Affiliation:
1. Ioffe Institute , Politekhnicheskaya 26, St Petersburg 194021 , Russia
2. Instituto de Astronomía, Universidad Nacional Autónoma de México , Apdo. Postal 877, Ensenada, Baja California 22800 , México
Abstract
ABSTRACT
We present the results of optical spectroscopy of stellar companions to three binary millisecond pulsars, PSRs J0621+2514, J2317+1439, and J2302+4442, obtained with the Gran Telescopio Canarias. The spectrum of the J0621+2514 companion shows a blue continuum and prominent Balmer absorption lines. The latter are also resolved in the spectrum of the J2317+1439 companion, showing that both are DA-type white dwarfs. No spectral features are detected for the J2302+4442 companion; however, its broad-band magnitudes and the spectral shape of the continuum emission imply that this is also a DA-type white dwarf. Based on the spectral analyses, we conclude that the companions of J0621+2514 and J2317+1439 are relatively hot, with effective temperatures Teff = 8600 ± 200 and 9600 ± 2000 K, respectively, while the J2302+4442 companion is significantly cooler, Teff<6000 K. We also estimated the distance to J0621+2514 of 1.1 ± 0.3 kpc and argue that its companion and the companion of J2317+1439 are He-core white dwarfs providing constraints on their cooling ages of $\lesssim$2 Gyr.
Funder
Russian Science Foundation
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics