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HD 203030B: An Unusually Cool Young Substellar Companion near the L/T Transition
We present the discovery of a brown dwarf companion to the star HD203030: a G8 V Solar analog with an estimated age between 130 and 400Myr old G8 V. Separated by 11.9" (487 AU in projection) from its hoststar, HD 203030B has an estimated mass of0.023+0.008-0.011 Msolar. The K-bandspectral type of L7.5+/-0.5 places HD 203030B near the critical L/Ttransition in brown dwarfs, which is characterized by the rapiddisappearance of dust in substellar photospheres. From a comparativeanalysis with well-characterized field L/T transition dwarfs, we findthat, despite its young age, HD 203030B has a bolometric luminositysimilar to the >1 Gyr old field dwarfs. Adopting a radius fromcurrent models of substellar evolution, we hence obtain that theeffective temperature of HD 203030B is only1206+74-116 K, markedly lower than the ~1440 Keffective temperatures of field L/T transition dwarfs. The temperaturediscrepancy can be resolved if either (1) the ages of field brown dwarfshave been overestimated by a factor of ~1.5, leading to underestimatedradii, or (2) the lower effective temperature of HD 203030B is relatedto its young age, implying that the effective temperature at the L/Ttransition is gravity dependent.
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Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...139.1163W&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Volpetta |
| Ascensione retta: | 21h11m26.22s |
| Declinazione: | +27°33'12.7" |
| Magnitudine apparente: | 7.763 |
| Distanza: | 617.284 parsec |
| Moto proprio RA: | 2.9 |
| Moto proprio Dec: | -9.4 |
| B-T magnitude: | 7.803 |
| V-T magnitude: | 7.767 |
Cataloghi e designazioni:
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