On the period of VY Ursae Majoris Page: 34
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On the period of VY Ursae Majoris
Figure 4. Observations of VY Ursae Majoris folded into 120 days.
this time span is written in the top left of the figure. Figure
2 is the same, for MJD 48600-49400. From eye judgement
alone it is clear that the star has a period of about 125- days.
Also seen is a long-term variability that manifests itself as
a change in the star's mean brightness.
In order to get a good periodogram, VY Ursae Majoris
observations in the two time spans (Figures 1 and 2) were
transformed to the same magnitude scale using their mean
brightness in the two time spans. The resultant power spec-
trum is shown in Figure 3. The power is normalised to a
maximum power of one, the highest peak corresponding to
a 120 day period.
Figure 4 presents VY Ursae Majoris observations folded
into this 120 day period. The observations are those which
have been normalised to the same mean brightness. The dots
are the observations, while the dashed line is the mean
magnitude within 1/40 of the period bin.
The 120 day period seems to be preserved in the four
years of observations discussed in this paper. From Figure
4 the mean range of pulsation is 0.25v magnitudes, but it
seems from Figures 1 and 2 that the amplitude of VY Ursae
Majoris is changing. The star's visual range as indicated
from the discussed observations is 5.8-7.0.
Figure 3. VY Ursae Majoris power spectrum.
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Fraction of Period (120 days)
We would like to thank IAA-VSS members Naomi Henri,
Asaf Bervald, Ron Barry and Gilad Rotem, who observed
VY Ursae Majoris. We also thank Ms Dorit Goldberg who
kindly helped with the SIMBAD database, and Igal Pat-El
who read and commented on the first draft of this paper.
This research has made use of the SIMBAD database,
operated at Centre de Donndes Astronomiques (CDA),
Address: Givatiyim Observatory, PO Box 149, Givatiyim 53101, Israel
1 Hoffleit D., The Bright Star Catalogue, 4th edn., Yale University
2 Kholopov P. N. et al., General Catalogue of Variable Stars, 4th edn.,
3 Ofek E. 0., Gabzo O. & Rotem G., 'EV Lacertae: Atmospheric extinc-
tion and visual observations of extreme coloured variables', in prepa-
Received 1994 April 26; accepted 1994 May 25
J. Br. Astron. Assoc. 105, 1, 1995
British Astronomical Association " Provided by the NASA Astrophysics Data System
0 0.02 0.04 0.06
-A ('tll M A . A ..,A AA~. A A AA
.. .. . . ......
dY 'V 1,JIIVVnAJIVVtr' IV"1 fWVl.-f/ 'VVVL-&ArVW '!tilvtti.n \/ JfV-PrvY LJ
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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/m1/2/: accessed December 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.