A UV-to-NIR Study of Molecular Gas in the Dust Cavity around RY Lupi

Arulanantham, Nicole; Hoadley, Keri; Manara, C. F.; Schneider, P. C.; Alcalá, J. M.; Banzatti, Andrea; Günther, H. M.; Miotello, A.; Marel, Nienke van der; Dishoeck, E. F. van; Walsh, Catherine; Williams, Jonathan P.

doi:10.3847/1538-4357/aaaf65

Cited by 19 publications

(21 citation statements)

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“…The fact that MY Lup shows up as a Class II disc for the gas properties is in line with other results from X-Shooter (e.g. Manara et al 2014) and HST observations (see the case of RY Lup in Arulanantham et al 2018, but also other objects in Hoadley et al 2015), and in many cases the gas is clearly present in the large dust cavities detected by ALMA (Miotello et al 2017;van der Marel et al 2018, and references therein). We also note that recent studies Alcalá et al 2014;Manara et al 2017a;Alcalá et al 2017;van der Marel et al 2018) find no substantial differences among the stellar and accretion properties of both primordial and transition discs (but see also Najita et al 2007Najita et al , 2015, for a different result), with the exception that the dusty transition discs with large cavities (r cav >15 AU) in Lupus tend to be more massive than the Class II disc systems (van der Marel et al 2018).…”

Section: The My Lup Discsupporting

confidence: 91%

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HST spectra reveal accretion in MY Lupi

Alcalá

Manara

Schneider

et al. 2019

A&A

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The mass accretion rate is a crucial parameter for the study of the evolution of accretion discs around young lowmass stellar and substellar objects (YSOs). We revisit the case of MY Lup, an object where VLT/X-Shooter data suggested a negligible mass accretion rate, and show it to be accreting on a level similar to other Class II YSOs in Lupus based on Hubble Space Telescope (HST) observations. In our HST-Cosmic Origins Spectrograph (HST-COS) and -Space Telescope Imaging Spectrograph (HST-STIS) spectra, we find many emission lines, as well as substantial far-ultraviolet (FUV) continuum excess emission, which can be ascribed to active accretion. The total luminosity of the C iv λ1549Å doublet is 4.1×10 −4 L . Using scalings between accretion luminosity, Lacc, and C iv luminosity from the literature, we derive Lacc∼2×10 −1 L , which is more than an order of magnitude higher than the upper limit estimated from the X-Shooter observations. We discuss possible reasons for the X-Shooter-HST discrepancy, the most plausible being that the low contrast between the continuum excess emission and the photospheric+chromospheric emission at optical wavelengths in MY Lup hampered detection of excess emission. The luminosity of the FUV continuum and C iv lines, strong H2 fluorescence, and a "1600 A Bump" place MY Lup in the class of accreting objects with gas-rich discs. So far, MY Lup is the only peculiar case in which a significant difference between the HST and X-ShooterṀacc estimates exists that is not ascribable to variability. The mass accretion rate inferred from the revisited Lacc estimate isṀacc ∼ 1( +1.5 −0.5 )×10 −8 M yr −1 . This value is consistent with the typical value derived for accreting YSOs of similar mass in Lupus and points to less clearing of the inner disc than indicated by near-and mid-infrared observations. This is confirmed by Atacama Large Millimeter Array (ALMA) data, which show that the gaps and rings seen in the sub-millimetre are relatively shallow.

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Section: The My Lup Discsupporting

confidence: 91%

“…The data processing has been done in the same way as described in Arulanantham et al (2018). Briefly, individual flux-calibrated spectra generated by the COS pipeline are coadded using a cross-correlation algorithm (Danforth et al 2010) that has been optimised for emission line sources (e.g.…”

Section: Observations and Data Processingmentioning

confidence: 99%

HST spectra reveal accretion in MY Lupi

Alcalá

Manara

Schneider

et al. 2019

A&A

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“…A ring of dust is resolved around RY Lup, surrounding an inner cavity with a diameter of 0.8 (radius ∼ 60 au). The results of the UV-to-NIR study performed by Arulanantham et al (2018) to probe the details of the cavity and inner disk are fully consistent with the presence of a gas gap within the millimeter(mm)-dust cavity, confirming the pre-transition disk nature of the system. The inclination and the position angle of the disk derived from these ALMA data are 67 • and 109 • , respectively (Francis & van der Marel 2020).…”

Section: Introductionsupporting

confidence: 55%

The GRAVITY young stellar object survey

Bouarour¹,

Perraut

Ménard

et al. 2020

A&A

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Context. Studies of the dust distribution, composition, and evolution of protoplanetary disks provide clues for understanding planet formation. However, little is known about the innermost regions of disks where telluric planets are expected to form. Aims. We aim constrain the geometry of the inner disk of the T Tauri star RY Lup by combining spectro-photometric data and interferometric observations in the near-infrared (NIR) collected at the Very Large Telescope Interferometer. We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes. Methods. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the spectral energy distribution (SED) and match the interferometric observations. MCFOST produces synthetic SEDs and intensity maps at different wavelengths from which we compute the modeled interferometric visibilities and closure phases through Fourier transform. Results. To match the SED from the blue to the millimetric range, our model requires a stellar luminosity of 2.5 L⊙, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 R⊙. These revised fundamental parameters, when combined with the mass estimates available (in the range 1.3–1.5 M⊙), lead to an age of 0.5–2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model (that has a transition disk geometry) nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12 au from the central star. This model corresponds to an inclination of the inner disk of 50°, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70° in NIR) and ALMA (67 ± 5°) images, but consistent with the inclination determination from the ALMA CO spectra (55 ± 5°). Increasing the inclination of the inner disk to 70° leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 L⊙ to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13 R⊙, leading to an age of 2–3 Ma, and a stellarmass of about 2 M⊙, in disagreement with the observed dynamical mass estimate of 1.3–1.5 M⊙. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY. Conclusions. The inner dust disk, as traced by the GRAVITY data, is located at a radius in agreement with the dust sublimation radius. An ambiguity remains regarding the respective orientations of the inner and outer disk, coplanar and mildly misaligned, respectively.As our datasets are not contemporary and the star is strongly variable, a deeper investigation will require a dedicated multi-technique observing campaign.

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“…In particular, these authors compare the radial distributions of full and transitional disks ( Figure 10), finding that the distribution in transitional disks is shifted towards larger radii. The H 2 and CO gas populations decline with dust disk dissipation [86,115], but the H 2 depletion lags behind the CO for disks with large inner dust cavities [84].…”

Section: Disk Dispersalmentioning

confidence: 99%

“…Right: Kinematic model for the H 2 emission including the effect of the COS line spread function (LSF). From Arulanantham et al[84]. Both figures: c AAS.…”

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confidence: 98%

The UV Perspective of Low-Mass Star Formation

Schneider¹,

Günther²

2020

Galaxies

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The formation of low-mass (M 2 M ) stars in molecular clouds involves accretion disks and jets, which are of broad astrophysical interest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also intimately connected, setting the starting point for planetary systems like our own. The ultraviolet (UV) spectral range is particularly suited to study star formation, because virtually all relevant processes radiate at temperatures associated with UV emission processes or have strong observational signatures in the UV. In this review, we describe how UV observations provide unique diagnostics for the accretion process, the physical properties of the protoplanetary disk, and jets and outflows.CTTSs were initially identified as a new class of objects due their optical variability. Very early on, it was realized that they also show signs of enhanced chromospheric activity, i.e., "emission lines resembling those of the solar chromosphere" [2]. These emission lines are superposed on a photospheric spectrum similar to main sequence stars of late spectral type. Initially, the source of emission in excess of a normal photosphere was speculated to be circumstellar or chromospheric in origin [3].The discovery that CTTSs are above and to the right of the main sequence in an HR-diagram demonstrated in conjunction with theoretical work [4], that these objects must be young and, thus, the progenitors of the large main sequence population [5,6]. This notion is corroborated by the presence of strong Li absorption, which requires ∼ 100× the Li abundance of the Sun [e.g. 7]. Because Li is depleted quickly in stellar interiors, the amount of surface lithium decreases with time in convective stars. Therefore, strong Li absorption can only be found in young stars and thus CTTS must be young [e.g. review by 8].Meanwhile the number of peculiarities found in CTTSs grew, but their established youth alone was insufficient to explain those peculiarities and the "mysteries" of CTTSs remained. Many features, like the origin of the "chromospheric emission" remained unexplained, until the early 1980s when a large variety of models were proposed to explain features of CTTSs including envelopes, outflows, infall, and dust disks.Specifically, the "ultraviolet excess" (measured around 3700 Å) and the "blue continuum", which go along with a weakening of photosperic absorption lines due to veiling [9,10], were shown to correlate with the strength of Hα [11,12]. Such a correlation indicates a common origin of both features as observed for chromospheric emission on the Sun. Thus, it was natural to ascribe the excess continuum emission at short wavelengths to a Balmer continuum, i.e., emission following the capture of a free electron by an ionized hydrogen atom. While that finding pinpoints neither the physical origin nor location of the emitting material, it paved the way for explanations involving a suitably tuned chromosphere for producing the observed (Balmer & Ca II H+K) line fluxes in CTTSs. Quantitative mod...

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A UV-to-NIR Study of Molecular Gas in the Dust Cavity around RY Lupi

Abstract: We present a study of molecular gas in the inner disk r 20 au < ( ) around RY Lupi, with spectra from HST-COS, HST-STIS, and VLT-CRIRES. We model the radial distribution of flux from hot gas in a surface layer between r=0

Cited by 19 publications

References 79 publications

HST spectra reveal accretion in MY Lupi

HST spectra reveal accretion in MY Lupi

The GRAVITY young stellar object survey

The UV Perspective of Low-Mass Star Formation

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