Weighing The Options: The Unseen Companion in LAMOST J2354 is Likely a Massive White Dwarf
Year: 2025
Type: article
Abstract: LAMOST J235456.73+335625 (J2354) is a binary system hosting a K dwarf and a dark companion, supposedly a neutron star, in a 0.48d orbit. Here we present high- and low-resolution spectroscopy to better constrain the properties of the system. The low-resolution spectrum confirms that the luminous star is a slightly metal-poor K dwarf and strengthens the limits on any optical flux from the dimmer companion. We use the high-resolution spectra to measure atmospheric parameters (, log g , [Fe/H], ) and abundances for 8 elements for the K dwarf. We refine the mass of the compact object to with a minimum mass of . The expected overabundance of intermediate-mass elements from the incident supernova ejecta is not detected in the K-dwarf atmosphere. This contrasts with known binaries hosting neutron stars where almost all companions show evidence for polluting material. Moving the neutron-star progenitor further from the K-dwarf at the time of explosion to minimize atmospheric pollution requires a finely-tuned kick to produce the current orbital separation of . Instead, we find that a massive white dwarf with a cooling age of ≳ 3 Gyr satisfies all observational constraints. The system likely experienced two common-envelope phases leading to its current state because the white dwarf progenitor was massive enough to ignite He-shell burning. The system will become a cataclysmic variable in the distant future when the K-dwarf evolves off of the main sequence. These short-period high- q binaries represent an intriguing formation pathway for compact double white dwarf binaries and thermonuclear supernovae. An ultraviolet spectrum is the most promising avenue for directly detecting the white dwarf companion.
Source: The Open Journal of Astrophysics
DOI: 10.33232/001c.138381
Institution: The Ohio State University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
Funders: Ohio State University, University of Minnesota, University of Notre Dame, Arizona Board of Regents, Bundesministerium für Bildung und Forschung, Brandenburger Staatsministerium für Wissenschaft, Forschung und Kultur, Istituto Nazionale di Astrofisica, Leibniz-Institut für Astrophysik Potsdam, European Centre for Medium-Range Weather Forecasts, Leibniz-Gemeinschaft
Awards: G3317225363, Fertigstellung des hochauflösenden optischen Spektralpolarimeters für das LBT, Entwurf, Bau und Betrieb eines hochauflösenden optischen Spektralpolarimeters für das Large Binocular Telescope in Arizona. Das Instrument wird es erlauben, die Stärke und die Geometrie von kosmischen Magnetfeldern zu messen.
OpenAlex ID: W4410528163