Quick search Find article
Quick search
Find article

A Photometric and Spectroscopic Search for White Dwarfs in the Open Clusters NGC 6633 and NGC 7063*

FREE ISSUE

Kurtis A. Williams1,3 and Michael Bolte2

Show affiliations


We present photometric and spectroscopic studies of the white dwarf (WD) populations in the intermediate-age open clusters NGC 6633 and NGC 7063 as part of the ongoing Lick-Arizona White Dwarf Survey. Using wide-field CCD imaging, we locate 41 candidate WDs in the two cluster fields: 32 in NGC 6633, and 9 in NGC 7063. Spectroscopic observations confirm 13 of these candidates to be bona fide WDs. We describe in detail our Balmer-line fitting technique for deriving effective temperatures and surface gravities from optical DA WD spectra and apply the technique to the 11 DA WDs in the sample. Of these, only two DA WDs are at the cluster distance moduli, one in each cluster. Two more DAs lie 0.75 mag foreground to NGC 6633, raising the possibility that these are double degenerate systems in the cluster. If they are nearly equal-mass binaries, both of these systems likely have combined masses above the Chandrasekhar limit. One DB WD is found to be consistent with membership in NGC 6633, which would make this the third confirmed He-atmosphere WD in an open cluster, although further data are needed to confirm cluster membership. The WD consistent with membership in the cluster NGC 7063 has a low mass (≈0.4 Modot), suggesting it may be a He-core WD resulting from close binary evolution. Three of the 11 hydrogen-atmosphere WDs in this study are observed to have Ca II absorption; the number of DAZs in this study is consistent with previous observations that ~25% of field WDs are DAZs.


Footnote
*  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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Keywords

open clusters and associations: individual (NGC 6633, NGC 7063); white dwarfs


Dates

Issue 4 (2007 April)

Received 2006 September 18, accepted for publication 2006 November 29

Published 2007 March 5



  1. A Photometric and Spectroscopic Search for White Dwarfs in the Open Clusters NGC 6633 and NGC 7063

    Kurtis A. Williams and Michael Bolte 2007 The Astronomical Journal 133 1490

  2. The TAROT Suspected Variable Star Catalog

    Y. Damerdji et al. 2007 The Astronomical Journal 133 1470

  3. An explicit harmonic code for black-hole evolution using excision

    Béla Szilágyi et al 2007 Class. Quantum Grav. 24 S275

  4. Brown Dwarf Disks at Ages of 5-10 Myr

    Basmah Riaz et al. 2009 ApJ 705 1173

  5. Consideration of user priorities when developing neural prosthetics

    Kim D Anderson 2009 J. Neural Eng. 6 055003

  6. Diffusion and dispersion of passive tracers: Navier-Stokes vs. MHD turbulence

    W.-C. Müller and A. Busse 2007 EPL 78 14003

  7. The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun

    Valeri V. Makarov 2003 The Astronomical Journal 126 1996

  8. Biases on Initial Mass Function Determinations. II. Real Multiple Systems and Chance Superpositions

    J. Maíz Apellániz 2008 ApJ 677 1278

  9. New Solar Composition: The Problem with Solar Models Revisited

    Aldo M. Serenelli et al 2009 ApJ 705 L123

  10. Performance of the WaveBurst algorithm on LIGO data

    S Klimenko et al 2004 Class. Quantum Grav. 21 S1685

Users also read

What's this?
This innovative new feature generates a list of articles 'also read' by other users based on them reading the original article. Article abstracts citations and references are all considered and weighted accordingly. We hope that this will help you find relevant papers for your research.

  1. Probing the Lower Mass Limit for Supernova Progenitors and the High-Mass End of the Initial-Final Mass Relation from White Dwarfs in the Open Cluster M35 (NGC 2168)

View by subject




Export








Please login to access our web services, or create an account if you don't yet have one.

You must have cookies enabled in your web browser to be able to login.

Username
Password

Forgotten your password? Get a new one here.