ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE

Xu, Yan; Cao, Wenda; Ding, M. D.; Kleint, Lucia; Su, Jiangtao; Liu, Chang; Ji, Heng; Chae, Jongchul; Jing, Ju; Cho, Kyuhyoun; Cho, Kyung-Suk; Gary, Dale E.; Wang, Haimin

doi:10.3847/0004-637x/819/2/89

Cited by 45 publications

(76 citation statements)

References 33 publications

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“…Due to an anomalous (up to 25%) absorption increase in the He i 10830Å line, we identified this flare as a negative flare (Kobanov et al 2018). Such solar events are rarely observed (Henoux et al 1990;Xu et al 2016), and a study of oscillation processes related to this flare, which is the aim of the paper, is of great interest. To the best of our knowledge, for such events has been presented no observational data that includes oscillations of Doppler velocity, intensity, profile half-width, and LOS magnetic field strength.…”

Section: Introductionmentioning

confidence: 91%

Oscillations Accompanying a He i 10830 Å Negative Flare in a Solar Facula

Chelpanov¹,

Кобанов²

2018

Sol Phys

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On September 21, 2012, we carried out spectral observations of a solar facula in the Si i 10827Å, He i 10830Å, and Hα spectral lines. Later, in the process of analyzing the data, we found a small-scale flare in the middle of the time series. Due to an anomalous increase in the absorption of the He i 10830Å line, we identified this flare as a negative flare.The aim of this paper is to study the influence of the negative flare on the oscillation characteristics in the facular photosphere and chromosphere.We measured line-of-sight (LOS) velocity and intensity of all the three lines as well as half-width of the chromospheric lines. We also used SDO/HMI magnetic field data. The flare caused modulation of all the studied parameters. In the location of the negative flare, the amplitude of the oscillations increased four times on average. In the adjacent magnetic field local maxima, the chromospheric LOS velocity oscillations appreciably decreased during the flare. The facula region oscillated as a whole with a 5-minute period before the flare, and this synchronicity was disrupted after the flare. The flare changed the spectral composition of the line-of-sight magnetic field oscillations, causing an increase in the low-frequency oscillation power.

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Section: Introductionmentioning

confidence: 91%

Oscillations Accompanying a He i 10830 Å Negative Flare in a Solar Facula

Chelpanov¹,

Кобанов²

2018

Sol Phys

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“…During small solar flares, the ratio of Hα line core emission to the underlying photospheric spectrum can reach ∼2.0-4.0 (Johns- Krull et al 1997;Xu et al 2016). The ratios measured for non-flaring faculae are closer to ∼1.2 (Ahn et al 2014) and very weak flares show ratios of ∼1.1-1.6, or q f ac = 0.1 − 0.6 (Deng et al 2013).…”

Section: Facular Spectramentioning

confidence: 99%

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Cauley

Redfield

Jensen

2017

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HD 189733 b is one of the most well-studied exoplanets due to its large transit depth and host star brightness. The focus on this object has produced a number of high-cadence transit observations using high-resolution optical spectrographs. Here we present an analysis of seven full Hα transits of HD 189733 b using HARPS on the 3.6 meter La Silla telescope and HIRES on Keck I, taken over the course of nine years from 2006 to 2015. Hα transmission signals are analyzed as a function of the stellar activity level, as measured using the normalized core flux of the Ca II H and K lines. We find strong variations in the strength of the Hα transmission spectrum from epoch to epoch. However, there is no clear trend between the Ca II core emission and the strength of the in-transit Hα signal, although the transit showing the largest absorption value also occurs when the star is the most active. We present simulations of the in-transit contrast effect and find that the planet must consistently transit active latitudes with very strong facular and plage emission regions in order to reproduce the observed line strengths. We also investigate the measured velocity centroids with models of planetary rotation and show that the small line profile velocities could be due to large velocities in the upper atmosphere of the planet. Overall, we find it more likely that the measured Hα signals arise in the extended planetary atmosphere, although a better understanding of active region emission for active stars such as HD 189733 are needed.

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“…For example, in the Ca II H faculae panel in Figure 2, a act ≈ 1.0, for Hα a act ≈ 0.6, and for Na I D a act ≈ 0.8. Thus we explore a range of a act consistent with the solar case but which includes values that may be more indicative of more active stars, e.g., a act can be as high as 3.0 or 4.0 in M-class flares (Johns-Krull et al 1997;Xu et al 2016).…”

Section: Simulations Of Active Stellar Surface Transitsmentioning

confidence: 99%

The Effects of Stellar Activity on Optical High-resolution Exoplanet Transmission Spectra

Cauley

Kuckein

Redfield

et al. 2018

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Chromospherically sensitive atomic lines display different spectra in stellar active regions, spots, and the photosphere, raising the possibility that exoplanet transmission spectra are contaminated by the contrast between various portions of the stellar disk. To explore this effect, we performed transit simulations of G and K-type stars for the spectral lines Ca II K at 3933Å, Na I 5890Å, H I 6563 A (Hα), and He I 10830Å. We find that strong facular emission and large coverage fractions can contribute a non-negligible amount to transmission spectra, especially for Hα, Ca II K, and Na I D, while spots and filaments are comparatively unimportant. The amount of contamination depends strongly on the location of the active regions and the intrinsic emission strength. In particular, active regions must be concentrated along the transit chord in order to produce a consistent in-transit signal. Mean absorption signatures in Na I and Hα for example, can reach ≈ 0.2% and 0.3%, respectively, for transits of active latitudes with line emission similar in strength to moderate solar flares. Transmission spectra of planets transiting active stars, such as HD 189733, are likely contaminated by the contrast effect, although the tight constraints on active region geometry and emission strength make it unlikely that consistent in-transit signatures are due entirely to the contrast effect. He I 10830Å is not strongly affected and absorption signatures are likely diluted, rather than enhanced, by stellar activity. He I 10830Å should thus be considered a priority for probing extended atmospheres, even in the case of active stars.

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ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE

Cited by 45 publications

References 33 publications

Oscillations Accompanying a He i 10830 Å Negative Flare in a Solar Facula

Oscillations Accompanying a He i 10830 Å Negative Flare in a Solar Facula

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

The Effects of Stellar Activity on Optical High-resolution Exoplanet Transmission Spectra

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