Using long-term optical, ultraviolet(UV) and X-ray data, we present a study of a classical T Tauri star CV Cha. The V-band light curve obtained from the All Sky Automated Survey(ASAS) shows short as well as long-term ...Using long-term optical, ultraviolet(UV) and X-ray data, we present a study of a classical T Tauri star CV Cha. The V-band light curve obtained from the All Sky Automated Survey(ASAS) shows short as well as long-term variability. The short-term variability could be due to rotational modulation of CV Cha. We derive the rotational period of 3.714 ± 0.001 d for CV Cha. UV light curves obtained from Swift also show the variations. X-ray light curves from XMM-Newton and Swift do not show any significant short as well as long-term variability. However, the light curve from Chandra appears to be variable, which could be due to the emergence of flaring activities. X-ray spectra from all observations are explained well by the single temperature plasma of 0.95 keV with X-ray luminosity of 1030.4erg s-1in the 0.5–7.5 keV energy band. It appears that variability in optical and UV bands could be due to the presence of both hot and cool spots on the surface, while X-ray emission is dominated by magnetic processes.展开更多
The results of optical spectroscopic monitoring observations of a young binary system, Z CMa, are presented in this study. Z CMa consists of a Herbig Be star and an FU Orionis object, and it shows irregular light vari...The results of optical spectroscopic monitoring observations of a young binary system, Z CMa, are presented in this study. Z CMa consists of a Herbig Be star and an FU Orionis object, and it shows irregular light variation in the quiescent phase and exploding brightening in the outburst phase. Medium-resolution spectra were obtained on 21 nights between 2015 and 2019 using the Nayuta telescope in Japan. We also used five high-resolution spectra, obtained between 2008 and 2011, with the Keck Telescope. During the outburst phase, the intensity of the He I absorption line increased with an increase in the luminosity of the system. Because the He I absorption line is a characteristic feature of an early-type star, we considered that the outbursts were caused by the Herbig Be star. The equivalent widths of the [O I] line decreased with an increase in the luminosity of the system. We claim steady mass loss at the rate of <img src="Edit_8c9ccc1e-fde4-4e49-bcde-5fae6e20252e.png" alt="" /> The intensities of the H<em>α</em> and Fe II emission lines did not change during the outbursts. However, the line intensities increased with an increase in the luminosity of the system in the quiescent phase. We consider that those lines are attributed to the FU Orionis object and the light variations in the quiescent phase were caused by the FU Orionis object.展开更多
In our previous papers we have improved the value of the orbital period of the binary Herbig Be star HD 200775 and showed that the [O I] and Si II 6347 and 6371 ?A emission lines displayed variations which correlate w...In our previous papers we have improved the value of the orbital period of the binary Herbig Be star HD 200775 and showed that the [O I] and Si II 6347 and 6371 ?A emission lines displayed variations which correlate with the orbital period. In this paper we provide evidences that other broad emission lines of metals in the spectra of HD 200775 also exhibit variability, which is probably related to the orbital cycle of the binary. Analysis was performed based on the high-resolution spectral data collected over a time span of 6 years at the Kourovka Astronomical Observatory of the Ural Federal University(Russia) and the Three College Observatory of the University of North Carolina at Greensboro(USA) as well as archival spectral data compiled since 1994. We report new data points in the radial velocity curve of the He I 5876 ?A line near the extremal values of the radial velocity.展开更多
基金the Italian CNAA and MURST (COFIN) grantsthe DST-RFBR project INT/RUS/RFBR/P271BRICS grant number DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G) for part of the present work
文摘Using long-term optical, ultraviolet(UV) and X-ray data, we present a study of a classical T Tauri star CV Cha. The V-band light curve obtained from the All Sky Automated Survey(ASAS) shows short as well as long-term variability. The short-term variability could be due to rotational modulation of CV Cha. We derive the rotational period of 3.714 ± 0.001 d for CV Cha. UV light curves obtained from Swift also show the variations. X-ray light curves from XMM-Newton and Swift do not show any significant short as well as long-term variability. However, the light curve from Chandra appears to be variable, which could be due to the emergence of flaring activities. X-ray spectra from all observations are explained well by the single temperature plasma of 0.95 keV with X-ray luminosity of 1030.4erg s-1in the 0.5–7.5 keV energy band. It appears that variability in optical and UV bands could be due to the presence of both hot and cool spots on the surface, while X-ray emission is dominated by magnetic processes.
文摘The results of optical spectroscopic monitoring observations of a young binary system, Z CMa, are presented in this study. Z CMa consists of a Herbig Be star and an FU Orionis object, and it shows irregular light variation in the quiescent phase and exploding brightening in the outburst phase. Medium-resolution spectra were obtained on 21 nights between 2015 and 2019 using the Nayuta telescope in Japan. We also used five high-resolution spectra, obtained between 2008 and 2011, with the Keck Telescope. During the outburst phase, the intensity of the He I absorption line increased with an increase in the luminosity of the system. Because the He I absorption line is a characteristic feature of an early-type star, we considered that the outbursts were caused by the Herbig Be star. The equivalent widths of the [O I] line decreased with an increase in the luminosity of the system. We claim steady mass loss at the rate of <img src="Edit_8c9ccc1e-fde4-4e49-bcde-5fae6e20252e.png" alt="" /> The intensities of the H<em>α</em> and Fe II emission lines did not change during the outbursts. However, the line intensities increased with an increase in the luminosity of the system in the quiescent phase. We consider that those lines are attributed to the FU Orionis object and the light variations in the quiescent phase were caused by the FU Orionis object.
基金supported by the Ministry of Education and Science (the basic part of theState assignment, RK No. AAAA-A17-117030310283-7)and by Act No. 211 of the Government of the Russian Federation, agreement 02.A03.21.0006
文摘In our previous papers we have improved the value of the orbital period of the binary Herbig Be star HD 200775 and showed that the [O I] and Si II 6347 and 6371 ?A emission lines displayed variations which correlate with the orbital period. In this paper we provide evidences that other broad emission lines of metals in the spectra of HD 200775 also exhibit variability, which is probably related to the orbital cycle of the binary. Analysis was performed based on the high-resolution spectral data collected over a time span of 6 years at the Kourovka Astronomical Observatory of the Ural Federal University(Russia) and the Three College Observatory of the University of North Carolina at Greensboro(USA) as well as archival spectral data compiled since 1994. We report new data points in the radial velocity curve of the He I 5876 ?A line near the extremal values of the radial velocity.
