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Extinction Law Survey Based on Near IR Photometry of OB Stars W. Wegner
ACTA ASTRONOMICA Vol. 43 (1993) pp. 209±234 Extinction Law Survey Based on Near IR Photometry of OB Stars by W. Wegner Pedagogical University, Institute of Mathematics, Chodkiewicza 30, 85-064 Bydgoszcz, Poland Received June 21, 1993 ABSTRACT The paper presents an extensive survey of interstellar extinction curves derived from the near IR photometric measurements of early type stars belonging to our Galaxy. This survey is more extensive and deeper than any other one, based on spectral data. The IR magnitudes of about 500 O and B type (B V ) stars with E 0 05 were selected from literature. The IR color excesses are determined with the aid of "arti®cial standards". The results indicate that the extinction law changes from place to place. The mean galactic extinction curve in the near IR is very similar in different directions and = changes very little from the value R 3 10 0 05 obtained in this paper. Key words: extinction ± Infrared: stars 1. Introduction The interstellar extinction is commonly believed to be caused by grains of interstellar dust. Their physical and geometrical properties are thus responsible for the wavelength dependence of the interstellar extinction (the extinction law or curve). Unfortunately, this curve is typically rather featureless (Savage and Mathis 1979) and thus the identi®cation of many, possibly different, grain parameters (chemical composition, sizes, shapes, crystalline structure etc.) is very dif®cult. Possible differences between extinction curves originating in different clouds may be very useful as probes of the physical conditions inside interstellar dark nebula. It is now rather well known that absorption spectra of single interstellar clouds (including extinction curves) differ very substantially (see e.g.,Kreøowski 1989 for review). -
Arxiv:2012.09981V1 [Astro-Ph.SR] 17 Dec 2020 2 O
Contrib. Astron. Obs. Skalnat´ePleso XX, 1 { 20, (2020) DOI: to be assigned later Flare stars in nearby Galactic open clusters based on TESS data Olga Maryeva1;2, Kamil Bicz3, Caiyun Xia4, Martina Baratella5, Patrik Cechvalaˇ 6 and Krisztian Vida7 1 Astronomical Institute of the Czech Academy of Sciences 251 65 Ondˇrejov,The Czech Republic(E-mail: [email protected]) 2 Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetsky pr. 13, 119234, Moscow, Russia 3 Astronomical Institute, University of Wroc law, Kopernika 11, 51-622 Wroc law, Poland 4 Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotl´aˇrsk´a2, 611 37 Brno, Czech Republic 5 Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, 35122, Padova, Italy, (E-mail: [email protected]) 6 Department of Astronomy, Physics of the Earth and Meteorology, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynsk´adolina F-2, 842 48 Bratislava, Slovakia 7 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege Mikl´os´ut15-17, Hungary Received: September ??, 2020; Accepted: ????????? ??, 2020 Abstract. The study is devoted to search for flare stars among confirmed members of Galactic open clusters using high-cadence photometry from TESS mission. We analyzed 957 high-cadence light curves of members from 136 open clusters. As a result, 56 flare stars were found, among them 8 hot B-A type ob- jects. Of all flares, 63 % were detected in sample of cool stars (Teff < 5000 K), and 29 % { in stars of spectral type G, while 23 % in K-type stars and ap- proximately 34% of all detected flares are in M-type stars. -