Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties

Details Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties

2008-01-04

arxiv.org/abs/0801.0741v1

Astronomy and Astrophysics

Astrophysics

10 pages, accepted by A&A

Scientific paper

10.1051/0004-6361:20078321

Since 1999, we have been conducting a radial velocity survey of 179 K giants using the CAT at UCO/Lick observatory. At present ~20-100 measurements have been collected per star with a precision of 5 to 8 m/s. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43 exhibit significant periodicities. Our aim is to investigate possible mechanism(s) that cause these observed RV variations. We intend to test whether these variations are intrinsic in nature, or possibly induced by companions, or both. In addition, we aim to characterise the parameters of these companions. A relation between log g and the amplitude of the RV variations is investigated for all stars in the sample. Furthermore, the hypothesis that all periodic RV variations are caused by companions is investigated by comparing their inferred orbital statistics with the statistics of companions around main sequence stars. A strong relation is found between the amplitude of the RV variations and log g in K giant stars, as suggested earlier by Hatzes & Cochran (1998). However, most of the stars exhibiting periodic variations are located above this relation. These RV variations can be split in a periodic component which is not correlated with log g and a random residual part which does correlate with log g. Compared to main-sequence stars, K giants frequently exhibit periodic RV variations. Interpreting these RV variations as being caused by companions, the orbital param eters are different from the companions orbiting dwarfs. Intrinsic mechanisms play an important role in producing RV variations in K giants stars, as suggested by their dependence on log g. However, it appears that periodic RV variations are additional to these intrinsic variations, consistent with them being caused by companions.

Affiliated with

Also associated with

No associations

Rating

Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-639710