MingMing Yang Yang & B. W. Jiang& B. W. Jiang

Beijing Normal UniversityBeijing Normal University

Red Super Giants in Red Super Giants in LMCLMC::

The Period-luminosity RThe Period-luminosity Relationselations

OutlinesOutlines

IntroductionIntroduction

Sample selectionSample selection

Data analysisData analysis

Period-luminosity relationsPeriod-luminosity relations

Concerned with SONGConcerned with SONG

IntroductionIntroduction

Evolved, moderately massive (10-25MEvolved, moderately massive (10-25M☉☉), He-bur), He-burning, very large radii (200-1500 Rning, very large radii (200-1500 R☉☉), low surface ), low surface temperature (3000-4000 K), heavy dusty envelotemperature (3000-4000 K), heavy dusty envelope, radiation transpot to infrared band(Levesque pe, radiation transpot to infrared band(Levesque et al. 2005).et al. 2005).

Long been known for low optical variations.Long been known for low optical variations.

Because of their great brightness, these stars miBecause of their great brightness, these stars might be a useful group of extra galactic distance ight be a useful group of extra galactic distance indicators (Wood & Bessell 1985).ndicators (Wood & Bessell 1985).

Sample selectionSample selection

Samples:Total: 191 stars

ASAS: 169 stars MACHO: 15 starsTime span: about 3000 days.

Feast et al. (1980) : 14 starsPierce et al. (2000) : 15 starsKastner et al. (2008): 25 starsMassey et al. (2003): 137 stars

Identification

“Luminous” and “Red” – Color-magnitude diagram and Two-color diagram

2MASS Point Source catalogSAGE Winter ’08 IRAC CatalogSAGE Winter ’08 MIPS 24 m Catalog

Search radius: 1 arcsec

For comparison, we add a background that is the 1268 massive stars (M > 8M⊙) in the LMC by Bonanos et al. (2009) which are collected from literatures and have been identified by the same criteria in the SAGE infrared data as we used.

It indicates that the RSGs locate in a distinctive region in CMD and TCD from the other massive stars in the LMC.

CMD and TCDCMD and TCD The boundary of

carbon-rich star, J - Ks = 1.6 defined by Hughes & Wood (1990)

Most of the M-supergiants are concentrated in 0.5≤ (J - K)≤1.5 (Josselin et al. 2000)

The region only defined by the data, not the theoretical calculation (including 95% targets).

Outliers which at least appear in two diagrams should not be considered in the next step of investigation due to their different properties compare with other candidates.

There are some massive sources from Bonanos et al. (2009) which locate in the same regions as RSGs but are not included in the sample.

Data analysisData analysis

Check DSS images.

A least-squares A least-squares (Savitzky-Golay) (Savitzky-Golay) polynomial polynomial smoothing filter is smoothing filter is applied for the applied for the ASAS data.ASAS data.

The points whose aThe points whose airmass larger than 2.irmass larger than 2.0 are dismissed (M0 are dismissed (MACHO).ACHO).

Phase Dispersion MinimizationPhase Dispersion Minimization （（ PDMPDM ） ） [Code is written by [Code is written by Marc W. Buie, Lowell Observatory]Marc W. Buie, Lowell Observatory]

•Semi-regular•Θ< 0.6 → Θ< 0.6 → Probability of correct period > 95% Probability of correct period > 95%

Fourier analysis (Period04; Lenz 2004) Fourier analysis (Period04; Lenz 2004)

• Only adopt the frequency which correponding to the highest peak in Fourier spctrum.

Light curves of ASAS and MACHOLight curves of ASAS and MACHO

Period-luminosity relationsPeriod-luminosity relations

Semi-regular RSGs: 3 targets from Feast et al. (1980) 4 targets from Pierce et al.(2000) 14 targets from Kastner et al. (2008) 14 targets from Massey & Olsen (2003)

Period-Ks band Period-Ks band magnitude magnitude relation. relation.

mmbolbol=m=mkk+3 (Jossel+3 (Josselin et al. 2000)in et al. 2000)

Distance modulus Distance modulus 18.41 is adopted18.41 is adopted (Macri et al. 200(Macri et al. 2006).6).

Mλ = a log P + b

AV = (0.81± 0.34)*LogP-(1.54±0.96)

Semi-regulars Semi-regulars overlay on all overlay on all candidates candidates RSGs.RSGs.

Concerned with SONGConcerned with SONG

Long-term observation for years??Long-term observation for years???????? (only need three or four days once)(only need three or four days once)

Suitable magnitude range? ( VSuitable magnitude range? ( Vminmin≈14 mag, ≈14 mag,

VVmaxmax=10 mag)=10 mag)

High precision (no doubt)High precision (no doubt)

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