3,124 research outputs found
The DIRECT project: Catalogs of stellar objects in nearby galaxies. II. Eastern arm and NGC 206 in M31
DIRECT is a project to directly obtain the distances to two important
galaxies in the cosmological distance ladder, M31 and M33, using detached
eclipsing binaries and Cepheids. As part of our search for these variables, we
have obtained photometry and positions for thousands of stellar objects within
the monitored fields, covering an area of 557.8 arcmin^2. In this research note
we present the equatorial coordinates and BVI photometry for 26712 stars in the
M31 galaxy, along the eastern arm and in the vicinity of the star forming
region NGC206.Comment: 2 LaTeX pages, 2 Postscript figures, submitted to Astronomy &
Astrophysic
On the Rotation Period of (90377) Sedna
We present precise, ~1%, r-band relative photometry of the unusual solar
system object (90377) Sedna. Our data consist of 143 data points taken over
eight nights in October 2004 and January 2005. The RMS variability over the
longest contiguous stretch of five nights of data spanning nine days is only
1.3%. This subset of data alone constrain the amplitude of any long-period
variations with period P to be A<1% (P/20 days)^2. Over the course of any given
5-hour segment, the data exhibits significant linear trends not seen in a
comparison star of similar magnitude, and in a few cases these segments show
clear evidence for curvature at the level of a few millimagnitudes per hour^2.
These properties imply that the rotation period of Sedna is O(10 hours), cannot
be 10 days, unless the intrinsic light curve has
significant and comparable power on multiple timescales, which is unlikely. A
sinusoidal fit yields a period of P=(10.273 +/- 0.002) hours and semi-amplitude
of A=(1.1 +/- 0.1)%. There are additional acceptable fits with flanking periods
separated by ~3 minutes, as well as another class of fits with P ~ 18 hours,
although these later fits appear less viable based on visual inspection. Our
results indicate that the period of Sedna is likely consistent with typical
rotation periods of solar system objects, thus obviating the need for a massive
companion to slow its rotation.Comment: 7 pages, 4 figures, 2.5 tables. Final ApJL version, minor changes.
Full light curve data in tex
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