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A Metal-rich Low-gravity Companion to a Massive Millisecond Pulsar

Kaplan, D. L. and Bhalerao, V. B. and van Kerkwijk, M. H. and Koester, D. and Kulkarni, S. R. and Stovall, K. (2013) A Metal-rich Low-gravity Companion to a Massive Millisecond Pulsar. Astrophysical Journal, 765 (2). Art. No. 158. ISSN 0004-637X.

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Most millisecond pulsars with low-mass companions are in systems with either helium-core white dwarfs or non-degenerate ("black widow" or "redback") stars. A candidate counterpart to PSR J1816+4510 was identified by Kaplan et al. whose properties were suggestive of both types of companions although identical to neither. We have assembled optical spectroscopy of the candidate companion and confirm that it is part of the binary system with a radial velocity amplitude of 343 ± 7 km s^(–1), implying a high pulsar mass, M_(psr)sin^3_i = 1.84 ± 0.11 M_☉, and a companion mass M_c sin^3_i = 0.193 ± 0.012 M_☉, where i is the inclination of the orbit. The companion appears similar to proto-white dwarfs/sdB stars, with a gravity log_(10)(g) = 4.9 ± 0.3, and effective temperature 16, 000 ± 500 K. The strongest lines in the spectrum are from hydrogen, but numerous lines from helium, calcium, silicon, and magnesium are present as well, with implied abundances of roughly 10 times solar (relative to hydrogen). As such, while from the spectrum the companion to PSR J1816+4510 is superficially most similar to a low-mass white dwarf, it has much lower gravity, is substantially larger, and shows substantial metals. Furthermore, it is able to produce ionized gas eclipses, which had previously been seen only for low-mass, non-degenerate companions in redback or black widow systems. We discuss the companion in relation to other sources, but find that we understand neither its nature nor its origins. Thus, the system is interesting for understanding unusual stellar products of binary evolution, as well as, independent of its nature, for determining neutron-star masses.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kaplan, D. L.0000-0001-6295-2881
Bhalerao, V. B.0000-0002-6112-7609
Kulkarni, S. R.0000-0001-5390-8563
Stovall, K.0000-0002-7261-594X
Additional Information:© 2013 American Astronomical Society. Received 2012 December 29; accepted 2013 January 23; published 2013 February 27. Partially based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We thank David Levitan, Assaf Horesh, and Yi Cao for assistance with observations; research at Caltech was funded by a grant from the NSF. We thank an anonymous referee for helpful suggestions. Facilities: Keck:I (LRIS), Hale (Double Spectrograph), ING:Herschel (ISIS)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: eclipsing; pulsars: individual (PSR J1816+4510); stars: atmospheres; stars: chemically peculiar; subdwarfs
Issue or Number:2
Record Number:CaltechAUTHORS:20130408-084150634
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Official Citation:A Metal-rich Low-gravity Companion to a Massive Millisecond Pulsar D. L. Kaplan et al. 2013 ApJ 765 158
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37798
Deposited By: Ruth Sustaita
Deposited On:08 Apr 2013 16:00
Last Modified:22 Nov 2019 19:25

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