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Issue A&A Volume 390, Number 3, August II 2002 Page(s) L27 - L30 Section Letters DOI 10.1051/0004-6361:20020928

A&A 390, L27-L30 (2002)
DOI: 10.1051/0004-6361:20020928

Letter

Search for nearby stars among proper motion stars selected by optical-to-infrared photometry

II. Two late M dwarfs within 10 pc

M. J. McCaughrean, R.-D. Scholz and N. Lodieu

Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
    e-mail: rdscholz@aip.de; nlodieu@aip.de

(Received 7 May 2002 / Accepted 17 June 2002 )

Abstract
We have identified two late M dwarfs within 10 pc of the Sun, by cross-correlating the Luyten NLTT catalogue of stars with proper motions larger than 0.18 arcsec/yr, with objects lacking optical identification in the 2MASS data base. The 2MASS photometry was then combined with improved optical photometry obtained from the SuperCOSMOS Sky Surveys. The two objects (LP 775- 31 and LP 655- 48) have extremely red optical-to-infrared colours () ~ ) and very bright infrared magnitudes ( < ): follow-up optical spectroscopy with the ESO 3.6-m telescope gave spectral types of M 8.0 and M 7.5 dwarfs, respectively. Comparison of their near-infrared magnitudes with the absolute magnitudes of known M 8 and M 7.5 dwarfs with measured trigonometric parallaxes yields spectroscopic distance estimates of pc and pc for LP 775- 31 and LP 655- 48, respectively. In contrast, Cruz & Reid (2002) recently determined spectral types of M 6 for both objects, and commensurately larger distances of pc and pc. LP 655- 48 is also a bright X-ray source (1RXS J044022.8-053020). With only a few late M dwarfs previously known within 10 pc, these two objects represent an important addition to the census of the Solar neighbourhood.

Key words: astrometry and celestial mechanics: astrometry -- astronomical data base: surveys -- stars: late-type -- stars: low mass, brown dwarfs

Offprint request: M. J. McCaughrean, mjm@aip.de

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© ESO 2002

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