Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21544122b&link_type=abstract
American Astronomical Society, AAS Meeting #215, #441.22; Bulletin of the American Astronomical Society, Vol. 42, p.404
Astronomy and Astrophysics
Astronomy
1
Scientific paper
Although ground-based parallax measurements remain an essential means of determining stellar distances, hardly any programs currently operate. Of the 3,125 northern-hemisphere stellar systems expected within 25 pc, only 1,131 systems are known (K. Slatten 2009, pc). Measurements at infrared wavelengths would be especially helpful in identifying solar neighborhood members, which may include many cooler objects. In August 2009, Dwarfarchives.org (Gelino, Kirkpatrick, & Burgasser 2004) listed 753 L and T dwarfs of which only 86 have parallaxes, including 40 preliminary ones from the USNO (Vrba et al. 2004).
After the Virginia Astronomical Instrumentation Laboratory developed an infrared camera, FanCam, for the 31-in (0.8-m) Tinsley reflector at the University of Virginia's Fan Mountain Observatory, its astrometric quality and suitability for a parallax program was evaluated. Positions of 16 astrometric evaluation stars were measured in 68 J-band exposures of an open cluster, NGC 2420, taken over a range of hour angles during 2005. The mean error in a single observation of unit weight (m.e.1) was used to judge the repeatability of those positions. The overall results indicate a precision of 1.3 ± 0.7 µm in x (RA) and 1.3 ± 0.8 µm in y (Dec), or 0.04" ± 0.02" in each axis, with an xy-averaged precision of ±1.3 µm (±0.04"). FanCam achieved precision comparable to that of the ESO NTT infrared parallax program (Tinney, Burgasser, & Kirkpatrick 2003) and better than that of the photographic plates used previously. Accordingly, a parallax program would be feasible.
If established, an infrared parallax program with FanCam could draw its first targets from the 119 northern-hemisphere brown dwarfs that are solar neighborhood candidates. FanCam could, thereby, contribute significantly to our knowledge of the solar neighborhood and of substellar bodies through its parallax measurements.
The Levinson Fund, UVa Governor's Fellowship and GSAS, and Hampden-Sydney College funded this research.
Bartlett Jennifer L.
Ianna Philip A.
Kanneganti Srikrishna
Park Chan
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