R. Hudec

The INTEGRAL Science Data Centre (ISDC)

The INTEGRAL Science Data Centre (ISDC) provides the INTEGRAL data and means to analyse them to the scientific community. The ISDC runs a gamma ray burst alert system that provides the position of gamma ray bursts on the sky within seconds to the community. It operates a quick-look analysis of the data within few hours that detects new and unexpected sources as well as it monitors the instruments. The ISDC processes the data through a standard analysis the results of which are provided to the observers together with their data.

OMC: An Optical Monitoring Camera for INTEGRAL Instrument description and performance

The Optical Monitoring Camera (OMC) will observe the optical emission from the prime targets of the gamma- ray instruments onboard the ESA mission INTEGRAL, with the support of the JEM-X monitor in the X-ray domain. This capability will provide invaluable diagnostic information on the nature and the physics of the sources over a broad wavelength range. Its main scientific objectives are: (1) to monitor the optical emission from the sources observed by the gamma- and X-ray instruments, measuring the time and intensity structure of the optical emission for comparison with variability at high energies, and (2) to provide the brightness and position of the optical counterpart of any gamma- or X-ray transient taking place within its field of view. The OMC is based on a refractive optics with an aperture of 50 mm focused onto a large format CCD (1024 2048 pixels) working in frame transfer mode (1024 1024 pixels imaging area). With a field of view of 5 5 it will be able to monitor sources down to magnitude V = 18. Typical observations will perform a sequence of dierent integration times, allowing for photometric uncertainties below 0.1 mag for objects with V 16.

The unprecedented optical outburst of the quasar 3C 454.3 : The WEBT campaign of 2004-2005

Context. The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was

The extraordinarily bright optical afterglow of GRB 991208 and its host galaxy

R=12.0

Predicting the Next Outbursts of OJ 287 in 2006-2010

, which represents the most luminous quasar state thus far observed (

The WEBT Campaign on the Blazar 3C 279 in 2006

M_B \sim -31.4

Search for gamma-ray burst classes with the RHESSI satellite

). Aims. In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT). Methods. Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005. Results. The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests that the optical and radio emissions come from two separate and misaligned jet regions, with the inner optical one acquiring a smaller viewing angle during the 2004-2005 outburst. Moreover, the colour-index behaviour (generally redder-when-brighter) during the outburst suggests the presence of a luminous accretion disc. A huge mm outburst followed the optical one, peaking in June-July 2005. The high-frequency (37-43 GHz) radio flux started to increase in early 2005 and reached a maximum at the end of our observing period (end of September 2005). VLBA observations at 43 GHz during the summer confirm the brightening of the radio core and show an increasing polarization. An exceptionally bright X-ray state was detected in May 2005, corresponding to the rising mm flux and suggesting an inverse-Compton nature of the hard X-ray spectrum. Conclusions. A further multifrequency monitoring effort is needed to follow the next phases of this unprecedented event.

GRB 050509b: the elusive optical/nIR/mm afterglow of a short-duration GRB

Broad-band optical observations of the extraordi- narily bright optical afterglow of the intense gamma-ray burst GRB 991208 started � 2.1 days after the event and continued until 4 Apr 2000. The flux decay constant of the optical after- glow in the R-band is 2.30 ± 0.07 up to � 5 days, which

Colors and luminosities of the optical afterglows of the γ-ray bursts

In its nearly regular cycle of outbursts the quasar OJ 287 is due for another outburst season in 2006-2010. The prediction for the exact timing depends on the adopted model. In the precessing binary model of Lehto and Valtonen the timing depends on the time delay between the impact on the primary disk and the time when the impacted gas becomes optically thin. The time delay in turn depends on the properties of the accretion disk, the accretion rate, and the viscosity parameter α, which are not exactly known. We study the flexibility in timing provided by the uncertainties. In order to fix the model, two methods are used: the wobble of the jet, induced by the secondary, and the timing of the 1956 outburst, which has not been previously used. As a result, rather definite dates for the outbursts are obtained, which are different from a straightforward extrapolation of the past light curve. A new optical light curve with many new historical as well as recent points of observation have been put together and has been analyzed in order to reach these conclusions. Also, the high-frequency radio observations are found to agree with the jet wobble picture.

Primary Black Hole Spin in OJ 287 as Determined by the General Relativity Centenary Flare

Thequasar3C279wasthetargetof anextensivemultiwavelengthmonitoringcampaignfrom2006Januarythrough April. An optical-IR-radio monitoring campaign by the Whole Earth Blazar Telescope (WEBT) collaboration was organized around target-of-opportunity X-ray and soft � -ray observations with Chandra and INTEGRAL in 2006 midJanuary, with additional X-ray coverage by RXTE and Swift XRT. In this paper we focus on the results of the WEBT campaign. Thesource exhibited substantial variability of opticalflux and spectralshape,witha characteristictimescale of a few days. The variability patterns throughout the optical BVRI bands were very closely correlated with each other, while there was no obvious correlation between the optical and radio variability. After the ToO trigger, the optical flux