Publications of The Korean Astronomical Society (천문학논총)

The Korean Astronomical Society (한국천문학회)
권호 표지
DOI QR코드

DOI QR Code

DISK OF Be STAR WITH EMISSION

Hα 방출선을 통한 Be 항성 원반

  • Published : 2007.12.31
Download PDF
⟨ Previous Next ⟩

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