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DISK OF Be STAR WITH EMISSION

Hα 방출선을 통한 Be 항성 원반

  • Published : 2007.12.31

Abstract

We have determined the disk size of Be stars by using $H{\alpha}$ emission. We observed spectra of Be stars with telescope in SNU, equipped with SB SGS (Santa Babara Self Guided Spectrograph) and CCD ST-8. The size of disk of Be stars was estimated with the Be star model of Grundstrom & Gies (2006). This study suggests that the medium resolution spectra taken with small telescope equipped with commercial spectrograph are useful to estimate the approximate size of the $H{\alpha}$ emitting disk around Be stars.

서울대학교의 61cm 망원경에 SGS 분광기를 부착하여 4개의 Be 항성에 대한 분광 관측을 수행하였다. 관측으로부터 얻은 각 항성의 $H{\alpha}$ 등가폭은 HD 5394가 $-26.4{\AA}$, HD 10516이 $-27.7{\AA}$, HD 200120이 $-10.2{\AA}$, HD 202904가 $-18.2{\AA}$이다. 이로부터 Grundstrom & Gies (2006)가 제시한 $H{\alpha}$ 방출선의 등가폭과 수소 방출선 영역의 크기 관계를 이용하여 구한 원반의 수소 방출선영역의 크기는 HD 5394가 $6.7{\pm}0.3R_{H{\alpha}}/R_s$, HD 10516이 $8.2{\pm}0.4R_{H{\alpha}}/R_s$, HD 200120이 $6.0{\pm}0.4R_{H{\alpha}}/R_s$, HD 202904가 $4.1{\pm}0.1R_{H{\alpha}}/R_s$이었다. HD 5394와 HD 10516에 대한 결과는 $H{\alpha}$ 간섭 관측으로부터 얻어진 결과와 약 20% 정도 차이가 났다. 항성의 광구에서 발생한 $H{\alpha}$ 흡수선의 등가폭을 정밀하게 보정하고, Grundstrom & Gies (2006)의 모형이 좀더 현실적으로 개선되며 정확한 항성 물리량 (유효온도, 원반 경사각, 원반 전체 크기)을 적용할 경우, 보다 정확한 원반크기를 구할 수 있을 것이다. 따라서 본 연구에서는 61cm 구경의 반사망원경과 범용의 중분산 분광기를 활용한 분광관측으로도 충분히 Be 항성의 원반 변화에 대한 연구를 수행할 수 있다는 것을 제시하고 있다.

Keywords

References

  1. Auer, L. H. & Mihalas, D., 1972, Non-Lte Model Atmospheres. VII. The Hydrogen and Helium Spectra of the O Stars, ApJS, 24, 193
  2. Gies, D. R., et al., 1998, Hubble Space Telescope Goddard High Resolution Spectrograph Observations of the Be + sdO Binary phi Persei, ApJ, 493, 440 https://doi.org/10.1086/305113
  3. Gies, D. R., et al., 2007, CHARA Array K'-Band Measurements of the Angular Dimensions of Be Star Disks, ApJ, 654, 527 https://doi.org/10.1086/509144
  4. Grundstrom, E. D. & Gies, D. R., 2006, Estimating Be Star Disk Radii using Ha Emission Equivalent Widths, ApJ, 651, L53 https://doi.org/10.1086/509635
  5. Harmanec, P., et al., 2000, Properties and nature of Be stars. XX. Binary nature and orbital elements of gamma Cas, A&A, 364, L85
  6. Harmanec, P., et al., 2002, Properties and nature of Be stars. XXI. The long-term and the orbital variations of V832 Cyg = 59 Cyg, A&A, 387, 580
  7. Maintz, M., Rivinius, T., Stahl, O., Stefl, S., Appenzeller, I., 2005, 59 Cyg - A second Be binary with a hot, compact companion, PAICz, 93, 21
  8. Neiner, C., et al., 2005, Rotation, pulsations and outbursts in the Be star ${\upsilon}$ Cygni (HD 202904), A&A, 437, 257 https://doi.org/10.1051/0004-6361:20041901
  9. Ochsenbein, F. & Halbwachs, J. L., 1982, A list of stars with large expected angular diameters, A&AS, 47, 523
  10. Papaloizou, J. C. B. & Savonije, G. J., 2006, One-armed oscillations in Be star discs, A&A, 456, 1097 https://doi.org/10.1051/0004-6361:20065407
  11. Peters, G. J., 1979, An analysis of the far-ultraviolet spectra of the pole-on Be stars Upsilon Cygni and MU Centauri, ApJ, 39, 175
  12. Poeckert, R., 1981, A spectroscopic study of the binary Be star Phi Persei, PASP, 93, 297 https://doi.org/10.1086/130828
  13. Robinson, R. D., Smith, M. A., & Henry, G. W., 2002, X-Ray and Optical Variations in the Classical Be Star ${\gamma}$ Cassiopeia: The Discovery of a Possible Magnetic Dynamo, ApJ, 575, 435
  14. Quirrenbach, A., et al., 1997, Constraints on the Geometry of Circumstellar Envelopes: Optical Interferometric and Spectropolarimetric Observations of Seven Be Stars, ApJ, 479, 477 https://doi.org/10.1086/303854
  15. Slettebak, A. & Howard, R. F., 1955, Axial Rotation in the Brighter Stars of Draper Types B2-B5., ApJ, 105, 121
  16. Smith, M. A., et al., 2004, High-Resolution Chandra Spectroscopy of Cassiopeiae (B0.5e), ApJ, 600, 972 https://doi.org/10.1086/379873
  17. Struve, O., 1931, On the Origin of Bright Lines in Spectra of Stars of Class B, ApJ, 73, 94 https://doi.org/10.1086/143298
  18. Telting, J. H., et al., 1993 Long-term changes in emission line and continuum spectrum of the Be star Gamma Cassiopeiae - H-beta V/R and IR continuum flux variations, A&A, 270, 355
  19. Thaller, M. L., Bagnuolo, W. G., Jr., Gies, D. R., & Penny, L. R., 1995, Tomographic Separation of Composite Spectra. III. Ultraviolet Detection of the Hot Companion of phi Persei, ApJ, 448, 878 https://doi.org/10.1086/176016
  20. Tycner, C., et al., 2005, Properties of the Ha-emitting Circumstellar Regions of Be Stars, ApJ, 624, 359 https://doi.org/10.1086/429126
  21. Tycner, C., et al., 2006, Constraining Disk Parameters of Be Stars using Narrowband Ha- Interferometry with the Navy Prototype Optical Interferometer, AJ, 131, 2710 https://doi.org/10.1086/502679
  22. Underhill, A. B., Divan, L., Prevot-Burnichon, M.-L., & Doazan, V., 1979, Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars, MNRAS, 189, 601