Simultaneous Multifrequency Observations of the BL Lac MS 0205.7+3509

Astronomy & Astrophysics 345, 414 (1999)

D. Watson [1], L. Hanlon [1], B. McBreen [1], N. Smith [2], M. Tashiro [3], A. R. Foley [4], L. Metcalfe [5], V. Beckmann [6], S. F. Sanchez [7], and H. Teräsranta [8]

  1. Department of Experimental Physics, University College Dublin, Belfield, Dublin 4, Ireland
  2. Dept. of Applied Physics and Instrumentation, Cork Institute of Technology, Cork, Ireland
  3. Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
  4. Netherlands Foundation for Research in Astronomy, Dwingeloo, The Netherlands
  5. ISO Science Operations Centre, Villafranca del Castillo, Madrid, Spain
  6. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
  7. IFCA-Dept de Fisica Moderna, CSIC Univ. de Cantabria, Santander, Spain
  8. Metsähovi Radio Research Station, Kylmälä, Finland.

Abstract

Radio and optical observations of the possible microlensed BL Lac source MS 0205.7+3509 were obtained simultaneously with ASCA x-ray measurements in February 1997. A single power law model, with a photon index of 2.61, is an adequate fit to the ASCA data, once hydrogenic absorption in excess of the Galactic value is permitted, confirming a previous ROSAT measurement. On the basis of our simultaneous data we have determined MS 0205.7+3509 to be a typical x-ray selected BL Lac with alphaox = -0.82. There is no indication of an inverse Compton (IC) component in the ASCA spectrum up to 10 keV. No evidence for variability on hour-long timescales is present in either the x-ray or the optical data. We discuss these results in the context of a gravitational microlensing scenario for MS 0205.7+3509.

Key words: BL Lacertae objects: individual: MS 0205.7+3509 -- gravitational lensing -- X-rays: galaxies

Contact: Volker Beckmann.

Preprint (compressed PS-File, 95 Kb)

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