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Project Progress

Laws continued to acquire high-resolution spectra of planet-hosting stars, proper motion pairs, and M67 turnoff stars with the echelle spectrograph at Apache Point Observatory. A collaborator, N .B. Suntzeff, obtained spectra of several southern targets in April 2001 with the echelle spectrograph on the Cerro Tololo 4-m Blanco telescope. Another collaborator, B. E. Reddy, observed additional southern targets in June 2002. Laws and Gonzalez are in the process of reducing and analyzing these data. The data acquisition part of this project is effectively complete.

Our paper reporting on the metallicities and masses of planet-hosting candidates observed by us through March 2002 was published in May 2003; a summary of the findings was reported by Laws at the Winter 2003 American Astronomical Society (AAS) meeting. The results of this study continue to confirm the findings of our previous studies that stars hosting giant planets have a higher mean metallicity than the overall nearby star population. We also report for the first time a statistically suggestive deficit of giant planets around low mass stars.

We are presently preparing our next paper (Paper VIII) in our series on the abundances of stars hosting giant planets, in which we will report on the non-Fe elemental abundances of the stars from our previous paper. We are additionally in the process of reducing and analyzing spectra of proper motion pairs and M67 turnoff stars; each of these topics will be addressed in a separate paper.

In Spring 2003 we completed a study of the unusual star, J37, an A star in the young cluster NGC 6633. No single known process can account for the elemental abundance pattern of J37. We find evidence suggestive of accretion of material similar in composition to the Earth. The paper has been accepted for publication in the Astrophysical Journal.