11 research outputs found
A Deep Proper Motion Catalog Within The Sloan Digital Sky Survey Footprint
A new proper motion catalog is presented, combining the Sloan Digital Sky
Survey (SDSS) with second epoch observations in the r band within a portion of
the SDSS imaging footprint. The new observations were obtained with the 90prime
camera on the Steward Observatory Bok 90 inch telescope, and the Array Camera
on the U.S. Naval Observatory, Flagstaff Station, 1.3 meter telescope. The
catalog covers 1098 square degrees to r = 22.0, an additional 1521 square
degrees to r = 20.9, plus a further 488 square degrees of lesser quality data.
Statistical errors in the proper motions range from 5 mas/year at the bright
end to 15 mas/year at the faint end, for a typical epoch difference of 6 years.
Systematic errors are estimated to be roughly 1 mas/year for the Array Camera
data, and as much as 2 - 4 mas/year for the 90prime data (though typically
less). The catalog also includes a second epoch of r band photometry.Comment: 14 pages, 17 figures, accepted for publication in the Astronomical
Journa
Trigonometric Parallaxes of Central Stars of Planetary Nebulae
Trigonometric parallaxes of 16 nearby planetary nebulae are presented,
including reduced errors for seven objects with previous initial results and
results for six new objects. The median error in the parallax is 0.42 mas, and
twelve nebulae have parallax errors less than 20 percent. The parallax for
PHL932 is found here to be smaller than was measured by Hipparcos, and this
peculiar object is discussed. Comparisons are made with other distance
estimates. The distances determined from these parallaxes tend to be
intermediate between some short distance estimates and other long estimates;
they are somewhat smaller than estimated from spectra of the central stars.
Proper motions and tangential velocities are presented. No astrometric
perturbations from unresolved close companions are detected.Comment: 24 pages, includes 4 figures. Accepted for A
Haze in Pluto's atmosphere: Results from SOFIA and ground-based observations of the 2015 June 29 Pluto occultation
On UT 29 June 2015, the occultation by Pluto of a bright star (r′ = 11.9) was observed from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and several ground-based stations in New Zealand and Australia. Pre-event astrometry allowed for an in-flight update to the SOFIA team with the result that SOFIA was deep within the central flash zone (~22 km from center). Analysis of the combined data leads to the result that Pluto's middle atmosphere is essentially unchanged from 2011 and 2013 (Person et al. 2013; Bosh et al. 2015); there has been no significant expansion or contraction of the atmosphere. Additionally, our multi-wavelength observations allow us to conclude that a haze component in the atmosphere is required to reproduce the light curves obtained. This haze scenario has implications for understanding the photochemistry of Pluto's atmosphere