COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2199 Konkoly Observatory Budapest 1982 September 24 HU ISSN 0374-0676 IS HD 90994 A "REDUCTION VARIABLE"? * Discrepant results in reducing uvby observations of HD 90994 (= HR 4119 = 30 Sex = beta Sex, B6V) led us to gather the photometric values given for that star in the literature. Original observational UBV data (i.e. not resulting from a compilation) are presented in Table I, while original uvby beta indices are given in Table II, together with the results of our own observing runs. The penultimate line of Table Ii corresponds to observations carried out with the Danish 50 cm telescope at La Silla. The indices in the seven-colour (Geneva) system are the following (Rufener, 1976, 1981): m_v = 5.055, U = 0.391, V = 1.119, B_1 = 0.825, B_2 = 1.572, V_1 = 1.819 and G = 2.344, with sigma_v = 0.006 and sigma(colours) = 0.003. In the DAO system where HD 90994 was selected as a standard star, the indices are (Hill et al., 1971): V = 5.04, c(35-44) = -0.683, c(38-44) = -0.474, c(38-42) = -0.372, c(44-54) = -0.094, c(42-56) = -0.168 and B-V = -0.12. Table I UBV observations of HD 90994 V U-B B-V n Ref. 5.00 -0.14 Bouige, 1959 -0.518 -0.145 Belyakina & Chugainov,1960 5.07 -0.50 -0.14 Cousins & Stoy,1962 5.09 -0.54 -0.13 Iriarte et al.,1965 5.09 -0.126 Haggkvist & Oja,1966 5.10 -0.53 -0.14 Johnson et al.,1971 5.07 -0.51 -0.14 5 Crawford et al.,1971 * Based on observations collected at the European Southern Observatory, La Silla, Chile Table II uvby beta observations of HD 90994 V b-y m_1 c_1 n beta n Ref. 2.730 3 Crawford & Mander,1966 -0.056 0.108 0.487 1 2.736 1 Cameron,1966 5.1 -0.064 0.116 0.466 7 Crawford & Barnes,1970 +-0.009 +-0.011 +-0.010 -0.059 0.116 0.475 2 2.731 2 Johnson & Gyldenkerne,1970 +-0.005 +-0.005 +-0.007 +-0.007 5.07 -0.064 0.116 0.466 std 2.730 std Crawford et al.,1971 5.04 2.738 4 Stokes,1972a 5.08 -0.065 0.113 0.480 7 2.727 7 Stokes,1972b 2.733 10 Claria,1974 2.722 7 Feinstein,1974 +-0.011 (obs. in 1970& 1972) -0.065 0.115 0.485 31 Gronbech et al.,1976 +-0.006 +-0.007 +-0.004 2.729 24 Gronbech & Olsen,1977 +-0.004 -0.062 0.107 0.478 2 2.732 4 Warren & Hesser,1977 +-0.008 +-0.008 +-0.001 +-0.003 -0.067 0.109 0.480 3 2.725 10 Warren & Hesser,1977 +-0.004 +-0.003 +-0.011 +-0.004 5.072 -0.064 0.116 0.481 4 Heck & Manfroid,1980 +-0.004 +-0.004 +-0.010 +-0.009 (obs. in June 1978) 5.077 -0.060 0.107 0.498 16 see text +-0.010 +-0.004 +-0.004 +-0.005 (obs. in March 1980) 5.076 -0.067 0.119 0.480 10 Manfroid & Renson,1982 +-0.004 +-0.003 +-0.004 +-0.002 HD 90994 is also known as a beta standard (Crawford & Mander, 1966) and has been extensively used as such in spite of the variations shown, amounting up to ~0.06m in V, 0.013m in b-y, 0.032m in c_1, 0.020m in m_1 to take only the uvby photometry. These variations might however result from reduction problems as HD 90994 has an extreme value in b-y (refer for instance to Oblak et al., 1976). If the standard stars used for a given run are not well spread enough in the ranges of the photometric indices, the extrapolation to extreme reduced values can be wrong. Since the (b-y) term appears in all the reduction equations (see e.g. Crawford & Barnes, 1970), all reduced color indices can be affected. This kind of problem will be treated in detail elsewhere (Manfroid & Heck, 1982). However in a recent paper, Manfroid & Renson (1982) believe HD 90994 could be also intrinsically variable by 0.01m or slightly more in y and by 0.02m in u. They even suspect this variation to be periodic, with P ~= 8d (or the double, with a double maximum). We would then urge a series of detailed observations with carefully selected standard stars in order to precise the type of possible variations of the star, independently from reduction problems. A. HECK ^1 AND J. MANFROID^2 ** 1 - IUE Observatory, Astronomy Division, ESTEC, European Space Agency, Villafranca Satellite Tracking Station, Apartado 54065, Madrid, Spain 2 - Departement d'Astrophysique de l'Universite de Liege, av. de Cointe 5, B-4200 Cointe-Ouqree, Belgium ** chercheur Qualifie F.N.R.S. References Belyakina, T.S., Chugainov, P.F. 1960, Izv. Krymsk. Astrophys. Obs. 22, 257 [BIBCODE 1960IzKry..22..257B ] Bouige, R. 1959, Ann. Toulouse 27, 47 Cameron, R.C. 1966, Georgetown Obs. Monograph 21 [BIBCODE 1966GeoOM..21....0C ] Claria, J.J. 1974, Astron. J. 79, 1022 [BIBCODE 1974AJ.....79.1022C ] Cousins, A.W.J., Stoy, R.H. 1962, Roy. Obs. Bull. 64 [BIBCODE 1962smer.book.....C ] Crawford, D.L., Barnes, J.V. 1970, Astron. 75, 978 [BIBCODE 1970AJ.....75..978C ] Crawford, D.L., Barnes, J.V., Golson, J.C. 1971, Astron. J. 76, 1058 [BIBCODE 1971AJ.....76.1058C ] Crawford, D.L., Mander, J. 1966, Astron. J. 71, 114 [BIBCODE 1966AJ.....71..114C ] Feinstein, A. 1974, Monthly Not. Roy. 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