Formation of Hydrogen Emission Lines in the Magnetospheres of Young Stars

Dmitriev, D. V.; Гринин, В. П.; Katysheva, N. A.

doi:10.1134/s1063773719050013

Cited by 12 publications

(11 citation statements)

References 19 publications

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“…At this point, our interpretation is that fainter and brighter M magnitudes, which cause the division between blue and red stars in Figs. 1, 3, and 4, correspond to stars with fainter and stronger Hβ emission lines, which in turn are slow and fast rotators (Dmitriev et al 2019). Furthermore, the difference derived between M and T 1 magnitudes of blue and red stars (−0.26 ± 0.07 mag) confirms the correlation found by Fang et al (2018) contribution of Hβ to the M magnitudes explains the eMSTO observed by Piatti & Cole (2017) in the M versus C − M CMD (their Fig.…”

Section: Analysis and Discussionsupporting

confidence: 77%

Multiple populations of Hβ emission line stars in the Large Magellanic Cloud cluster NGC 1971

Piatti

2020

A&A

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We revisited the young Large Magellanic Cloud star cluster NGC 1971 with the aim of providing additional clues to our understanding of its observed extended main-sequence turnoff (eMSTO), a feature commonly seen in young star clusters that has recently been argued to be caused by a real age spread similar to the cluster age (∼160 Myr). We combined accurate Washington and Strömgren photometry of stars with high membership probability to explore the nature of this eMSTO. From different ad hoc defined pseudo-colors, we found that bluer and redder stars distributed throughout the eMSTO do not show any inhomogeneities of light- and heavy-element abundances. These blue and red stars are split into two clearly different groups only when the Washington M magnitudes are employed, which delimites the number of spectral features that cause the appearance of the eMSTO. We speculate that Be stars populate the eMSTO of NGC 1971 because (i) Hβ contributes to the M passband, (ii) Hβ emissions are common features of Be stars, and (iii) the Washington M and T1 magnitudes are tightly correlated; the latter measuring the observed contribution of Hα emission line in Be stars, which is in turn correlated with Hβ emissions. This is the first observational result to our knowledge that indicates that Hβ emissions are the origin of eMSTOs observed in young star clusters. Our results certainly open new possibilities of studying eMSTO from photometric systems with passbands centered at features commonly seen in Be stars.

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Section: Analysis and Discussionsupporting

confidence: 77%

Multiple populations of Hβ emission line stars in the Large Magellanic Cloud cluster NGC 1971

Piatti

2020

A&A

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“…5. The densities indicated by these best fits appear consistent with predictions of accretion stream models (Hartmann et al 1994;Muzerolle et al 2001;Dmitriev et al 2019) and other observational studies that compare hydrogen line strengths to predictions of the Kwan & Fischer (2011) grid to infer densities of accretion columns (e.g., Edwards et al 2013;Rigliaco et al 2015;Antoniucci et al 2017). Taken together, these studies support a picture where the density increases along typical CTTS accretion streams from n H ∼ 10 9.6 (as indicated by the highest-opacity Balmer decrements; Antoniucci et al 2017) to n H ∼ 10 11 (as traced by the higher-opacity Paschen and Pfund lines; Edwards et al 2013;Rigliaco et al 2015;Antoniucci et al 2017), and reach values as high as n H ∼ 10 12 for the densest regions of the most heavily accreting systems, as revealed by the lowestopacity Brackett decrements reported here.…”

Section: Discussionsupporting

confidence: 77%

“… see their Figure 16). Computational advances have also allowed significantly more complex radiative transfer methods to compute emergent line profiles (see, e.g., Kurosawa et al 2011;Esau et al 2014; Dmitriev et al 2019;Wilson et al 2022), and point to more complex geometries than implied in a simple dipole model (e.g., Romanova et al 2003Romanova et al , 2008Ingleby et al 2013). Nonetheless, the formalism used by Hartmann et al (1994) and Muzerolle et al (2001) appears sufficient to describe the density and temperature structure of the accreting material in even nondipolar flows and provides significant explanatory power for modern observations.…”

Section: Accretion Physicsmentioning

confidence: 99%

Pre-main-sequence Brackett Emitters in the APOGEE DR17 Catalog: Line Strengths and Physical Properties of Accretion Columns

Campbell

Khilfeh

Covey

et al. 2022

ApJ

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Very young (t ≲ 10 Myr) stars possess strong magnetic fields that channel ionized gas from the interiors of their circumstellar disks to the surface of the star. Upon impacting the stellar surface, the shocked gas recombines and emits hydrogen spectral lines. To characterize the density and temperature of the gas within these accretion streams, we measure equivalent widths of Brackett (Br) 11–20 emission lines detected in 1101 APOGEE spectra of 326 likely pre-main-sequence accretors. For sources with multiple observations, we measure median epoch-to-epoch line strength variations of 10% in Br11 and 20% in Br20. We also fit the measured line ratios to predictions of radiative transfer models by Kwan & Fischer. We find characteristic best-fit electron densities of n e = 1011–1012 cm−3, and excitation temperatures that are inversely correlated with electron density (from T ∼ 5000 K for n e ∼ 1012 cm−3 to T ∼ 12,500 K at n e ∼ 1011 cm−3). These physical parameters are in good agreement with predictions from modeling of accretion streams that account for the hydrodynamics and radiative transfer within the accretion stream. We also present a supplementary catalog of line measurements from 9733 spectra of 4255 Brackett emission-line sources in the APOGEE Data Release 17 data set.

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“…Models of the disk wind and magnetospheric accretion were used to calculate spectral line profiles (see, e.g., Kurosawa et al, 2011;Dmitriev et al, 2019). A comparison of the calculated profiles with the observed ones allows us to ascertain parameters of models and estimate the mass loss rate.…”

Section: Wind and Circumstellar Dustmentioning

confidence: 99%

Classical T Tauri stars: accretion, wind, dust

Petrov

2021

Acta Astrophys. Tau.

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Classical T Tauri stars (CTTS) are at the early evolutionary stage when the processes of planet formation take place in the surrounding accretion disks. Most of the observed activity in CTTS is due to magnetospheric accretion and wind flows. Observations of the accreting gas flows and appearance of the line-dependent veiling of the photospheric spectrum in CTTS are considered. Evidence for the dusty wind causing the observed irregular variability of CTTS is presented. Photometric and spectroscopic monitoring of two CTTS, RY Tau and SU Aur, has been carried out atthe Crimean Astrophysical Observatory since 2013 aimed at studying the dynamics of accretion and wind flows on time scales from days to years. The observed variations in the dynamical parameters may be caused by changes in the accretion rate and in the global magnetic fields of CTTS.

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Formation of Hydrogen Emission Lines in the Magnetospheres of Young Stars

Cited by 12 publications

References 19 publications

Multiple populations of Hβ emission line stars in the Large Magellanic Cloud cluster NGC 1971

Multiple populations of Hβ emission line stars in the Large Magellanic Cloud cluster NGC 1971

Pre-main-sequence Brackett Emitters in the APOGEE DR17 Catalog: Line Strengths and Physical Properties of Accretion Columns

Classical T Tauri stars: accretion, wind, dust

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