On the asymmetry of selected Fraunhofer lines

Kostyk, R. I.; Orlova, T. V.

doi:10.1007/bf00160278

Cited by 12 publications

(3 citation statements)

References 2 publications

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“…This is due to a significant difference in physical conditions at different effective formation depths of each segment of the line where the bisector is measured. Early studies of the solar spectrum [7,14,29,32] established that the bisector has a typical shape similar to the letter C. The upper part of the profile near the continuum has a small blue shift due to significant contributions of radiation from intergranules in the deep layers of the photosphere. The largest blue shift occurs closer to the middle of the profile due to the predominant fraction of radiation from hot rising granules.…”

Section: Introductionmentioning

confidence: 90%

“…Öå ïî â'ÿ çà íî ç ³ñòîòíîþ â³äì³íí³ñòþ ô³çè÷ íèõ óìîâ íà ð³çíèõ åôåê òèâ íèõ ãëè áè íàõ ôîðìó âàí íÿ êîae íî¿ ä³ëÿí êè ë³í³¿, äå âèì³ðþºòüñÿ á³ñåê òîð. Ðàíí³ äîñë³äaeåííÿ ñî íÿ÷ íî ãî ñïåê òðó [7,14,29,32] âñòà íî âè ëè, ùî á³ñåê òîð ìàº òè ïî âó ôîð ìó, ñõî aeó íà ë³òå ðó «C». Âåð õíÿ ÷àñ òè íà ïðîô³ëþ ïî áëè çó êîí òè íó ó ìó ìàº íå âå ëè êå ñèíº çì³ùåí íÿ ÷å ðåç çíà÷ íèé âêëàä âèïðî -ì³íþ âàí íÿ â³ä ì³aeãðà íóë ó ãëè áî êèõ øà ðàõ ôî òîñ ôå ðè.…”

Section: âñòóïunclassified

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The line asymmetry in the spectra of the Sun and solar-type stars

Sheminova¹

2020

Kinemat. fiz. nebesnyh tel (Online)

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We have analysed the asymmetry of lines Fe I and Fe II in spectra of a solar flux using three FTS atlases and the HARPS atlas and also in spectra of 13 stars using observation data on the HARPS spectrograph. To reduce observation noise individual line bisectors of each star have been averaged. The obtained average bisectors in the stellar spectra are more or less similar to the shape C well known to the Sun. In stars with rotation velocities greater than 5 km/s the shape of the bisectors is more like /. The curvature and span of the bisectors increase with the temperature of the star. Our results confirm the known facts about strong influence of rotation velocity on the span and shape of bisectors. The average convective velocity was determined based on the span of the average bisector, which shows the largest difference between the velocity of cold falling and hot rising convective flows of the matter. It’s equal to -420 m/s for the Sun as a star. In stars, it grows from -150 to -700 m/s with an effective temperature of 4800 to 6200 K, respectively. For stars with greater surface gravity and greater metallicity, the average convective velocity decreases. It also decreases with star age and correlates with the velocity of micro and macroturbulent movements. The results of solar flux analysis showed that absolute wavelength scales in the atlases used coincide with an accuracy of about -10 m/s, except for the FTS-atlas of Hinkle et al., whose scale is shifted and depends on the wavelength. In the range from 450 to 650 nm, the scale shift of this atlas varies from -100 to -330 m/s, respectively, and it equals on average of 240 m/s. The resulting average star bisectors contain information about the fields of convective velocities and may be useful for hydrodynamic modeling of stellar atmospheres in order to study the characteristic features of surface convection.

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Section: Introductionmentioning

confidence: 90%

Section: âñòóïunclassified

The line asymmetry in the spectra of the Sun and solar-type stars

Sheminova¹

2020

Kinemat. fiz. nebesnyh tel (Online)

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“…This point may have a net shift since the average bisector is not a straight line. When the spectral lines form in solar granulation, the bisector shows a typical C shape caused by the correlations of the velocity and intensity fields (Kostik & Orlova 1977;Dravins 1982). In the penumbra the shape of the average bisector is also affected by the correlations between the velocity, intensity, and magnetic fields (see, e.g., Wiehr et al 1984;Ichimoto 1988) with the asymmetry in the same direction as the displacement.…”

Section: Velocities Of Fe I and Fe Ii Linesmentioning

confidence: 99%

Evershed flow observed in neutral and singly ionized iron lines

Khomenko

Collados

Shchukina

et al. 2015

A&A

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The amplitudes of the Evershed flow are measured using pairs of carefully selected Fe i and Fe ii spectral lines that are close in wavelength and registered simultaneously. A sunspot belonging to the NOAA 11582 group was scanned using the spectrograph of the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife). Velocities were extracted from intensity profiles using the λ-meter technique. The formation heights of the observed spectral lines were calculated using semi-empirical models of a bright and dark penumbral filament taking into account the sunspot location at the limb. Our objective is to compare azimuthally averaged amplitudes of the Evershed flow extracted from neutral and ion lines. We find measurable differences in the radial component of the flow. All five pairs of lines show the same tendency; the flow measured from the Fe i lines has an amplitude that is a few hundred m s −1 larger than that of the Fe ii lines. This tendency is preserved at all photospheric heights and radial distances in the penumbra. We discuss the possible origin of this effect.

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Solar physics at the Main Astronomical Observatory of the Ukrainian Academy of Sciences

Gurtovenko¹

1982

Sol Phys

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On the asymmetry of selected Fraunhofer lines

Cited by 12 publications

References 2 publications

The line asymmetry in the spectra of the Sun and solar-type stars

The line asymmetry in the spectra of the Sun and solar-type stars

Evershed flow observed in neutral and singly ionized iron lines

Solar physics at the Main Astronomical Observatory of the Ukrainian Academy of Sciences

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