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A Dense Companion to the Short-period Millisecond Pulsar Binary PSR J0636+5128

Kaplan, D. L. and Stovall, K. and van Kerkwijk, M. H. and Fremling, C. and Istrate, A. G. (2018) A Dense Companion to the Short-period Millisecond Pulsar Binary PSR J0636+5128. Astrophysical Journal, 864 (1). Art. No. 15. ISSN 1538-4357. doi:10.3847/1538-4357/aad54c.

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PSR J0636+5128 is a millisecond pulsar in one of the most compact pulsar binaries known, with a 96 minute orbital period. The pulsar mass function suggests a very low mass companion, similar to that seen in so-called "black widow" binaries. Unlike in most of those, however, no radio eclipses by material driven off from the companion were seen leading to the possibility that the companion was a degenerate remnant of a carbon–oxygen white dwarf. We report the discovery of the optical counterpart of its companion in images taken with the Gemini North and Keck I telescopes. The companion varies between r' = 25 and r' = 23 on the 96 minute orbital period of the binary, caused by irradiation from the pulsar's energetic wind. We modeled the multicolor light curve using parallax constraints from pulsar timing and determine a companion mass of (1.71 ± 0.23) × 10^(−2) M_⊙, a radius of (7.6 ± 1.4) × 10^(−2) R_⊙, and a mean density of 54 ± 26 g cm^(-3), all for an assumed neutron star mass of 1.4 M_⊙. This makes the companion to PSR J0636+5128 one of the densest of the "black widow" systems. Modeling suggests that the composition is not predominantly hydrogen, perhaps due to an origin in an ultracompact X-ray binary.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kaplan, D. L.0000-0001-6295-2881
Stovall, K.0000-0002-7261-594X
Fremling, C.0000-0002-4223-103X
Istrate, A. G.0000-0002-8811-8171
Additional Information:© 2018. The American Astronomical Society. Received 2018 June 28; revised 2018 July 19; accepted 2018 July 20; published 2018 August 27. Partially based on observations obtained at the Gemini Observatory under program GN-2014B-Q-81 (PI: Stovall), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. Some 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 the National Aeronautics and Space Administration. 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. Support for D.L.K. and K.S. was provided by the NANOGrav NSF Physics Frontiers Center award number 1430284. A.G.I. acknowledges support from the NASA Astrophysics Theory Program through NASA grant NNX13AH43G. Facilities: Gemini North (GMOS) - , Keck:I (LRIS). - Software: Astropy (Astropy Collaboration et al. 2013), corner (Foreman-Mackey 2016), emcee (Foreman-Mackey et al. 2013) Icarus (, LPIPE (, MESA (Paxton et al. 2011), photutils (Bradley et al. 2017).
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: general; pulsars: individual (PSR J0636+5128)
Issue or Number:1
Record Number:CaltechAUTHORS:20180827-144724040
Persistent URL:
Official Citation:D. L. Kaplan et al 2018 ApJ 864 15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89178
Deposited By: George Porter
Deposited On:27 Aug 2018 22:10
Last Modified:16 Nov 2021 00:33

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