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HIGH RESOLUTION SPECTROSCOPIC STUDY OF SYMBIOTIC STAR AG DRACONIS

  • Received : 2022.07.28
  • Accepted : 2022.08.22
  • Published : 2022.08.31
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Abstract

We observed the symbiotic star AG Dra for a total of 61 nights between April 2004 and December 2021 using the 1.8-m telescope and the high-resolution Echelle spectrograph BOES at the Bohyunsan Optical Astronomy Observatory and obtained 355 frames of spectroscopic data to investigate the variations in its spectral lines. Overnight short-term and long-term changes in prominent emission lines are examined. No short-term changes are found in the line profiles. However, the peak intensity of the Hα emission line exhibits very small variation. In the long-term period, many emission lines including He I λ5875, λ6678, λ7065 and Fe II λ5018 are found to vary reflecting the symbiotic outburst activities. It is noted that He II λ4686 and Raman-scattered O VI λ6830, λ7088 are exceptions, where no significant variations are discernible. One of the noticeable lines is the λ5018 line. Its appearance and disappearance pattern are different from other emission lines, and the line is found to appear in outburst states. The Hα and Hβ lines remain very similar in our spectroscopic monitoring campaign.

Keywords

Acknowledgement

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science & ICT (grant number: 2017R1A2B4007147). We thank the developers of the Bohyunsan Observatory Echelle Spectrograph BOES, especially Dr. Kang Min Kim who lead the project of BOES, and all staff of the Bohyunsan Optical Astronomy Observatory during the observation periods. Many thanks must be given to the anonymous referees who improve the paper a lot. We also appreciate the AAVSO whose data collection made Figure 1 possible.

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