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Astron. Astrophys. 350, L62-L64 (1999)


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Letter to the Editor

APMPM J0559-2903: The coolest extreme subdwarf known

A. Schweitzer 1, R.-D. Scholz 2, J. Stauffer 3, M. Irwin 4 and M.J. McCaughrean 2

1 Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany (A.Schweitzer@lsw.uni-heidelberg.de)
2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany (rdscholz@aip.de,mjm@aip.de)
3 Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA (jstauffer@cfa.harvard.edu)
4 Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK (mike@ast.cam.ac.uk)

Received 16 September 1999 / Accepted 24 September 1999

Abstract

We present the discovery of the coolest extreme subdwarf known to date. APMPM J0559-2903 was measured to be esdM7. Unlike for solar metallicity dwarfs, there are no very late type objects known among the extreme subdwarfs.

APMPM J0559-2903 was discovered in a new southern high proper motion survey. Follow up spectroscopy at Keck was used to identify the spectral type with the help of spectral indices.

Using the NextGen grid of model atmospheres by Hauschildt et al. (1999) we measured the effective temperature to be 3100 K and the metallicity to be [FORMULA]=-1.5. The theoretical parameters place APMPM J0559-2903 at a distance of 100 pc with a space velocity of 260  km s-1 relative to the local standard of rest.

Key words: stars: individual: APMPM J0559-2903 – stars: subdwarfs – stars: late-type – stars: low-mass, brown dwarfs – stars: fundamental parameters

Present address: Department of Physics and Astronomy, University of Georgia, Athens, GA 30602-2451, USA

Send offprint requests to: A. Schweitzer

© European Southern Observatory (ESO) 1999

Online publication: October 14, 1999

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