Charge exchange - Induced x-ray emission from comet C/1999 S4 (LINEAR)

Science

Volumn 292, Issue 5520, 2001, Pages 1343-1348

  Lisse, C M ^a   Christian, D J ^a   Dennert, K ^a   Meech, K J ^a   Petre, R ^a   Weaver, H A ^a   Wolk, S J ^a  

^a NONE

Author keywords

[No Author keywords available]

Indexed keywords

EMISSION SPECTROSCOPY; IONIZATION OF GASES; MORPHOLOGY; ULTRAVIOLET RADIATION; X RAY ANALYSIS;

COMET; NEUTRAL GASES;

SOLAR SYSTEM;

CARBON; NITROGEN; OXYGEN;

COMET; X-RAY;

ARTICLE; ASTRONOMY; ELECTRICITY; GAS; PRIORITY JOURNAL; SOLAR ENERGY; ULTRAVIOLET RADIATION; X RAY ANALYSIS;

EID: 0035907046     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.292.5520.1343     Document Type: Article

References (41)

1. C. M. Lisse et al., Science 274, 205 (1996).
2. C. M. Lisse et al., Icarus 141, 316 (1999).
3. K. Dennerl et al., Science 277, 1625 (1997).
4. A. Owens et al., Astrophys J. 493, 47 (1998).
5. C. M. Lisse et al., Earth Moon Planets 77, 283 (1999).
6. V. A. Krasnopolsky et al., Science 277, 1488 (1997).
7. M. J. Mumma, V. A. Krasnopolsky, M. J. Abott, Astrophys. J. 49, L125 (1998).
8. V. A. Krasnopolsky, M. J. Mumma, Astrophys. J. 549, 629 (2001).
9. T. E. Cravens, Geophys. Res. Lett. 24, 105 (1997).
10. R. M. Häberli et al., Science 276, 939 (1997).
11. R. Wegmann et al., Planet. Space Sci. 46, 603 (1998).
12. V. Kharchenko, A. Dalgarno, J. Geophys. Res. 105, 18351 (2000).
13. R. Bingham et al., Science 275, 49 (1997).
14. R. Bingham et al., Astrophys. J. Suppl. Ser. 127, 233 (2000).
15. T. G. Northrop et al., Icarus 127, 246 (1997).
16. T. G. Northrop, Icarus 128, 480 (1997).
17. M. Uchida et al., Astrophys. J. 498, 863 (1998).
18. C. M. Lisse et al., in preparation.
19. T. L. Farnham et al., Science 292, 1348 (2001).
20. D. Bockelée-Morvan et al., Science 292, 1339 (2001).
21. gaussian = 49 eV] from 0.25 to 0.8 keV. The observations consist of a list of time-tagged detections of individual photon pulse heights and spatial locations. CXO was able to follow the comet's nonsidereal motion using multiple pointings, and the target was centered in the back-illuminated CCD chip S3, the most optimal for x-ray spectroscopy. Using a preliminary version of the "sso_freeze" algorithm, part of the Chandra Interactive Analysis of Observations (CIAO) software, we constructed a comet image remapped into a coordinate system moving with the comet (38). To create light curves, a circular source aperture of 3.7′ radius was chosen in CIAO, and several background apertures were extracted >4′ away from the comet's diffuse emission and toward the outer edge of the chip (39). Spectra were extracted in an identical fashion, and the effect of energy-dependent instrument sensitivity was removed using the effective areas given in the CXO on-orbit measured instrument response matrices. Upon examination of the extracted spectra, only photons of energy 200 to 800 eV were found to be statistically significant against the sky and instrumental backgrounds. Comparison of the EUVE 0.09- to 0.25-keV images and CXO images demonstrated that the comet over-filled the entire S3 field-of-view, and all absolute CXO count rates have been corrected for vignetting using aperture photometry curves from the two cameras.
22. H. Mikunz, personal communication.
23. Supplementary material is available at www. sciencemag.org/cgi/content/full/292/5520/1343/ DC1
24. 4, C, O, Ne, and Fe were found at http://sd-www.jhuapl.edu/ACE/ULEIS/ spec_gadget.html Our observations of C/LINEAR using the EUVE scanners and of the solar-terrestrial environment using the SOHO, WIND, and ACE spacecraft were performed in the same manner as used to observe comets Encke (2) and Hale-Bopp (6).
25. The bowshock is the region of the coma where the fluid solar wind, impinging on the much thicker cometary coma ionosphere, picks up enough coma mass ("mass loading") to abruptly slow down in a gentle shock while increasing markedly in density and magnetic field strength. The contact surface is the location in the coma inside of which ionic species and interplanetary magnetic field lines are excluded. The existence of both of these predicted regions in the cometary coma was verified during the in situ flybys of comet 1P/Halley 1986 by the Giotto and Vega spacecraft. For a good review of the flybys, see H. Reme et al. [Astron. Astrophys. 187, 33 (1987)].
26. K. R. Flammer, in Comets in the Post-Halley Era, IAU Colloqium 121, Bamberg, Germany, 24 to 28 April 1989, R. L. Newburn, M. Neugebauer, J. Rahe, Eds. (Kluwer Academic, Dordecht, Netherlands, 1991), p. 1125.
27. M. Neugebauer et al., Astron. Astrophys. 187, 21 (1987).
28. M. Neugebauer et al., J. Geophys. Res. 103, 14587 (1998).
29. T. Mukai et al., Astron. Astrophys. 187, 129 (1987).
30. The location of the shock near the edges of the wings is typically, at most, a factor of 2 farther from the nucleus than at the subsolar point.
31. See Web table 1 (23).
32. +8 lines have recently been confirmed in the laboratory, at the interaction energies present in the solar wind- comet system, by J. Greenwood et al. [Astrophys. J. 533, L175 (2000)].
33. +8 lines have recently been confirmed in the laboratory, at the interaction energies present in the solar wind-comet system, by J. Greenwood et al. [Astrophys. J. 533, L175 (2000)].
34. P. Beiersdorfer et al., Astrophys. J. 549, L147 (2001).
35. M. Kidger, IAU Circular 7467 (2000).
36. H. A. Weaver et al., Science 292, 1329 (2001).
37. D. G. Scheliecher, C. Eberhardy, IAU Circular 7455 (2000); personal communication (2001).
38. Although it is based on the overly simplified Wegmann model (11), a good discussion of how to interpret the x-ray spectra for variable solar wind flux and composition is given by N. A. Schwadron and T. E. Cravens [Astrophys. J. 544, 558 (2000)].
39. We have used the cometary ephemerides (DE-405, mid-June 2000, epoch = 4 August 2000) of D. K. Yeomans et ai found at http://ssd.jpLnasa.gov/horizons.html to target the comet and to remap our observations into a comet-centered reference frame. The estimated pointing uncertainties for the CXO and EUVE spacecraft are 1″ and 10″, respectively. The estimated ephemeris uncertainties for C/LINEAR are large, due to the large non-gravitational (i.e., jet) forces created during the comet's prolonged breakup in July 2000, on the order of 10″ or so, and along with the 1′ HEW of the EUVE scanner telescopes, dominate the EUVE positional uncertainties of our observations. For the CXO observations, the limited number of detected photons (∼13,000) restricted the effective detector resolution, due to statistical counting uncertainties, to pixels of 10″ extent.
40. E. Feigelson et al., Bull. Am. Astron. Soc. 32, 27.02 (2000), http://www.aas.org/publications/baas/ v32n3/head2001/173.htm
41. The SOHO and WIND data were graciously provided by R. Lepping of NASA/Goddard Spaceflight Center and H. Ogawa of University of Southern California. The ACE data were provided courtesy of S. Nyland of Johns Hopkins University. We are grateful for the cometary ephemeredes of D. K. Yeomans et al., found at the Jet Propulsion Laboratory Horizons website used to reduce our data. The optical images and photometry of C/LINEAR on 14 July 2000 was provided by H. Mikuz of the Crni Vrh Observatory, Slovenia. We thank the Chandra X-ray Center, especially R. Hain for reconstructing the comet images, and B. Stroozas and the EUVE Science Operations team for working with us to schedule the moving target observations. C.M.L was supported in part by NASA Planetary Astronomy Program Grant No. NAGW188 and by observing grants NAG5-6141 and NAG5-6155. K.D. gratefully acknowledges support from the German Burdesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF/DARA) and the Max-Planck-Gesellschaft. S.J.W. was supported by NASA contract NAS8-39073.