The Coronae of AR Lac

Abstract

We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma. Line widths interpreted in terms of Doppler broadening suggest that both binary stellar components are active. From line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. A strong maximum was found in the differential emission measure, characterized by peaks at log T = 6.9 and 7.4, together with a weak but significant cooler maximum near log T=6.2, and a moderately strong hot tail from log T= 7.6-8.2. Coronal abundances have a broad distribution and show no simple correlation with first ionization potential. While the resulting model spectrum generally agrees very well with the observed spectrum, there are some significant discrepancies, especially among the many Fe L-lines. Both the emission measure and abundance distributions are qualitatively similar to prior determinations from other X-ray and ultraviolet spectra, indicating some long-term stability in the overall coronal structure.

31 pages, 8 figures, 3 tables; Accepted for publication in the Astrophysical Journal (tentatively October 1, 2003)

References in corpus (11)

• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
• An Overview of the Performance and Scientific Results from the Chandra X-Ray Observatory (CXO)
• Evidence for Accretion: High-Resolution X-ray Spectroscopy of the Classical T Tauri Star TW Hydrae
• X-ray photoionized plasma diagnostics with Helium-like ions. Application to Warm Absorber-Emitter in Active Galactic Nuclei
• First Light Measurements with the XMM-Newton Reflection Grating Spectrometers: Evidence for an Inverse First Ionisation Potential Effect and Anomalous Ne A bundance in the Coronae of HR 1099
• X-Ray Spectroscopy of II Pegasi: Coronal Temperature Structure, Abundances, and Variability
• The Structure of Stellar Coronae in Active Binary Systems
• Multiwavelength optical observations of chromospherically active binary systems. I. Simultaneous H{alpha}, NaI D{1}, D{2}, and HeI D{3} observations
• The X-ray spectrum of Fe XVII revisited with a multi-ion model
• The Radio Corona of AR Lacertae

Cited by in corpus (40)

• Estimation of the XUV radiation onto close planets and their evaporation
• The FIP and Inverse FIP Effects in Solar and Stellar Coronae
• X-Ray Spectroscopy of Stars
• Resolving the Xi Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "FIP Effect"
• A Unified Picture of the FIP and Inverse FIP Effects
• The Sun in Time: Activity and Environment
• Coronal Evolution of the Sun in Time: High-Resolution X-Ray Spectroscopy of Solar Analogs with Different Ages
• The Density of Coronal Plasma in Active Stellar Coronae
• Three years in the coronal life of AB Dor. I. Plasma emission measure distributions and abundances at different activity levels
• Modeling the NeIX Triplet Spectral Region of Capella with the Chandra and XMM-Newton Gratings
• High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex
• Coronal versus photospheric abundances of stars with different activity levels
• The Coronal X-ray Spectrum of the Multiple Weak-Lined T Tauri Star System HD 98800
• High resolution X-ray spectroscopy of the multiphase interstellar medium toward Cyg X-2
• Abundance variations and first ionization potential trends during large stellar flares
• X-ray Variability in the Young Massive Triple theta2 Ori A
• Coronal Emission Measures and Abundances for Moderately Active K Dwarfs Observed by Chandra
• The Coronae of AB Dor and V471 Tau: Primordial angular momentum vs tidal spin-up
• X-ray Spectroscopy of the Contact Binary VW Cephei
• Detection of X-ray Resonance Scattering in Active Stellar Coronae
• Inverse FIP Effects in Giant Solar Flares Found from Earth X-Ray Albedo with Suzaku/XIS
• Stellar Coronae, Solar Flares: a Detailed Comparison of sigma Gem, HR 1099, and the Sun in High-resolution X-rays
• High Resolution X-ray Spectroscopy of the Post-T Tauri Star PZ Tel
• Chandra observations of the elusive pulsar wind nebula around PSR B0656+14
• On X-ray Optical Depth in the Coronae of Active Stars
• A 33 year constancy of the X-ray coronae of AR Lac and eclipse diagnosis of scale height
• Some Like it Hot: The X-Ray Emission of The Giant Star YY Mensae
• Coronal Structure and Abundances in Young Fast Rotators
• Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm?
• Spectral Implications of Atomic Uncertainties in Optically-thin Hot Plasmas
• Are coronae of late type stars made of solar-like structures? The Fx-HR diagram and the pressure-temperature correlation
• The Coronal Abundances of Mid-F Dwarfs
• X-rays from the Mira AB Binary System
• Chandra High Resolution X-ray Spectroscopy of AM Her
• Pointing Chandra Toward the Extreme Ultraviolet Fluxes of Very Low-Mass Stars
• An XMM-Newton Study of the Coronae of ${\sigma }^2$ Coronae Borealis
• New Solar Flare Calcium Abundances with no Surprises: Results from the SMM Bent Crystal Spectrometer
• X-ray Properties of Low-Mass Pre-Main Sequence Stars in the Orion Trapezium Cluster
• A multiwavelength study of the hierarchical triple HD 181068: A test bed for studying star-planet-interaction?
• Chandra X-ray Observatory High-resolution X-ray Spectroscopy of Stars: Modeling and Interpretation