Monitoring of the optical and 2.5-11.7 μm spectrum and mid-IR imaging of the Seyfert 1 galaxy Mrk 279 with ISO ^*,**

¹ XMM Science Operations Center, Astrophysics Division, ESA Space Science Department, PO Box 50727, 28080 Madrid, Spain
² ISO Science Operations Center, Astrophysics Division, ESA Space Science Department, PO Box 50727, 28080 Madrid, Spain
³ Integral Science Operations Center, Astrophysics Division, ESA Space Science Department, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
⁴ European Southern Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chile
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁶ Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
⁷ Mailing address: Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
⁸ Computer Sciences Corporation, Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
⁹ Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
¹⁰ School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
¹¹ School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, Scotland, UK
¹² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹³ Department of Physics and Astronomy, The John Hopkins University, Baltimore, MD 21218, USA
¹⁴ Department of Astronomy, University of California, Math-Science Building, Los Angeles, CA 90024, USA
¹⁵ Crimean Astrophysical Observatory, P/O Nauchny, 334413 Crimea, Ukraine
¹⁶ Isaac Newton institute of Chile, Crimean Branch
¹⁷ Shanghai Astronomical Observatory, 80 Nandan Road, 200030 Shanghai, PR China
¹⁸ Raytheon ITSS, Space Science Data Operations Office, NASA Goddard Space Flight Center, Code 631, Greenbelt, MD 20771, USA
¹⁹ Universidad Europea de Madrid, Departamento de Física, C/ Tajo sn, Urb. El Bosque, Villaviciosa de Odón, 28670 Madrid, Spain
²⁰ ESA IUE Observatory, PO Box 50727, 28080 Madrid, Spain

Corresponding author: M. Santos-Lleó, msantos@xmm.vilspa.esa.es

Received: 3 January 2000
Accepted: 12 January 2001

Abstract

Mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO satellite are presented together with the results of a one-year monitoring campaign of the 2.5-11.7 μm spectrum. Contemporaneous optical photometric and spectrophotometric observations are also presented. The galaxy appears as a point-like source at the resolution of the ISOCAM instrument (4-5″). The 2.5-11.7 μm average spectrum of the nucleus in Mrk 279 shows a strong power law continuum with () and weak PAH emission features. The Mrk 279 spectral energy distribution shows a mid-IR bump, which extends from 2 to 15-20 μm. The mid-IR bump is consistent with thermal emission from dust grains at a distance of lt-d. No significant variations of the mid-IR flux have been detected during our observing campaign, consistent with the relatively low amplitude (~10% rms) of the optical variability during the campaign. The time delay for Hβ line emission in response to the optical continuum variations is days, consistent with previous measurements.