Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
권호 표지
DOI QR코드

DOI QR Code

TIME VARIATIONS OF THE RADIAL VELOCITY OF H2O MASERS IN THE SEMI-REGULAR VARIABLE R CRT

  • Received : 2017.07.21
  • Accepted : 2017.10.16
  • Published : 2017.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

$H_2O$ maser emission at 22 GHz in the circumstellar envelope is one of the good tracers of detailed physics and kinematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an $H_2O$ maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the $H_2O$ maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a $0.1kms^{-1}$ scale. This analysis result shows that the radial velocity of red-shifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of $H_2O$ masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation. However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.

Keywords

References

  1. Bowers, P. F. 1992, Location of the Dust Formation Region for Mira Variables, ApJ, 390, L27 https://doi.org/10.1086/186364
  2. Comoretto, G., Palagi, F., Cesaroni, R., Felli, M., Bettarini, A., et al. 1990, The Arcetri Atlas of $H_2O$ Maser Sources, A&AS, 84, 179
  3. Decin, L., Richards, A. M. S., Neufeld, D., Steffen, W., Melnick, G., & Lombaert, R. 2015, ALMA Data Suggest the Presence of Spiral Structure in the Inner Wind of CW Leonis, A&A, 574, 5
  4. Deguchi, S. 1977, Water Maser and Envelope of Infrared Stars, PASJ, 29, 669
  5. Dickinson, D. F., & Chaisson, E. J. 1973, Long-Period Variables: Correlation of Stellar Period with OH Radial-Velocity Pattern, ApJ, 181, L135 https://doi.org/10.1086/181200
  6. Edelson, R. A., & Krolik, J. H. 1988, The Discrete Correlation Function - A New Method for Analyzing Unevenly Sampled Variability Data, ApJ, 333, 676
  7. Elitzur, M. 1992, Astronomical Masers, ARA&A, 30, 75 https://doi.org/10.1146/annurev.aa.30.090192.000451
  8. Etoka, S., Blaszkiewics, L., Szymczak, M., & Le Squeren, A. M. 2001, Monitoring of Long Term Behaviour of OH Masers in Semiregular Variables: R Crt, W Hya and RT Vir, A&A, 378, 522 https://doi.org/10.1051/0004-6361:20011184
  9. Etoka, S., Le Squeren, A. M., & Gerard, E. 2003, Detection of 1612 MHz OH Emission in the Semiregular Variable Stars RT Vir, R Crt and W Hya, A&A, 403, L51 https://doi.org/10.1051/0004-6361:20030578
  10. Gomez Balboa, A. M., & Lepine, J. R. D. 1986, Time Variation of the $H_2O$ and SiO Masers in Late-Type Stars, A&A, 159, 166
  11. Hinkle, K. H., Lebzelter, T., & Scharlach, W. W. G. 1997, Infrared Velocities of Long Period Variables: CO ${\Delta}v=3$ in Four Miras and Five SR Variables, AJ, 114, 2686 https://doi.org/10.1086/118679
  12. Hofner, S. 2008, Winds of M-Type AGB Stars Driven by Micron-Sized Grains, A&A, 491, L1 https://doi.org/10.1051/0004-6361:200810641
  13. Hofner, S. 2009, Dust Formation andWinds around Evolved Stars: The Good, the Bad and the Ugly Cases, in Cosmic Dust - Near And Far, (ed.) T. Henning, E. Grun, & J. Steinacker (Heidelberg: ASP), 414, 3
  14. Imai, H., Shibata, K. M., Sasao, T., Miyoshi, M., Kameya, O., et al. 1997, Measurement of Shifts in Line-Of-Sight Velocities of StellarWaterMasers Using VLBI, A&A, 319, L1
  15. Ishitsuka, J. K., Imai, H., Omodaka, T., Ueno, M., Kameya, O., et al. 2001, VLBI Monitoring Observations of Water Masers around the Semi-Regular Variable Star R Crateris, PASJ, 53, 1231 (I01) https://doi.org/10.1093/pasj/53.6.1231
  16. Jewell, P. R., Snyder, L. E., Walmsley, C. M., Wilson, T. L., & Gensheimer, P. D. 1991, Observational Properties of V = 1, J = 1 - 0 SiO Masers, A&A, 242, 211
  17. Kholopov, P. N., Samus, N. N., Durlevich, O. V., Kazarovets, E. V., Kireeva, N. N., & Tsvetkova, T. M. 1987, (4th ed.) The 68th Name-List of Variable Stars, General Catalogue of Variable Stars (Moscow: Nauka)
  18. Khouri, T., Waters, L. B. F.M., de Koter, A., Decin, I., Min, M., de Vries, B. L., Lombert, R., & Cox, N. L. J. 2015, Dusty wind of W Hydrae. Multi-Wavelength Modelling of the Present-Day and Recent Mass Loss, A&A, 577, 114 https://doi.org/10.1051/0004-6361/201425092
  19. Kim, J., Cho, S.-H., & Kim, S. J. 2010, Simultaneous Observations of SiO and $H_2O$ Masers toward Known Stellar $H_2O$ Maser Sources, AJ, 145, 22
  20. Kim, J., Cho, S.-H., & Kim, S. J. 2014, Statistical Studies Based on Simultaneous SiO and $H_2O$ Maser Surveys toward Evolved Stars, AJ, 147, 22
  21. Kim, J., Cho, S.-H., & Yoon, D.-H. 2016, Monitoring Observatinos of $H_2O$ and SiO Masers Toward Post-AGB Stars, JKAS, 49, 261
  22. Lebzelter, T., Kiss, L. L., & Hinkle, K. H. 2000, A Comparison of Light and Velocity Variations in Semiregular Variables, A&A, 361, 167
  23. Lekht, E. E., Mendoza-Torres, J. E., Rudnitskij, G. M., & Tolmachev, A. M. 2001, Variability of the $H_2O$ Maser Associated with the Mira Variable RS Virginis, A&A, 376, 928 https://doi.org/10.1051/0004-6361:20010967
  24. Lekht, E. E., Rudnitskij, G. M., Mendoza-Torres, J. E., & Tolmachev, A. M. 2005, Variability of the $H_2O$ Maser Associated with the M-Supergiant S Persei, A&A, 437, 127 https://doi.org/10.1051/0004-6361:20052635
  25. Lindner, R. R., Vera-Ciro, C., Murray, C. E., Stanimirovic, S., et al. 2015, Autonomous Gaussian Decomposition, ApJ, 149, 138 https://doi.org/10.1088/0004-6256/149/4/138
  26. O'Gorman, E., Vlemmings, W., Richards, A. M. S., Baudry, A., De Beck, E., et al. 2015, ALMA Observations of Anisotropic Dust Mass Loss in the Inner Circumstellar Environment of the Red Supergiant VY Canis Majoris, A&A, 573, L1 https://doi.org/10.1051/0004-6361/201425101
  27. Omodaka, T., Morimoto, M., Kawaguchi, N., Kitamura, Y., Tanaka, M., et al. 1994, The 6m mm-VLBI Telescope at Kagoshima; Japan, Astronomy with Millimeter and Submillimeter Wave Interferometry, IAU Colloq. 140, ed. M. Ishiguro & J. Welch (San Francisco: ASP), 64
  28. Pojmanski, G. 1997, The All Sky Automated Survey, Acta Astron., 47, 467
  29. Richards, A. M. S., & Yates, J. A. 1998, Maser Mapping of Dust-Driven Winds from Red Supergiants, Irish Astronomical Journal, 25, 7
  30. Rudnitskij, G. M. 2005, Monitoring of Spectral Variations of Mira-Type and Semiregular Variable Stars, Odessa Astronomical Publications, 18, 90
  31. Rudnitskij, G. M., Pashchenko, M. I., & Colom, P. 2010, Polarization Observations of Circumstellar OH Masers, Astronomy Reports, 54, 400 https://doi.org/10.1134/S1063772910050045
  32. Shintani, M., Imai, H., Ando, K., Nakashima, K., Hirota, T., et al. 2008, Statistical Properties of Stellar $H_2O$ Masers - Results of Three-Year Single-Dish Observations with the VERA Iriki Telescope, PASJ, 60, 1077 https://doi.org/10.1093/pasj/60.5.1077
  33. Sudou, H., Omodaka, T., Imai, H., Sasao, T., Takaba, H., Nishio, M., Hasegawa, W., & Nakajima, J. 2002, VLBI Observations of Water Masers in the Circumstellar Envelope of IRC+60169, PASJ, 54, 757 https://doi.org/10.1093/pasj/54.5.757
  34. Szymczak, M., & Le Squeren, A. M. 1999, A Comparison of OH and $H_2O$ Maser Properties of Mira and Semiregular Variable Stars, MNRAS, 304, 415 https://doi.org/10.1046/j.1365-8711.1999.02321.x
  35. Takaba, H., Ukita, N., Miyaji, T., & Miyoshi, M. 1994, Spectral Evolution of the $H2_O$ Maser in Late-Type Stars, PASJ, 46, 629
  36. Valdettaro, R., Palla, F., Brand, J., Cesaroni, R., Comoretto, G., et al. 2001, The Arcetri Catalog of $H_2O$ Maser Sources: Update, 2000, A&A, 368, 845 https://doi.org/10.1051/0004-6361:20000526
  37. Yoon, D.-H., Cho, S.-H., Kim, J., Yun, Y. J., & Park, Y.-S. 2014, SiO and $H_2O$ Maser Survey toward Post-Asymptotic Giant Branch and Asymptotic Giant Branch Stars, ApJS, 211, 15 https://doi.org/10.1088/0067-0049/211/1/15
  38. Winnberg, A., Engels, D., Brand, J., Baldacci, L., & Walmsley, C. M. 2008, Water Vapour Masers in Long-Period Variable Stars. I. RX Bootis and SV Pegasi, A&A, 482, 431
  39. Wood, P. R. 1979, Pulsation and Mass Loss in Mira Variables, ApJ, 227, 220 https://doi.org/10.1086/156721