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ASCA Guest Observer Facility

GOF Status Report

N. E. White


The ASCA mission continues to operate on a routine basis, with no operational problems. We are now midway through the AO3 program and the fourth announcement of opportunity for ASCA guest observations was released on 1995 June 15, with a deadline on 1995 September 15. The technical appendices describing the submission process and the instrument details can be obtained from the HEASARC ftp site in the directory asca/nra_info or by sending e-mail to The AO4 interval will include a one year observaton period beginning in mid-December 1995.

The front cover features a spectacular detection of neon line emission from the X-ray pulsar 4U1626-67. This result by Angelini et al recently appeared in the 1995 August 10 issue of the Astrophysical Journal Letters. These data are now in the public archive along with 472 other sequences. The public domain data can be found in the HEASARC anonymous ftp area under asca/data/rev1 and a list of the public sequence numbers in the file asca/data/ascapublic.txt. The archive catalog can also be searched through the HEASARC world wide web browse facility which is accessible from the HEASARC home page at . More details about the archive structure and its access can be found in the previous ASCANews (number 2), or on the ASCA GOF world wide web page, which is also accessible from the HEASARC home page.

This issue of ASCANews concentrates on calibration articles from the instrument teams. While all four instruments continue to perform well, the major concern is the accumulated radiation damage to the CCD detectors in SIS0 and SIS1, and an article by Dotani et al in this issue of ASCANews fully describes the current state of knowledge. While 1-CCD mode continues to function with close to nominal performance, noticable degradation of 4-CCD mode is now taking place, with a decrease in resolution and increase in hot and flickering pixles. The operational impact of this degradation is to reduce the field of view to either 11x11 arcmin or 11x22 arcmin for 1- and 2-CCD mode, respectively. Current projections indicate that 1-CCD mode will continue to function well for the many years to come. The two GIS instruments continue to perform flawlessly and their performance history is described in a number of articles in this issue (see e.g., "GIS Status Report", Tashiro, et al. on page 9). An ongoing project to catalog all the serendipitous sources detected in the GIS field of view is also described by Ishisaki, et al in "ASCA Medium Sensitivity Survey with the GIS" on page 19. A recent deep calibration of the telescope off-axis point spread function using Cyg X-1, and a recommended approach to make extended source analysis are described in an article by Takahashi, et al. on page 34.

For the convenience of our readers, we have included the e-mail addresses of the authors of the articles appearing in this ASCANews. The addresses can be found in the lower left hand corner of the title bar at the top of each article.

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