[Iaude] CBET 5345: COMET C/2024 B2

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5345
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2024 B2 (LEMMON)
     An apparently asteroidal object discovered on Jan. 31 with the Mt. Lemmon
Survey's 1.5-m reflector in Arizona has been found to show cometary appearance
after posting on the Minor Planet Center's PCCP webpage.  The discovery
observations are tabulated below.

     2024 UT             R.A. (2000) Decl.       Mag.
     Jan. 31.25544    8 42 46.00   +57 36 25.6   20.6
          31.26070    8 42 45.07   +57 36 24.2
          31.26596    8 42 44.25   +57 36 21.2   20.3
          31.27122    8 42 43.27   +57 36 18.8   20.8

R. Weryk (Department of Physics and Astronomy, University of Western Ontario)
writes that he found this object in pre-discovery exposures taken with both
the Pan-STARRS1 and the Pan-STARRS2 1.8-m Ritchey-Chretien reflectors at
Haleakala, Hawaii.  Pan-STARRS1 images show the comet on 2023 Dec. 29.5 (mag
21.2-21.5) and 30.52-30.55 UT (mag 20.6-21.3), along with images from both
Pan-STARRS1 and Pan-STARRS2 on 2023 Dec. 31.6 (mag 20.8-22.2) and 2024 Jan.
23.4 (mag 20.9-22.6), and from Pan-STARRS2 alone on 2024 Jan. 27.5 (mag 20.6-
21.5).  Four 45-s Pan-STARRS2 w-band survey images taken on 2024 Feb. 3.4 in
1".5-1".7 seeing show a diffuse coma of size 2".1 (full-width-at-half-maximum)
and no tail.
     S. Deen (Simi Valley, CA, USA) writes that he found pre-discovery images
of this object in 300-s exposures taken on 2023 May 14.28-14.39 and 15.28-
15.35 UT with the 3.6-m Canada-France-Hawaii Telescope by J.-C. Cuillandre for
the "Ultraviolet Near Infrared Optical Northern Survey".  The comet is trailed
but shows a coma, and in some images it appears to have a faint tail roughly
8" long in p.a. 90-135 degrees.  The red magnitude was measured as 22.2-22.6
on May 14 and 22.3-22.5 on May 15.
     Twenty-four stacked 60-s CCD exposures taken remotely by H. Sato
(Bunkyo-ku, Tokyo, Japan) with a 0.43-m f/6.8 astrograph located at the Utah
Desert Remote Observatory (near Beryl Junction, UT, USA) on 2024 Feb. 4.3 UT
show a strongly condensed coma 6" in diameter and no tail.  The magnitude was
20.1 as measured within a circular aperture of radius 5".7.
     The astrometry appears on MPEC 2024-C87.  The following nearly parabolic
orbital elements by S. Nakano (Central Bureau) are from 66 observations
spanning 2023 May 14-2024 Feb. 6 (mean residual 0".3), with corresponding
"original" and "future" values of 1/a being +0.001009 and +0.001111 (+/-
0.000005) AU**-1, respectively.  These indicate that the comet passed 4.47 AU
from Saturn on 2019 Aug. 16 and will pass 3.11 AU from Jupiter on 2025 Apr. 1
UT.

                    Epoch = 2023 Oct. 23.0 TT
     T = 2023 Oct.  5.96412 TT        Peri. = 130.30602
     e = 0.9994130                    Node  = 294.37687 2000.0
     q = 4.0764471 AU                 Incl. =  99.84050

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 12.5 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2024 01 11    09 41.66   +58 38.9    3.395    4.159   136.1     9.4  20.1
2024 01 21    09 12.66   +58 30.0    3.375    4.177   139.9     8.7  20.1
2024 01 31    08 43.49   +57 38.3    3.393    4.196   140.0     8.7  20.1
2024 02 10    08 16.86   +56 05.6    3.449    4.217   136.2     9.3  20.2
2024 02 20    07 54.65   +54 00.9    3.541    4.239   129.5    10.4  20.3
2024 03 01    07 37.53   +51 36.7    3.664    4.263   121.2    11.5  20.4
2024 03 11    07 25.27   +49 04.5    3.815    4.288   112.1    12.4  20.5
2024 03 21    07 17.24   +46 32.7    3.986    4.315   102.7    13.0  20.6
2024 03 31    07 12.66   +44 07.0    4.171    4.343    93.2    13.3  20.7
2024 04 10    07 10.83   +41 49.9    4.363    4.373    84.0    13.2  20.8
2024 04 20    07 11.16   +39 42.4    4.558    4.404    74.9    12.7  20.9
2024 04 30    07 13.14   +37 44.3    4.749    4.436    66.0    12.0  21.1
2024 05 10    07 16.38   +35 54.8    4.933    4.470    57.4    11.0  21.2


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2024 CBAT
2024 February 8                  (CBET 5345)              Daniel W. E. Green