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Session 12 - Binary Stars.
Display session, Monday, June 08
Atlas Ballroom,
The HIPPARCOS catalog lists the young rapidly rotating F0 V star 47 Cassiopeiae as a close visual binary. The orbit of the photocenter yields a semi-major axis of 39.3 mas and a period of 1616 days. Gudel et al. (1998, Tenth Cambridge Conference on Cool Stars and the Sun) discuss the puzzle of this system as evidenced by its high X-Ray flux (ROSAT All-Sky Survey), its strong radio flux (6 cm), and indications of rotational modulation in these bands with a period of about one day. Such signatures of coronal activity are not normally associated with early F-type main-sequence stars. Photometry (1996-1997) and spectroscopy (1994-1997) from SDSU's Mount Laguna Observatory will be presented and discussed in connection with the anomalous behavior of the system. Our photometry shows no evidence of rotational modulation, which might be consistent with large star-spot groups, nor any evidence of flaring events. Our spectroscopy does not show any evidence of emission or other forms of line variability at H-alpha that are normally associated with chromospheric activity. However, we do find evidence of radial velocity variations that are consistent with those expected from the HIPPARCOS orbit. Our preliminary orbit is consistent with the interpretation by Gudel et al. that the source of the anomalous X-Ray and radio flux is a very close, chromospherically active solar-type companion. This work was supported by NASA/AURA grant GO-06691 for HST and NSF grant AST94-17035.
