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Meeting the Cool Neighbors. V. A 2MASS-Selected Sample of Ultracool Dwarfs
We present the initial results of our effort to create a statisticallyrobust, volume-limited sample of ultracool dwarfs from the Two MicronAll Sky Survey Second Incremental Data Release. We are engaged in amultifaceted search for nearby late-type objects, and this is the firstinstallment of our search using purely photometric selection. The goalof this work is a determination of the low-mass star and brown dwarfluminosity function in the infrared. Here we outline the construction ofthe sample, dubbed 2MU2, and present our first results, including thediscovery of 186 M7-L6 dwarfs-47 of which are likely to be within 20 pcof the Sun. These results represent 66% of the ultracool candidates inour sample yet constitute a 127% increase in the number of ultracooldwarfs known within the volume searched (covering 40% of the sky out to20 pc). In addition, we have identified 10 M4-M6.5 objects that arelikely to be within 20 pc (or within 1 σ). Finally, based on theseinitial data, we present a preliminary luminosity function and discussseveral interesting features of the partial sample presented here. Onceour sample is complete, we will use our measured luminosity function toconstrain the mass function of low-mass stars and brown dwarfs.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
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Observation and Astrometry data
| Constellation: | Ταύρος |
| Right ascension: | 04h20m16.67s |
| Declination: | +18°09'43.6" |
| Apparent magnitude: | 10.025 |
| Proper motion RA: | -1.4 |
| Proper motion Dec: | -7.8 |
| B-T magnitude: | 12.712 |
| V-T magnitude: | 10.247 |
Catalogs and designations:
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