Optical dimming of RW Aur associated with an iron rich corona and exceptionally high absorbing column density

Abstract

RW Aur is a binary system composed of two young, low-mass stars. The primary, RW Aur A, has undergone visual dimming events ($\Delta V=2-3$~mag) in 2011, 2014-16, and 2017-2018. Visual and IR observations indicate a gray absorber that moved into the line-of-sight. This dimming is also associated with changes in the outflow. In 2017, when the optical brightness was almost 2~mag below the long-term average we triggered a Chandra observation to measure the absorbing column density $N_{\mathrm{H}}$ and to constrain dust properties and the gas-to-dust ratio of the absorber. In 2017, the X-ray spectrum is more absorbed than it was in the optically bright state ($N_{\mathrm{H}}=(4\pm 1)\times 10^{23}{\mathrm{cm}}^{-2}$) and shows significantly more hot plasma than in X-ray observations taken before. Also, a new emission feature at $6.63\pm 0.02$ keV (statistic) $\pm 0.02$ keV (systematic) appeared indicating an Fe abundance an order of magnitude above Solar, in contrast with previous sub-Solar Fe abundance measurements. Comparing X-ray absorbing column density $N_{\mathrm{H}}$ and optical extinction $A_V$, we find that either the gas-to-dust ratio in the absorber is orders of magnitude higher than in the ISM or the absorber has undergone significant dust evolution. Given the high column density coupled with changes in the X-ray spectral shape, this absorber is probably located in the inner disk. We speculate that a break-up of planetesimals or a terrestrial planet could supply large grains causing gray absorption; some of these grains would be accreted and enrich the stellar corona with iron which could explain the inferred high abundance.

arXiv commentaccepted by AJ

References in corpus (61)

• Astropy: A Community Python Package for Astronomy
• The chemical composition of the Sun
• Validation of the new Hipparcos reduction
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective
• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• A Major Asymmetric Dust Trap in a Transition Disk
• Updated Atomic Data and Calculations for X-ray Spectroscopy
• Ringed Substructure and a Gap at 1 AU in the Nearest Protoplanetary Disk
• The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project
• Asteroids Were Born Big
• Observational Constraints on the Formation and Evolution of Binary Stars
• Protoplanetary Disk Structures in Ophiuchus II: Extension to Fainter Sources
• X-ray astronomy of stellar coronae (Review)
• Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim
• Observations of gas flows inside a protoplanetary gap
• Photoionization Modeling and the K Lines of Iron
• Infrared Signatures of Disrupted Minor Planets at White Dwarfs
• The FIP and Inverse FIP Effects in Solar and Stellar Coronae
• Dust Evolution and the Formation of Planetesimals
• Bright X-ray flares in Orion young stars from COUP: evidence for star-disk magnetic fields?
• Determination of the gas-to-dust ratio in nearby dense clouds using X-ray absorption measurements
• Solar models with accretion. I. Application to the solar abundance problem
• Dust Migration and Morphology in Optically Thin Circumstellar Gas Disks
• Planetesimal formation by sweep-up: How the bouncing barrier can be beneficial to growth
• Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
• Can dead zones create structures like a transition disk?
• On the sizes of stellar X-ray coronae
• A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core
• AA Tau's sudden and long-lasting deepening: enhanced extinction by its circumstellar disk
• A Disk-Wind Model for the Near-Infrared Excess Emission in Protostars
• CSI 2264: Characterizing Young Stars in NGC 2264 with Short-Duration, Periodic Flux Dips in their Light Curves
• Relating jet structure to photometric variability: the Herbig Ae star HD 163296
• On the origin of [NeII] 12.81 micron emission from pre-main sequence stars: Disks, jets, and accretion
• Scattered light images of spiral arms in marginally gravitationally unstable discs with an embedded planet
• A tidal encounter caught in the act: modelling a star-disc fly-by in the young RW Aurigae system
• Iron Fluorescent Line Emission from Young Stellar Objects in the Orion Nebula
• Theoretical values of convective turnover times and Rossby numbers for solar-like, pre-main sequence stars
• Accretion of a Terrestrial-Like Minor Planet by a White Dwarf
• Observations of Solids in Protoplanetary Disks
• Mass ratios of the components in T Tauri binary systems and implications for multiple star formation
• Variability of the transitional T Tauri star T Chamaeleontis
• Occultation of the T Tauri Star RW Aurigae A by its Tidally Disrupted Disk
• The imprint of photoevaporation on edge-on discs
• YSOVAR: Mid-IR variability in the star forming region Lynds 1688
• Violent environment of the inner disk of RW Aur A probed by the 2010 and 2015 dimming events
• Where are the hot ion lines in classical T Tauri stars formed?
• Generating large misalignments in gapped and binary discs
• Another deep dimming of the classical T Tauri star RW Aur A
• The disappearing act: A dusty wind eclipsing RW Aur
• A dearth of small particles in debris disks: An energy-constrained smallest fragment size
• Observation of enhanced X-ray emission from the CTTS AA Tau during a transit of an accretion funnel
• X-ray to NIR emission from AA Tauri during the dim state - Occultation of the inner disk and gas-to-dust ratio of the absorber
• Stable and Unstable Regimes of Mass Accretion onto RW Aur A
• The nature of the 2014-2015 dim state of RW Aur revealed by X-ray, optical, and NIR observations
• Probing the Inner Regions of Protoplanetary Disks with CO Absorption Line Spectroscopy
• Recollimation boundary layers as X-ray sources in young stellar jets
• The jet of the young star RW Aur A and related problems
• The nature of the fluorescent iron line in V 1486 Ori
• Multi-epoch, high spatial resolution observations of multiple T Tauri systems
• Evidence for Variable, Correlated X-ray and Optical/IR Extinction toward the Nearby, Pre-main Sequence Binary TWA 30

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• Flybys in protoplanetary discs: II. Observational signatures
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• The dimming of RW Auriga. Is dust accretion preceding an outburst?
• Time-Variable Jet Ejections from RW Aur A, RY Tau and DG Tau
• Inhomogeneous dust eclipses in young stars. The case of CQ Tauri
• RW Aur B: a modest UX Ori type companion of the famous primary
• RW Aur A : SpeX Spectral Evidence for Differentiated Planetesimal Formation, Migration and Destruction in an 3 Myr Old Excited CTTS System
• MINDS. Young binary systems with JWST/MIRI: Variable water-rich primaries and extended emission
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