[Iaude] CBET 5393: COMET C/2024 J1

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5393
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 P/2024 J1 (PANSTARRS)
     R. Weryk, Department of Physics and Astronomy, University of Western
Ontario, reports the discovery of another comet in images obtained with the
Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on May 1 (discovery
observations tabulated below).  Four stacked 45-s w-band survey images taken
on May 1 in 1".3-1".5 seeing show a diffuse head of size 1".9 (full-width-at-
half-maximum) with a short tail 4" long toward p.a. 45 degrees.

     2024 UT             R.A. (2000) Decl.       Mag.
     May   1.31557   12 30 26.83   -22 29 47.3   20.8
           1.32680   12 30 26.48   -22 29 44.3   21.0
           1.33841   12 30 26.15   -22 29 41.7   21.0
           1.34964   12 30 25.80   -22 29 38.7   20.9

Two stacked 60-s follow-up w-band Pan-STARRS1 images taken on May 2.3 UT in
1".25 seeing show a condensed coma of size 1".8 (FWHM) with a 5" tail toward
p.a. 45 degrees.  Weryk further notes that four 60-s gri-band follow-up
observations were obtained with the 3.6-m Canada-France-Hawaii telescope at
Mauna Kea on May 4.26 (PI R. Wainscoat; queue observer A. Acohido; queue
coordinator T. Burdullis) in 0".7 seeing, showing a very condensed coma of
size 1".4 (FWHM) and a broad tail 5" long spanning p.a. 350-75 degrees.
Weryk subsequently identified pre-discovery Pan-STARRS1 observations of the
comet taken on Mar. 19.48 and Apr. 1.4 (mag 20.7-20.9).  Pre-discovery
observations obtained with the Mt. Lemmon 1.5-m reflector obtained on Apr.
29.2 were also reported later (mag 20.3-20.7).
     After the comet was posted on the Minor Planet Center's PCCP webpage,
other CCD astrometrists commented on the comet's appearance.  Sixteen stacked
60-s exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a
0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, on May
2.45-2.46 UT show a strongly condensed coma 7" in diameter with no tail; the
magnitude was 19.6 as measured within a circular aperture of radius 6".6.
S. Deen (Simi Valley, CA, USA) writes that two 30-min exposures taken with a
0.43-m reflector at Rio Hurtado, Chile, on May 2.1 UT show the object to be
"distinctly cometary" with a condensed coma of size around 3" (FWHM) in 2"
seeing, with no clear tail.
     The available astrometry appears on MPEC 2024-J133.  The following
elliptical orbital elements by S. Nakano (Central Bureau) are from 24
observations spanning 2024 Mar. 19-May 4 (mean residual 0".2).  The comet
passed 0.48 AU from Jupiter in 1974 June.

     T = 2023 Nov. 11.20342 TT        Peri. = 200.33910
     e = 0.3074578                    Node  = 321.95380 2000.0
     q = 2.6366295 AU                 Incl. =  13.15693
       a =  3.8071753 AU   n = 0.13267826   P =   7.43 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 15.0 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2024 05 10    12 27.27   -21 54.0    1.970    2.834   142.0    12.7  20.1
2024 05 20    12 25.86   -21 16.7    2.068    2.855   133.0    15.0  20.2
2024 05 30    12 26.84   -20 47.3    2.182    2.876   124.2    17.0  20.4
2024 06 09    12 30.05   -20 28.4    2.310    2.898   115.7    18.4  20.5
2024 06 19    12 35.28   -20 20.9    2.447    2.921   107.7    19.4  20.7
2024 06 29    12 42.26   -20 24.7    2.591    2.945   100.1    19.9  20.8
2024 07 09    12 50.76   -20 39.1    2.740    2.969    92.8    20.0  21.0
2024 07 19    13 00.56   -21 03.0    2.891    2.993    85.8    19.8  21.1
2024 07 29    13 11.46   -21 34.9    3.042    3.018    79.0    19.3  21.3
2024 08 08    13 23.31   -22 13.6    3.192    3.044    72.4    18.5  21.4
2024 08 18    13 35.98   -22 57.6    3.338    3.069    66.0    17.5  21.5
2024 08 28    13 49.36   -23 45.7    3.479    3.096    59.7    16.4  21.6
2024 09 07    14 03.36   -24 36.5    3.614    3.122    53.6    15.0  21.7


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

                         (C) Copyright 2024 CBAT
2024 May 10                      (CBET 5393)              Daniel W. E. Green