Gamma-ray bursts (GRBs) are the most brilliant objects in the Universe but efforts to estimate the total energy released in the explosion -- a crucial physical quantity -- have been stymied by their unknown geometry: spheres or cones. We report on a comprehensive analysis of GRB afterglows and derive their conical opening angles. We find that the gamma-ray energy release, corrected for geometry, is narrowly clustered around 5x10**50 erg. We draw three conclusions. First, the central engines of GRBs release energies that are comparable to ordinary supernovae, suggesting a connection. Second, the wide variation in fluence and luminosity of GRBs is due entirely to a distribution of opening angles. Third, only a small fraction of GRBs are visible to a given observer and the true GRB rate is at least a factor of 500 times larger than the observed rate.Comment: Nature, submitte

The global properties of elliptical galaxies, such as luminosity, radius, projected velocity dispersion, projected luminosity, etc., form a two-dimensional family. This " fundamental plane " of elliptical galaxies can be defined in observable terms by the velocity dispersion and mean surface brightness. Its thickness is given at present by the present measurement error bars, and there are no significant indications of nonlinearity (deviation from power laws which define the surface), or higher dimensionality. This is indicative of a strong regularity in the process of galaxy formation. The equations of the plane can be used as new, substantially improved distance indicators for elliptical galaxies. However, all morphological parameters which describe the shape of the light distribution (ellipticity, ellipticity gradient, isophotal twist rate, slope of the surface brightness profile), and reflect dynamical anisotropies of stars, are completely independent of this fundamental plane, and thus, the elliptical galaxies are actually a "2 +AT" parameter family. The M/L ratios correlate only with the velocity dispersions and show a small intrinsic scatter, perhaps only ~30%, in a luminosity range spanning some four orders of magnitude; this suggests a constant fraction of the dark matter contribution in elliptical galaxies.

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Prepared by the LSST Science Collaborations, with contributions from the LSST Project. PrefaceMajor advances in our understanding of the Universe over the history of astronomy have often arisen from dramatic improvements in our ability to observe the sky to greater depth, in previously unexplored wavebands, with higher precision, or with improved spatial, spectral, or temporal resolution. Aided by rapid progress in information technology, current sky surveys are again changing the way we view and study the Universe, and the next-generation instruments, and the surveys that will be made with them, will maintain this revolutionary progress. Substantial progress in the important scientific problems of the next decade (determining the nature of dark energy and dark matter, studying the evolution of galaxies and the structure of our own Milky Way, opening up the time domain to discover faint variable objects, and mapping both the inner and outer Solar System) all require wide-field repeated deep imaging of the sky in optical bands.The wide-fast-deep science requirement leads to a single wide-field telescope and camera which can repeatedly survey the sky with deep short exposures. The Large Synoptic Survey Telescope (LSST), a dedicated telecope with an effective aperture of 6.7 meters and a field of view of 9.6 deg 2 , will make major contributions to all these scientific areas and more. It will carry out a survey of 20,000 deg 2 of the sky in six broad photometric bands, imaging each region of sky roughly 2000 times (1000 pairs of back-to-back 15-sec exposures) over a ten-year survey lifetime.The LSST project will deliver fully calibrated survey data to the United States scientific community and the public with no proprietary period. Near real-time alerts for transients will also be provided worldwide. A goal is worldwide participation in all data products. The survey will enable comprehensive exploration of the Solar System beyond the Kuiper Belt, new understanding of the structure of our Galaxy and that of the Local Group, and vast opportunities in cosmology and galaxy evolution using data for billions of distant galaxies. Since many of these science programs will involve the use of the world's largest non-proprietary database, a key goal is maximizing the usability of the data. Experience with previous surveys is that often their most exciting scientific results were unanticipated at the time that the survey was designed; we fully expect this to be the case for the LSST as well.The purpose of this Science Book is to examine and document in detail science goals, opportunities, and capabilities that will be provided by the LSST. The book addresses key questions that will be confronted by the LSST survey, and it poses new questions to be addressed by future study. It contains previously available material (including a number of White Papers submitted to the ASTRO2010 Decadal Survey) as well as new results from a year-long campaign of study and evaluation. This book does not attempt to be complete; there are many ...

Abstract. We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight system and the standard Johnson B and V systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.

With the discovery of the first transiting extrasolar planetary system back in 1999, a great number of projects started to hunt for other similar systems. Because the incidence rate of such systems was unknown and the length of the shallow transit events is only a few percent of the orbital period, the goal was to monitor continuously as many stars as possible for at least a period of a few months. Small aperture, large field of view automated telescope systems have been installed with a parallel development of new data reduction and analysis methods, leading to better than 1% per data point precision for thousands of stars. With the successful launch of the photometric satellites CoRoT and Kepler, the precision increased further by one-two orders of magnitude. Millions of stars have been analyzed and searched for transits. In the history of variable star astronomy this is the biggest undertaking so far, resulting in photometric time series inventories immensely valuable for the whole field. In this review we briefly discuss the methods of data analysis that were inspired by the main science driver of these surveys and highlight some of the most interesting variable star results that impact the field of variable star astronomy.

The Palomar Transient Factory (PTF) is a fully-automated, wide-field survey aimed at a systematic exploration of the optical transient sky. The transient survey is performed using a new 8.1 square degree camera installed on the 48-inch Samuel Oschin telescope at Palomar Observatory; colors and light curves for detected transients are obtained with the automated Palomar 60-inch telescope. PTF uses eighty percent of the 1.2-m and fifty percent of the 1.5-m telescope time. With an exposure of 60-s the survey reaches a depth of m g ′ ≈21.3 and m R ≈20.6 (5σ, median seeing). Four major experiments are planned for the five-year project: 1) a 5-day cadence supernova search; 2) a rapid transient search with cadences between 90 seconds and 1 day; 3) a search for eclipsing binaries and transiting planets in Orion; and 4) a 3π sr deep H-alpha survey. PTF provides automatic, realtime transient classification and followup, as well as a database including every source detected in each frame. This paper summarizes the PTF project, including several months of on-sky performance tests of the new survey camera, the observing plans and the data reduction strategy. We conclude by detailing the first 51 PTF optical transient detections, found in commissioning data.

Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic, can be due to a variety of physical mechanisms, and is well-described statistically in terms of a damped random walk model 1 . The recent availability of large collections of astronomical time series of flux measurements (light curves) 2-5 offers new data sets for a systematic exploration of quasar variability. Here we report on the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302-102 with a mean observed period of 1,884 ± 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of ∼ 9 years. While the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution.Subparsec supermassive black-hole (SMBH) binary systems are not resolvable except possibly with long baseline radio interferometry. An alternative approach to their detection is through a modulated variability -caused by, for example, perturbations in their accretion disks or precession of relativistic jets, if they are present (see Fig. 1). The best known candidate, OJ 287 6 , has shown a pair of outburst peaks every 12.2 years for at least the past century: this object can be interpreted as a secondary SMBH perturbing the accretion disk of the primary SMBH at regular intervals 7 . Systematic searches for equivalent systems to date 8-10 have attempted to identify them from broad-line velocity offsets in their optical and near-infrared spectra but cannot detect the closest pairs (with 0.1 pc separation).We applied a novel joint wavelet and autocorrelation function (ACF) based technique that identifies objects exhibiting strongly periodic behavior in their light curves (M.J.G. et al, manuscript in preparation) to the largest set of quasar time series currently available. These are drawn from the Catalina Real-time Transient Survey (CRTS) [11][12][13] . PG 1302-102 (see Fig. 2) is the strongest 1 arXiv:1501.01375v1 [astro-ph.GA] 7 Jan 2015 periodic candidate out of twenty objects meeting the selection criteria: strong constant wavelet peak, strong ACF detection of periodic behaviour, sufficient temporal coverage for 1.5 or greater cycles at the detected period, and a phased light curve well-described by a sinusoid. For statistical comparison, we have also generated a simulated light curve for each known quasar based on a damped random walk (DRW) model, a standard statistical description of the optical variability of quasars 1 , using the CRTS time sampling. We find that only one object from the simulated data of 247,000 quasars satisfies the same selection criteria, showing that the number of quasars selected is statistically significant and...