LAMOST J2354 binary hosts an unseen massive white dwarf, study suggests

Astronomers from the Ohio State College (OSU) and College of Hawai’i’ve carried out spectroscopic observations of a recently-discovered binary system often known as LAMOST J2354, which accommodates a darkish companion star. Outcomes of the observational marketing campaign, presented July 26 on the pre-print server arXiv, recommend that the unseen object is an enormous white dwarf.

Found in 2023, LAMOST J2354 consists of a Ok dwarf orbited by an unseen companion each 0.48 days. The first star is estimated to have a mass of about 0.7 solar lots, whereas the companion object is assumed to be a neutron star about 40–60% extra huge than the sun. The system is situated some 416 gentle years away.

With a view to shed extra gentle on the properties of LAMOST J2354 and to unveil the character of the companion object, a crew of astronomers led by OSU’s Michael Tucker determined to conduct follow-up high- and low-resolution spectroscopic observations of this method. For this objective, they employed the College of Hawaii 2.2-meter telescope and the Giant Binocular Telescope (LBT).

“We offered follow-up spectroscopy of the enigmatic binary LAMOST J2354 to raised perceive the Ok dwarf and its unseen, huge companion,” the researchers wrote within the paper.

The observations discovered that the Ok dwarf is about 35% smaller and fewer huge than the sun. The obtained spectra revealed that the star has a metallicity at a degree of -0.48 dex, with no peculiar chemical abundances.

Primarily based on the collected knowledge, the astronomers estimate that the mass of the companion object is almost definitely 1.3 solar lots and its minimal mass was derived to be 1.23 solar lots. The orbital separation between the 2 objects was measured to be 3.3 solar radii.

In accordance with the authors of the paper, the obtained parameters of LAMOST J2354, along with the chemical abundance of the Ok dwarf, point out that the unseen companion is an enormous white dwarf. They disfavor the situation during which this object could also be a neutron star born from a core-collapse supernova.

“We discover {that a} huge white dwarf with a cooling age of ≳ 3 Gyr satisfies all observational constraints,” the researchers conclude.

Given the unseen white dwarf is simply too huge to have a pure helium core, the astronomers observe that the system probably skilled two phases of common-envelope (CE) evolution. Throughout these phases, the white dwarf progenitor started hydrogen-shell and helium-shell burning.

The scientists add that LAMOST J2354 will virtually definitely expertise one other phase of mass-transfer sooner or later when the Ok dwarf evolves off of the primary sequence, leading to secure mass-transfer and the formation of a cataclysmic variable.

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