INTEGRAL Status Report - February 2006
Operations and Archiving
The 7th SPI annealing is planned for early January 2006. During this activity, the other instruments will be operated nominally, performing observations of targets that do not require SPI data. The annealing procedure has been further optimized to allow better out-gassing of the cold box around the detectors.
An INTEGRAL observation of the Earth's shadow on the cosmic X-ray background is planned for late January 2006. This observation will be useful both for instrument calibration and for scientific investigation. In contrast to the situation in low-energy X-rays where >80% of the cosmic X-ray background has been resolved into individual sources, the nature of the cosmic X-ray background in the prime INTEGRAL energy range (>20 keV) is still poorly understood after many years of investigation with only 3% of the 20-60 keV background resolved into sources. All the instruments (including the Optical Monitor Camera) will be operated providing images of the Earth in the optical, X-ray and gamma-ray wavebands. Data from all these observations will be made immediately public.
The INTEGRAL User Group met for the second time in November. They strongly supported the AWG recommendation to implement "key programmes". For INTEGRAL, with its large field of view, key programmes are planned to be observations of fields, which require very deep exposures such as for nucleosynthesis. The IUG recommended that these be fully implemented in AO-5 with a dedicated AO to solicit key programme proposals prior to a second announcement, which would be for the remaining observation time and for specific targets within the accepted key programme fields. This approach allows second round proposers to choose targets contained within the already selected fields, so improving the probability of having a target accepted. Since there is insufficient time for an additional announcement in the next round, the IUG recommended that a 1-2 million second galactic centre key programme observation be performed as a pilot study in AO-4. This is currently being implemented in the INTEGRAL long-term observing plan.
The ISDC continues to routinely dispatch data products to observers within 6-8 weeks of their observation. As of 2005 December, the on-line ISDC public archive includes nearly all public observations made until 2004 September. In collaboration with the ISDC, the ISOC Science Data Archive (ISDA) at ESAC continues to be updated with the latest data and products. These will shortly include products from the 2nd IBIS/ISGRI soft gamma-ray catalog containing >200 sources accepted for publication in the Astrophysical Journal.
The results of detailed studies of the diffuse galactic line emission from the radioactive decay of 26Al (1.81 MeV) are reported in the January 5 edition of Nature (Diehl et al., MPE). This emission is a key tracer of recent star formation as 26Al is produced during core collapse supernovae and in the preceding intense stellar winds and rapidly decays within ~1 Myr. The line has been observed by INTEGRAL at high significance in the inner galaxy and, for the first time, small energy shifts (of the order of one tenth of a keV) due to galactic rotation have been measured. This supports a Galaxy wide origin for the 26Al emission and allows an independent estimate of the galactic core collapse supernova rate of 1.9 ± 1.1 per century. This rate corresponds to a star formation rate of ~4 solar masses per year, or ~7.5 stars per year and is typical of spiral galaxies similar to our own.
As of the end of 2005 November, there have been 127 refereed and 299 non-refereed papers containing results from INTEGRAL.