Abstract Details
| Name: Avrajit Bandyopadhyay Affiliation: IIA, Bengaluru Conference ID: ASI2019_502 Title : New discoveries of globular cluster escapees and other results from GOMPA(Galactic survey Of Metal Poor stArs) survey Authors and Co-Authors : Avrajit Bandyopadhyay, Sivarani Thirupathi Abstract Type : Poster Abstract Category : Stars, ISM and Galaxy Abstract : We present early results of metal poor stars observed by the Hanle Echelle SpectrograPh (HESP) at spectral resolution R=30000 & 60000. We have studied about 50 stars in the metallicity range of halo Globular clusters, that includes 8 new EMP ([Fe/H] < -2.5) stars, 24 new VMP stars. We have identified three globular cluster escapees that show the typical light-element anomalies(CH-CN,Na-O,Mg-Al anticorrelations) associated with second generation GC stars. Two of them are RGBs and one is a blue straggler star, which is a rare class of object among halo stars. The blue straggler shows strong overabundances of Na([Na/Fe]=+1.50) along with a very depleted Mg and Ca([Mg/Fe]=-0.30;[Ca/Fe]=-0.50). Li could also be detected in these GC escapees which is very important to constrain the nature of the original polluters of the GC. Detailed study of these objects is very helpful in determining the self-enrichment and pre-enrichment in GCs which is otherwise difficult. Additional interesting objects include an r-II star with [Eu/Fe]=+1.02 and [Th/Fe]=1.28 and six R-I stars with +0.30<[Eu/Fe]<+1.2. We also identified 3 CEMP-no stars and one CEMP-s star. We have conducted a comparative study of CEMP-no and EMP stars in their heavy element enrichment. Lithium was detected in many of the stars which include giants and dwarfs and they exhibit the expected depletion from Spite plateau as they ascend the giant branch. We found Lithium to have a similar distribution among CEMP-no and EMP stars. Identification of bright EMP stars is useful for detailed isotopic abundances and key waiting point nuclei to probe the nucleosynthesis sites. The current study is limited to SDSS MARVELS pre-survey with Vmag=8-13, that primarily targets the low latitudes for exoplanet studies. |