The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey

Using a sample of over 25000 spectroscopically confirmed quasars from the Sloan Digital Sky Survey, we show how quasar variability in the rest frame optical/UV regime depends upon rest frame time lag, luminosity, rest wavelength, redshift, the presence of radio and X-ray emission, and the presence of broad absorption line systems. The time dependence of variability (the structure function) is well-fit by a single power law on timescales from days to years. There is an anti-correlation of variability amplitude with rest wavelength, and quasars are systematically bluer when brighter at all redshifts. There is a strong anti-correlation of variability with quasar luminosity. There is also a significant positive correlation of variability amplitude with redshift, indicating evolution of the quasar population or the variability mechanism. We parameterize all of these relationships. Quasars with RASS X-ray detections are significantly more variable (at optical/UV wavelengths) than those without, and radio loud quasars are marginally more variable than their radio weak counterparts. We find no significant difference in the variability of quasars with and without broad absorption line troughs. Models involving multiple discrete events or gravitational microlensing are unlikely by themselves to account for the data. So-called accretion disk instability models are promising, but more quantitative predictions are needed.Comment: 41 pages, 21 figures, AASTeX, Accepted for publication in Ap

GRB Afterglows and Other Transients in the SDSS

The Sloan Digital Sky Survey (SDSS) will image one quarter of the sky centered on the northern galactic cap and produce a 3‐D map of galaxies and quasars found in the sample. An additional 225 deg2 southern survey will be imaged repeatedly on varying timescales. Here we discuss both archival searches in the SDSS catalog (such as SDSS J24602.54+011318.8) and active searches with the SDSS instruments (such as for GRB 010222) for GRB afterglows and other transient objects. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87288/2/349_1.pd

Impact 2003

Index Competitive Agricultural Systems in a Global Economy Biosecurity Education .................................................. 1 Calf Scours Prevention System .................................................. 2 Center for Agricultural & Food Industrial Organization .................................................. 3 Chickpeas as an Alternative Crop .................................................. 5 .................................................. 6 Dry Ethanol Byproducts for Farms and Ranches .................................................. 7 Indoor Prawn Production .................................................. 8 National Drought Mitigation Center .................................................. 9 Republican River Basin Irrigation Management Project .................................................. 11 Small Farm and Ranch Profitability Project .................................................. 12 Sorting and Mixing Pigs .................................................. 14 WeedSOFT Aids Weed Management Decisions ....................................15 New Beef Products Add Value* ....................................16 Panhandle Chicory Production* ....................................18 Ranch Practicum* .................................... 19 Turf Grass Seed Production* .................................... 20 Safe and Secure Food and Fiber Systems Biosecurity Education ................................................ 21 E. coli Research .................................... 22 Testing Oil Freshness .................................... 24 Healthy, Well-Nourished Population Food Safety and Nutrition Web Site ....................................25 Improving Young Adults\u27 Eating Habits ....................................26 Nutrition Education Programs* ....................................27 Smoking and Diet* .................................... 28 Sun-Protective Clothing Standards* ....................................29 Greater Harmony Between Agriculture and the Environment Buffer Strip Assessment Tool .................................... 30 Irrigation Management Home Study Course .......................................................................................... 31 Livestock and Poultry Environmental Stewardship Curriculum ........................................................ 32 Monitoring Lake Water Quality ....................................33 Nitrogen Management in Crop Production ............................................................................................. 34 Republican River Basin Irrigation Management Project ....................................35 Rootworm Resistance Research ....................................36 WeedSOFT Aids Weed Management Decisions ....................................37 Cleaning Up Pesticide-Contaminated Soil* ....................................38 Measuring Carbon Storage in Cropland* ....................................40 Pivots, Nitrogen Management Protect Water Quality* .............................................. 41 Reducing Livestock Methane* ....................................42 Economic Development and Quality of Life for People and Communities Bridging the Technology Gap ....................................43 Consumer Preference and Economic Leakage Study Program ....................................44 Decorative Millet Earns All-America Selections. Gold ....................................45 Distance Counseling Improves Access for Rural Residents ................................................................. 46 Drought Web Site .................................... 47 Forensic Entomology .................................... 48 National Drought Mitigation Center ....................................49 Nebraska Rural Poll Provides Rural Perspective ....................................51 Protecting Water Quality Along the Lower Platte River ........................................................................ 53 Rural Women\u27s Concerns .................................... 54 Small Farm and Ranch Profitability Project ............................................................................................. 55 Technical Assistance for Geothermal Systems ........................................................................................ 57 Building Nebraska Families* .................................... 58 Coping with Divorce* .................................... 59 Food Processing Center Entrepreneurship Services* ............................................................................. 60 Giving Entrepreneurs an EDGE* ....................................61 Meat Plants Changing Rural Communities* ....................................62 New Beef Products Add Value* ................................................. 63 Panhandle Chicory Production* ....................................65 Sandhills Leadership Program* ................................................ 66 Technologies Across Nebraska* ....................................67 Society-Ready Graduates Animal Welfare Class ..................................................................... 68 Employment Seminar ............................................................. 69 Entomology Distance Education Master\u27s Degree ........................................... 70 Feedlot Management Specialization Internship ............................ 71 Food Product Development Class ................................................ 72 Innovative Uses for Soybeans ........................................................ 73 Pollution Prevention Internship .................................................................. 74 Student Development Initiative ..................................................... 76 Agricultural Science Magnet Schools*............................................... 77 America\u27s Farm* ...................................................................... 78 Bug Bash* .................................................................................. 79 Nebraska Beef Team* ........................................................ 8