Long Period Variables in the LMC: Results from MACHO and 2Mass

Journal Article · Mon Jul 19 04:00:00 EDT 2004 · The Astronomical Journal

OSTI ID:15011522

Fraser, O J; Cook, K H; Keller, S C; Hawley, S L

We use the eight year light curve database from the MACHO (MAssive Compact Halo Objects) project together with infrared colors and magnitudes from 2MASS (the Two Micron All Sky Survey) to identify a sample of 22,000 long period variables in the Large Magellanic Cloud (referred to hereafter as LMC LPVs). A period luminosity diagram of these stars reveals six well defined sequences, in substantial agreement with previous analyses of samples from OGLE (Optical Gravitational Lensing Experiment). In our analysis we identify analogues to galactic LPVs in the LMC LPV sample. We find that carbon dominated AGB stars populate only two of the sequences, one of which includes the Mira variables. The high luminosity end of the same two sequences are also the location of the only stars with J K{sub s} > 2, indicating that they are enshrouded in dust. The unknown mechanism that produces the variability of the last sequence--those stars with long secondary periods--produces different morphology in the period luminosity diagram than what is seen in the first four sequences, which are thought to be caused by pulsation. In particular, the last sequence extends to lower luminosity RGB stars and the luminosity function does not peak among the AGB stars. We point out several features which will constrain new models of the period luminosity sequences.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15011522
• Report Number(s): UCRL-JRNL-205457
• Journal Information: The Astronomical Journal, Journal Name: The Astronomical Journal Vol. 129
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
99 GENERAL AND MISCELLANEOUS
CARBON
LUMINOSITY
MAGELLANIC CLOUDS
MORPHOLOGY
SKY
STARS