COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3501 Konkoly Observatory Budapest 8 August 1990 HU ISSN 0374 - 0676 HD 90892: A NEW VARIABLE IN HYDRA While engaged in an observing program devoted to the study of the long-term light variations of Be stars, it was noted that one of the stars chosen as a comparison was in itself variable. This star, HD 90892, was found to change irregularly in V magnitude from 50 observations over the time period JD 2447124-8015 by a range of approximately 0.247 V magnitudes. Differential BV photometry of HD 90892 was obtained with 3 separate observing systems. The majority of magnitudes were taken with the 0.6-m. telescope of the Corralitos Observatory and its uncooled single channel photon-counting photometer. The 5 magnitudes on JD 7182-6 were derived from the Kitt Peak Observatory's #2 0,9-m. telescope and its automated 1P21-based filter photometer. Finally, Stromgren by magnitudes were obtained on JD 7938-9 with the Lowell Observatory 1.1-m. telescope and red photometer. These were then transformed to BV magnitudes. Observations of a sufficient number of standard stars with the Kitt Peak and Lowell Observatory photometric systems allowed their magnitudes to be well integrated with those from the Corralitos. Three comparison stars were utilized to derive magnitudes for HD 90892. Initially, HD 91120 (V=5.583; B-V=-.028; B9 IVe) and HD 90045 (V=6.592; B-V=+.497; F6/7 V) were chosen. Despite the fact that HD 91120 is a Be star and potentially variable, its magnitude was found to be entirely constant during the time period of observation. Therefore, its use as a comparison star was justified. [FIGURE 1] FIGURE 1: V MAGNITUDES FOR HD 90892 In the last observing season another comparison star (HD 91816; V=8.040; B-B=+.860; K3 V) was added in an attempt to provide a fainter star for the observations. The mean standard errors in V and B-V for the comparison stars were 0.017 and 0.015 magnitudes respectively. Figure 1 presents the V changes for HD 90892, and Table I the magnitudes themselves. Clearly, the star is variable in V, though perhaps not in B-V (mean B-V = +.371 +/- .020). Previous history for HD 90892 is quite sparse, undoubtably due to its relative faintness, It does not appear in either the GENERAL CATALOGUE OF VARIABLE STARS or the CATALOGUE OF SUSPECTED VARIABLES. The only published spectral type would appear to be that of Houk & Smith-Moore (1988) who give A1/2 V + (G/K) composite. No other references could be located with the exception of a spectral type of A2 V from Buscombe & Foster (1990). The type of variability which HD 90892 displays is at present considered to be irregular or unknown, and perhaps derives from some consequence of binarity or from variations of the G/K companion. An analysis for possible periodic behavior was carried TABLE I JD V B-V JD V B-V 7124.9933 9.551 +.390 7541.8250 9.552 +.375 7167.8944 9.462 .370 7560.8499 9.609 .359 7170.8606 9.499 7560.8660 9.566 .379 7182.9184 9.616 .399 7561.8035 9.558 .373 7183.8852 9.582 7590.7597 9.599 .386 7184.8921 9.579 .392 7591.8222 9.575 .395 7185.8950 9.582 .397 7592.8063 9.565 .378 7186.9103 9.710 .406 7593.7443 9.548 .391 7212.8287 9.528 7594.7417 9.535 .376 7230.7733 9.579 .392 7595.7597 9.542 .323 7232.7545 9.578 .341 7624.7049 9.565 .396 7233.7559 9.678 .358 7625.6507 9.546 .384 7234.7747 9.570 .342 7644.6660 9.609 .374 7235.7441 9.601 .391 7915.8486 9.600 .378 7236.7691 9.565 .388 7916.8812 9.542 .389 7256.7039 9.505 .339 7917.8618 9.545 .401 7259.7038 9.590 .386 7938.8151 9.667 7260.7058 9.557 .405 7938.8521 9.674 7275.6744 9.488 .346 7939.7877 9.564 7276.6715 9.504 7952.7028 9.644 .386 7277.6895 9.463 7985.7021 9.504 7278.6776 9.467 .346 7986.6986 9.500 7300.6731 9.542 .399 8001.7326 9.561 7303.6583 9.555 .377 8002.6819 9.569 .392 7540.8674 9.552 .375 8015.7278 9.486 out using the Minimum Phase Dispersion Method of Stellingwerf (1978) for the range in possible periods of 0.5 to 396 days. A possible period of 55.052 days was indicated, though not strongly. Examination of the phase diagram for that period showed unconvincing regularity. Therefore, at present it is considered that no periodicity was found. HD 90892 would seem to be an interesting star to examine for spectroscopic changes in view of its relatively large photometric range. Sincere thanks are rendered to C. Gullixson and T. Kreidl for their assistance with the Lowell telescope and photometry system E.M. HALBEDEL Corralitos Observatory P.O. Box 16314 Las Cruces, NM 88004 U.S.A. REFERENCES Buscombe, W. & Foster, B.E. (1990) MK SPECTRAL CLASSIFICATIONS, 8TH GENERAL CATALOGUE (Evanston: Northwestern Univ.). [BIBCODE 1990msce.book.....B ] Houk, N. & Smith-Moore, M. (1988) MICHIGAN CATALOGUE OF TWO- DIMENSIONAL SPECTRAL TYPES FOR THE HD STARS (Ann Arbor: Univ. of Michigan). [BIBCODE 1988mcts.book.....H ] Stellingwerf, R. (1978) Astrophys. J., 224, 953. [BIBCODE 1978ApJ...224..953S ]