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Photometric data obtained by use of FOCAS-II software

                                    10x10  20x20  30x30  40x40  50x50  60x60   SNR   SB   COD

COMET         UTC                    +/-    +/-    +/-    +/-    +/-    +/-     N  FWHM  CAT

------------  -------------------  -----  -----  -----  -----  -----  -----  ----  ----  ---

141P          05/03/2021 19:45:30  16.93  15.95  15.38  14.98  14.73  14.56   5.0  17.9  B96

141P          05/03/2021 19:45:30*  0.08   0.08   0.10   0.11   0.15   0.22     4   3.3  Gai

141P          06/03/2021 19:14:40  17.28  16.32  15.72  15.37  15.14  14.98   5.1  17.9  B96

141P          06/03/2021 19:14:40*  0.06   0.16   0.15   0.12   0.13   0.12     4   3.2  Gai

                                                                     AFRHO         LOG

COMET         UTC                   DELTA    r    BOX "   MAG   RSR    CM    +/-  AFRHO  OBS

------------  -------------------   -----  -----  -----  -----  ---  -----  ----  -----  ---

141P          05/03/2021 19:45:30    0.93   1.44  29.50  15.44    5     12     2  1.062  B96

141P          06/03/2021 19:14:40    0.95   1.45  29.05  15.84    5      8     2  0.922  B96

141P - Kronck’s Cometography

Comet 141P/MACHOLZ (astro Van Buitenen)

Discovery in 1994:

The nucleus was split in 1994, and it was discovered because it became bright in outburst. Five components, A to E, were observed in 1994.

This comet was discovered by Donald E. Machholz (Colfax, California, USA) on 1994 August 13.42 with a 0.25-m reflector. He estimated the brightness as magnitude 10 and said the coma diameter was 3 to 4 arc minutes across. Machholz added that the comet was diffuse with little condensation. The comet was confirmed in twilight by T. Kojima (YGCO Chiyoda Observatory, Japan) on April 13.80. He said the comet was diffuse with condensation.  The first orbit was determined by S. Nakano (Sumoto, Japan) and was published on 1994 August 15. It was parabolic and indicated a perihelion date of 1994 September 13.76, a perihelion date of 0.757 AU, and an inclination of 15 degrees. The first elliptical orbit was computed by Daniel W. E. Green of the Central Bureau for Astronomical Telegrams and was published on August 23. He found a perihelion date of 1994 September 17.82, a perihelion distance of 0.753 AU, and an orbital period of 6.81 years. By late September, further observations generally confirmed this early short-period orbit, although the period had been revised to 5.23 years.

Recovery in 1999:

The comet was recovered by R. H. McNaught (Siding Spring Observatory, Australia) on 1999 August 3.55. The comet then appeared stellar, with the magnitude estimated as 20.3-20.8. Calculations revealed this was comet "A", as designated from 1994, with the predicted orbit requiring a correction of only +0.8 day. A search for other components failed to reveal anything.

Five components, A to E, were observed in 1994. Two of them, A and D, returned in the next return in 1999. In the next return in 2005, only the component A was observed due to the bad condition.  In 1999, the main component A became fainter than discovery by 3 mag.

Return 2005:

The characteristic of the light curve changed. But in the next return in 2005, it was observed as bright as in 1999. The characteristic of the light curve was also similar, which is rapid along a 20 log r formula and it becomes brightest 10 days after the perihelion passage.

In 1999, another fragment D also became fainter than discovery by 2-3 mag. It behaved unusually both in 1994 and 1999. In 1994, it brightened after the perihelion passage and became brighter than the main component. On the other hand, it started fading before the perihelion passage in 1999.

Retrun 2015:

The comet was recovered at its 2015 return by the NEOWISE space observatory in 2015 May.  In August it was reported in outburst, brightening from around 15th magnitude at the beginning of the month to 12th magnitude on the 22nd.  In addition a secondary component was discovered some 22 minutes from the primary.  Gareth Williams noted in MPEC 2015-R12 [2015 September 6]:

Initially reported as a new comet, this object was immediately recognized as being a potential fragment of 141P. The current astrometry is rather noisy, which precludes an unambiguous linkage to a known fragment. Computations by both Gareth Williams and S. Nakano suggest that this object 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 November 1994. In no case is the linkage to a known fragment satisfactory. Therefore, in the absence of a definitive linkage, the new fragment designation "H" is being assigned. Also, the opportunity is being taken to publish rough orbits for three other fragments seen in 1994 that have not been published previously.

Return 2020:

PanSTARRS 2 discovered an apparently asteroidal object on 2020 August 13.27 which was posted on the NEOCP as PP213Rbq.  The MPC noted that it had the motion expected of 141P and it is assumed that this is component A.  The comet passed 0.93 au from Jupiter in 2017 October and passes 0.53 au from Earth in 2021 January.  [CBET 4834, 2020 August 19].  Michael Jaeger imaged the comet on December 7.7, noting the main body and two much fainter fragments.  The main body was about 13th magnitude, which is a bit fainter than predicted, though the next day JJ Gonzalez was able to see it visually at 12th magnitude.  The comet reached 10th magnitude between the time of perihelion in December and closest approach in January, this was slightly fainter than originally expected, but perhaps a consequence of the perihelion distance being slightly greater than at the last return.

ATLAS reported on Twitter an outburst of three magnitudes between Feb 23 and Mar 3 2021.