Session 102 - Pulsating Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

## [102.14] Multi-longitude campaigns on \gamma Doradus stars

K. Krisciunas (JAC)

\gamma Doradus stars constitute a new class of variables (Krisciunas 1995). They have spectral types near F0 V and are variable up to 0.10 mag in V on time scales of 0.5 to 3 days. Krisciunas amp; Handler (1995) list 17 bona fide examples and candidates. The mechanism for variability appears to be non-radial gravity mode pulsations. This conclusion derives from the time scale of the variability (an order of magnitude longer than the fundamental radial pulsation period for stars of this density), radial velocity and spectral line profile variations that correlate with the photometric variations (Krisciunas et al. 1995; Balona et al. 199[6]), and lack of evidence for other explanations. Starspots are proposed by some (e.g. Zerbi 199[6]) as an alternative explanation to non-radial g-modes, but with at least 3 periods for two of the stars and lack of evidence for chromospheric activity, we do not see how the starspot idea is viable. Recently Aerts amp; Krisciunas (199[6]) and Balona et al. (199[6]) have identified the pulsation modes of two stars, V398 Aur (= 9 Aur) and \gamma Doradus itself.

In this poster we present results of multi-longitude campaigns carried out from November 1994 through October 1995 on \gamma Dor, V398 Aur, HD 164615, BS 8799, HD 224638, and HD 224945. Multi-longitude campaigns are necessary for the proper identification of the frequencies of variation, owing to aliasing that results from observations, at a single site, of stars with periods on the order of one day.

\refs

Aerts C., Krisciunas K., 199[6], MNRAS, in press Balona L. A. et al. 199[6], MUSICOS conference proceedings, in press

Krisciunas K., 1995, What is known and not known about \gamma Doradus stars,'' Delta Scuti Star Newsletter, Issue 9, 17

Krisciunas K. et al.\ 1995, MNRAS, 273, 662

Krisciunas K., Handler G., 1995, IBVS 4195

Zerbi F. M., 199[6], Vienna meeting on Stellar Surface Structure, IAU Symposium 176, in press

\unrefs