent efforts in this regard include the studies of Zheng et al (2023) and Lin et al (2023). Zheng et al (2023) discovered an NS candidate, J2354, located approximately 128 pc away from the solar system, in which the unseen compact object has a mass of 1.4 ∼ 1.6 M e .…”

“…Zheng et al (2023) discovered an NS candidate, J2354, located approximately 128 pc away from the solar system, in which the unseen compact object has a mass of 1.4 ∼ 1.6 M e . In the work of Lin et al (2023), the authors claim to have identified a binary system, J1527, located 118 pc from the solar system, with an unseen NS candidate of approximately 0.98 M e .…”