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 comet 274P/TOMBAUGH-TENAGRA ( = 1931 AN = 2003 WZ141 =  2012 WX32)

Photometric data obtained by use of FOCAS-II software

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

OBJECT        DATE       TIME        +/-    +/-    +/-    +/-    +/-    +/-     N  FWHM  CAT

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

274P          11/01/2013 23:37:04  17.12  16.59  16.29  16.09  16.10          9.7  18.1  B96

274P          11/01/2013 23:37:04*  0.04   0.08   0.12   0.10   0.10            4   3.2  USN

274P          14/03/2013 20:15:26  17.61  16.75  16.27  16.07  16.07          4.1  17.9  B96

274P          14/03/2013 20:15:26*  0.21   0.17   0.07   0.01   0.06            3   3.5  CMC

Discovery:

comet C/1931 AN was discovered by C.W. Tombaugh (Lowel Observatory, Arizona, USA) on plates taken by the 0.33-m A.Lawrence Lowell Astrograph. Especially on plate 327 that was exposed on 1931 jan. 13.29.  The plates are initially taken for search of planets, but the plates are not carefully examined and examining was slowing down. So it tooks several months before C.W. Tombaugh examined this plate very carefully on 1932 march 11 and 12. He then noted the precense of a probable comet, but his heavy workload and the fact that the comet would be hopelessly lost after so long an interval promted him to not measure his position.  The existence was forgotten for over 50 years.  The author wrote to Tombaugh in mid-1984 and recevied a letter on july 30 which mentioned that 2 comets had been found; however, he had no notes providing details. Interesingly, just a year later, D.H. Levy began series of biographical interviews with Tombaugh. After being informed of the comet, he drove to nearby Lowel Observatory in 1986 febr. to look for Tombaugh's notes and plates.  With the help of staff astronomer B. Skiff, Levy began the search and after several hours he finally came across the notes of plate 327, which mentioned the image of a possible comet. After examine the plates of 11, 12 and 13 jan. the comet was found and Levy described it as a magnitude 12 object showing traces of a tail. The coordinates were send to Brian G. Marsden but he said that the coordinates are not sufficient to calculate an accurate orbit, he provide a preleminary orbit. (source: Cometography vol.3 G.W. Kronk)

Recovery:

An asteroid was discovered at the Tenagra II observatory by Michael Schwartz and Paulo Holvorcem with the 0.41m astrograph on November 27.50. On December 3 they noted cometary features during follow-up observations and these were confirmed by other observers.

Syuichi Nakano then linked the comet to asteroid 2003 WZ141 which was observed by Spacewatch and LINEAR in 2003, and to a comet discovered by Clyde Tombaugh in 1932 on plates taken in 1931 January and which was originally logged as asteroid 1931 AN. Details of the chain of events surrounding 1931 AN are given by Gary Kronk in Volume 3 of Cometography. Gareth Williams then computed an orbit linking the three apparitions. The new orbit is very different to that calculated for 1931 AN, largely on account of large errors in the position from the first of its three plates. The new orbit has the 1931 perihelion at 2.4 AU cf the 0.9 AU calculated from four positions, and is periodic rather than parabolic. The current period is 9.1 years, and this is the 10th return, reaching perihelion in 2013 February. It seems likely that the comet may have outburst in 1931, as it was estimated at 12th magnitude on the plates, some 6 magnitudes brighter than suggested by the ephemeris. Alternatively it may have a linear type light curve.