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Spectroscopy of Bright QUEST RR Lyrae Stars: Velocity Substructures toward Virgo
A. Katherina Vivas, Yara Jaffe, Robert Zinn +3
Using a sample of 43 bright (V<16.1, distance <13 kpc) RR Lyrae stars (RRLS) from the QUEST survey with spectroscopic radial velocities and metallicities, we find that several sepa…
Spitzer observations of the Orion OB1 association: disk census in the low mass stars
Jesus Hernandez, Nuria Calvet, C. Briceno +6
We present new Spitzer Space Telescope observations of two fields in the Orion OB1 association. We report here IRAC/MIPS observations for 115 confirmed members and 41 photometric c…
Searching for RR Lyrae stars in the Canis Major Overdensity
Cecilia Mateu, A. Katherina Vivas, Robert Zinn +2
The Canis Major overdensity (CMa) was initially proposed to be the remnant of a tidally disrupting dSph galaxy. Since its nature is still subject of debate, the goal of the present…
25 Orionis: A Kinematically Distinct 10 Myr Old Group in Orion OB1a
Cesar Briceno, Lee Hartmann, Jesus Hernandez +4
We report here on the photometric and kinematic properties of a well defined group of nearly 200 low-mass pre-main sequence stars, concentrated within ~ 1 deg of the early-B star 2…
Spitzer Space Telescope study of disks in the young Orionis cluster
Jesus Hernandez, L. Hartmann, T. Megeath +9
We report new Spitzer Space Telescope observations from the IRAC and MIPS instruments of the young (~ 3 Myr) sigma Orionis cluster. We identify 336 stars as members of the cluster…
Sub-Structures in the Halo of the Milky Way
A. Katherina Vivas, R. Zinn, Y. Subero +1
The latest results of the QUEST survey for RR Lyrae stars are described. This survey, which is designed to find and characterize sub-structures in the halo of our Galaxy, has cover…
The QUEST RR Lyrae Survey II: The Halo Overdensities in the First Catalog
A. Katherina Vivas, Robert Zinn
The first catalog of the RR Lyrae stars (RRLS) in the Galactic halo by the QUEST Survey has been searched for significant overdensities that may be debris from disrupted dwarf gala…
Spectroscopy of QUEST RR Lyrae Variables: the new Virgo Stellar Stream
Sonia Duffau, Robert Zinn, A. Katherina Vivas +4
Eighteen RR Lyrae variables (RRLs) that lie in the "$12\fh 4$ clump" identified by the QUEST survey have been observed spectroscopically to measure their radial velocities and meta…
RR Lyrae search and stellar populations study in Canis Major: Preliminary Results
Cecilia E. Mateu, A. Katherina Vivas, Robert Zinn +1
We present preliminary results of a RR Lyrae star search and stellar populations study performed in the Canis Major overdensity, spanning an area of 8.35sq deg. The observations we…
The CIDA Variability Survey of Orion OB1. I: the low-mass population of Ori OB 1a and 1b
Cesar Briceno, Nuria Calvet, Jesus Hernandez +4
We present results of a large scale, multi-epoch optical survey of the Ori OB1 association, carried out with the QuEST camera at the Venezuela National Astronomical Observatory. We…
VLT Spectroscopy of RR Lyrae Stars in the Sagittarius Tidal Stream
A. Katherina Vivas, Robert Zinn, Carme Gallart
Sixteen RR Lyrae variables from the QUEST survey that lie in the leading arm of the tidal stream from the Sagittarius dSph galaxy have been observed spectroscopically to measure th…
Mc Neil's Nebula in Orion: The Outburst History
C. Briceno, A. K. Vivas, J. Hernandez +6
We present a sequence of I-band images obtained at the Venezuela 1m Schmidt telescope during the outburst of the nebula recently discovered by J.W. McNeil in the Orion L1630 molecu…
The Selection of RR Lyrae Stars Using Single-epoch Data
Zeljko Ivezic, A. Katherina Vivas, Robert H. Lupton +1
We utilize a complete sample of RR Lyrae stars discovered by the QUEST survey using light curves to design selection criteria based on SDSS colors. Thanks to the sensitivity of the…
New Quasars Detected via Variability in the QUEST1 Survey
A. W. Rengstorf, S. L. Mufson, C. Abad +31
By observing the high galactic latitude equatorial sky in drift scan mode with the QUEST (QUasar Equatorial Survey Team) Phase 1 camera, multi-bandpass photometry on a large strip…
Velocities of RR Lyrae Stars in the Sagittarius Tidal Stream
A. Katherina Vivas, Robert Zinn, Carme Gallart
We have measured radial velocities and metallicities of 16 RR Lyrae stars, from the QUEST survey, in the Sagittarius tidal stream at 50 kpc from the galactic center. The distributi…
Reddening-Independent Quasar Selection from a Wide-Field Optical and Near-IR Imaging Survey
R. G. Sharp, C. N. Sabbey, A. K. Vivas +4
We combine deep, wide-field near-IR and optical imaging to demonstrate a reddening-independent quasar selection technique based on identifying outliers in the (g-z) / (z-H) colour…
A Large Area CCD Camera for the Schmidt Telescope at the Venezuelan National Astronomical Observatory
C. Baltay, J. A. Snyder, P. Andrews +25
We have designed, constructed and put into operation a large area CCD camera that covers a large fraction of the image plane of the 1 meter Schmidt telescope at Llano del Hato in V…
The low-mass young stellar population in Orion OB1
Cesar Briceño, Nuria Calvet, Anna K. Vivas +2
We present recent results from our ongoing large scale variability survey of the Orion OB1 Association. In an area of ~ 25 square degrees we have unveiled new populations of low-ma…
The QUEST RR Lyrae Survey: Confirmation of the Clump at 50 kpc and Other Over-Densities in the Outer Halo
A. K. Vivas, R. Zinn, P. Andrews +33
We have measured the periods and light curves of 148 RR Lyrae variables from V=13.5 to 19.7 from the first 100 sq. degrees of the QUEST RR Lyrae survey. Approximately 55% of these…
The CIDA-QUEST Large Scale Variability Survey in the Orion OB Association: initial results
Cesar Briceno, A. Katherina Vivas, Nuria Calvet +2
Using the 8k x 8k CCD Mosaic Camera on the 1m Schmidt telescope in Venezuela, we are conducting a large-scale, deep optical, multiepoch, photometric (BVRIHa) survey over 120 sq.deg…