We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 quasars for which the spectral energy distributions include X-ray spectral indices and UV data. Of these, 29 are radio quiet, and 18 are radio loud. The SEDs are presented both in figures and in tabular form, with additional tabular material published on CD-ROM. Previously unpublished observational data for a second set of quasars excluded from the primary sample are also tabulated. The effects of host galaxy starlight contamination and foreground extinction on the UVSX sample are considered and the sample is used to investigate the range of SED properties. Of course, the properties we derive are influenced strongly by the selection effects induced by quasar discovery techniques. We derive the mean energy distribution (MED) for radio-loud and radio-quiet objects and present the bolometric corrections derived from it. We note, however, that the dispersion about this mean is large (-one decade for both the infrared and ultraviolet components when the MED is normalized at the near-infrared inflection). At least part of the dispersion in the ultraviolet may be due to time variability, but this is unhkely to be important in the infrared. The existence of such a large dispersion indicates that the MED reflects only some of the properties of quasars and so should be used only with caution. Subject headings: atlases-galaxies: photometry-quasars: general

We present the Ðnal results of a ROSAT PSPC program to study the soft X-ray emission properties of a complete sample of low-z quasars. This sample includes all 23 quasars from the Bright Quasar Survey with z ¹ 0.400 and cm~2. Pointed ROSAT PSPC observations were made for all N H I Gal \ 1.9 ] 1020 quasars, yielding high signal-to-noise (S/N) spectra for most objects, which allowed an accurate determination of the spectral shape. The following main results were obtained :1. The spectra of 22 of the 23 quasars are consistent, to within D30%, with a single power-law model at rest-frame 0.2È2 keV. There is no evidence for signiÐcant soft excess emission with respect to the bestÐt power law. We place a limit (95% conÐdence) of D5 ] 1019 cm~2 on the amount of excess foreground absorption by cold gas for most of our quasars. The limits are D1 ] 1019 cm~2 in the two highest S/N spectra.2. The mean 0.2È2 keV continuum of quasars agrees remarkably well with an extrapolation of the mean 1050È350 continuum recently determined by et al. for z [ 0.33 quasars. This sug-A Zheng (1996) gests that there is no steep soft component below 0.2 keV.3. SigniÐcant X-ray absorption (q [ 0.3) by partially ionized gas ("" warm absorber ÏÏ) in quasars is rather rare, occurring for of the population, which is in sharp contrast to lower luminosity active [5% galactic nuclei (AGNs), where signiÐcant absorption probably occurs for D50% of the population.4. Extensive correlation analysis of the X-ray continuum emission parameters with optical emissionline parameters indicates that the strongest correlation is between the spectral slope and the Hb a x FWHM. A possible explanation for this remarkably strong correlation is a dependence of on a x L /L Edd , as seen in Galactic black hole candidates.5. The strong correlations between and Fe II/Hb, and the peak [O III] to Hb Ñux ratio are a x L *O III+ , veriÐed. The physical origin of these correlations is still not understood.6. There appears to be a distinct class of "" X-rayÈweak ÏÏ quasars, which form D10% of the population (three out of 23), where the X-ray emission is smaller, by a factor of 10È30, than expected based on their luminosity at other bands and on their Hb luminosity. These may be quasars in which the direct X-ray source is obscured and only scattered X-rays are observed. 7. Thin accretion disk models cannot reproduce the observed 0.2È2 keV spectral shape, and they also cannot reproduce the tight correlation between the optical and soft X-ray emission. An as yet unknown physical mechanism must be maintaining a strong correlation between the optical and soft X-ray emission.8. The H I/He I ratio in the high Galactic latitude ISM must be within 20%, and possibly within 5%, of the total H/He ratio of 10, which indicates that He in the di †use H II gas component of the interstellar medium is mostly ionized to He II or He III.We Ðnally note the intriguing possibility that although in radio-loud quasars ([1.15^0.14) is Sax T signiÐcantly Ñatter than in radio-quiet quasars ([1.72^0.09) the X...

The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public Advanced CCD Imaging Spectrometer imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents 30. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1σ uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of 1 false source per field for a 100 ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.

We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains the largest number of homogeneously observed and reduced nearby SNe Ia (z 0.08) published to date. It more than doubles the nearby sample, bringing SN Ia cosmology to the point where systematic uncertainties dominate. Our natural system photometry has a precision of 0.02 mag in BV RI r i and 0.04 mag in U for points brighter than 17.5 mag. We also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system BV RI r i photometry and 0.07 mag for U. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars, where available for the same SN, reveal agreement at the level of a few hundredths mag in most cases. We find that 1991bg-like SNe Ia are sufficiently distinct from other SNe Ia in their color and light-curve-shape/ luminosity relation that they should be treated separately in light-curve/distance fitter training samples. The CfA3 sample will contribute to the development of better light-curve/distance fitters, particularly in the few dozen cases where near-infrared photometry has been obtained and, together, can help disentangle host-galaxy reddening from intrinsic supernova color, reducing the systematic uncertainty in SN Ia distances due to dust.

The CIAO (Chandra Interactive Analysis of Observations) software package was first released in 1999 following the launch of the Chandra X-ray Observatory and is used by astronomers across the world to analyze Chandra data as well as data from other telescopes. From the earliest design discussions, CIAO was planned as a generalpurpose scientific data analysis system optimized for X-ray astronomy, and consists mainly of command line tools (allowing easy pipelining and scripting) with a parameter-based interface layered on a flexible data manipulation I/O library. The same code is used for the standard Chandra archive pipeline, allowing users to recalibrate their data in a consistent way.We will discuss the lessons learned from the first six years of the software's evolution. Our initial approach to documentation evolved to concentrate on recipe-based "threads" which have proved very successful. A multidimensional abstract approach to data analysis has allowed new capabilities to be added while retaining existing interfaces. A key requirement for our community was interoperability with other data analysis systems, leading us to adopt standard file formats and an architecture which was as robust as possible to the input of foreign data files, as well as re-using a number of external libraries. We support users who are comfortable with coding themselves via a flexible user scripting paradigm, while the availability of tightly constrained pipeline programs are of benefit to less computationally-advanced users. As with other analysis systems, we have found that infrastructure maintenance and re-engineering is a necessary and significant ongoing effort and needs to be planned in to any long-lived astronomy software.