Warm Gas in the Inner Disks around Young Intermediate‐Mass Stars

Brittain, S.; Simon, Theodore; Najita, J.; Rettig, T. W.

doi:10.1086/511255

Cited by 126 publications

(229 citation statements)

References 80 publications

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“…This makes the stellar accretion rate inferred from the Hα emission, 10 −8 M ☉ yr −1 , surprising (Mendigutía et al 2017b). One solution to this puzzle comes from the fact that HD141569 is rotating near its break-up velocity and the H I emission is double peaked (Brittain et al 2007). This situation is consistent with a picture of the H I emission arising from a decretion disk rather than an accretion disk.…”

Section: Appendix D Comment On Individual Systemsmentioning

confidence: 99%

Spiral Arms in Disks: Planets or Gravitational Instability?

Dong

Najita

Brittain

2018

ApJ

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Spiral arm structures seen in scattered-light observations of protoplanetary disks can potentially serve as signposts of planetary companions. They can also lend unique insights into disk masses, which are critical in setting the mass budget for planet formation but are difficult to determine directly. A surprisingly high fraction of disks that have been well studied in scattered light have spiral arms of some kind (8/29), as do a high fraction (6/11) of wellstudied Herbig intermediate-mass stars (i.e., Herbig stars >1.5 M e ). Here we explore the origin of spiral arms in Herbig systems by studying their occurrence rates, disk properties, and stellar accretion rates. We find that two-arm spirals are more common in disks surrounding Herbig intermediate-mass stars than are directly imaged giant planet companions to mature A and B stars. If two-arm spirals are produced by such giant planets, this discrepancy suggests that giant planets are much fainter than predicted by hot-start models. In addition, the high stellar accretion rates of Herbig stars, if sustained over a reasonable fraction of their lifetimes, suggest that disk masses are much larger than inferred from their submillimeter continuum emission. As a result, gravitational instability is a possible explanation for multiarm spirals. Future observations can lend insights into the issues raised here.

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Section: Appendix D Comment On Individual Systemsmentioning

confidence: 99%

Spiral Arms in Disks: Planets or Gravitational Instability?

Dong

Najita

Brittain

2018

ApJ

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“…The UV pumping requires considerable UV flux from the central star, which is a characteristic of Herbig Ae/Be stars rather than smaller T Tauri stars. Considering that the CO may be excited up to to 10 AU by UV fluorescence (Brittain et al 2007(Brittain et al , 2009 in Hebig Ae/Be stars, planet orbiting at larger distances than 2 AU may be also detectable by CO ro-vibrational line profile distortions.…”

Section: Discussionmentioning

confidence: 99%

Detectability of giant planets in protoplanetary disks by CO emission lines

Regály

Sándor

Dullemond

et al. 2010

A&A

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Context. Planets are thought to form in protoplanetary accretion disks around young stars. Detecting a giant planet still embedded in a protoplanetary disk would be very important and give observational constraints on the planet-formation process. However, detecting these planets with the radial velocity technique is problematic owing to the strong stellar activity of these young objects. Aims. We intend to provide an indirect method to detect Jovian planets by studying near infrared emission spectra originating in the protoplanetary disks around T Tauri stars. Our idea is to investigate whether a massive planet could induce any observable effect on the spectral lines emerging in the disks atmosphere. As a tracer molecule we propose CO, which is excited in the ro-vibrational fundamental band in the disk atmosphere to a distance of ∼2−3 AU (depending on the stellar mass) where terrestrial planets are thought to form. Methods. We developed a semi-analytical model to calculate synthetic molecular spectral line profiles in a protoplanetary disk using a double layer disk model heated on the outside by irradiation by the central star and in the midplane by viscous dissipation due to accretion. 2D gas dynamics were incorporated in the calculation of synthetic spectral lines. The motions of gas parcels were calculated by the publicly available hydrodynamical code FARGO which was developed to study planet-disk interactions. Results. We demonstrate that a massive planet embedded in a protoplanetary disk strongly influences the originally circular Keplerian gas dynamics. The perturbed motion of the gas can be detected by comparing the CO line profiles in emission, which emerge from planet-bearing to those of planet-free disk models. The planet signal has two major characteristics: a permanent line profile asymmetry, and short timescale variability correlated with the orbital phase of the giant planet. We have found that the strength of the asymmetry depends on the physical parameters of the star-planet-disk system, such as the disk inclination angle, the planetary and stellar masses, the orbital distance, and the size of the disk inner cavity. The permanent line profile asymmetry is caused by a disk in an eccentric state in the gap opened by the giant planet. However, the variable component is a consequence of the local dynamical perturbation by the orbiting giant planet. We show that a forming giant planet, still embedded in the protoplanetary disk, can be detected using contemporary or future high-resolution near-IR spectrographs like VLT/CRIRES and ELT/METIS.

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“…The bands are rotationally excited up to high J (>30), resulting in a T rot between 900 and 2500 K. The rotational temperature is much lower for 13 CO at ∼250 K . UV fluorescence can cause super-thermal level populations, as observed (Brittain et al 2007) and modelled (Thi et al 2013) in UV-bright HAEBEs, where T vib > 5000 K, and in TTS (Bast et al 2011;Brown et al 2013). While some HAEBEs have CO extending to the dust sublimation radius (Salyk et al 2011), others have evidence of significant inner disc gas clearing (Goto et al 2006;Brittain et al 2007;Pontoppidan et al 2008;van der Plas et al 2009).…”

Section: Introductionmentioning

confidence: 90%

“…The fundamental ro-vibrational CO band (∆v = 1) at 4.7 µm traces warm (T > 100 K) gas in the terrestrial planet-forming region (0.1-10 AU). This band is often observed in HAEBEs (e.g., Blake & Boogert 2004;Brittain et al 2007) and in TTS (e.g., Najita et al 2003;Salyk et al 2011). The bands are rotationally excited up to high J (>30), resulting in a T rot between 900 and 2500 K. The rotational temperature is much lower for 13 CO at ∼250 K .…”

Section: Introductionmentioning

confidence: 92%

DIGIT survey of far-infrared lines from protoplanetary discs

Meeus

Salyk

Bruderer

et al. 2013

A&A

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CO is an important component of a protoplanetary disc as it is one of the most abundant gas phase species. Furthermore, observations of CO transitions can be used as a diagnostic of the gas, tracing conditions in both the inner and outer disc. We present Herschel/PACS spectroscopy of a sample of 22 Herbig Ae/Be (HAEBEs) and eight T Tauri stars (TTS), covering the pure rotational CO transitions from J = 14 → 13 up to J = 49 → 48. CO is detected in only five HAEBEs, namely AB Aur, HD 36112, HD 97048, HD 100546, and IRS 48, and in four TTS, namely AS 205, S CrA, RU Lup, and DG Tau. The highest transition detected is J = 36 → 35 with E up of 3669 K, seen in HD 100546 and DG Tau. We construct rotational diagrams for the discs with at least three CO detections to derive T rot and find average temperatures of 270 K for the HAEBEs and 485 K for the TTS. The HD 100546 star requires an extra temperature component at T rot ∼ 900-1000 K, suggesting a range of temperatures in its disc atmosphere, which is consistent with thermo-chemical disc models. In HAEBEs, the objects with CO detections all have flared discs in which the gas and dust are thermally decoupled. We use a small model grid to analyse our observations and find that an increased amount of flaring means higher line flux, as it increases the mass in warm gas. CO is not detected in our flat discs as the emission is below the detection limit. We find that HAEBE sources with CO detections have high L UV and strong PAH emission, which is again connected to the heating of the gas. In TTS, the objects with CO detections are all sources with evidence of a disc wind or outflow. For both groups of objects, sources with CO detections generally have high UV luminosity (either stellar in HAEBEs or due to accretion in TTS), but this is not a sufficient condition for the detection of the far-IR CO lines.

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Warm Gas in the Inner Disks around Young Intermediate‐Mass Stars

Cited by 126 publications

References 80 publications

Spiral Arms in Disks: Planets or Gravitational Instability?

Spiral Arms in Disks: Planets or Gravitational Instability?

Detectability of giant planets in protoplanetary disks by CO emission lines

DIGIT survey of far-infrared lines from protoplanetary discs

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