Continuum Variability of Deeply Embedded Protostars as a Probe of Envelope Structure

Abstract

Stars may be assembled in large growth spurts, however the evidence for this hypothesis is circumstantial. Directly studying the accretion at the earliest phases of stellar growth is challenging because young stars are deeply embedded in optically thick envelopes, which have spectral energy distributions that peak in the far-IR, where observations are difficult. In this paper, we consider the feasibility of detecting accretion outbursts from these younger stars by investigating the timescales for how the protostellar envelope responds to changes in the emission properties of the central source. The envelope heats up in response to an outburst, brightening at all wavelengths and with the emission peak moving to shorter wavelengths. The timescale for this change depends on the time for dust grains to heat and re-emit photons and the time required for the energy to escape the inner, optically-thick portion of the envelope. We find that the dust response time is much shorter than the photon propagation time and thus the timescale over which the emission varies is set by time delays imposed by geometry. These times are hours to days near the peak of the spectral energy distribution and weeks to months in the sub-mm. The ideal location to quickly detect continuum variability is therefore in the mid- to far-IR, near the peak of the spectral energy distribution, where the change in emission amplitude is largest. Searching for variability in sub-mm continuum emission is also feasible, though with a longer time separation and a weaker relationship between the amount of detected emission amplitude and change in central source luminosity. Such observations would constrain accretion histories of protostars and would help to trace the disk/envelope instabilities that lead to stellar growth.

25 pages, 6 figures, accepted for publication in the Astrophysical Journal

References in corpus (7)

• A 0.2 solar mass protostar with a Keplerian disk in the very young L1527 IRS system
• An Ammonia Spectral Atlas of Dense Cores in Perseus
• The James Clerk Maxwell Telescope Legacy Survey of Nearby Star-forming Regions in the Gould Belt
• Results of the ROTOR-program. II. The long-term photometric variability of weak-line T Tauri stars
• LAMP: The Long-term Accretion Monitoring Program of T Tauri stars in Chamaeleon-I
• Long-wavelength excesses of FU Orionis objects: flared outer disks or infalling envelopes?
• Herschel far-infrared photometric monitoring of protostars in the Orion Nebula Cluster

Cited by in corpus (78)

• An extraordinary outburst in the massive protostellar system NGC6334I-MM1: quadrupling of the millimeter continuum
• Formation and recondensation of complex organic molecules during protostellar luminosity outbursts
• APEX-CHAMP+ high-J CO observations of low-mass young stellar objects: IV. Mechanical and radiative feedback
• Episodic accretion: the interplay of infall and disc instabilities
• CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope
• HOPS 383: An Outbursting Class 0 Protostar in Orion
• Methanol and its relation to the water snowline in the disk around the young outbursting star V883 Ori
• Molecule sublimation as a tracer of protostellar accretion: Evidence for accretion bursts from high angular resolution C18O images
• Quantifying Variability of YSOs in the Mid-IR Over Six Years with NEOWISE
• Outflows, infall and evolution of a sample of embedded low-mass protostars. The William Herschel Line Legacy (WILL) survey
• Chemical tracers of episodic accretion in low-mass protostars
• How do stars gain their mass? A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star Forming Regions
• A Masing Event in NGC6334I: Contemporaneous Flaring of Hydroxyl, Methanol and Water Masers
• Sub-arcsecond (sub)millimeter imaging of the massive protocluster G358.93-0.03: Discovery of 14 new methanol maser lines associated with a hot core
• Giant burst of methanol maser in S255IR-NIRS3
• The Massive Protostellar Cluster NGC6334I at 220 AU Resolution: Discovery of Further Multiplicity, Diversity and a Hot Multi-Core
• A Simple Calculation in Service of Constraining the Rate of FU Orionis Outburst Events from Photometric Monitoring Surveys
• The JCMT Transient Survey: Stochastic and Secular Variability of Protostars and Disks In the Sub-Millimeter Observed Over Eighteen Months
• The extraordinary outburst in the massive protostellar system NGC6334I-MM1: Flaring of the water masers in a north-south bipolar outflow driven by MM1B
• The chemistry of episodic accretion in embedded objects. 2D radiation thermo-chemical models of the post-burst phase
• Origins Space Telescope Mission Concept Study Report
• On the accuracy of the ALMA flux calibration in the time domain and across spectral windows
• Protostellar accretion traced with chemistry. High resolution C18O and continuum observations towards deeply embedded protostars in Perseus
• A Submillimeter Burst of S255IR~SMA1 - The Rise And Fall Of Its Luminosity
• The JCMT Transient Survey: Detection of sub-mm variability in a Class I protostar EC 53 in Serpens Main
• The JCMT Transient Survey: Data Reduction and Calibration Methods
• An Analysis of the Environments of FU Orionis Objects with Herschel
• A low-mass protostar's disk-envelope interface: disk-shadowing evidence from ALMA DCO+ observations of VLA1623
• The Relationship between Mid-Infrared and Sub-Millimetre Variability of Deeply Embedded Protostars
• Young Faithful: The Eruptions of EC 53 as It Cycles through Filling and Draining the Inner Disk
• Water in Low-Mass Star-Forming Regions with Herschel: The Link Between Water Gas and Ice in Protostellar Envelopes
• A 1.3 mm SMA Survey of 29 Variable Young Stellar Objects
• M17 MIR: A massive protostar with multiple accretion Outbursts
• ALMA View of the Infalling Envelope around a Massive Protostar in S255IR SMA1
• Radiative Transfer modeling of EC 53: An Episodically Accreting Class I Young Stellar Object
• The JCMT Transient Survey: Identifying Submillimetre Continuum Variability over Several Year Timescales Using Archival JCMT Gould Belt Survey Observations
• Water around IRAS15398-3359 observed with ALMA
• Collisional evolution of dust and water ice in protoplanetary discs during and after an accretion outburst
• Episodic excursions of low-mass protostars on the Hertzsprung-Russell diagram
• Probing the cold magnetized Universe with SPICA-POL (B-BOP)
• Protostellar accretion traced with chemistry: Comparing synthetic C18O maps of embedded protostars to real observations
• A UV-to-MIR monitoring of DR Tau: exploring how water vapor in the planet formation region of the disk is affected by stellar accretion variability
• Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations
• The circumstellar environment around the embedded protostar EC 53
• Imaging the water snowline in a protostellar envelope with H${}^{13}$CO${}^{+}$
• The JCMT Transient Survey: An Extraordinary Submillimetre Flare in the T Tauri Binary System JW 566
• Discovery of a mid-infrared protostellar outburst of exceptional amplitude
• Dissecting the different components of the modest accretion bursts of the very young protostar HOPS 373
• 6.7 GHz variability characteristics of new periodic methanol maser sources
• Accretion Burst Echoes as Probes of Protostellar Environments and Episodic Mass Assembly
• Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639
• The accretion burst of the massive young stellar object G323.46 -0.08
• CCAT-prime: Science with an Ultra-widefield Submillimeter Observatory at Cerro Chajnantor
• An ALMA Study of the FU-Ori Type Object V900 Mon: Implications for the Progenitor
• The outbursting protostar 2MASS~22352345+7517076 and its environment
• The Mid-Infrared Evolution of the FU Orionis Disk
• Identifying Variability in Deeply Embedded Protostars with ALMA and CARMA
• Color Variability of HBC 722 in the Post-Outburst Phases
• Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers
• The JCMT Transient Survey: Single Epoch Transients and Variability of Faint Sources
• Photometric and Spectroscopic monitoring of YSOs in nearby star forming regions. I. Eruptive YSOs
• The structure of young embedded protostellar discs
• A Parsec-scale Bipolar H${}_2$ Outflow in the Massive Star Forming Infrared Dark Cloud Core MSXDC G053.11+00.05 MM1
• VVV-WIT-01: highly obscured classical nova or protostellar collision?
• A new phase of massive star formation? A luminous outflow cavity centred on an infrared quiet core
• Time-dependent response of protoplanetary disk temperature to an FU Ori-type luminosity outburst
• The extraordinary far-infrared variation of a protostar: Herschel/PACS observations of LRLL54361
• Synthetic observations of protostellar multiple systems
• Submillimeter continuum variability in Planck Galactic cold clumps
• Time-dependent Monte Carlo continuum radiative transfer
• Observations of 12.2 GHz methanol masers towards northern high-mass protostellar objects
• Discovery of recurrent flares of 6.7 GHz methanol maser emission in Cepheus A HW2
• The JCMT Transient Survey: Four Year Summary of Monitoring the Submillimeter Variability of Protostars
• NEW-MUSIC: The Next-generation Extended-Wavelength Multiband Sub/millimeter Inductance Camera
• Magnetic Fields Studies in the Next Decade: EAO Submillimetre Futures White Paper Series, 2019
• Submillimetre Transient Science in the Next Decade: EAO Submillimetre Futures White Paper Series, 2019
• Infrared observations of the flaring maser source G358.93-0.03 -- SOFIA confirms an accretion burst from a massive young stellar object
• ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Deriving Inclination Angle and Velocity of the Protostellar Jets from their SiO Knots