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H-R diagrams for star clusters

H-R diagrams for star clusters. H-R Diagram. Relation between luminosity L , temperature T and radius R : L = 4  R 2  T 4. H-R diagram for closest stars. Stellar evolution on H-R diagram. Theoretical isochrones. Observational diagrams H-R.

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H-R diagrams for star clusters

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  1. H-R diagrams for star clusters

  2. H-R Diagram

  3. Relation between luminosity L, temperature T and radius R:L = 4R2T4

  4. H-R diagram for closest stars

  5. Stellar evolution on H-R diagram

  6. Theoretical isochrones

  7. Observational diagrams H-R Instead of luminosity L – observed flux in V filter: V = -2.5log10(FV/FV0) Instead of temperature – difference of fluxes in filters BandV: B-V whereB = -2.5log10(FB/FB0)

  8. Middle-aged open cluster NGC 7789

  9. Young open cluster M46 (NGC 2437)

  10. Globular cluster 47 Tuc (NGC 104)

  11. Problems • Calibration Standard stars with known values of Vsi Bs should be observed; values of reference fluxes FV0 i FB0 can be calculated from the formula: Vs= -2.5log10(Fs/FV0) Information about standard stars can be found at: http://cadcwww.hia.nrc.ca/cadcbin/wdb/astrocat/stetson/query • Interstellar extinction (reddening) Hint: observe clusters with b < –10orb > +10 • Stars in clusters may vary in brightness by a few orders of magnitude One should make observations of different length or – better – make several observations and combine the data

  12. Strategy • Choose suitable clusters Information about open clusters can be found at: http://www.seds.org/~spider/ngc/ngc.html http://www.univie.ac.at/webda//navigation.html • Choose suitable field with standard stars • Observe standard stars and the cluster • Using SalsaJ software make photometric measurements of stars • Export results to Excel and create H-R diagram

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