[Iaude] CBET 4834: COMET 141P/MACHHOLZ

quai at eps.harvard.edu quai at eps.harvard.edu
Wed Aug 19 13:52:52 EDT 2020


                                                  Electronic Telegram No. 4834
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 141P/MACHHOLZ
     An apparently asteroidal object reported as an apparent new minor
planet from images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien
reflector at Haleakala (discovery observations tabulated below), and posted
on the Minor Planet Center's NEOCP webpage, has been found by P. Veres and
D. Bell (MPC) to have motion similar to that of comet 141P (which had not
been seen since 2015) after follow-up astrometry was reported.  R. Weryk
notes that the Pan-STARRS2 images do not appear cometary.  R. Holmes,
Ashmore, IL, USA, reports that the object appears stellar in 2".6 seeing
on images taken with a 1.3-m f/4.0 astrograph on Aug. 15.1 UT.  M. Micheli
writes that thirty-eight stacked exposures (corresponding to a total
integration of 57 min) taken by E. Kuusela with the 1.0-m f/4.4 reflector
of the ESA Optical Ground Station, Tenerife, show the comet to be completely
stellar in 2".0 seeing; he was unable to find any additional fragments in
the images but adds that the field is heavily crowded with stars.

     2020 UT             R.A. (2000) Decl.       Mag.   Observer
     Aug. 13.26514   16 56 13.18   - 8 29 51.4   21.6   Pan-STARRS2
          13.27539   16 56 12.89   - 8 29 51.3   21.7     "
          13.28565   16 56 12.58   - 8 29 51.1   21.5     "
          15.08524   16 55 29.86   - 8 29 26.2   21.5   Holmes
          15.09133   16 55 29.71   - 8 29 25.9   22.0     "
          15.10046   16 55 29.49   - 8 29 26.0   22.1     "
          16.87731   16 54 55.30   - 8 29 22.9   21.5   Kuusela
          16.89106   16 54 55.05   - 8 29 23.2   21.6     "
          16.90536   16 54 54.74   - 8 29 23.2   21.6     "

     Shortly after this comet was first discovered in 1994 (cf. IAUC 6053),
it was found to have a nearby (about 48' distant) diffuse companion nearly as
bright as the primary component (cf. IAUC 6066), followed by the discovery of
three additional fainter components (cf. IAUCs 6071, 6071); the original
component remained the brightest and was called component A (cf. IAUC 6081).
Component D, meanwhile, split into two fragments, and became nearly as bright
as component A (cf. IAUCs 6082, 6090).  Two additional components were
reported also in 1994 (cf. MPEC 2017-R12), leading to the use of component
letters A-G at that apparition.
     After the comet's recovery in 1999 (cf. IAUC 7231), linkages of what was
presumed to be component A to the 1994 observations were not possible without
resorting to allowance for non-gravitational forces. As the comet approached
perihelion in late 1999, a second component (only) was detected and presumed
to be component D from 1994 (cf. IAUC 7299), and the two components remained
within a couple of magnitudes of each other in brightness for weeks (cf. IAUC
7334).  Only a single component of the comet was recovered in 2005, and it
was presumed to be component A (cf. IAUC 8495).
     Note that the comet was missed at its 2010 return.  The comet was
observed extensively at its 2015 return, starting on 2015 May 24 (cf. MPEC
2015-K133).  Beginning on 2015 Aug. 19, another component was widely
observed and designated H by G. V. Willams, who wrote (MPEC 2015-R12) that
the 2015 astrometry of component H "precludes an unambiguous linkage to a
known fragment.  Computations by both [myself] and S. Nakano suggest that
[component H] can be linked to either fragment C or fragment D (equally
well), or to fragment B (less satisfactorily).  Fragment D was observed in
both 1994 and 1999, while fragment B faded rapidly over the course of a week
in Nov. 1994.  In no case is the linkage to a known fragment satisfactory."
     S. Nakano's previous orbit for component A from 258 observations
spanning 2000-2015 (mean residual 0".9) yielded non-gravitational parameters
A1 = -0.12 and A2 = +0.0274 (cf. NK 3435 and the ICQ's 2020 Comet Handbook),
and the 2020 observations suggest a correction Delta(T) = +0.025 day; the
residuals for the 2020 astrometry are -18" in R.A. and -9" in Decl. from
that prediction.  The following new orbital elements by Nakano assume that
the recovery in 2020 is of component A and use 266 observations spanning
2005-2020 (mean residual 0".9), with non-gravitational parameters A1 = +0.37
and A2 = +0.0304.  The comet passed 0.93 AU from Jupiter on 2017 Oct. 13 UT
and will pass 0.53 AU from the earth on 2021 Jan. 19.  Nakano adds that the
prediction for component H at this return would be T = 2020 Dec. 14.6 TT.

                    Epoch = 2005 Mar. 11.0 TT
     T = 2005 Feb. 28.24835 TT        Peri. = 149.27843
     e = 0.7501302                    Node  = 246.16572 2000.0
     q = 0.7528003 AU                 Incl. =  12.79585
       a =  3.0127704 AU   n = 0.18847555   P =   5.23 years

                    Epoch = 2010 June 13.0 TT
     T = 2010 May  24.52279 TT        Peri. = 149.36131
     e = 0.7489010                    Node  = 246.08989 2000.0
     q = 0.7577396 AU                 Incl. =  12.80307
       a =  3.0176926 AU   n = 0.18801460   P =   5.24 years

                    Epoch = 2015 Aug.  6.0 TT
     T = 2015 Aug. 25.02115 TT        Peri. = 149.47494
     e = 0.7481753                    Node  = 246.01793 2000.0
     q = 0.7608722 AU                 Incl. =  12.80987
       a =  3.0214359 AU   n = 0.18766531   P =   5.25 years

                    Epoch = 2020 Dec. 17.0 TT
     T = 2020 Dec. 16.26997 TT        Peri. = 153.54399
     e = 0.7356668                    Node  = 241.84951 2000.0
     q = 0.8079340 AU                 Incl. =  13.94456
       a =  3.0564980 AU   n = 0.18444543   P =   5.34 years

                    Epoch = 2026 Apr. 30.0 TT
     T = 2026 Apr. 23.13453 TT        Peri. = 153.64837
     e = 0.7358060                    Node  = 241.77030 2000.0
     q = 0.8074757 AU                 Incl. =  13.96016
       a =  3.0563737 AU   n = 0.18445668   P =   5.34 years

                    Epoch = 2031 Aug.  2.0 TT
     T = 2031 Aug. 20.05162 TT        Peri. = 154.81822
     e = 0.7437472                    Node  = 240.99513 2000.0
     q = 0.7742034 AU                 Incl. =  14.52203
       a =  3.0212489 AU   n = 0.18768273   P =   5.25 years

The following ephemeris by the undersigned from the above elements uses
photometric power-law parameters H = 12.0 and 2.5n = 30.0 for the magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2020 08 19    16 54.41   -08 29.8    1.288    1.851   106.6    31.6  20.6
2020 08 29    16 54.53   -08 38.6    1.306    1.749    97.3    34.9  19.9
2020 09 08    16 58.66   -08 55.8    1.320    1.645    88.9    37.7  19.1
2020 09 18    17 06.63   -09 18.5    1.326    1.540    81.4    40.2  18.2
2020 09 28    17 18.29   -09 43.3    1.320    1.433    74.8    42.4  17.3
2020 10 08    17 33.52   -10 07.0    1.301    1.327    69.0    44.7  16.3
2020 10 18    17 52.34   -10 26.6    1.266    1.221    64.0    47.2  15.1
2020 10 28    18 14.86   -10 39.1    1.215    1.118    59.8    50.2  13.9
2020 11 07    18 41.27   -10 41.9    1.147    1.022    56.5    54.0  12.6
2020 11 17    19 11.91   -10 33.5    1.062    0.936    54.1    58.9  11.3
2020 11 27    19 47.29   -10 14.0    0.964    0.867    52.7    65.0  10.1
2020 12 07    20 28.13   -09 46.1    0.857    0.822    52.4    71.8   9.1
2020 12 17    21 15.72   -09 14.2    0.748    0.808    53.5    78.3   8.6
2020 12 27    22 12.07   -08 38.9    0.650    0.827    56.5    82.6   8.6
2021 01 06    23 19.11   -07 49.9    0.574    0.875    62.0    82.6   9.1
2021 01 16    00 35.84   -06 27.2    0.536    0.947    70.2    77.7   9.9
2021 01 26    01 55.13   -04 22.4    0.544    1.035    79.6    69.3  11.1
2021 02 05    03 07.10   -01 57.0    0.598    1.133    87.7    60.4  12.5
2021 02 15    04 06.75   +00 20.1    0.690    1.236    93.2    52.9  14.0
2021 02 25    04 54.71   +02 14.0    0.810    1.342    95.9    47.2  15.4
2021 03 07    05 33.72   +03 42.4    0.952    1.449    96.3    42.9  16.7
2021 03 17    06 06.41   +04 47.8    1.111    1.555    95.1    39.6  18.0
2021 03 27    06 34.71   +05 33.1    1.282    1.660    92.7    36.9  19.1
2021 04 06    06 59.87   +06 00.9    1.462    1.764    89.4    34.6  20.2
2021 04 16    07 22.77   +06 13.6    1.651    1.866    85.6    32.4  21.2


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

                         (C) Copyright 2020 CBAT
2020 August 19                   (CBET 4834)              Daniel W. E. Green



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