ARTICLE IN PRESS YICAR:8214 Please cite this article in press as: C.M. Lisse et al., Chandra observations of Comet 9P/Tempel 1 during the Deep Impact campaign, Icarus (2007), doi:10.1016/j.icarus.2007.03.004 JID:YICAR AID:8214 /FLA [m5+; v 1.72; Prn:30/05/2007; 13:37] P.1 (1-15) Icarus ••• (••••) •••–••• www.elsevier.com/locate/icarus Chandra observations of Comet 9P/Tempel 1 during the Deep Impact campaign C.M. Lisse a,∗ , K. Dennerl b , D.J. Christian c , S.J. Wolk d , D. Bodewits e , T.H. Zurbuchen f , K.C. Hansen f , R. Hoekstra e , M. Combi f , C.D. Fry g , M. Dryer h,i , T. Mäkinen i , W. Sun j a Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA b Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany c Department of Astronomy and Physics, Queens University Belfast, Belfast, BT7 1NN, UK d Chandra X-ray Center, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e KVI Atomic Physics, Rijkuniversiteit Groningen, Zernikelaan 25, 9747 AA Groningen, The Netherlands f Department of Atmospheric, Oceanic and Space Sciences, Space Research Building, The University of Michigan, Ann Arbor, MI 48109-2143, USA g Exploration Physics International, Inc., 6275 University Drive NW, Suite 37-105, Huntsville, AL 35806-1776, USA h NOAA Space Environment Center, 325 Broadway, Boulder, CO 80305, USA i Finnish Meteorological Institute, Space Research, P.O. Box 503, FIN-00101 Helsinki, Finland j Geophysical Institute, University of Alaska, Fairbanks, AK 99775, USA Received 17 April 2006; revised 5 March 2007 Abstract We present results from the Chandra X-ray Observatory’s extensive campaign studying Comet 9P/Tempel 1 (T1) in support of NASA’sDeep Impact (DI) mission. T1 was observed for ∼295 ks between 30th June and 24th July 2005, and continuously for ∼64 ks on July 4th during the impact event. X-ray emission qualitatively similar to that observed for the collisionally thin Comet 2P/Encke system [Lisse, C.M., Christian, D.J., Dennerl, K., Wolk, S.J., Bodewits, D., Hoekstra, R., Combi, M.R., Mäkinen, T., Dryer, M., Fry, C.D., Weaver, H., 2005b. Astrophys. J. 635 (2005) 1329–1347] was found, with emission morphology centered on the nucleus and emission lines due to C, N, O, and Ne solar wind minor ions. The comet was relatively faint on July 4th, and the total increase in X-ray flux due to the Deep Impact event was small, ∼20% of the immediate pre-impact value, consistent with estimates that the total coma neutral gas release due to the impact was 5 × 10 6 kg (∼10 h of normal emission). No obvious prompt X-ray flash due to the impact was seen. Extension of the emission in the direction of outflow of the ejecta was observed, suggesting the presence of continued outgassing of this material. Variable spectral features due to changing solar wind flux densities and charge states were clearly seen. Two peaks, much stronger than the man-made increase due to Deep Impact, were found in the observed X-rays on June 30th and July 8th, 2005, and are coincident with increases in the solar wind flux arriving at the comet. Modeling of the Chandra data using observed gas production rates and ACE solar wind ion fluxes with a CXE mechanism for the emission is consistent, overall, with the temporal and spectral behavior expected for a slow, hot wind typical of low latitude emission from the solar corona interacting with the comet’s neutral coma, with intermittent impulsive events due to solar flares and coronal mass ejections.  2007 Elsevier Inc. All rights reserved. Keywords: Comet Tempel-1; Comets, coma; Comets, plasma; Solar wind; Spectroscopy 1. Introduction Since the surprise discovery of X-rays from comets in the mid-1990s using ROSAT and EUVE (Lisse et al., 1996; * Corresponding author. Fax: +1 240 228 8939. E-mail address: carey.lisse@jhuapl.edu (C.M. Lisse). Mumma et al., 1997; Dennerl et al., 1997; Krasnopolsky et al., 2000) over 20 comets have been detected in the X-ray regime, including many with the most advanced X-ray observa- tories, Chandra, CHIPS, and XMM-Newton (Lisse et al., 2001; Krasnopolsky et al., 2002; Dennerl et al., 2003; Wegmann et al., 2004; Lisse et al., 2005a, 2005b; Sasseen et al., 2006; Bodewits et al., 2007). These results have further refined our understand- 0019-1035/$ – see front matter  2007 Elsevier Inc. All rights reserved. doi:10.1016/j.icarus.2007.03.004