High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.

Abstract. The Flexible Image Transport System -FITS -has been in use in the astronomical community for over two decades. A newly updated version of the standard has recently been approved by the International Astronomical Union FITS Working Group. This new version of the standard appears here in its entirety. As a preface we briefly describe the process by which the standard evolves and revisions are approved, and note two minor changes to NOST 100-2.0 which were adopted by the IAU FWG.

The Flexible Image Transport System (FITS) has been used by astronomers for over 30 years as a data interchange and archiving format; FITS files are now handled by a wide range of astronomical software packages. Since the FITS format definition document (the "standard") was last printed in this journal in 2001, several new features have been developed and standardized, notably support for 64-bit integers in images and tables, variable-length arrays in tables, and new world coordinate system conventions which provide a mapping from an element in a data array to a physical coordinate on the sky or within a spectrum. The FITS Working Group of the International Astronomical Union has therefore produced this new version 3.0 of the FITS standard, which is provided here in its entirety. In addition to describing the new features in FITS, numerous editorial changes were made to the previous version to clarify and reorganize many of the sections. Also included are some appendices which are not formally part of the standard. The FITS standard is likely to undergo further evolution, in which case the latest version may be found on the FITS Support Office Web site at http://fits.gsfc.nasa.gov/, which also provides many links to FITS-related resources.Key words. instrumentation: miscellaneous -methods: miscellaneous -techniques: miscellaneous -reference systemsstandards -astronomical databases: miscellaneous ForewordSince its inception in the late 1970s, the Flexible Image Transport System (FITS) data format has enjoyed wide acceptance in the astronomical community. Indeed, FITS is used as the archival format for most digital archives of astronomical data, FITS is one of the most common run-time file formats for analysis applications, and FITS is seeing continued utility as a component of data formats for the Virtual Observatory. After the initial FITS definition papers appeared (Wells et al. 1981; The FITS standard has evolved in many significant ways during the last decade. In 2005 the IAUFWG approved use of the 64-bit integer data type in FITS images and tables and added support for variable-length arrays within tables. But some of the most significant extensions to FITS did not appear in the standard document per se, but in a series of papers (Greisen & Calabretta 2002;Calabretta & Greisen 2002;Greisen et al. 2006) that described formalisms for the support of world coordinate systems (WCSs), i.e., the mapping from a position in a data array to a physical coordinate system such as a position on the sky or within a spectrum. Although the IAUFWG officially recognized the content of these papers as a part of the standard, they were not formally mentioned in the FITS standard document itself.In late 2006 the IAUFWG appointed a technical panel to address specific ambiguities that had been identified in the standard over the years, to clarify the meaning of some portions of the text, and to consider how to incorporate all the approved elements of the standard into one document. This work was completed by mid-2007, and ...

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A deep (98.2 ks) Chandra Cycle-1 observation has revealed a wealth of discrete X-ray sources as well as diffuse emission in the nearby face-on spiral galaxy M101. From this rich dataset we have created a catalog of the 110 sources from the S3 chip detected with a significance of > 3σ. This detection threshold corresponds to a flux of ∼ 10 −16 ergs cm −2 s −1 and a luminosity of ∼ 10 36 ergs s −1 for a distance to M101 of 7.2 Mpc. The sources display a distinct correlation with the spiral arms of M101 and include a variety of X-ray binaries, supersoft sources, supernova remnants, and other objects of which only ∼ 27 are likely to be background sources. There are only a few sources in the interarm regions, and most of these have X-ray colors consistent with that of background AGNs. The derived log N −log S relation for the sources in M101 (background subtracted) has a slope of −0.80 ± 0.05 over the range of 10 36 − 10 38 ergs s −1 . The nucleus is resolved into 2 nearly identical X-ray sources, each with a 0.5 -2.0 keV flux of 4 × 10 37 ergs s −1 . One of these sources coincides with the optical nucleus, and the other coincides with a cluster of stars 110 pc to the south. The field includes 54 optically identified SNR, of which 12 are detected by Chandra. Two of the SNR sources are variable and hence must be compact objects. In total, 8 of the X-ray sources show evidence for short term temporal variation during this observation. Two of these variable sources are now brighter than the ROSAT detection threshold, but they were not detected in the previous ROSAT observations taken in 1992 and 1996. There are also 2 variable sources previously seen with ROSAT that apparently have faded below the Chandra detection threshold. The brightest