Igrins Spectroscopy of Class I Sources: Iras 03445+3242 and Iras 04239+2436

Lee, Seokho; Lee, Jeong Eun; Park, Sunkyung; Lee, Jae‐Joon; Kidder, Benjamin; Mace, Gregory N.; Jaffe, D. T.

doi:10.3847/0004-637x/826/2/179

“…Our model does not include CO overtone emission, common to smaller EX Lup-type outbursts (e.g., Lorenzetti et al 2009;Aspin et al 2010;Kóspál et al 2011;Giannini et al 2022) and other accretion disks (e.g., Najita et al 1996;Lee et al 2016). This emission is likely generated in a heated disk surface, though a wind origin is possible (see Pontoppidan et al 2011 for an analysis of CO fundamental bands), and requires a more sophisticated approach that includes chemistry to incorporate into our synthetic spectra.…”

Section: Equivalent Widths Of Prominent K-band Featuresmentioning

confidence: 99%

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

Liu

¹

,

Herczeg

²

,

Johnstone

³

et al. 2022

ApJ

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FU Ori-type objects (FUors) are decades-long outbursts of accretion onto young stars that are strong enough to viscously heat disks so that the disk outshines the central star. We construct models for FUor objects by calculating emission components from a steady-state viscous accretion disk, a passively-heated dusty disk, magnetospheric accretion columns, and the stellar photosphere. We explore the parameter space of the accretion rate M ̇ and stellar mass M * to investigate implications on the optical and near-infrared spectral energy distribution and spectral lines. The models are validated by fitting to multiwavelength photometry of three confirmed FUor objects, FU Ori, V883 Ori, and HBC 722, and then comparing the predicted spectra to the observed optical and infrared spectra. The brightness ratio between the viscous disk and the stellar photosphere, η, provides an important guide for identifying viscous accretion disks, with η = 1 (“transition line”) and η = 5 (“sufficient dominance line”) marking turning points in diagnostics, evaluated here in the near-infrared. These turning points indicate the emergence and complete development of FUor-characteristic strong CO absorption, weak metallic absorption, the triangular spectral continuum shape in the H band, and location in color–magnitude diagrams. Lower M * and higher M ̇ imply larger η; for M * = 0.3 M ⊙, η = 1 corresponds to M ̇ = 2 × 10 − 7 M ⊙ yr−1 and η = 5 to M ̇ = 6 × 10 − 7 M ⊙ yr−1. The “sufficient dominance line” also coincides with the expected accretion rate where accreting material directly reaches the star. We discuss implications of the models on extinction diagnostics, FUor brightening timescales, viscous disks during initial protostellar growth, and eruptive young stellar objects associated with FUors.

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“…GNIRS CO overtone band spectrum. The IGRINS spectrum of IRAS 03445+3242(Lee et al 2016), multiplied by 13, is overlaid with red. The spectrum of HOPS 373 is not continuum subtracted.…”

mentioning

confidence: 99%

Dissecting the Different Components of the Modest Accretion Bursts of the Very Young Protostar HOPS 373

Yoon

¹

,

Herczeg

²

,

Lee

³

et al. 2022

ApJ

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Observed changes in protostellar brightness can be complicated to interpret. In our James Clerk Maxwell Telescope (JCMT) Transient Monitoring Survey, we discovered that a young binary protostar, HOPS 373, is undergoing a modest 30% brightness increase at 850 μm, caused by a factor of 1.8–3.3 enhancement in the accretion rate. The initial burst occurred over a few months, with a sharp rise and then a shallower decay. A second rise occurred soon after the decay, and the source is still bright one year later. The mid-IR emission, the small-scale CO outflow mapped with ALMA, and the location of variable maser emission indicate that the variability is associated with the SW component. The near-IR and NEOWISE W1 and W2 emission is located along the blueshifted CO outflow, spatially offset by ∼3 to 4″ from the SW component. The K-band emission imaged by UKIRT shows a compact H2 emission source at the edge of the outflow, with a tail tracing the outflow back to the source. The W1 emission, likely dominated by scattered light, brightens by 0.7 mag, consistent with expectations based on the submillimeter light curve. The signal of continuum variability in K band and W2 is masked by stable H2 emission, as seen in our Gemini/GNIRS spectrum, and perhaps by CO emission. These differences in emission sources complicate IR searches for variability of the youngest protostars.

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“…The intrinsic line width ∆v of the single bandhead components is a very interesting parameter related to the turbulence level. However, this parameter is very difficult to measure even at high spectral resolution, as its value is typically much lower than the line Keplerian broadening (Lee et al 2016). In the case of 51 Oph, we find acceptable values of ∆v in the range of A50, page 7 of 21 A&A 645, A50 (2021) Fig.…”

Section: Modelling the Co Spectrummentioning

confidence: 99%

The GRAVITY young stellar object survey

Koutoulaki

¹

,

Lopez²,

Natta³

et al. 2021

A&A

9

0

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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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Igrins Spectroscopy of Class I Sources: Iras 03445+3242 and Iras 04239+2436

Cited by 14 publications

References 55 publications

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

Dissecting the Different Components of the Modest Accretion Bursts of the Very Young Protostar HOPS 373

The GRAVITY young stellar object survey

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