• 천문학논총
• /
• 제37권2호
• /
• pp.13-31
• /
• 2022

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.

• 한국지구과학회지
• /
• 제38권1호
• /
• pp.1-10
• /
• 2017

공생별 AG Peg는 적색거성(GS)과 백색왜성(WD)으로 구성된 성운으로 둘러싸인 쌍성계이다. AG Peg의 분광자료는 1998년, 2001년, 그리고 2002년의 세 시기에 미국 Lick 천문대에서 관측한 자료로 HI 발머 방출선 자료를 분석하였다. AG Peg의 선세기와 폭은 각 시기에 따라 변하는데, $H{\alpha}$와 $H{\beta}$ 선에서 모두 청색편이, 적색편이, 넓은 폭 성분이 나타났다. 가스 성운의 운동학적 특성을 보여주는 방출선은 WD주변에 형성된 강착원반의 반경이 매우 큼을 보여준다. 관측자의 시선 방향을 고려하면, 1998년 관측은 AG Peg의 GS와 WD가 나란히 하늘에 있는 반면, 2002년에는 WD가 GS의 전면에, 2001년에는 WD가 GS의 뒷면에 위치하였다. 이러한 상대적인 위치와 분광선의 변화를 고려하여, 우리는 GS에서 WD로의 가스유입이 지속적으로 이루어지고, 그 결과 형성된 두꺼운 원반의 회전이 관측된 분광선 윤곽의 형성을 가져온 것으로 결론지었다.

• 한국지구과학회지
• /
• 제35권5호
• /
• pp.313-323
• /
• 2014

We secured the high dispersion spectra of the symbiotic star CI Cyg. The HI, HeI, and HeII line profiles were analyzed using the relatively long exposure data including 1800 sec (Sep. 12, 1998, phase=0.90), 3600 sec (Aug. 12, 2002, ${\phi}=0.47$), and 1800 sec (Oct. 21, 2009, ${\phi}=0.54$). Although a minor outburst was reported in 2008, our three observation periods were generally known to be quiescent in earlier photometric studies. With the help of hydrodynamic simulations, we identified the two emission zones responsible for the blue- and red-shifted line components: (a) an accretion disk around a hot white dwarf star which consists of the outer cool HeI emission zone and the inner hot HeII emission part, and (b) a high density zone near the inner Lagrangian point responsible for the HeI line flux variation and the broadening of its line profile. The HeII line fluxes indicate that the HeII emission zone of the accretion disk is relatively stable, implying a constant gas inflow from the giant star throughout the quiescent period. The 2002 HeI data showed that the notable mass flow activity through the inner Lagrangian point occurred during this period and its flux intensity became strongest, whereas the HeII line width in the same period indicates that its flow activity forced the accretion disk to expand. The [OIII] lines were observed in 1998 but not detected in 2002 and 2009, implying the disappearance of the low density zone. Based on our kinematical studies upon the line profiles, we conclude that CI Cyg was stable in 1998 among the three observation periods selected in this research.

• 천문학회보
• /
• 제24권2호
• /
• pp.103-103
• /
• 1999

• 천문학회보
• /
• 제25권1호
• /
• pp.25-25
• /
• 2000

• 천문학회지
• /
• 제41권3호
• /
• pp.49-58
• /
• 2008

Resonance doublets including O VI 1032, 1038, NV 1239, 1243 and C IV 1548, 1551 constitute prominent emission lines in symbiotic stars and planetary nebulae. Spectroscopic studies of symbiotic stars and planetary nebulae from UV space telescopes show various line ratios of these doublets deviating from the theoretical ratio of 2:1. Using a Monte Carlo technique, we investigate the collisional de-excitation effect in these emission nebulae. We consider an emission nebula around the hot component of a symbiotic star characterized by the collisional de-excitation probability $p_{coll}\;{\sim}\;10^{-3}\;-\;10^{-4}$ per each resonance scattering, and the line center optical depths for major resonance doublets in the range ${\tau}_0\;{\sim}\;10^2\;-\;10^5$. We find that various line ratios are obtained when the product $p_{coll}{\tau}_0$ is of order unity. Our Monte Carlo calculations show that the flux ratio can be approximately fitted by a linear function of ${\log}{\tau}_0$ when ${\tau}_0p_{coll}\;{\sim}\;1$. It is briefly discussed that this corresponds to the range relevant to the emission nebulae of symbiotic stars.

• 천문학회보
• /
• 제40권1호
• /
• pp.90.2-90.2
• /
• 2015

We present the high-resolution spectrum of the S-type symbiotic star V455 Sco obtained with the Dupont telescope in 2014 June. We note that the Raman-scattered O VI ${\lambda}1032$ at $6825{\AA}$ exhibits a triple-peak profile. Adopting an accretion disk model with an additional contribution from a collimated bipolar outflow, we attempt to fit the profile. We propose that the blue and central peaks are formed via Raman-scattering of O VI line photons from the accretion flow and that the bipolar flow is responsible for the remaining red peak. It is also noted that V455 Sco exhibits the Raman-scattered He II features blueward of $H{\alpha}$ and $H{\beta}$.

• 천문학회지
• /
• 제42권4호
• /
• pp.93-103
• /
• 2009

This article reports the spectral behavior of CH Cygni, using data obtained in October 2005 and June 2006. In these epochs, CH Cygni showed emission lines of H I, Fe II, [Fe II], [O III], [N II], [Ne III] and [S II]. Many of these lines were more enhanced since 2004. The underlying M-type spectrum was removed to get the intrinsic emission profile, and the resulting profiles were deconvoluted into several Gaussian components. Also, the radial velocities for all the lines that appeared in these spectra of CH Cygni were measured. The resultant lines were compared with each other and with those obtained in 2004; the findings are explained in terms of an accretion disk and jets.

• 천문학회보
• /
• 제39권2호
• /
• pp.88.2-88.2
• /
• 2014

The symbiotic star V1016 Cygni shows the Raman scattered O VI features at $6825{\AA}$ and $7088{\AA}$. These are formed through inelastic scattering of O VI 1032, 1038 by atomic hydrogen. They exhibit characteristic double peak profiles with a stronger red peak, which is explained by the accretion flow around the white dwarf. In addition, the two Raman features have different profiles in such a way that the blue part of the Raman 7088 feature is relatively more suppressed than the Raman 6825 counterpart. We produced the Doppler maps of the two Raman features in order to trace the origin of the disparate profiles. We conclude that the profile difference is due to various O VI 1032 to O VI 1038 flux ratios in the accretion region. This is consistent with the picture where the slow stellar wind from the giant interacts with the accretion flow around the white dwarf.

• 천문학회보
• /
• 제39권1호
• /
• pp.83.2-83.2
• /
• 2014

We present the two high resolution spectra of the symbiotic star V1016 Cygni obtained with the Bohyunsan Optical Echelle Spectrograph in 2003 and 2005, from which we note the existence of the broad emission feature at 4881 ${\AA}$. We propose that this broad feature is formed from Raman scattering of Ne $VII{\lambda}973$ by atomic hydrogen. Thus far, the detection of Raman scattered lines by atomic hydrogen is limited to O $VI{\lambda\lambda}1032$, 1038 and He $II{\lambda\lambda}940$, 972 and 1025. We perform Monte Carlo simulations to fit the Raman scattered Ne $VII{\lambda}4881$ to investigate the basic spectroscopic properties concerning Ne $VII{\lambda}973$.