The XMM-Newton/Chandra monitoring campaign of the Galactic center region

Description of the program and preliminary results

¹ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ, The Netherlands e-mail: [rudy;michiel;jmiller]@science.uva.nl
² SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands e-mail: jeanz@sron.nl
³ National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801, USA
⁴ NASA, Goddard Space Flight Center, Greenbelt, MD 20711, USA e-mail: [mrupen;craigm]@milkyway.gsfc.nasa.gov
⁵ School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK e-mail: [tjm;cornelis]@astro.soton.ac.uk;rpf@phys.soton.ac.uk
⁶ Center for Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA e-mail: jeroen@space.mit.edu
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: josh@cfa.harvard.edu
⁸ ISOC, ESA/ESAC, Urb. Villafranca del Castillo, PO Box 50727, 28080 Madrid, Spain e-mail: Erik.Kuulkers@esa.int
⁹ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁰ Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA e-mail: wqd@astro.umass.edu

Received: 30 August 2005
Accepted: 10 December 2005

Abstract

We present the first results of our X-ray monitoring campaign on a 1.7 square degree region centered on Sgr A* using the satellites XMM-Newton and Chandra. The purpose of this campaign is to monitor the behavior (below 10 keV) of X-ray sources (both persistent and transient) which are too faint to be detected by monitoring instruments aboard other satellites currently in orbit (e.g., Rossi X-ray Timing Explorer; INTEGRAL). Our first monitoring observations (using the HRC-I aboard Chandra) were obtained on June 5, 2005. Most of the sources detected could be identified with foreground sources, such as X-ray active stars. In addition we detected two persistent X-ray binaries (1E 1743.1–2843; 1A 1742–294), two faint X-ray transients (GRS 1741.9–2853; XMM J174457–2850.3), as well as a possible new transient source at a luminosity of a few times 10³⁴ erg s^-1. We report on the X-ray results on these systems and on the non-detection of the transients in follow-up radio data using the Very Large Array. We discuss how our monitoring campaign can help to improve our understanding of the different types of X-ray transients (i.e., the very faint ones).