.dvi
,
.ps
or
.PDF
format.
Circular No. 8889 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html ISSN 0081-0304 Phone 617-495-7440/7244/7444 (for emergency use only) COMET 17P/HOLMES D. Schleicher, Lowell Observatory, obtained eight sets of narrowband photometry of comet 17P/Holmes on Nov. 1 (r = 2.47 AU) using the Hall 1.1-m telescope at Lowell Observatory. Projected aperture radii ranged from 14500 to 120200 km, and derived production rates exhibited large trends with aperture size for all species -- with the highest values always at the largest apertures, consistent with a slowly decreasing rate of overall activity since the initial outburst. Production-rate ranges for each species are: log Q(OH) = 29.60-29.80; equivalent log Q(water; vectorial) = 29.54-29.74; log Q(NH) = 27.65-27.89; log Q(CN) = 27.26-27.51; log Q(C_2) = 27.33-27.61; log Q(C_3) = 26.64-26.87; log [Af(rho)] (526 nm) = 5.13-5.74 (cf. IAUC 7342). The resulting abundance ratios indicate that comet 17P has 'typical' composition (based on A'Hearn et al. 1995, Icarus 118, 223), but an exceptionally high dust-to- gas ratio, possibly associated with the finite lifetimes of the gas molecules released at the onset of the outburst as compared to long- lived dust grains. A significant contribution to relatively high dust abundance may also be caused by a portion of the dust tail remaining within the photometer apertures due to projection effects from the comet's small phase angle. Further naked-eye total-magnitude estimates (cf. IAUC 8887): Oct. 27.63 UT, 2.4 (Y. Nagai, Gunma, Japan); 28.10, 2.5 (J. Rao, Putnam Valley, NY, U.S.A.); 28.75, 2.5 (H. Dahle, Les Olives, France); 29.54, 2.3 (S. Yoshida, Ibaraki, Japan); 30.76, 2.4 (T. Karhula, Vasteras, Sweden); 31.76, 2.5 (K. Cernis, Vilnius, Lithuania); Nov. 1.79, 2.3 (J. J. Gonzalez, Leon, Spain); 2.96, 2.5 (A. Pereira, Cabo da Roca, Portugal). COMETS C/2007 L12, C/2007 L13, AND C/2007 M4 (SOHO) Further to IAUC 8888, additional Kreutz sungrazing comets have been found on SOHO website images ("discovery" observations tabulated below). C/2007 L12 was extremely faint (mag about 8.5- 9.0). C/2007 L13 and C/2007 M4 were stellar (mag about 5.5) in C3 images. C/2007 L13 appeared slightly diffuse with a very faint tail in C2 images. C/2007 M4 was slightly diffuse and showed a short, thin, faint tail in C2 images. Comet 2007 UT R.A.(2000)Decl. Inst. F MPEC C/2007 L12 June 14.854 5 25.8 +21 22 C2 RM 2007-T122 C/2007 L13 15.138 5 26.2 +19 58 C3/2 AK 2007-T122 C/2007 M4 24.696 6 01.0 +19 16 C3/2 TH 2007-U15 (C) Copyright 2007 CBAT 2007 November 2 (8889) Daniel W. E. Green
.dvi
,
.ps
or
.PDF
format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.