1 / 28

Department of Astronomy Beijing Normal University

Frequency analysis of RR Lyrae stars in the LMC. Bingqiu Chen & Biwei Jiang Beijing Normal University 2010.4. Department of Astronomy Beijing Normal University. Overview. Introduction The data & the method of analysis Variable classification Conclusion Discussion. RR Lyrae stars:

tola
Download Presentation

Department of Astronomy Beijing Normal University

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Frequency analysis of RR Lyrae stars in the LMC Bingqiu Chen & Biwei Jiang Beijing Normal University 2010.4 Department of Astronomy Beijing Normal University

  2. Overview • Introduction • The data & the method of analysis • Variable classification • Conclusion • Discussion

  3. RR Lyrae stars: Period : 0.1 to 1 day Amplitude in V : up to 1.5 magnitudes Spectral type : A5 to F5 Absolute visual magnitude : about +0.5 Mass : about half a solar mass Low metal abundance Z : 0.00001 ~ 0.01 Evolutionary stage: Away from the main sequence & burning Helium in their core. Useful tracer of galactic evolution. Obey a period-luminosity-color relation & used as distanceindicators.( Like the Cepheids) Types : RRab stars, RRc stars , RRd stars, RRe stars RR Lyrae Star

  4. A long-term modulation of the amplitude, shape, and phase of the light and radial velocity curve. Blazhko effect period : 11 to 533 days Occurs in 1/3 RRab stars, & a few RRc stars .(The incidence is lower in LMC). A century of study: Nonradial modes triggered by resonance effects Magnetic field e.g. : Dziembowski and Mizerski (2004). The Blazhko effect

  5. 24906 light curves from the OGLE-III (Soszynski et al. 2009) Exclude I <18m & Observed dots’ number <1000 671 stars Data

  6. Frequency analysis based on a PDM method : f0 In the [1 5] 1/d band Fit the light curve with five harmonics of f0: Frequency analysis with the residual: f1 In the [0.5 5.5] 1/d band Fit the residual with f1 …f2…f3…f4 Visual inspection of lightcurves to check Method

  7. RR-S • Singly-periodic RR Lyrae : • 495 stars 73.7% • RR0: (fundamental mode): 369~74.5% • RR1: (1st overtone mode) : 124~25.1% • RR2: (2nd overtone mode) : 2~0.4%

  8. PDM & fitting

  9. Period distribution

  10. Period–amplitude diagram

  11. RR-01 • Double modes RR Lyrae : 12 ~1.8% • There main pulsation modes are all 1st overtone (RR1-01)

  12. Phased lightcurves

  13. A1 to A0 ratios Wide range A0,only 1 exceeds A1

  14. Petersen diagram

  15. RR-BL1 • RR Lyrae with 1 close frequency component: • Number : 84 stars 12.5% • RR1-BL1: 18 ~ 21.4% • RR0-BL1: 66 ~ 78.6%

  16. Phased lightcurves

  17. Frequency difference: RR0: f1>f0  48 stars 72.7% RR1: f1>f0  3 stars 16.7% RR-BL1

  18. RR-BL2 • RR Lyrae with 2 close symmetric frequencycomponents: 28 4.2% • RR1-BL2 : 12~42.8% • RR0-BL2 : 16~57.2%

  19. Phased lightcurves

  20. Relation of Δf & f0

  21. RR-BL3+ • RR Lyrae with several close components :29 4.2% • RR1-BL3+ : 14~48.3% • RR0-BL3+ : 15~51.7%

  22. RR-BL3+

  23. Relation of Δf & f0

  24. RR-D & RR-unknown 6 RR-D & 17 unknown type double period RR Lyrae stars

  25. Conclusion

  26. Discussion • Blazhko effect occurs more frequently in RR0 than RR1. • The Blazhko period is short in RR1, while sometimes long in RR0 than in RR1. • With the number of oscillating components, the numbers of the RR0-BLn and RR1-BLn stars have a trend to be the same, sothe Blazhko effect depends on the mode of pulsation and thenumber of oscillating components. • For the RR-BL1,RR-BL2, & RR-BL3+, it seems the Blazhko can lead the period to split for any number (1-4) of components, so nonradial mode of oscillation seems better explain for Blazhko effect.

  27. Thank You!

More Related