Comet 8P/Tuttle
Abstract
M. Drahus, C. Jarchow, and P. Hartogh, Max-Planck-Institut fuer Sonnensystemforschung; and W. Waniak, Astronomical Observatory, Jagiellonian University; T. Bonev and G. Borisov, Institute of Astronomy, Bulgarian Academy of Sciences; K. Czart, Torun Center for Astronomy; and M. Kueppers, European Space Astronomy Center, report on millimeter-wavelength spectroscopy of the HCN molecule in comet 8P using the Arizona Radio Observatory Submillimeter Telescope on Mount Graham. The molecule was observed through the J(3-2) line at 265.9 GHz with spectral resolution up to 1 million. The half-power radius of the beam was 14.5 arcsec, corresponding to 2600 km at the comet. With five hours of monitoring on 2007 Dec. 30, three hours on Dec. 31, and five hours on 2008 Jan. 1, clear variability of the line profile is present, most likely stimulated by the nucleus' rotation. The repeatability of the spectra from different nights is consistent with rotation periods of 5.7 hr, 7.4-7.6 hr, and their multiplicities. Very similar values have been found previously (cf. IAUCs 8906, 8909); however, the period of 7.4 hr phases the spectra noticeably better than does the period of 5.7 hr. Multiplicities of both base periods cannot be excluded, though they are difficult to evaluate (especially periods longer than 15 hr), as they suffer from poor overlap or/and coverage of the observed rotation phases. The gas-expansion velocity, suggested by the line profiles, is equal to 0.8 km/s. The line area remains constant to a precision of about 30 percent, suggesting that the production rate log Q(HCN) = 25.45, assuming a constant rotational temperature of 60 K.
- Publication:
-
Central Bureau Electronic Telegrams
- Pub Date:
- March 2008
- Bibcode:
- 2008CBET.1294....1D