Diagnosing FUor-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-IR

Abstract

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 and stellar mass to investigate implications on the optical and near-infrared spectral energy distribution and spectral lines. The models are validated by fitting to multi-wavelength photometry of three confirmed FUor objects, FU Ori, V883 Ori and HBC 722 and then comparing the predicted spectrum to observed optical and infrared spectra. The brightness ratio between the viscous disk and the stellar photosphere, $\eta$, provides an important guide for identifying viscous accretion disks, with $\eta =1$ ("transition line") and $\eta =5$ ("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 stellar mass $M_{\ast }$ and higher accretion rate $\dot{M}$ lead to larger $\eta$; for $M_{\ast }=0.3{\mathrm{M}}_{\odot }$, $\eta =1$ corresponds to $\dot{M}=2\times 10^{-7}{\mathrm{M}}_{\odot }/$yr and $\eta =5$ to $\dot{M}=6\times 10^{-7}{\mathrm{M}}_{\odot }/$yr. 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 (YSO) associated with FUors.

32 pages, 23 figures, accepted for publication in ApJ

References in corpus (42)

• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Initial Performance of the NEOWISE Reactivation Mission
• The Magnetic Fields of Classical T Tauri Stars
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• The Gould's Belt Distances Survey (GOBELINS) II. Distances and structure towards the Orion Molecular Clouds
• Imaging the water-snow line during a protostellar outburst
• Accreting Circumplanetary Disks: Observational Signatures
• The Hot Inner Disk of FU Ori
• Placing the spotted T Tauri star LkCa 4 on an HR diagram
• Milky Way Mid-Infrared Spitzer Spectroscopic Extinction Curves: Continuum and Silicate Features
• Quantifying Variability of YSOs in the Mid-IR Over Six Years with NEOWISE
• IN-SYNC I: Homogeneous Stellar Parameters from High Resolution APOGEE Spectra for Thousands of Pre-main Sequence Star
• Gaia 17bpi: An FU Ori Type Outburst
• Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance
• Physical and chemical fingerprint of protostellar disc formation
• Determining the recurrence timescale of long-lasting YSO outbursts
• Resolving the FU Ori System with ALMA: Interacting Twin Disks?
• Constraining the Rate of Protostellar Accretion Outbursts in the Orion Molecular Clouds
• Multi-epoch Ultraviolet HST Observations of Accreting Low-mass Stars
• High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars
• The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex: Results from Kinematic Analysis of Stars and Gas
• Gaia 18dvy: a new FUor in the Cygnus OB3 association
• The Rate, Amplitude and Duration of Outbursts from Class 0 Protostars in Orion
• Multi-wavelength study of the low-luminosity outbursting young star HBC 722
• Massive compact disks around FU Orionis-type young eruptive stars revealed by ALMA
• Young Faithful: The Eruptions of EC 53 as It Cycles through Filling and Draining the Inner Disk
• The ALMA Early Science View of FUor/EXor objects. II. The Very Wide Outflow Driven by HBC 494
• Short and long term near-infrared spectroscopic variability of eruptive protostars from VVV
• Radiative Transfer modeling of EC 53: An Episodically Accreting Class I Young Stellar Object
• Analysis of physical processes in eruptive YSOs with near infrared spectra and multi-wavelength light curves
• The circumstellar environment around the embedded protostar EC 53
• Application of a Steady-State Accretion Disk Model to Spectrophotometry and High-Resolution Spectra of Two Recent FU Ori Outbursts
• Viscous Heating and Boundary Layer Accretion in the Disk of Outbursting Star FU Orionis
• PTF 14jg: The Remarkable Outburst and Post-Burst Evolution of a Previously Anonymous Galactic Star
• High Resolution Optical and NIR Spectra of HBC 722
• Dissecting the different components of the modest accretion bursts of the very young protostar HOPS 373
• A global two-layer radiative transfer model for axisymmetric, shadowed protoplanetary disks
• EXORCISM: a spectroscopic survey of young eruptive variables (EXor and candidates)
• The Near Stellar Environment of Class 0 Protostars: A First Look with Near-Infrared Spectroscopy
• Color Variability of HBC 722 in the Post-Outburst Phases

Cited by in corpus (13)

• Magnetically-activated accretion outbursts of pre-main sequence discs
• Brightness and mass accretion rate evolution during the 2022 burst of EX~Lupi
• Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey
• Variability of the inner dead zone edge in 2D radiation hydrodynamic simulations
• Modeling the Multiwavelength Evolution of the V960 Mon System
• The most variable VVV sources: eruptive protostars, dipping giants in the Nuclear Disc and others
• Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO
• Photometric and Spectroscopic monitoring of YSOs in nearby star forming regions. I. Eruptive YSOs
• Gaia20bdk -- a new FUor in Sh 2-301 Star Forming Region
• Quiescence of an Outburst of a Low-Mass Young Stellar Object: LDN1415-IRS
• Dust and Water in V883 Ori: Relics of a Retreating Snowline
• VVV-WIT-13: an eruptive young star with cool molecular features
• Characterizing and spectrally modeling embedded FUor eruptions in the near-infrared