Спектрофотометрическое исследование RW Возничего / მეეტლის RW–ს სპექტროფოტომეტრიული გამოკვლევა / Spectrophotometric study of RW Aurigae

Kharadze, E.K. and ხარაძე, ე.კ. and Харадзе, Е.К. and Bartaya, R.A. and ბართაია, რ. and Бартая, Р.А. (1964) Спектрофотометрическое исследование RW Возничего / მეეტლის RW–ს სპექტროფოტომეტრიული გამოკვლევა / Spectrophotometric study of RW Aurigae. აბასთუმნის ასტროფიზიკური ობსერვატორიის ბიულეტენი / Bulletin of the Abastumani Astrophysical Observatory (30). pp. 3-20.


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There are some well known peculiarities of stars of the type T Tau. They are expressed in the shape of the light curves and in spectral characteristics. The interest shown in this respect, caused both by these peculiarities and by spatial connection with associations, is also well known. The analysis of photometric and all the more of spectrophotometric peculiarities is important from the point of view of study of laws and mechanisms of intrastellar energy release and of its transfer towards the outer layers in the light of the known V. A. Ambartsumian's ideas. Meanwhile the observations available are so far scarce and lack both continuous and complex observations so important for the study of these stars. At tho end of 1962, while taking part in the co-operated observations of the stars RW Aurigae, we obtained rather abundant spectral material, on the basis of which we have made spectrophotometric study of the above mentioned stars. The results of our study are given in this paper. The spectral material was obtained with the 70 cm meniscus type telescope and 8 objective prism attached to it. The dispersion wu 166 A per 1mm. The material is given in Table I. A general characteristic of the spectrum, illustrated by Figs. I,a, b, c and photo I is given in this paper. The results of Identification of lines and of measurements of their wave lengths are represented in Table 2. The curves of energy distribution of the stars are given in Fig 3. The numerical data are to be found in Table 3. The character of the change of the continuous ultra-violet emission depending on the change of light is considered, therefore monochromatic light curves are plotted which are shown in Fig. 4. The curve of colour change of RW Aur is given in Fig. 5a. The colour U-B does not strictly correlate with the star light, but it is in close correlation with the change of the continuous ultra-violet emission as it is caused in the main by this latter one. The colour changes in the range—0.1--0.7; it does not correspond to the spectral class of the given star (G5 — F6) and may be explained by the excess of ultra violet emission. The curves of variation of equivalent widths of the lines H and K are given in Fig. 5b. There is a complete correlation between the change of the equivalent widths of emission lines and tho change of colour, the same as with the change of a continuous ultra-violet emission. The analysis of the obtained material and of the plotted curves leads to the following conclusions. The curves of energy distribution of the star RW Aur show some excess of ultra-violet radiation- Though it was almost absent during the night of maximum light and the energy curve was similar to that of the stars F6. But before the maximum as well as after it there was some Intensification of ultra-violet emission. As to the night of tho minimum tho emission took there also the place though it was less pronounced. Hence continuous ultra-violet emission is not in strict correlation with the change of the star light. Monochromatic light curves show that the amplitude of tho light change is in general wider in the photographic region than in the ultraviolet one- The colour U — B is not in strict correlation with the star light. Meanwhile It correlates with the continuous emission and thus it is caused in tho main by the latter. There is a well pronounced correlation between the change of the equivalent width of emission lines and continuous ultra-violet emission. Interpreting our results and proceeding from the considerations based on V- A. Ambartsumlan's conception we obtain tho following picture. Tho release of energy, carried out of the depths of the star by some unknown mechanism, in the given case almost incessantly, takes place in tho main in photospheric layers and consequently the energy is transformed here into thermal radiation- A small part of energy is released in tho upper layers of tho atmosphere and as a result continuous ultra-violet emission of non thermal origin appears. It is clear that the visible effect of the latter reaches the observer sooner than the effect associated with transformation into thermal energy. Therefore there is no strict correlation in time with the light change, which is caused in the main by radiation emitted from the photosphere and therefore of thermal character. The results of J. J. Knmsishvili and of his co-authors, published in this issue of the Bulletin (page 33), do not contradict this conclusion. One can say that these authors do not indicate the fact of the excess of radiation in the photographic region with respect to the visual one. But one can understand that; firstly, in their case emission lines also take part in creation of the light It and V, therefore one cannot be sure of the direct reason of the light change. Here one should note that B and V should be distorted because of the influence of the second component RW Aur. Secondly if the above mentioned about the dominating value of thermal radiation is true, then we should have such a result. It is relevant to recall that the light of RW Aur changed in the range of 10.40— 12.08 pg. mg. during the period of our observations. However as it is seen in Fig. 3 in the paper by J. J. Knmsishvili et al.. the colour B—V is not in complete correlation with the light and at certain rate it simultaneously correlates with the continuous ultra-violet emission; in the period preceding the maximum the changes of the colours B-V and U —B are quite identical. Hence there is some though slightly pronounced excess of emission in the photographic region. We shall consider now the data of L- N. Mosidze [3]. They are interesting because they embrace a longer period and besides they are in three colours. As it is seen B—V clearly correlates with the light though there is no complete correlation- This fact indicates that besides the change of the star light (caused mainly by thermal radiation) and tho influence of the second component of RW Aur (this fact can only increase tho first effect), there is some other factor acting there. As to U—B it is almost not in correlation with light, which means that in this case there acts another factor than in B—V- The range of U—B change clearly shows the presence of excess of ultra violet emission. But in L. N. Mosidie's case it is quantitatively smaller. The reason should be found in the fact that as in tho previous case omission lines take part in tho formation of the magnitudes U and B- The latter ones as we have already noted more than once strengthen more tho photographic region than the ultra-violet one and produce some so to say compensation of ultra-violet excess. Tho comparison of spectrophotometric data with those of photometry convinces us once more that for emission stars and that means for stars RW Aur type only photometric data, the more as they do not involve colours of U, can not give any real or complete picture- They give little and in more or less distorted form and therefore without spectrophotometric data they may lead into error at the interpretation of the observed facts. Hence the study of BW Aur type stars demands inevitably the use of spectral methods. Only together with spectral data the photometric ones give us material for more detailed study of the results. In conclusion we should like to emphasize that the form of co-operated observations and investigations proved to be very fruitful according to the example of the last campaign. Apparently study of such problems should be conducted only in this way, by wide co-operation of complex observations carried on sinchronically. As to RW Aur itself one should remember besides that, as it is known, the maximum amplitude of light change for it reaches 4 mgs (9.6 — 13.6) and during the periods of our observations it reached only about 1.5. Thus we have not watched the change of the star light sufficiently and in full measure; hence to study more thoroughly tho problems arising in association of tho investigations of tho stars of T Tauri typo it is necessary to find out the recurrence of the observed facts or the character of their change. Certainly, the study I used on the farther observations should be continued. We intend to continue observations of RW Aur further supplying their with spectral observations in the visual region, which will allow to estimate with higher reliability the influence of the second component on the results.

Item Type: Article
Subjects: Q Science > QB Astronomy
Divisions: Institutes > Evgeny Kharadze Abastumani National Astrophysical Observatory
Depositing User: თამარ ჭაღიაშვილი
Date Deposited: 28 May 2018 09:52
Last Modified: 10 Jun 2018 10:53
URI: http://eprints.iliauni.edu.ge/id/eprint/8013

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