On the period of VY Ursae Majoris Page: 33
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On the period of VY Ursae Majoris
Eran O. Ofek, Ohad Shemmer & Ofer Gabzo
The carbon star VY Ursae Majoris is catalogued as an Lb irregular variable. Visual observations indicate that the star is more
likely to be a semi-regular variable. Visual observations made in 1990-1993 reveal a clear period of 120 days for the star, with
probably long-term changes in mean brightness.
VY Ursae Majoris (=HD 92839, =SAO 15274, =BD +68
617, =HR 4195, =AG +67 480, =PPM 17570, =IRAS
10416+6740, =DO 33415, =CCS 1736) is a sixth magni-
tude carbon star of spectral type C511.1 The General
Catalogue of Variable Stars (GCVS)2 lists VY Ursae
Majoris as an irregular variable of Lb type with no known
period. The star's amplitude is stated by the same source to
VY Ursae Majoris was observed by members of the Israeli
Astronomical Association, Variable Stars Section, in the
1990-1993 observing seasons. About 500 observations
were made in these four years. Of these, 424 were made by
0. Gabzo and since they are the dominant part of the obser-
vations they are used in this paper exclusively, in order to
minimise possible sources of noise.
The star's red colour, B-V= 2.39, U-B= 4.62, R-I= 1.27,
made it vulnerable to a second order extinction problem as
described in Ofek et al. (in preparation).3 Hence this effect
was checked and found to be insignificant.
Figures 1 and 2 present the whole light curve of VY Ursae
Majoris. Figure 1 shows the light curve for Modified Julian
Days (MJD) 47900-48700; the star's mean magnitude in
8600 8700 8800 8900 9000 9100
Julian Day - 2440000
Figure 1. (top): Light curve for VY Ursae Majoris, MJD 47900-48700.
Figure 2. (bottom): Light curve for VY Ursae Majoris, MJD 48600-49400.
J. Br. Astron. Assoc. 105, 1, 1995
British Astronomical Association " Provided by the NASA Astrophysics Data System
62- - --- --- -- - -
7900 8000 8100 8200 8300 8400 8500 8600 8700
Julian Day - 2440000
9200 9300 9400
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Ofek, Efran; Shemmer, Ohad & Gabzo, Ofer. On the period of VY Ursae Majoris, article, May 25, 1994; London, United Kingdom. (digital.library.unt.edu/ark:/67531/metadc1225769/m1/1/: accessed December 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.