BD+48 740

Hi all!  For my first post I wanted to share some news that I found interesting.  Last summer I came across a paper by Adamow, Niedzielski et al. reporting the discovery of a giant star believed to have recently engulfed a planet.  BD+48 740 is an evolved giant star that is unique for two reasons: it has an overabundance of lithium, and it has a planetary companion in a highly eccentric orbit.  It is rare for evolved giants to have a companion with a highly eccentric orbit and, according to the authors, even more rare is a lithium-rich red giant.  When a star leaves the main sequence and enters its red giant phase, the lithium abundance should drop.  They conclude that the most likely source of lithium overabundance is due to external contamination from a planetary companion.  They also conclude that the star previously had another planet in its orbit and explain the high eccentricity of the companion as a planet-planet scattering, sending one into the stellar surface and kicking the other into a more eccentric orbit.  The paper, titled BD+48 740—Li OVERABUNDANT GIANT STAR WITH A PLANET: A CASE OF RECENT ENGULFMENT?, can be found in the Astrophysical Journal Letters published 2012 July 20.

Source:

Adamow, M., Niedzielski, E., et al. 2009, ApJ, 754, L15, doi:10.1088/2041-8205/754/1/L15

For more information, see also:

Johnson, J. A. et al., ApJ, RETIRED A STARS AND THEIR COMPANIONS: EXOPLANETS ORBITING THREE INTERMEDIATE-MASS SUBGIANTS 665:785Y793, 2007

Villaver, E., Livio, M., 2009 ApJ, 705:L81–L85, 2009, doi:10.1088/0004-637X/705/1/L81