Constraining Temperature and Density of Accretion Flows in T Tauri Stars from Brackett Line Ratios

Gutiérrez, Miguel; Catlett, Victoria; Tofflemire, Benjamin M.; Mace, Gregory N.; Kraus, Adam L.

doi:10.3847/2515-5172/ab6738

Cited by 2 publications

(2 citation statements)

References 12 publications

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“…We thank R. van Boekel, M. The work of Hummer & Storey (1987) and Storey & Hummer (1995) is often used to analyze accretion line intensities or their ratios in the stellar context (e.g., Kóspál et al 2011;A . Antoniucci et al 2017;Gutiérrez et al 2020;see Section 4.3 of Rigliaco et al 2015), and was recently used by Szulágyi & Ercolano (2020) for the planetary case. Storey & Hummer (1995) assume an equilibrium distribution of electrons.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Spectral appearance of the planetary-surface accretion shock: Global spectra and hydrogen-line profiles and fluxes

Aoyama,

Marleau,

Mordasini

et al. 2020

Preprint

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Hydrogen-line emission, thought to come from an accretion shock, has recently been observed at planetarymass objects, and current and upcoming dedicated instruments should reveal many more sources. Previous work predicted the shock spectrum in the case of a shock on the circumplanetary disc. However no extensive investigation has been done on the planet-surface shock. Our main goals are to calculate the global spectral energy distribution (SED) of an accreting planet by combining our model emission spectra with photospheric SEDs, and to predict the line-integrated flux for different hydrogen lines, focusing on H 𝛼 but including also H 𝛽, Pa 𝛼, Pa 𝛽, Pa 𝛾, Br 𝛼, and Br 𝛾. We apply our non-equilibrium emission calculations to the surface accretion shock for the relevant large parameter space of accretion rate 𝑀 and mass 𝑀 p . In contrast to our previous model, fits to formation calculations provide radii and effective temperatures. We do not consider extinction by the preshock material in this work. We find that the H 𝛼 line luminosity increases monotonically with 𝑀 and 𝑀 p , ranging from 10 −8 to 10 −4 𝐿 , depending mostly on the accretion rate and weakly on the mass for the relevant range of parameters. We apply the result to the observed planets around PDS 70 and demonstrate that the estimated accretion rate is consistent with previous studies. The Lyman, Balmer, and Paschen continua can be visible above the photosphere. The H 𝛽 line ranges between 0.1 and ≈ 1 times the H 𝛼 flux, whereas other lines are weaker (∼ 0.001-0.1). Based on spectroscopic observations, a shock on the planetary surface and on the CPD surface can be distinguished at very high spectral resolution. The planet surface shock however likely dominates in total intensity if both are present. These predictions of the luminosity in H 𝛼 and other lines serve as a baseline prediction or conversely as a tool for interpreting observations of accreting planets.

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Section: Acknowledgmentsmentioning

confidence: 99%

Spectral appearance of the planetary-surface accretion shock: Global spectra and hydrogen-line profiles and fluxes

Aoyama,

Marleau,

Mordasini

et al. 2020

Preprint

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show abstract

“…However, other H lines, both higher-level lines in the Balmer series, as well as in other series, can also often be observed in emission in particularly active accretors. Through using multiple transitions it is possible to determine the properties of the infalling gas, such as its temperature and density (Kwan & Fischer 2011;Antoniucci et al 2017;Gutiérrez et al 2020). In turn, the bulk census of sources for which these parameters are known yields better constraints on the accretion models of YSOs.…”

Section: Introductionmentioning

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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Constraining Temperature and Density of Accretion Flows in T Tauri Stars from Brackett Line Ratios

Cited by 2 publications

References 12 publications

Spectral appearance of the planetary-surface accretion shock: Global spectra and hydrogen-line profiles and fluxes

Spectral appearance of the planetary-surface accretion shock: Global spectra and hydrogen-line profiles and fluxes

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

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