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Probable Nova in the Globular Cluster M 14.

1964; Institute of Physics; Volume: 69; Linguagem: Inglês

10.1086/109475

1538-3881

Helen Sawyer Hogg, Amelia Wehlau,

History and Developments in Astronomy

The globular cluster M14 in Ophiuchus has been photographed on 124 nights in 23 of the years from 1932-1963 inclusive by H. Sawyer Hogg with one of the two large Canadian reflectors, the 72-inch of the Dominion Astrophysical Observatory or the 74-inch of the David Dunlap. During the past year a systematic program of photometry of these plates has been carried out with the Becker iris photometer at the Hume Cronyn Observatory. In the course of this program, Amelia Wehlau has discovered the image of a star on the David Dunlap plates of 1938. The star is present on all eight plates taken in 1938 and does not appear on any of the other 247 plates in our collection. The 1938 plates cover an interval of one week, with the first on 21 June and the last one 28 June, with average exposure time of 35 min. The nova is close to variables Nos. 67 and 42 (Dominion Astrophys. Obs. Publ. 7, No. 5, Plate II, 1938), with coordinates of x= 30", y = 411 on the same center. Ironically, a 5-yr systematic hunt for variables in the cluster had ended just before the nova appeared. Our observations apparently rule out the star as a U Gem variable like those in MS and M30. If the identification of this star as a nova is not disproved, it is the second nova recorded in a globular cluster and the first to be recorded photographically. Nova T Scorpii reached visual magnitude 7 in M80 in 1860. The magnitude of our nova hovers around 16.0, with 15.6 and 16.25 as extreme values, but there is some background effect so near the cluster center. For 15 RR Lyrae variables whose periods and light curves we have determined in this cluster, the average mean magnitude is 17.87 and the average median is 18.03. It is probable that the nova which we caught so fleetingly on David Dunlap plates reached a maximum brighter than 10. We appreciate the support of National Research Council of Canada in this program.