Index

1. Introduction
2. The Sun
  • Main Features
  • Solar Structure
  • Surface and Atmosphere
  • Photosphere
  • Chromosphere
  • Corona
  • Solar Activity
  • Sunspots
  • 3. What are RS CVn Stars?!
  • Binaries
  • Algol star (eclipsing binary)
  • Capella - the brightest and the best learned RS CVn type of star
  • 4. Electrophotometry of SV Cam
  • General info
  • History of studying SV Cam
  • Graphs
  • Conclusion

  • Our Team
    References





    Our observations
    The subject of our project is the SV Cam star. It belongs to the RS CVn type of variable stars. These are close binary systems with chromospherically active components. The existence of spots on the stars' surface (similar to the Sun ones) causes special features in the light curve to appear. Besides that the SV Cam star is a spectroscopic binary system like Algol. The star is fairly bright - V=8m.4 and this makes it accessible even for smaller telescopes. Except that it is with a short period, which allows obtaining almost the whole light curve in a night. But to study the variations in the light curve, caused by the cold spots, a longer period of time is needed. The proximity of our town with NAO "Rozhen" as also the politeness and the readiness of professional astronomers working there teaching youths, which are interested in astronomy, made our research possible for which we thank them.
    Working under this project we had the opportunity to familiarize with all the steps that a researching of an astronomy object requires - from receiving the data, through its processing and finally its interpretation. Unfortunately, the short time in which we had to make our project and the bad meteorological conditions didn't allow us to personally take part in the stars' observation.
    At this stage of our work we used information published in different astronomical editions and also the data given us by PhD Ina Barzova from NAO "Rozhen". The last ones haven't been published until now.
    Of particular importance is also the fact that when we collected the information about the star we enriched our knowledge in lots of areas in the astrophysics.

    General info

    SV Cam = AN 1928.0427 = BD +82 0174 = HD 044982 = SAO 001038

    ID: 110022
    Variable star: SV Cam
    RA 2000: 064119.1
    DE 2000: +821602
    RA 1950: 063036.9
    DE 1950: +821847
    Max (mag): 8.40
    Min (mag): 9.11
    Photometric system: V
    Epoch (JD): 42594.61518
    Period (d): 0.59306995
    Spectrum: G5V+G3V
    Mass 1: 1.1M = R1 = 1.18R
    Mass 2: 0.7M = R2 = 0.76R
    Radial velocity: 13.8 km/s
    Paralaxes (mas): 11.7


    History
    The light variability of SV CAM was firstly discovered by Guthnick(1929). Wood (1946) reported an asymmetry in the system's light curve. According to his analysis, the primary component is close to its Roche limit. Hence, the observed period and light curve variations were considered reasonable due to the instability of the primary near its limiting surface. The long-term variation in the O-C curve of SV Cam has been subjected to studies by Sommer (1956), Friboes-Conde and Herczeg (1973), Hilditch et al. (1979), and Cellino et al. (1985) who reported different light-time periods ranging from 57.5 to 74.7 years. Hall (1976) included the system into his list of short-period RS CVn-type binaries.
    The figures below show the observation in B and V filters made with the 48 cm Cassegrian reflector of Ede University Observatory on three nights in October 1985 by M. C. Akan, Z.Tunca, C. Ibanoglu, S. Erven, and V. Keskin. The results of that time - photoelectric light curves of the system were presented along with the unpublished photoelectric ones, obtained by Celikezer(1976) in their observatory during the observing season of 1975. They demonstrate in what manner the system's brigthness changes.




    Fig. 1


    Fig. 2

    Another observations also show the light curve of the star, made in 1999 by Lukas Kral (Fig. 3). Here is what he remarks: 'We caught all the primary eclipse, which behaved in accordance with the prediction, with only a small difference'.


    Fig. 3


    For studing the behaviour of the SV CAM we used electrophotometric observations, made in a few separate nights during the period - 2001-2003. The observations are made by using UBV single-channel star electrophotometer type E1, installed on 60 cm Cassegrian telescope in NAO "Rozhen". They were given to us by PhD Ina Barzova - astronomer from NAO "Rozhen".

    An outline of the UBV single-channel electrophotometer:

    1, 2 - neutral filters
    3 - an ocullar for identification of the subject in the visual zone
    4 - mobile input prism
    5 - a diaphragm wheel
    6 - an ocullar for centering the object in the diaphragm
    7 - standard source for controlling the "zero-point"
    8 - a filter wheel
    9 - a quarz Fabri-lens
    10 - a shutter
    11 - a photomultiplier tube type EMI-9789QB, wide-band puls amplifiår


    At the observations of the SV CAM a standard star is used for comparison:

    star BD Sp V B 2000 2000
    Comp +82o168 G0 8m.6 9m.6 06h35m42s.03 +82o32'24''.8

    The observations are made in filters:
    V: OG 515 + BG 18,
    B: BG 12 + BG 38 + GG 385,
    U: UG 2 + BG 38






    SV Cam and the comparison star are labeled. Click to enlarge.
    SV Cam and the comparison star are labeled. Click to enlarge.


    60 cm Cassegrian telescope


    Graphs
    Because of the observations we have are just a few and they don't allow us to build the whole light curve so that we decided to compare our data with curves which we built based on data for the same period obtained by other astronomers - Albayrak, B. X., Zboril M. etc.
    The data of Albayrak, B. contains the observation moments in JD and the star's magnitude in B, V, and R filters. The total number of the measurements is 242. The observations are made in 2000. The graphics below illustrate the light curve of the star in B, V, and R filters. Y shows the ΔB, ΔV and ΔR while X shows the phase which we calculated using the following formula:

    (HJD-2426949.3939)/0d.5930718

    0d.5930718 is the value of the star's period according to Lehmann, H..
    All the intermediate calculations and building the plots we made in Excel.


    Light Curve - B filter (Albayrak, B.)


    Light Curve - V filter (Albayrak, B.)


    Light Curve - R filter (Albayrak, B.)



    Using the same method we built the light curves' plots in B and V based on the observations of Zboril M. and Djurasevic G. made during the period 2001-2002.


    Light Curve - B filter (Zboril M. and Djurasevic G., 2001-2002)


    Light Curve - V filter (Zboril M. and Djurasevic G., 2001-2002)


    After that we combined the two figures and got what is shown:




    Over this figure we also added the points, responding to our observations (they are in red). The primary processing of the observing material was made with a standard for NAO "Rozhen" software - APR by Anton Iliev. It is taken into account the influence of the Earth's atmosphere (extinction) and after that the measurements were transferred into the photometric UBV system. The data we obtained we processed using the same method shown upper in the project.

    Date Phase DB
    2001-Feb-11 0.22315 -0.037
    2001-Feb-11 0.2253 -0.068
    2001-Feb-11 0.23952 -0.048
    2001-Feb-11 0.24163 -0.043
    2001-Feb-11 0.25486 -0.082
    2001-Feb-11 0.25572 -0.078
    2001-Feb-11 0.26797 -0.1
    2001-Feb-11 0.26885 -0.097
    2001-Feb-11 0.28072 -0.078
    2001-Feb-11 0.28158 -0.093
    2001-Feb-11 0.295 -0.095
    2001-Feb-11 0.29588 -0.084
    2001-Feb-11 0.30819 -0.077
    2001-Feb-11 0.30907 -0.077
    2001-Feb-11 0.33134 -0.095
    2001-Feb-11 0.3322 -0.1
    2001-Feb-11 0.3474 -0.081
    2001-Feb-11 0.34828 -0.097
    2001-Feb-11 0.36153 -0.083
    2002-Feb-21 0.962652 0.682
    2002-Feb-21 0.974455 0.769
    2002-Mar-02 0.56758 -0.175
    2002-Mar-02 0.613106 -0.276
    2002-Mar-03 0.253717 -0.073
    2002-Mar-03 0.312731 -0.45

    Conclusion
    On the composed graph can be clearly seen that there is depth of the star's brightness in the area of the secondary minimum during one of the observation season (Albayrak, B.'s data). This indicates the existence of cold chromospherical spots. For tracing the brightness's variation in result of the availability of these colder spots (similar to the Sun's cycle) a longer period of observations is needed.

    Our special thanks to PhD Ina Barzova and PhD Ilian Iliev for the consultations


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