INTEGRAL Status Report - April 2005
Operations and Archiving
INTEGRAL experienced its first Emergency Sun Acquisition Mode (ESAM) on 8 January 2005. The ESAM was triggered by an incorrect calculation at MOC following a re-planning request for a ToO observation, rather than an on-board anomaly. The recovery from the ESAM was very smooth and only 12 hours observing time was lost, together with fuel corresponding to approximately 3 weeks normal observing. Indeed, during January, solar activity forced the suspension of science operations on a number of occasions, resulting in a much larger loss of observing time.
The 5th SPI annealing took place from 20 January to 3 February 3 2005. This procedure is necessary to maintain the SPI high spectral resolution. The SPI switch-on was nominal and the energy resolution appears to have recovered, as expected. It is worth recalling that following the losses of two (out of 19) SPI detectors approximately 2 weeks after the ends of the previous annealing cycles, extensive ground tests were conducted. However, these failed to reveal any link between annealing and the failures and as a precaution, the procedure for the last annealing was modified to minimize the thermal stresses on the pre-amplifiers. Currently, some 2 months after the end of the last annealing cycle, there have been no additional SPI detector failures.
The ISDC continues to routinely dispatch data products to observers within 6-8 weeks of their observation. As of 5 April 2005, the on-line ISDC public archive includes nearly all public observations made until 7 March 2004. The INTEGRAL source results archive (http://isdc.unige.ch/index.cgi?Data+sources) allows easy access to downloadable IBIS and JEM-X lightcurves, spectra and images of the brightest ~180 sources in various energy bands. In addition, data from the recent ToO observations of the bright transient V0332+53 are available from the ISDC site.
As of the end of March 2005, there have been 80 refereed and 263 non-refereed papers containing results from INTEGRAL.
The galactic bulge is a region rich in bright and variable X- and gamma-ray sources. From 17 February 2005 onwards, as part of an approved AO-3 programme, INTEGRAL has been making monitoring observations of this region every 3 days. As a service to the scientific community, light curves and images are made publicly available as soon as possible after the observations are performed. The results, as well as more information about the program, can be retrieved from http://isdc.unige.ch/Science/BULGE/.
On 27 December 2004, the Earth was hit by a huge wave front of gamma- and X-rays. It was the strongest flux of highly energetic gamma radiation ever recorded from an astronomical object. It was detected by the INTEGRAL Burst Alert System (IBAS) and the anticoincidence shield of the SPI spectrometer. A Max-Planck-Institut für extraterrestrische Physik (MPE) press release was prepared by Drs. R. Diehl and G. Lichti. Within the first 0.2 seconds of the burst the same amount of energy was emitted as from the Sun in about a quarter of a million years.
An even more remarkable aspect of this discovery is the origin of this radiation: it comes from a tiny celestial body with an extremely high density, a neutron star, or so-called "magnetar". These are objects with incredibly strong magnetic fields – about 1014 times stronger than on the Earth's surface. The magnetar that emitted this burst is called SGR 1806-20 and is located on the other side of our Milky Way galaxy at a distance of about 50 000 light years. The astrophysicists from MPE are confident that this event will cast new light on the physics of magnetars and contribute to solving the puzzle of the origin of gamma-ray bursts.