HEAD 2000, November 2000
Session 4. Seyfert Galaxies
Display, Monday, November 6, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[4.02] Chandra HETG Observations of the Seyfert 2 galaxy Circinus

R.M. Sambruna (PSU/GMU), H. Netzer (Tel Aviv University), S. Kaspi, W.N. Brandt, G. Chartas, G. Garmire, E.D. Feigelson, J. Nousek (PSU), K. Weaver (GSFC)

We present results from a Chandra HETG observation of the nearby (z=0.0014) Seyfert 2 galaxy Circinus. The source was observed for 60 ks on June 16, 2000, as part of the GTO program at PSU. The zeroth order image is spatially complex, with a bright nucleus and several point sources within ~ 1 kpc (50 arcsec), at least four of which are within ~ 6 arcsec from the nucleus. The point sources account for ~ 40% of the total X-ray emission from 0.2-8 keV. Their intrinsic 0.2-8 keV luminosities are in the range 1038-1039 erg/s suggesting that they may be X-ray binaries. Diffuse soft X-ray emission around the nucleus is also detected, elongated in a N-W direction. Its intrinsic 0.2-8 keV luminosity is ~8x1039 erg/s, at the low end of the distribution previously measured for Seyfert galaxies with ROSAT.

The HETG spectrum of the nucleus is entirely dominated by a host of emission lines. The brightest line is the "neutral" 6.4 keV Fe Kalpha line, which appears unresolved at the HEG resolution, accompanied by the Fe Kbeta line at 7.08 keV. The soft X-ray lines are mostly due to ionized species, with all the H- and He-like lines of Mg, Si, S, and Ar being detected. No lines of neutral elements at softer energies are detected, contrary to previous claims based on ASCA and SAX data. We will discuss the origin of the lines and the physical and dynamical conditions of the emitting gas using specific ionization models.

RMS acknowledges support from NASA contract NAS-38252 and NASA grant NAG5-7925.

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