JUNE 25 - 29, 2007

WEDNESDAY, JUNE 27

12:30 pm: High Energy Astrophysics Division Lunch Talk. "Wolf-Rayet/Black-Holes X-ray binaries," Dr. Stefania Carpano, European Space Astronomy Centre, Spain. Pratt Conference Room.

Abstract: A small number of high-mass binary systems should end up with a compact neutron star or black hole orbiting a Wolf-Rayet star. An even smaller number would be strong accreting X-ray sources with luminosities of about 1038 erg/s. Until recently, the famous Cyg X-3 was the only recognised example for such system. Few years ago, the brightest source in the nearby galaxy IC 10, has been discovered to be the first extragalactic counterpart. Thanks to XMM data, we recently discovered the second extragalactic candidate in the spiral galaxy NGC 300. Furthermore, Swift observations of these objects, NGC 300 X-1 and IC 10 X-1, have shown them both to have very similar periods of 32.8+-0.4 and 34.8+-0.9 hours, respectively, that are probably the orbital periods of 30 or 40 solar mass black holes around almost identical Wolf-Rayet stars. It seems a surprise that these modulations are so similar and yet so large compared to the short 4.8-hour period of Cyg X-3. How do these systems form and become such bright X-ray sources?

THURSDAY, JUNE 28

11:00 am: Science Education Seminar and Open Discussion. Weekly sessions focus on current department programs, literature reviews, and recent trends in science education and assessment. Some sessions feature outside speakers or guests. All members of the CfA community are welcome. Please contact Bruce Ward at bward@cfa, if you wish to attend any session. Phillips Auditorium.

4:00 pm: Summer Colloquium Series. "The First Steps of Star Formation," Erik Rosolowsky. These talks are aimed at undergraduate summer students, but all CfA staff and visitors are welcome. Preceded by refreshments at 3:30 pm. For more information, contact Jonathan McDowell (jcm@cfa, 5-7176). Phillips Auditorium.

Abstract: All contemporary star formation occurs exclusively within molecular clouds, but these clouds are destroyed by intense radiation and winds from their progeny. Thus, the first step in making stars is forming molecular clouds -- but where do these clouds come from? Several theories have been forwarded to explain molecular cloud formation, but there are few observational constraints on this process. In this talk, I will present the molecular cloud formation problem, several viable theories, and new observational constraints. The constraints come from observations of molecular clouds in the nearby galaxies M31 and M33 using the BIMA millimeter-wave interferometer. These data yield measurements of the angular momentum of these clouds which, when compared to the predictions of several theories, rule out several possible cloud formation mechanisms. I will conclude by discussing additional measurements of the molecular cloud populations in other galaxies and how these measurements can be compared to simulations of galaxies to further explore this problem.

FRIDAY, JUNE 29

12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Age Dating Young and Old Stars Using Light Elements," Dr. Sofia Randich, INAF-Arcetri. Room M-340, 160 Concord Avenue.

Abstract: Lithium and beryllium measurements in stars offer a secure and independent way to derive stellar ages. Specifically, determination of surface Li abundance in fully convective, low-mass members of young clusters provide a very useful clock to estimate nuclear ages that can be compared to the isochronal ages derived from the star's location in the HR diagram. On the other hand, observations of Be in old Pop. II stars represent an ideal "cosmic clock" for age dating the first stages of Galactic halo evolution. In this context, I will present recent results from Li measurements in young associations and Be determinations in old globular clusters, respectively. The implications for the young cluster star formation histories, as well as for our understanding of Galaxy formation and early evolution will be discussed.

SAO HUMAN RESOURCES NOTES

Leave Donations Requested

Due to a medical emergency, Donna Coletti of the Library has been approved as a leave donor recipient in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Donna should complete a Leave Donor Form and send it to MS17.

Under the Leave Transfer Program, Trust Fund employees may only donate annual leave to other Trust Fund employees and Federal employees may donate annual leave only to other Federal employees. If you should have any questions or are not able to access the form, please contact Anne LeBlanc, ext. 5-7371.

Job Vacancies

An online listing of all current SAO job openings is available. For more information, please call Human Resources, ext. 5-7371, or view your nearest bulletin board.

A list of scientists currently visiting the CfA is available here.