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J/A+A/499/567       BV differential photometry of HR 7224       (Krticka+, 2009)

The nature of the light variability of the silicon star HR 7224. Krticka J., Mikulasek Z., Henry G.W., Zverko J., Ziznovsky J., Skalicky J., Zverina P. <Astron. Astrophys. 499, 567 (2009)> =2009A&A...499..567K
ADC_Keywords: Stars, peculiar ; Photometry, UBV Keywords: stars: chemically peculiar - stars: early type - stars: variables: general - stars: individual HR 7224 Abstract: Although photometric variations of chemically peculiar (CP) stars are frequently used to determine their rotational periods, the detailed mechanism of their light variability remains poorly understood. We simulate the light variability of the star HR 7224 using the observed surface distribution of silicon and iron. We used the TLUSTY model atmospheres calculated for the appropriate silicon and iron abundances to obtain the emergent flux and to predict the rotationally modulated light curve of the star. We also obtained additional photometric measurements and employed our own regression procedure to derive a more precise estimate of the light elements. We show that the light variation of the star can be explained as a result of i) the uneven surface distribution of the elements, ii) the flux redistribution from the ultraviolet to the visible part of the spectrum, and iii) rotation of the star. We show that the silicon bound-free transitions and iron bound-bound transitions provide the main contribution to the flux redistribution, although an additional source of opacity is needed. We confirm that numerous iron lines significantly contribute to the well-known depression at 5200Å and discuss the connection between iron abundance and the value of peculiarity index a. The uneven surface distribution of silicon and iron is able to explain most of the rotationally modulated light variation in the star HR 7224. Description: Johnson BV photometric observations of HR 7224 obtained using T3 automatic photoelectric telescope at Fairborn Observatory are presented. Objects: --------------------------------------------- RA (2000) DE Designation(s) --------------------------------------------- 18 58 52.6 +69 31 53 HR 7224 = V* EE Dra --------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file bmag.dat 20 478 B differential photometry vmag.dat 20 462 V differential photometry
See also: J/A+AS/122/249 : uvby photometry of 4 CP stars (Adelman, 1997) J/A+A/457/1033 : Radial velocity of HR 7224 (Lehmann+, 2006) Byte-by-byte Description of file: bmag.dat vmag.dat
Bytes Format Units Label Explanations
1- 12 F12.4 d HJD Heliocentric Julian day 14- 20 F7.4 mag Dmag Differential magnitude (in B or V)
Acknowledgements: Jiri Krticka, krticka(at) Gregory W. Henry, henry(at)
(End) Patricia Vannier [CDS] 08-Apr-2009
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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