High-resolution optical spectroscopy of Praesepe white dwarfs
Abstract
We present the results of a high-resolution optical spectroscopic study of nine white dwarf candidate members of Praesepe undertaken with the VLT and Ultraviolet and Visual Echelle Spectrograph. We find, contrary to a number of previous studies, that WD0836+201 (LB390, EG59) and WD0837+199 (LB393, EG61) are magnetic and non-magnetic white dwarfs, respectively. Subsequently, we determine the radial velocities for the eight non-magnetic degenerates and provide compelling evidence that WD0837+185 is a radial velocity variable and possibly a double-degenerate system. We also find that our result for WD0837+218, in conjunction with its projected spatial location and position in initial mass-final mass space, argues it is more likely to be a field star than a cluster member. After eliminating these two white dwarfs, and WD0836+199 which has no clean Sloan Digital Sky Survey photometry, we use the remaining five stars to substantiate modern theoretical mass-radius relations for white dwarfs. In light of our new results, we re-examine the white dwarf members of Praesepe and use them to further constrain the initial mass-final mass relation (IFMR). We find a near-monotonic IFMR, which can still be adequately represented by simple linear function with only one outlier which may have formed from a blue straggler star.
Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme ID 076.D-0751. E-mail: slc25@star.le.ac.uk- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2009
- DOI:
- 10.1111/j.1365-2966.2009.14593.x
- arXiv:
- arXiv:0901.4464
- Bibcode:
- 2009MNRAS.395.1795C
- Keywords:
-
- white dwarfs;
- open clusters and associations: general;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Galaxy Astrophysics
- E-Print:
- 10 pages, 7 figures. Accepted for publication in MNRAS