[Iaude] CBET 5310: COMET C/2023 S3

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5310
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/2023 S3 (LEMMON)
     An apparently asteroidal object discovered on Sept. 25 with the 1.5-m
reflector at Mt. Lemmon (discovery observations tabulated below) has been
found to show cometary appearance by CCD astrometrists elsewhere after it was
posted on the Minor Planet Center's PCCP webpage.

     2023 UT             R.A. (2000) Decl.       Mag.
     Sept.25.45385    5 30 00.50   +23 59 40.2   19.9
          25.45900    5 30 00.37   +23 59 35.1   20.4
          25.46414    5 30 00.16   +23 59 30.9   20.1
          25.46927    5 29 59.99   +23 59 27.7   20.1

Following a request from the Central Bureau, D. Rankin notes that examination
of Mt. Lemmon images from Oct. 11.4 UT reveals a highly condensed coma with no
tail.  L. Buzzi, Varese, Italy, writes that the object appeared stellar (mag
20.1) on CCD exposures taken on Oct. 8.1 by G. Galli and himself with a 0.84-m
f/3.5 reflector (measured by Buzzi, Galli, and A. Aletti).  Sixteen stacked
60-s exposures taken remotely on Oct. 10.4 by H. Sato (Bunkyo-ku, Tokyo,
Japan) with a 0.51-m f/6.8 astrograph located at the Utah Desert Remote
Observatory (near Beryl Junction, UT, USA) show a strongly condensed coma 8"
in diameter with a hint of tail 10" long toward p.a. 260 degrees; the
magnitude was 19.2 as measured within a circular aperture of radius 4".9.
D. Buczynski reports that images obatined on Oct. 23.0 with a 0.35-m f/6.0
Schmidt-Cassegrain reflector at Tarbatness, Scotland, show only a stellar
appearance (mag 18.1-18.3).
     The available astrometry appears on MPEC 2023-V1.  The following
elliptical orbital elements by S. Nakano (Central Bureau) are from 325
observations spanning 2023 Sept. 25-Nov. 1 (mean residual 0".4).

     T = 2024 Jan. 19.63561 TT        Peri. = 281.59284
     e = 0.9705330                    Node  = 233.83107 2000.0
     q = 0.8299306 AU                 Incl. = 140.49410
       a = 28.1647377 AU   n = 0.00659395   P = 149.5 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 16.0 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2023 10 23    04 36.32   +10 22.7    0.837    1.715   138.6    22.5  17.5
2023 10 28    04 10.86   +04 32.2    0.720    1.650   148.3    18.4  17.0
2023 11 02    03 36.31   -03 15.8    0.628    1.585   155.2    15.2  16.6
2023 11 07    02 51.24   -12 46.8    0.574    1.520   151.2    18.3  16.2
2023 11 12    01 57.00   -22 28.2    0.566    1.455   136.6    27.9  16.1
2023 11 17    00 59.44   -30 11.3    0.604    1.390   119.6    38.2  16.1
2023 11 22    00 06.37   -35 01.7    0.678    1.327   104.0    46.3  16.1
2023 11 27    23 22.56   -37 32.9    0.773    1.264    91.0    51.3  16.3
2023 12 02    22 48.46   -38 40.0    0.881    1.202    80.0    53.9  16.4
2023 12 07    22 22.35   -39 02.7    0.993    1.143    70.6    54.4  16.4
2023 12 12    22 02.13   -39 03.6    1.106    1.086    62.2    53.4  16.5
2023 12 17    21 46.08   -38 54.1    1.216    1.032    54.7    51.1  16.5
2023 12 22    21 32.89   -38 39.8    1.320    0.982    47.8    47.9  16.5

2024 02 20    19 52.72   -32 09.8    1.585    1.008    37.9    37.0  17.0
2024 02 25    19 44.54   -31 08.4    1.521    1.060    43.9    40.3  17.1
2024 03 01    19 35.61   -29 59.6    1.448    1.116    50.3    43.1  17.2
2024 03 06    19 25.62   -28 41.8    1.369    1.175    57.0    45.1  17.2
2024 03 11    19 14.17   -27 12.1    1.285    1.235    64.2    46.4  17.3
2024 03 16    19 00.77   -25 26.8    1.198    1.298    71.9    46.8  17.3
2024 03 21    18 44.88   -23 20.7    1.112    1.361    80.2    46.2  17.3
2024 03 26    18 25.94   -20 47.1    1.028    1.425    89.4    44.4  17.3
2024 03 31    18 03.39   -17 38.3    0.952    1.490    99.6    41.4  17.3
2024 04 05    17 36.87   -13 47.8    0.888    1.555   110.8    37.0  17.3
2024 04 10    17 06.49   -09 14.4    0.842    1.620   122.8    31.3  17.3
2024 04 15    16 33.06   -04 08.4    0.819    1.686   135.1    24.8  17.4
2024 04 20    15 58.25   +01 06.7    0.825    1.751   146.2    18.6  17.5
2024 04 25    15 24.17   +06 00.3    0.859    1.816   153.5    14.3  17.7
2024 04 30    14 52.71   +10 09.0    0.921    1.881   154.4    13.4  18.0
2024 05 05    14 25.13   +13 23.4    1.006    1.945   149.8    15.1  18.3
2024 05 10    14 01.87   +15 46.4    1.110    2.009   142.8    17.7  18.7


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

                         (C) Copyright 2023 CBAT
2023 November 1                  (CBET 5310)              Daniel W. E. Green