Volume 545, September 2012
|Number of page(s)||14|
|Published online||18 September 2012|
The relative and absolute timing accuracy of the EPIC-pn camera on XMM-Newton, from X-ray pulsations of the Crab and other pulsars
1 University College Dublin, School of Physics, Space Science Group, Belfield, Dublin 4, Ireland
2 European Space Astronomy Centre (ESAC), ESA, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
3 European Space Operations Centre (ESOC), ESA, Robert-Bosch-Str. 5, 64293 Darmstadt, Germany
4 CEA Saclay, DSM/IRFU/SAp – UMR AIM (7158) CNRS/CEA/Universite P. Diderot, 91191 Gif-sur-Yvette, France
5 Institut für Astronomie und Astrophysik der Universität Tübingen, Abteilung Astronomie, Sand 1, 72076 Tübingen, Germany
6 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
7 Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India
8 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
9 University of California San Diego, Center for Astronomy and Space Sciences, 9500 Gilman Drive #0425, La Jolla, CA, 92093-0424, USA
10 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, RH5 6 NT Dorking, UK
11 Université de Toulouse,UPS-OMP, IRAP, Toulouse, France
12 CNRS, IRAP, 9 avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
Received: 25 January 2011
Accepted: 2 April 2012
Aims. Reliable timing calibration is essential for the accurate comparison of XMM-Newton light curves with those from other observatories, to ultimately use them to derive precise physical quantities. The XMM-Newton timing calibration is based on pulsar analysis. However, because pulsars show both timing noise and glitches, it is essential to monitor these calibration sources regularly. To this end, the XMM-Newton observatory performs observations twice a year of the Crab pulsar to monitor the absolute timing accuracy of the EPIC-pn camera in the fast timing and burst modes. We present the results of this monitoring campaign, comparing XMM-Newton data from the Crab pulsar (PSR B0531+21) with radio measurements. In addition, we use five pulsars (PSR J0537-69, PSR B0540-69, PSR B0833-45, PSR B1509-58, and PSR B1055-52) with periods ranging from 16 ms to 197 ms to verify the relative timing accuracy.
Methods. We analysed 38 XMM-Newton observations (0.2–12.0 keV) of the Crab taken over the first ten years of the mission and 13 observations from the five complementary pulsars. All data were processed with SAS, the XMM-Newton Scientific Analysis Software, version 9.0. Epoch-folding techniques coupled with χ2 tests were used to derive relative timing accuracies. The absolute timing accuracy was determined using the Crab data and comparing the time shift between the main X-ray and radio peaks in the phase-folded light curves.
Results. The relative timing accuracy of XMM-Newton is found to be better than 10-8. The strongest X-ray pulse peak precedes the corresponding radio peak by 306 ± 9 μs, which agrees with other high-energy observatories such as Chandra, INTEGRAL and RXTE. The derived absolute timing accuracy from our analysis is ± 48 μs.
Key words: stars: neutron / X-rays: stars / pulsars: general / pulsars: individual: Crab
© ESO, 2012
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