First Results from the Swarms Survey. SDSS 1257+5428: A Nearby, Massive White Dwarf Binary with a Likely Neutron Star or Black Hole Companion

TL;DR

This paper reports the discovery of a nearby white dwarf binary system with an unseen companion likely being a neutron star or black hole, identified through the SWARMS survey using SDSS data.

Contribution

It presents the first results from SWARMS, demonstrating its effectiveness in finding compact white dwarf binaries with potential neutron star or black hole companions.

Findings

Binary system with 4.56 hr period and 322.7 km/s velocity amplitude

White dwarf mass estimated at 0.92 Msun

Unseen companion likely a neutron star or black hole, within 48 pc

Abstract

We present the first results from SWARMS (Sloan White dwArf Radial velocity data Mining Survey), an ongoing project to identify compact white dwarf (WD) binaries in the spectroscopic catalog of the Sloan Digital Sky Survey. The first object identified by SWARMS, SDSS 1257+5428, is a single-lined spectroscopic binary in a circular orbit with a period of 4.56 hr and a semiamplitude of 322.7+-6.3 km/s. From the spectrum and photometry, we estimate a WD mass of 0.92(+0.28,-0.32) Msun. Together with the orbital parameters of the binary, this implies that the unseen companion must be more massive than 1.62(+0.20,-0.25) Msun, and is in all likelihood either a neutron star or a black hole. At an estimated distance of 48(+10,-19) pc, this would be the closest known stellar remnant of a supernova explosion.