Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA million asteroid observations in the Sloan Digital Sky Survey
99
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Context. The populations of small bodies of the Solar System (asteroids, comets, Kuiper-Belt objects) are used to constrain the origin and evolution of the Solar System. Both their orbital distribution and composition distribution are required to track the dynamical pathway from their regions of formation to their current locations. Aims. We aim at increasing the sample of Solar System objects that have multi-filter photometry and compositional taxonomy. Methods. We search for moving objects in the archive of the Sloan Digital Sky Survey. We attempt at maximizing the number of detections by using loose constraints on the extraction. We then apply a suite of filters to remove false-positive detections (stars or galaxies) and mark out spurious photometry and astrometry. Results. We release a catalog of 1 542 522 entries, consisting of 1 036 322 observations of 379 714 known and unique SSOs together with 506 200 observations of moving sources not linked with any known SSOs. The catalog completeness is estimated to be about 95% and the purity to be above 95% for known SSOs.
rate research
Read More
We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u,g,r,i,z) photometry is used to determine the comets colors, sizes, surface brightness profiles, and rates of dust production in terms of the Af{rho} formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(< H) propto 10(0.49pm0.05)H for H < 18, with evidence of a much shallower fit N(< H) propto 10(0.19pm0.03)H for the faint (14.5 < H < 18) comets. The resolved comets show an extremely narrow distribution of colors (0.57 pm 0.05 in g - r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.
The discovery of an optical counterpart to GRB010222 (detected by BeppoSAX; Piro 2001) was announced 4.4 hrs after the burst by Henden (2001a). The Sloan Digital Sky Surveys 0.5m photometric telescope (PT) and 2.5m survey telescope were used to observe the afterglow of GRB010222 starting 4.8 hours after the GRB. The 0.5m PT observed the afterglow in five, 300 sec g band exposures over the course of half an hour, measuring a temporal decay rate in this short period of F_nu propto t^{-1.0+/-0.5}. The 2.5m camera imaged the counterpart nearly simultaneously in five filters (u g r i z), with r = 18.74+/-0.02 at 12:10 UT. These multicolor observations, corrected for reddening and the afterglows temporal decay, are well fit by the power-law F_nu propto nu^{-0.90+/-0.03} with the exception of the u band UV flux which is 20% below this slope. We examine possible interpretations of this spectral shape, including source extinction in a star forming region.
Galaxies are usually classified as star forming or active by using diagnostic diagrams, such as [N II]/Halpha vs. [O III]/Hbeta. Active galaxies are further classified into Seyfert or LINER-like sources. We claim that a non-negligible fraction of galaxies classified as LINERs in the Sloan Digital Sky Survey are in fact ionized by hot post-AGB stars and white dwarfs.
To obtain a better statistics on the occurrence of magnetism among white dwarfs, we searched the spectra of the hydrogen atmosphere white dwarf stars (DAs) in the Data Release 7 of the Sloan Digital Sky Survey (SDSS) for Zeeman splittings and estimated the magnetic fields. We found 521 DAs with detectable Zeeman splittings, with fields in the range from around 1 MG to 733 MG, which amounts to 4% of all DAs observed. As the SDSS spectra have low signal-to-noise ratios, we carefully investigated by simulations with theoretical spectra how reliable our detection of magnetic field was.
We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, and contains 58 million photometric observations in the SDSS ugriz system for 1.4 million unresolved sources. In each photometric bandpass we compute various low-order lightcurve statistics and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g=20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands. The majority (2/3) of these variable sources are low-redshift (<2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding low-redshift quasars as is the UV excess color selection (at high Galactic latitudes). We analyze the distribution of lightcurve skewness for quasars and find that is centered on zero. We find that about 1/4 of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level. The distribution of lightcurve skewness in the g-r vs. u-g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior). Using over six hundred RR Lyrae stars, we demonstrate rich halo substructure out to distances of 100 kpc. We extrapolate these results to expected performance by the Large Synoptic Survey Telescope and estimate that it will obtain well-sampled 2% accurate, multi-color lightcurves for ~2 million low-redshift quasars, and will discover at least 50 million variable stars.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
