Variable Accretion onto Protoplanet Host Star PDS 70

Thanathibodee, Thanawuth; Molina, Brandon; Calvet, Nuria; Serna, Javier; Bae, Jaehan; Reynolds, M. T.; Hernández, Jesús; Muzerolle, James; Hernández, Ramiro Franco

doi:10.3847/1538-4357/ab77c1

Cited by 36 publications

(48 citation statements)

References 62 publications

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“…Kurosawa & Romanova 2013) indeed find that both stable and unstable accretors have stochastically changing line profiles, with paradoxically a more stationary appearance of the line profile for unstable accretors. The estimate of Thanathibodee et al (2020) for the variability of Ṁ onto the PDS 70 star, 0.56 dex over the rotation cycle, is indeed consistent with these typical estimates of accretion variability for CTTSs. Time variability has also been seen in low-mass brown dwarfs, for example in the ≈47 M J , ≈1-Myr-old brown dwarf candidate DENIS 1538-1038(Nguyen-Thanh et al 2020.…”

Section: Time Variabilitysupporting

confidence: 82%

“…This wind could be dusty, with the radiation pressure playing a key role and the dust porosity and size evolving significantly while being transported by the wind (Vinković & Čemeljić 2021). Thanathibodee et al (2020) find that the mass-loss rate in the wind of PDS 70 is Ṁwind ∼ 10 −11 M yr −1 ∼ 10 −8 M J yr −1 , which might lead to a very small surface density given the large area over which it is spread. However, estimating the absorption by a disc wind in detail is well beyond the scope of this work.…”

Section: Other Possible Sources Of Extinctionmentioning

confidence: 89%

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Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

Marleau

Aoyama

Kuiper

et al. 2021

A&A

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Context. Accreting planetary-mass objects have been detected at H α, but targeted searches have mainly resulted in non-detections. Accretion tracers in the planetary-mass regime could originate from the shock itself, making them particularly susceptible to extinction by the accreting material. High-resolution (R > 50 000) spectrographs operating at H α should soon enable one to study how the incoming material shapes the line profile. Aims. We calculate how much the gas and dust accreting onto a planet reduce the H α flux from the shock at the planetary surface and how they affect the line shape. We also study the absorption-modified relationship between the H α luminosity and accretion rate. Methods. We computed the high-resolution radiative transfer of the H α line using a one-dimensional velocity–density–temperature structure for the inflowing matter in three representative accretion geometries: spherical symmetry, polar inflow, and magnetospheric accretion. For each, we explored the wide relevant ranges of the accretion rate and planet mass. We used detailed gas opacities and carefully estimated possible dust opacities. Results. At accretion rates of Ṁ ≲ 3 × 10−6 MJ yr−1, gas extinction is negligible for spherical or polar inflow and at most AH α ≲ 0.5 mag for magnetospheric accretion. Up to Ṁ ≈ 3 × 10−4 MJ yr−1, the gas contributes AH α ≲ 4 mag. This contribution decreases with mass. We estimate realistic dust opacities at H α to be κ ~ 0.01–10 cm2 g−1, which is 10–104 times lower than in the interstellar medium. Extinction flattens the LH α –Ṁ relationship, which becomes non-monotonic with a maximum luminosity LH α ~ 10−4 L⊙ towards Ṁ ≈ 10−4 MJ yr−1 for a planet mass ~10 MJ. In magnetospheric accretion, the gas can introduce features in the line profile, while the velocity gradient smears them out in other geometries. Conclusions. For a wide part of parameter space, extinction by the accreting matter should be negligible, simplifying the interpretation of observations, especially for planets in gaps. At high Ṁ, strong absorption reduces the H α flux, and some measurements can be interpreted as two Ṁ values. Highly resolved line profiles (R ~ 105) can provide (complex) constraints on the thermal and dynamical structure of the accretion flow.

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Section: Time Variabilitysupporting

confidence: 82%

Section: Other Possible Sources Of Extinctionmentioning

confidence: 89%

Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

Marleau

Aoyama

Kuiper

et al. 2021

A&A

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“…We note that this approach assumes that the photometry in the considered spectral range is dominated by continuum emission from the star and inner disk. Therefore, potential Brα emission due to accretion onto the star is ignored, but that is a reasonable assumption given the low accretion rate of (0.6-2.2) × 10 −10 M yr −1 for PDS 70 (Thanathibodee et al 2020).…”

Section: Data Processing and Calibrationmentioning

confidence: 99%

MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4–5 μm

Stolker

Marleau

Cugno

et al. 2020

A&A

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The circumstellar disk of PDS 70 hosts two forming planets, which are actively accreting gas from their environment. The physical and chemical characteristics of these planets remain ambiguous due to their unusual spectral appearance compared to more evolved objects. In this work, we report the first detection of PDS 70 b in the Brα and M′ filters with VLT/NACO, a tentative detection of PDS 70 c in Brα, and a reanalysis of archival NACO L′ and SPHERE H23 and K12 imaging data. The near side of the disk is also resolved with the Brα and M′ filters, indicating that scattered light is non-negligible at these wavelengths. The spectral energy distribution (SED) of PDS 70 b is well described by blackbody emission, for which we constrain the photospheric temperature and photospheric radius to Teff = 1193 ± 20 K and R = 3.0 ± 0.2 RJ. The relatively low bolometric luminosity, log(L∕L⊙) = −3.79 ± 0.02, in combination with the large radius, is not compatible with standard structure models of fully convective objects. With predictions from such models, and adopting a recent estimate of the accretion rate, we derive a planetary mass and radius in the range of Mp ≈ 0.5–1.5 MJ and Rp ≈ 1–2.5 RJ, independently of the age and post-formation entropy of the planet. The blackbody emission, large photospheric radius, and the discrepancy between the photospheric and planetary radius suggests that infrared observations probe an extended, dusty environment around the planet, which obscures the view on its molecular composition. Therefore, the SED is expected to trace the reprocessed radiation from the interior of the planet and/or partially from the accretion shock. The photospheric radius lies deep within the Hill sphere of the planet, which implies that PDS 70 b not only accretes gas but is also continuously replenished by dust. Finally, we derive a rough upper limit on the temperature and radius of potential excess emission from a circumplanetary disk, Teff ≲ 256 K and R ≲ 245 RJ, but we do find weak evidence that the current data favors a model with a single blackbody component.

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“…The He I infrared triplet line around 10830 Å 2 that is seen in young stars carries traces of accretion and ejection processes (e.g., Thanathibodee et al 2020;Fischer et al 2008;Edwards et al 2006). In Fig.…”

Section: Infrared Emission Linesmentioning

confidence: 99%

Star-disk interaction in the T Tauri star V2129 Ophiuchi: An evolving accretion-ejection structure

Sousa¹,

Bouvier²,

Alencar³

et al. 2021

A&A

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Context. Classical T Tauri stars are young low-mass systems still accreting material from their disks. These systems are dynamic on timescales of hours to years. The observed variability can help us infer the physical processes that occur in the circumstellar environment. Aims. In this work, we aim at understanding the dynamics of the magnetic interaction between the star and the inner accretion disk in young stellar objects. We present the case of the young stellar system V2129 Oph, which is a well-known T Tauri star with a K5 spectral type that is located in the ρ Oph star formation region at a distance of 130 ± 1 pc. Methods. We performed a time series analysis of this star using high-resolution spectroscopic data at optical wavelengths from CFHT/ESPaDOnS and ESO/HARPS and at infrared wavelengths from CFHT/SPIRou. We also obtained simultaneous photometry from REM and ASAS-SN. The new data sets allowed us to characterize the accretion-ejection structure in this system and to investigate its evolution over a timescale of a decade via comparisons to previous observational campaigns. Results. We measure radial velocity variations and recover a stellar rotation period of 6.53 days. However, we do not recover the stellar rotation period in the variability of various circumstellar lines, such as Hα and Hβ in the optical or HeI 10830 Å and Paβ in the infrared. Instead, we show that the optical and infrared line profile variations are consistent with a magnetospheric accretion scenario that shows variability with a period of about 6.0 days, shorter than the stellar rotation period. Additionally, we find a period of 8.5 days in Hα and Hβ lines, probably due to a structure located beyond the corotation radius, at a distance of ∼0.09 au. We investigate whether this could be accounted for by a wind component, twisted or multiple accretion funnel flows, or an external disturbance in the inner disk. Conclusions. We conclude that the dynamics of the accretion-ejection process can vary significantly on a timescale of just a few years in this source, presumably reflecting the evolving magnetic field topology at the stellar surface.

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Variable Accretion onto Protoplanet Host Star PDS 70

Cited by 36 publications

References 62 publications

Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4–5 μm

Star-disk interaction in the T Tauri star V2129 Ophiuchi: An evolving accretion-ejection structure

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