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The Cepheid Period-Luminosity Relation and Astronomy Education in Rural Upstate New York. Shashi M. Kanbur SUNY Oswego, February 28 2007. Collaborators. Chow Choong Ngeow (University of Illinois)

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the cepheid period luminosity relation and astronomy education in rural upstate new york

The Cepheid Period-Luminosity Relation and Astronomy Education in Rural Upstate New York

Shashi M. Kanbur

SUNY Oswego, February 28 2007.

collaborators
Collaborators
  • Chow Choong Ngeow (University of Illinois)
  • Douglas Leonard (San Diego State University), Lucas Macri (NOAO),Nial Tanvir (University of Hertfordshire, UK) Alan Ominisky (SCC High School)
  • Daniel Crain, Greg Feiden, Richard Stevens, Christina Phelps, Sean Scott, Jim Young, Dylan Wallace.
slide13
WHY?
  • Precision comsology: affects H0 to the level of 1-2%.
  • Zero Point errors are being reduced – NGC 4258.
  • Theory of Stellar Pulsation/Evolution.
  • Constrain Mass-Luminosity relations and Cepheid atmospheric/pulsation/evolutionary effects.
  • Nature of convection in stellar interiors.
statistical physical tests
Statistical/Physical Tests
  • F tests, Least Absolute Deviation.
  • Testimators (estimation plus smooting), Schwarz Information Criteria – likelihood based methods.
  • Robust Estimation, non-parametric LOESS, least absolute deviation.
  • Adding data: OGLE plus SEBO, MACHO plus SEBO, CALDWELL and LANEY etc.
statistical physical tests1
Statistical/Physical Tests
  • So far, LMC data is consistent with two lines of significantly differing slope with the “break” at a period of 10 days.
  • Break is present for U,B,V,R,I,J, marginal at K.
  • SMC/Galactic PL relations do not show the break.
  • 2 weeks of time on NOAO/SMARTS facilities in Chile yielded over 100Gb of data for SUNY Oswego undergraduates to analyze.
period color and amplitude color relations in cepheids
Period-Color and Amplitude-Color Relations in Cepheids.
  • Stefan Boltzmann law:
  • logL(max) – logL(min) =4logT(max) – 4logT(min).
  • Period-Color relation flat at maximum/minimum then Amplitude-Color relation flat at minimum/maximum.
  • Properties at mean light are really an average of properties at all phases.
  • PC/AC relations change abruptly at a period of 10 days in the LMC.
  • PL relation changes strongly related to PC relation changes due to PLC.
the photosphere hif interaction
The Photosphere/HIF Interaction
  • Hydrogen Ionization front (HIF): region of rapid spatial change in temperature. Photosphere (optical depth 2/3) are NOT comoving as the star pulsates.
  • When the photosphere is located at the base of the HIF, photospheric temperature and hence color is related to the temperature at which hydrogen ionizes.
  • At low densities, this temperature is almost independent of global stellar parameters, leading to a rapid change in the PC and hence PL relation.
  • This interaction may affect observational properties of other variable stars eg. RR Lyraes and other parts of the HR diagram.
undergraduate involvement
Undergraduate Involvement
  • Need to study PC/AC relations as a function of phase.
  • Usually only studied at mean light.
  • Download data, Fourier decomposition with simulated annealing, Principal Component Analysis.
  • Construct PC/AC relations. Perform statistical tests on these and PL relations as a function of phase.
  • Unix, numerical methods, statistical methods, stellar evolution/pulsation, cosmology.
current undergraduate projects
Current Undergraduate Projects
  • Analysis of M31 RR Lyrae light curves taken by HST: Dylan Wallace.
  • Analysis of SDSS RR Lyrae light curves: Christina Phelps.
  • Analysis of M31/M33/IC 1613 Cepheid data: Dan Crain/Jim Young/Sean Scott
  • Hydrodynamic modeling of Cepheids/RR Lyraes: Greg Feiden.
  • Development of generalized bootstrap methods to estimate confidence intervals for “break” period: Dan Crain, Richard Stevens.
jhk observations of lmc cepheids
JHK Observations of LMC Cepheids
  • Using NOAO/SMARTS facilities and CPAPIR intsruments.
  • 100Gb of new data taken in Nov 2006/Jan 2007.
  • Addition to exisiting data.
  • PL relations, light curve structure, modeling, data reduction methods.
  • Statistical methods.
southern caygua school observatory involvement
Southern Caygua School Observatory Involvement
  • SCCS has a 14” GOTO telescope on a reasonably dark site – Alan Ominisky.
  • SUNY Oswego purchased a ST9XE CCD camera from SBIG with some filters (UBVRI).
  • Galactic Cepheid data needs to be enhanced.
  • Such Cepheids are pretty bright – about 6-8th magnitude. Easily observable.
  • Primarily educational, but could result in some new publishable data points, especially for longer period Cepheids.
references
References
  • Kanbur and Ngeow, MNRAS, 2004
  • Ngeow and Kanbur 2005, 2006a 2006b
  • Kanbur and Ngeow 2006a
  • Kanbur, Ngeow, Nanthakumar and Stevens, 2006b (submitted)
  • Kanbur and Mariani 2004, MNRAS
  • Kanbur and Fernando 2005, MNRAS