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

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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.


We q42fxxts 23

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


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