Electronic Telegram No. 4146 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network COMET P/2015 S1 = P/1998 QP_54 (LONEOS-TUCKER) A slightly fuzzy comet that was found by A. R. Gibbs on CCD exposures taken in good seeing but bright moonlight with the Catalina 0.68-m Schmidt telescope on Sept. 30.1 UT was suggested by Gibbs to possibly be a recovery of comet P/1998 QP_54 (cf. IAUCs 7012, 7013, 7024), which was missed at its 2007 return to perihelion; Gibbs notes that four co-added 30-s exposures show a 10"-long tapered tail in p.a. 60 degrees. 2015 UT R.A. (2000) Decl. Mag. Observer Sept.30.13009 20 55 23.58 -21 04 32.9 17.9 Gibbs 30.13460 20 55 23.59 -21 04 28.2 17.9 " 30.13910 20 55 23.60 -21 04 25.2 17.9 " 30.14361 20 55 23.64 -21 04 21.3 17.9 " After the object was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists have also commented on the cometary appearance. G. Hug (Scranton, KS, U.S.A., 0.56-m reflector) notes that his CCD images taken on Oct. 1.1 UT show the comet to be diffuse with a somewhat-condensed nuclear condensation and a coma diameter of about 20". W. H. Ryan writes that V-band images taken by E. V. Ryan and himself on Oct. 1.3 with the Magdalena Ridge Observatory 2.4-m reflector show a distinct tail toward p.a. about 80 deg. H. Sato, Tokyo, Japan, reports that six stacked 60-s exposures taken with a 0.70-m f/6.6 astrograph + luminance filter) at Siding Spring on Oct. 1.41 show the comet to be condensed with a coma 8" in diameter and a faint tail 20" long toward p.a. 85 degrees; the w-band magnitude was 18.3 as measured within a circular aperture of radius 4".4. Images taken on Oct. 1.76 by M. Tichy, J. Ticha, and M. Kocer with the 1.06-m KLENOT Telescope at the Klet Observatory reveal the comet to be diffuse with a coma diameter of 10". P. Birtwhistle (Great Shefford, Berkshire, England; 0.40-m f/6 Schmidt- Cassegrain reflector) writes that his images from Oct. 1.8 show the comet to be diffuse with a coma diameter of 8" and red magnitude 18.5, and a tail 15" long in p.a. 100 deg. R. Weryk, Institute for Astronomy, University of Hawaii, notes that w-band exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on Oct. 2.3 and 3.23-3.26 show clear evidence of a tail extending for at least 10" towards position angle approximately 70 degrees. J. V. Scotti writes that images obtained with the Spacewatch 0.9-m f/3 reflector at Kitt Peak on Oct. 3.1 show a coma of diameter 14" and a tail extending 0'.24 in p.a. 79 degrees. R-band images obtained by T. Lister, S. Greenstreet, and E. Gomez with a 1.0-m f/8 Ritchey-Chretien reflector at Sutherland, South Africa, on Oct. 3.86 show a fan-shaped tail about 10" long. The indicated correction to the prediction by S. Nakano in the ICQ 2014 Comet Handbook is Delta(T) = -1.86 day; the indicated correction to the prediction by B. G. Marsden on MPC 79352 is Delta(T) = -1.87 day. The available astrometry, the following linked orbital elements by G. V. Williams (from 250 observations spanning 1998 Aug. 27-2015 Oct. 4; mean residual 0".9), and an ephemeris appear on MPEC 2015-T06: Epoch = 2007 May 20.0 TT T = 2007 May 11.24787 TT Peri. = 30.33266 e = 0.5519380 Node = 341.81200 2000.0 q = 1.8799041 AU Incl. = 17.71115 a = 4.1956337 AU n = 0.11468529 P = 8.59 years Epoch = 2016 Jan. 13.0 TT T = 2015 Dec. 24.12263 TT Peri. = 30.61380 e = 0.5511956 Node = 341.60048 2000.0 q = 1.8865544 AU Incl. = 17.64914 a = 4.2035118 AU n = 0.11436303 P = 8.62 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2015 CBAT 2015 October 5 (CBET 4146) Daniel W. E. Green