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EURO­ASIAN ASTRONOMICAL SOCIETY

R o u n d

Prac

XX XX International Astr onomy Olympiad
, , 15 ­ 23. X. 2015 Kazan, Tatarstan, Russia

G r o u p





language

English

Practical round. Problems to solve
6. The extinction in terrestrial atmosphere. Extinction is a term used in astronomy to describe light attenuation due to its absorption and scattering. A star was observed at different zenith distances during one night at the Engelgardt's Astronomical Observatory in the program of atmospheric extinction study at blue. Astronomers use parameter , air mass, as an extinction characteristic. This parameter corresponds to relative length of the ray's way in the atmosphere. That means = 1 for zenith, = 2/31/2 for z = 30є; = 2 for z = 60є and so on. The determination of the star's brightness was performed with the method of photon counting. The 3rd column includes number n ­ the quantity of photons which z n mb were detected during one second. A luminescent source was used 39.7 15135 for calibration the data of observations. It produces a stable flow of 45.6 13816 photons N = 9900 ± 100 per second, which is equal to magnitude m 49.5 13180 mb = 9.64 beyond the terrestrial atmosphere. 6.1. Draw the table (similar to that you see right) in your answer 53.0 12246 st book. Calculate the air mass for given zenith distances in 1 54.9 11800 column, and write the result into the 2nd column. 58.2 10089 6.2. Calculate relative magnitude of the star mb (blue), and write the result into the 4th column. Use the luminescent source as standard for the relative magnitudes. 6.3. Find functional relation between m b and with a help of graphical method. 6.4. Determine the magnitude of this star as it was observed in zenith. 7. Variable star. A variable star was explored at the RTT-150 Russian-Turkish telescope in 2003. The observations were performed during whole night at the first time, the 1st table. The brightness of the variable star was measured occasionally during the other nights, and moments of maximal values of brightness (15.59m) were received on nights 2­5, the 2nd table. The time is in Julian days, and mV is the yellow spectral colour magnitude. 7.1. Plot the light curve (magnitude vs time function), determine the moment of maximum in the first night and write result (in Julian days) in form of «T0 = ...». 7.2. Calculate the period of the variable star using the data of all 5 nights. Here period means the time between two closest maximums of the brightness. But actually astronomers usually do not know how many periods were passed between two observed maximums, because appropriate weather can not be same every day and a few periods can pass between two observed maximums. 7.3. W hat type of variable star is this ­ eclipsing binary or pulsating variable star. (W rite in English: Eclipsing or Pulsating respectively.)

JD 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. 2452805. N 1 2 3 4 5

3543 3712 3869 4026 4161 4512 5152 5848 6676 7734 8421 8643 9068

mV 16.67 16.57 16.03 15.69 15.59 15.80 16.14 16.32 16.58 16.68 16.63 16.62 16.73 mV 15.59 15.59 15.59 15.59 15.59

JDmax 2452830. 2452831. 2452839. 2452854. 5089 5772 5858 5340

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2015

Kazan, Tatarstan, Russia