Electronic Telegram No. 4264 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 B4 (LEMMON-PANSTARRS) A comet discovered with the 1.8-m Pan-STARRS1 telescope at Haleakala on 2016 Mar. 13 has been linked by G. V. Williams with apparently asteroidal objects reported on single nights last year (discovery observations all tabulated below) by the Mt. Lemmon Survey (2015 Jan. 16) and with the 1.8-m Pan-STARRS1 telescope (2015 Feb. 16) that were both posted on the Minor Planet Center's NEOCP but had no known follow-up then. Additional observations have subsequently been identified from the Pan-STARRS1 telescope (2015 Jan. 18 and 22, and Apr. 10), Mt. Lemmon (2015 Mar. 11), and Purple Mountain Observatory (2015 Feb. 9), as well as earlier this year from Pan-STARRS1 (2016 Jan. 16, Feb. 9, and Mar. 4 and 12). 2015 UT R.A. (2000) Decl. Mag. Observer Jan. 16.40248 9 02 08.87 +15 16 11.7 20.4 Kowalski 16.41034 9 02 08.66 +15 16 12.5 20.4 " 16.41817 9 02 08.43 +15 16 12.9 20.4 " The Pan-STARRS1 "discovery" observations are as follows: 2015 UT R.A. (2000) Decl. Mag. Feb. 16.29072 8 46 31.88 +16 10 42.4 20.6 16.31542 8 46 31.17 +16 10 44.9 20.6 2016 UT R.A. (2000) Decl. Mag. Mar. 13.43645 13 02 02.38 - 8 53 32.9 21.1 13.45151 13 02 02.00 - 8 53 30.8 21.1 13.46654 13 02 01.62 - 8 53 28.8 21.0 13.48163 13 02 01.24 - 8 53 26.6 21.1 R. Weryk and R. J. Wainscoat write that the four w-band exposures taken with the Pan-STARRS1 telescope on 2016 Mar. 13 UT show clear evidence of a tail, extending towards position angle approximately 300 degrees for approximately 10"; the FWHM of the comet is approximately 1'.2 (vs. 1".0 for nearby stars). Three 60-s w-band follow-up images taken by Wainscoat and L. Wells with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on Mar. 15.53 UT (measured by M. Micheli and Wainscoat) show a low-surface-brightness tail that extends for at least 30" toward p.a. approximately 295 deg; the coma is slightly larger (FWHM about 1".0) than nearby stars of similar brightness (seeing 0".7), being elongated slightly north-south, and the red magnitude was measured to be 20.3-20.4. The available astrometry, the following elliptical orbital elements by Williams, and an ephemeris appear on MPEC 2016-F01. Epoch = 2015 Feb. 27.0 TT T = 2015 Feb. 19.92947 TT Peri. = 227.59285 e = 0.5706329 Node = 267.21537 2000.0 q = 3.7585234 AU Incl. = 1.74895 a = 8.7536361 AU n = 0.03805584 P = 25.9 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2016 CBAT 2016 March 16 (CBET 4264) Daniel W. E. Green