Browsing by Author "Graham, M."
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- ItemCataclysmic variables from the Catalina Real-time Transient Survey(2014) Drake, A.; Gaensicke, B.; Djorgovski, S.; Wils, P.; Mahabal, A.; Graham, M.; Yang, T.; Catelan, Márcio
- ItemDiscovery of Thousands of RR Lyrae by the Catalina Surveys(2013) Drake, Andrew J.; Djorgovski, S. G.; Catelan, Márcio; Torrealba, G.; Graham, M.; Mahabal, A. A.; Donalek, C.; Prieto, J.; McNaught, R.; Larson, S. M.; Christensen, E.; Beshore, E. C.We have performed an extensive search for RR Lyrae among the 500 million sources observed by the Catalina Surveys. We detect 23,000 type-ab RR Lyrae (of which 18,700 are new discoveries) from a region spanning 3/4 of the sky. By combining calibrated Catalina photometry with RR Lyrae absolute magnitude estimates, we derive accurate distances and investigate the spatial distribution of structures within the Galactic halo. We identify hundreds of new RR Lyrae belonging to the Sagittarius tidal streams system and compare their observed properties with predictions from existing N-body models. We discover significant evidence that firmly establishes the existence of a tidal stream reaching Galactocentric distances beyond 100 kpc. This stream remains to be explained by any Sagittarius model. For 1,500 of the RR Lyrae we find matches with targets observed by past SDSS spectroscopic surveys. Combining the radial velocities and metallicity estimates from the SDSS spectra, with photometric distances, we investigate the kinematics and abundances of halo tidal stream populations....
- ItemResults from the Catalina Real-time Transient Survey(2009) Drake, Andrew J.; Djorgovski, S. G.; Mahabal, A. A.; Graham, M.; Williams, R.; Catelan, Marcio; Beshore, E.; Larson, S.; Christensen, E.The Catalina Real-time Transient Survey (CRTS) is a collaborative effort between Caltech and LPL that uses data from Catalina Sky Survey's 0.7m Schmidt telescope to search for optical transients. This survey currently covers a total of 26,000 square degrees on the sky between declinations -30 and 70. Observations covering 1200 square degrees are taken 21 nights per lunation and reach magnitudes of 19 to 20. CRTS is sensitive to transients with timescales from minutes to years since images are taken in sequences separated by 10 minutes and past observations date back over four years. Transient classification is performed using follow up imaging and spectroscopy in combination with VO-enabled archival analysis of CSS and Palomar Quest synoptic datasets and DSS, 2MASS, SDSS, GALEX and UKIDSS surveys. To date more than 600 unique transients have been identified by CRTS. These include more than 200 newly discovered Supernovae, Cataclysmic Variables and Blazars. Initial results of note include in the discovery of hyper-luminous supernovae, as well as a high rate of supernovae associated with intrinsically faint galaxies. In the near future we expect to expand the survey area and depth by utilizing data from two additional operational Catalina Sky Survey telescopes. All CRTS transients are discovered and distributed openly within minutes of observation using VOEvent technology as well as html tables, RSS feeds and GoogleSky (from VOEventNet.org). Astronomers will soon be able to automatically select transients of particular interest by using the personalized event selection available via the SkyAlert system....
- ItemSixty Thousand Periodic Variables from the Catalina Surveys(2014) Drake, Andrew J.; Graham, M.; Djorgovski, S. G.; Catelan, Marcio; Mahabal, A. A.; Prieto, J.; Donalek, C.; Christensen, E. J.; Larson, S. M.; Boattini, A.; Gibbs, A.; Grauer, A. D.; Hill, R.; Kowalski, R.; Johnson, J.; Shelly, F.; Torrealba, G.We have performed an in-depth search for periodic variable stars within the photometry from the Catalina Surveys Data Releases. Our analysis reveals ~40,000 new periodic variable stars with brightness ranging from V=11 to 20, from a region covering ~20,000 square degrees on the sky. Each source is classified based on lightcurve morphology and multi-color photometry from WISE and SDSS. The variable stars discovered include eclipsing binaries, such as Algol, beta Lyrae, W UMa and WD+dM types, and pulsators including delta Scuti's, SX Phe, LPVs, RR Lyrae and Cepheids. We combine these sources with type-ab RR Lyrae from our prior analysis to produce a periodic variable catalog containing 60,000 stars. Using ~5,500 optical spectra from SDSS DR10 we determine the metallicities, surface gravities and radial velocities of the major types. The photometry, classifications and periods will all be made publicly available through the Catalina Surveys data release website....
- ItemTHE CATALINA SURVEYS PERIODIC VARIABLE STAR CATALOG(2014) Drake, A.; Graham, M.; Djorgovski, S.; Mahabal, A.; Catelan, Márcio; García Alvarez, D.; Donalek, C.; Torrealba, G.
- ItemThe First Data Release of the Catalina Surveys(2012) Drake, Andrew J.; Beshore, E.; Djorgovski, S. G.; Larson, S.; Boattini, A.; Catelan, Marcio; Christensen, E.; Donalek, C.; Gibbs, A.; Graham, M.; Grauer, A.; Hill, R.; Kowalski, R.; Mahabal, A.; Prieto, J. L.; Williams, R.The Catalina Surveys consists of the Catalina Sky Survey (CSS) and the Catalina Real-time Transient Survey (CRTS). These two surveys work synergistically to extract the maximum scientific return from the data gathered by Catalina telescopes. In order to further facility the wealth of time-domain science that is possible with this data, the Catalina Surveys are now releasing Catalina Schmidt telescope photometry for 200 million objects. Each source has been measured over a period of six years and comes from a 24,000 square degree region between declination -30 and +70 degrees (with 10 degree avoidance of the galactic plane). On average each location in the data release has been observed more than 200 times to a depth of V=19.5. We will provide the details of the open-access data services as well as future data releases and recent discoveries....
- ItemULTRA-SHORT PERIOD BINARIES FROM THE CATALINA SURVEYS(2014) Drake, A.; Djorgovski, S.; García Alvarez, D.; Graham, M.; Catelan, Márcio; Mahabal, A.; Donalek, C.; Torrealba, G.