[Iaude] CBET 5424: COMET C/2024 O1

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5424
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 O1 (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 July
28 (discovery observations tabulated below).  Four 45-s w-band survey images
taken in variable seeing of 1".0-1".5 show a possible assymetry toward p.a.
115 degrees but no obvious coma and no obvious tail.

     2024 UT             R.A. (2000) Decl.       Mag.
     July 28.39663   21 02 48.52   +14 26 10.6   21.0
          28.41936   21 02 47.85   +14 26 13.8   21.1
          28.43073   21 02 47.51   +14 26 15.7   21.1

Weryk adds that three 60-s gri-band confirming observations were made on July
29.48 UT with the 3.6-m Canada-France-Hawaii Telescope atop Mauna Kea (with
R. Wainscoat's observing time; queue observer J. Silva; queue coordinator H.
Flewelling) in 0".9 seeing show a very broad tail 5" long spanning p.a.
80-180 degrees with a head of size 1".9 (full-width-at-half-maximum).
Additional pre-discovery Pan-STARRS1 observations from 2023 June 18.5 (mag
21.7-21.8) and 2023 Sept. 12.3 (mag 21.5-21.7) were subsequently found in
the Minor Planet Center's "isolated tracklet file" (which is accessible
publicly), as were observations from 2023 Sept. 15.3 (at mag 21.5-21.6)
obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala.
The comet was posted on the MPC's PCCP website, leading to other observations.
     S. Deen (Simi Valley, CA, USA) then identified two observations each on
two nights that were obtained with the 4-m Cerro Tololo reflector (+ DECam) on
2023 July 16.14-16.15 (magnitude g = 21.5-21.7) and on 2023 July 28.2 (mag
z = 20.6-20.7).  On July 16, the comet showed slight activity with a coma of
size 1".5 (FWHM) in 1".0 seeing and no tail; on July 28, it showed a coma of
size 1".4 in 0".9 seeing with no tail.  Deen adds that he was unable to find
the comet in any 2022 images, noting that a 2022 Sept. 19 DECam frame of the
comet's predicted position shows nothing to limiting mag g = 23.4; an image
from 2022 Aug. 16 might show the comet at the limit (i = 23.1), but Deen
was not confident in the detection.
     Seventeen stacked 60-s CCD exposures taken remotely by H. Sato (Tokyo,
Japan) with a 0.51-m f/6.8 astrograph at Siding Spring, NSW, Australia, on
2024 July 30.6 UT show a moderately condensed coma 5" in diameter with no
tail; the magnitude was 20.9 as measured within a circular aperture of radius
3".2.
     The available astrometry appears on MPEC 2024-P21.  The following orbital
elements by S. Nakano (Central Bureau) are from 25 observations spanning 2023
June 18-2024 July 29 (mean residual 0".2); the corresponding "original" and
"future" values of 1/a are +0.000027 and +0.000143 (+/- 0.000002) AU**-1,
respectively.  There are no close approaches to major planets.

                    Epoch = 2023 Jan. 16.0 TT
     T = 2023 Jan. 29.15824 TT        Peri. = 349.93217
     e = 1.0024928                    Node  = 303.32958 2000.0
     q = 6.6084350 AU                 Incl. =  59.05398

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 10.0 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2024 07 29    21 02.51   +14 27.6    6.671    7.535   146.0     4.3  21.1
2024 08 08    20 57.60   +14 47.4    6.680    7.566   148.8     4.0  21.2
2024 08 18    20 52.76   +14 59.0    6.716    7.598   148.5     4.0  21.2
2024 08 28    20 48.24   +15 03.5    6.778    7.630   145.2     4.3  21.2
2024 09 07    20 44.22   +15 01.8    6.866    7.662   139.6     4.9  21.3
2024 09 17    20 40.88   +14 55.4    6.978    7.695   132.7     5.5  21.3
2024 09 27    20 38.33   +14 46.0    7.109    7.728   125.0     6.1  21.4
2024 10 07    20 36.67   +14 35.1    7.258    7.761   116.9     6.6  21.4
2024 10 17    20 35.91   +14 24.5    7.420    7.795   108.6     7.0  21.5
2024 10 27    20 36.06   +14 15.4    7.591    7.830   100.3     7.2  21.6
2024 11 06    20 37.08   +14 09.1    7.767    7.864    92.0     7.2  21.6
2024 11 16    20 38.92   +14 06.7    7.944    7.899    83.8     7.2  21.7
2024 11 26    20 41.48   +14 08.8    8.118    7.934    75.8     6.9  21.7
2024 12 06    20 44.69   +14 16.1    8.285    7.970    68.1     6.6  21.8
2024 12 16    20 48.46   +14 29.0    8.442    8.005    60.6     6.1  21.9
2024 12 26    20 52.68   +14 47.7    8.587    8.041    53.6     5.6  21.9
2025 01 05    20 57.25   +15 12.4    8.716    8.078    47.0     5.1  22.0


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

                         (C) Copyright 2024 CBAT
2024 August 1                    (CBET 5424)              Daniel W. E. Green