Issue |
A&A
Volume 450, Number 1, April IV 2006
|
|
---|---|---|
Page(s) | 295 - 303 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20054316 | |
Published online | 03 April 2006 |
The ultra-cool white dwarf companion of PSR J0751+1807
1
Astronomical Institute, Utrecht University, PO Box 80 000, 3508 TA Utrecht, The Netherlands e-mail: c.g.bassa@astro.uu.nl
2
Department of Astronomy and Astrophysics, University of Toronto, 60 Saint George Street, Toronto, ON M5S 3H8, Canada
3
Palomar Observatory, California Institute of Technology 105-24, Pasadena, CA 91125, USA
Received:
7
October
2005
Accepted:
29
December
2005
We present optical and near-infrared observations with Keck
of the binary millisecond pulsar PSR J0751+1807. We detect a faint,
red object – with ± 0.07,
± 0.3, and
± 0.10 – at the celestial position of the pulsar and
argue that it is the white dwarf companion of the pulsar. The
colours are the reddest among all known white dwarfs, and indicate a
very low temperature,
K. This implies that
the white dwarf cannot have the relatively thick hydrogen envelope
that is expected on evolutionary grounds. Our observations pose two
puzzles. First, while the atmosphere was expected to be pure
hydrogen, the colours are inconsistent with this
composition. Second, given the low temperature, irradiation by the
pulsar should be important, but we see no evidence for it. We
discuss possible solutions to these puzzles.
Key words: stars: pulsars: individual: PSR J0751+1807 / stars: binaries: close / stars: neutron / stars: white dwarfs
© ESO, 2006
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