Exploring the dimming event of RW Aurigae A through multi-epoch VLT/X-shooter spectroscopy

Koutoulaki, M.; Facchini, Stefano; Manara, C. F.; Natta, A.; Lopez, R. Garcia; Fedriani, R.; Garatti, A. Caratti o; Coffey, Deirdre; Ray, T. P.

doi:10.1051/0004-6361/201834713

Cited by 31 publications

(43 citation statements)

References 60 publications

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“…A slope in the extinction law flatter than that of the ISM and sometimes a nearly gray extinction have been reported for AA Tau, the prototype of dippers, by Bouvier et al (1999Bouvier et al ( , 2003 and for the dips of LkCa 15 by Alencar et al (2018). Koutoulaki et al (2019) were able to reproduce the extinction curve observed during a dimming event of RW Aur observed with X-shooter, which is much flatter than the ISM, with a power-law distribution of the grain size from a minimum value a min = 0.1 µm to a maximum a max = 150 µm, including the scattering in the effective optical depth. Neglecting the scattering would require even larger grains.…”

Section: Discussionmentioning

confidence: 71%

“…In Fig. 3 we overplot the extinction model by Koutoulaki et al (2019), scaled to the observed extinction in the g band. We note that this curve is flatter than our data, suggesting different conditions for the region that causes the dips in ISO-ChaI 52, as is also expected based on the much deeper dips of RW Aur (2−3 mag in the V band) compared to 0.3 mag dips in r for ISO-ChaI 52.…”

Section: Discussionmentioning

confidence: 99%

“…The smaller dips might be Cardelli et al (1989). The dotted black line is the model by Koutoulaki et al (2019). The dashed line represents our two-component model (Eq.…”

Section: Rem Light Curvesmentioning

confidence: 99%

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ISO-ChaI 52: a weakly accreting young stellar object with a dipper light curve

Frasca

Manara

Alcalá

et al. 2020

A&A

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We report the discovery of periodic dips in the multiband light curve of ISO-ChaI 52, a young stellar object in the Chamaeleon I dark cloud. This is one of the peculiar objects that display very low or negligible accretion in their UV continuum and spectral lines, although they present a remarkable infrared excess emission characteristic of optically thick circumstellar disks. We have analyzed a spectrum obtained at the Very Large Telescope with the X-shooter spectrograph with the tool ROTFIT to determine the stellar parameters. The latter, along with photometry from our campaign with the Rapid Eye Mount telescope and from the literature, have allowed us to model the spectral energy distribution and to estimate the size and temperature of the inner and outer disk. Based on the rotational period of the star-disk system of 3.45 days, we estimate a disk inclination of 36°. The depth of the dips in different bands has been used to gain information about the occulting material. A single extinction law is not able to fit the observed behavior, while a two-component model of a disk warp composed of a dense region with a gray extinction and an upper layer with an extinction as in the interstellar medium provides a better fit to the data.

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Section: Discussionmentioning

confidence: 71%

Section: Discussionmentioning

confidence: 99%

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ISO-ChaI 52: a weakly accreting young stellar object with a dipper light curve

Frasca

Manara

Alcalá

et al. 2020

A&A

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“…We use a CO local thermodynamic equilibrium (LTE) model (see Koutoulaki et al 2019, for a detailed description of model, code and error estimates) to derive the main physical parameters of the gas. We model the CO bandhead profiles with a single ring in LTE with four free parameters: temperature T CO , column Notes.…”

Section: Co Physical Parametersmentioning

confidence: 99%

The GRAVITY young stellar object survey

Garatti¹,

Fedriani²,

Lopez³

et al. 2020

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Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3–2.4 μm). Methods. We present the first GRAVITY/VLTI observations at high spectral (ℛ = 4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS 2. Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (≤8°). Our best ellipsoid model provides a disc inclination of 34° ±1°, a disc major axis position angle (PA) of 166° ± 1°, and a disc diameter of 3.99 ± 0.09 mas (or 1.69 ± 0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74±0.070.08 mas (1.16 ± 0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M* ∼ 14.7−3.6+2 M⊙ by combining our interferometric and spectral modelling results.

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“…been proved to trace gas in Keplerian rotation very close to the star, very likely in the disc itself (Carr 1989;Kraus et al 2000;Bik & Thi 2004;Tatulli et al 2008;GRAVITY Collaboration 2020). By model-fitting the line profile of the CO bandhead emission obtained with high spectral resolution observations, several authors showed that the emission comes from a relatively warm (T ∼ 2000-5000 K) and dense gas (N CO ∼ 10 20 −10 22 cm −2 ) in Keplerian rotation (Carr 1989;Najita et al 1996;Ilee et al 2014;Koutoulaki et al 2019). However, this information has so far not been used to further constrain the physical, chemical, and thermal processes occurring in the inner disc.…”

Section: Introductionmentioning

confidence: 99%

The GRAVITY young stellar object survey

Koutoulaki

Lopez²,

Natta³

et al. 2021

A&A

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Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 μm, most likely originating in the innermost regions of a circumstellar disc. Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc. Methods. We used the second-generation Very Large Telescope Interferometer instrument GRAVITY to spatially resolve the continuum and the CO overtone emission. We obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases as a function of wavelength. We used a simple local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements. Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of ~10.58 ± 2.65R⊙. The K-band continuum emission from the disc is inclined by 63° ± 1°, with a position angle of 116° ± 1°, and 4 ± 0.8 mas (0.5 ± 0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted within the dust-sublimation radius. By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot (T = 1900–2800 K) and dense (NCO = (0.9–9) × 1021 cm−2) gas. The analysis of the CO line displacement with respect to the continuum allows us to infer that the CO is emitted from a region 0.10 ± 0.02 au across, well within the dust-sublimation radius. The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc. Conclusions. Our spatially resolved interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost disc regions, that can compute the properties of the dust-free inner disc, are therefore required.

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Exploring the dimming event of RW Aurigae A through multi-epoch VLT/X-shooter spectroscopy

Cited by 31 publications

References 60 publications

ISO-ChaI 52: a weakly accreting young stellar object with a dipper light curve

ISO-ChaI 52: a weakly accreting young stellar object with a dipper light curve

The GRAVITY young stellar object survey

The GRAVITY young stellar object survey

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