15 years of combined XMM and Swift Observations

Post by Vladimir Yershov

Good news! The UVOT/OM team of the MSSL Astrogroup has finished processing of two UV source catalogues based on the 10 years long series of observations from XMM and 5 years from Swift satellites!

Both satellites have relatively small (0.3 m) Ritchey-Chretien ultraviolet telescopes on-board which provide photometry in three near-ultraviolet (UVW2, UVM2 and UVW1) and three visible (U, B, V) spectral bands. The telescope photodetectors use microchannel plate photomultipliers coupled to CCDs which allows single-event detections within the 17′ by 17′ fields of view.

The XMM Newton mission was launched by ESA on 10th of December 1999, and Swift was launched by NASA on 20th of November 2004. Since then, they made thousands of observations of different targets, each field including many serendipitous sources.

The distribution of 6240 XMM Newton observations on the sky is shown in the left panel of the Figure below, and the right panel shows a similar distribution for 23428 Swift observations. It is seen that the in the second case the observations cover the sky more uniformly, which corresponds to the more uniform distribution on the sky of gamma-ray bursts — the principle targets of Swift.

Distribution of the XMM OM (left) and Swift UVOT (right) targets across the sky (lighter colours correspond to higher accumulated exposures). The distribution of the Swift targets is more random as this telescope mostly observe gamma-ray bursts which are distributed randomly.

Distribution of the XMM OM (left) and Swift UVOT (right) targets across the sky (lighter colours correspond to higher accumulated exposures). The distribution of the Swift targets is more random as this telescope mostly observe gamma-ray bursts which are distributed randomly.

The purpose of this work is to get photometric parameters of these sources by processing the series of observations made by the OM and UVOT telescopes, applying the appropriate instrument calibrations and compiling the catalogues of these parameters.

We have used a 5 years long series of observations from Swift and 10 years from XMM and compiled two catalogues of these sources. Both telescopes have similar registration systems, but during the manufacturing of UVOT detecting system,  it was achieved a higher sensitivity for the filters UVM2 and UVW2 compared to the same filters of the OM (compare the plots in the Figure below). Due to that, UVOT can detect more UV sources than OM.

Comparison of the effective areas of the Swift UVOT (above) and XMM OM (below) filters

Comparison of the effective areas of the Swift UVOT (above) and XMM OM (below) filters

The ultraviolet source catalogues for 10+ years of XMM Newton and 5+ years of Swift observations will be  powerfool tools for studying extreme physical processes in compact objects, selecting UV sources for additional follow-up, finding and studying variable UV sources, characterising dust clouds in different regions and regimes of star formation, detecting dust in stellar winds, determining the fraction of young generation stars in galaxies with high star formation rates, constraing the initial mass function and many other important studies.

These catalogues are presented on behalf of the Swift UVOT and XMM OM teams:

M. Page, M. Siegel, A. Talavera, A. Breeveld, S. Oates, N.P.M. Kuin, W. Landsman, R. Mignani, M. De Pasquale, P.J. Smith, S. Hunsberger, M. Carter, P.W.A. Roming, M. Cropper, S.T. Holland, F.E. Marshall, M. Chester, P.J. Brown, T.S. Koch, E.A. Hoversten.

 

 

 

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