A Review of Abundance Anomalies in Globular Clusters

1
UV Spectroscopy of the Post-AGB Star PG 1159-034

• Siti Jamiah Mohamad Yob
• Supervisors Ana Inez Gomez de Castro
• Isabella Pagano
• COSPAR2008

2
Objectives

• To detect the C, N, O lines in post-AGB
  (asymptotic giant branch) stars from UV spectra
• To calculate abundances of CNO elements.
• To understand the evolution in AGB stars

3
Structure of AGB Star
H envelope
He burning
He intershell thermal pulses
C in intershell dredged to surface after every
thermal pulse. Hot Bottom Burning (HBB) occurs
when mass ? 5 solar masses. H burning via CNO
cycle at base of convective envelope causes C ?
and N?
C-O

• HBB more effective for lower metallicity. (Marigo
  2007)?
• HBB more effective for lower metallicity and
  higher mass (Izzard et al. 2007, Lattanzio et al.
  2004, Marigo et al. 1998)?

H burning
4
Dataset
Target star PG 1159-034 RA 180.441583, DEC
-3.761333 Instrument Far Ultraviolet
Spectroscopic Explorer (FUSE)? Aperture LWRS
Instrument Mode TTAG Exp Time (sec) 6324 s
Obs date May-10, 2001 ? 905 1187 Å
5
Data analysis

• IDL -Interactive Data Language (Boyce, Kappleman
  
• Mahabir 2008)?
• Add spectra from the same detector together
• - For each exposure, select ?? to align spectra
• - If necessary align according to the strongest
  line
• Combine all spectra of different detectors into 1
  spectrum
• Plot the spectrum
• Identify the absorption/emission lines

6
Spectra of PG1159-034
7
Absorption lines of C, N, O in PG1159-034
1.Jahn et al. (2008)
8
Discussion

• Visual inspection shows strong C and O lines
  indicating intershell abundances
• Spectrum is crowded with many blended lines
• Future work - Determination of abundances by
  fitting with synthetic spectra eg TMAP

9
Thank You

• COSPAR faculty, secretariat, new and old friends