The binary system RW Aur consists of two classical T Tauri stars (CTTSs). The primary recently underwent its second observed major dimming event (ΔV ∼ 2 mag). We present new, resolved Chandra X-ray and UKIRT near-IR (NIR) data as well as unresolved optical photometry obtained in the dim state to study the gas and dust content of the absorber causing the dimming. The X-ray data show that the absorbing column density increased from NH < 0.1 × 1022 cm-2 during the bright state to ≈2 × 1022cm-2 in the dim state. The brightness ratio between dim and bright state at optical to NIR wavelengths shows only a moderate wavelength dependence and the NIR color-color diagram suggests no substantial reddening. Taken together, this indicates gray absorption by large grains (≳ 1 μm) with a dust mass column density of ≳ 2 × 10-4 g cm-2. Comparison with NH shows that an absorber responsible for the optical/NIR dimming and the X-ray absorption is compatible with the ISM's gas-to-dust ratio, i.e., that grains grow in the disk surface layers without largely altering the gas-to-dust ratio. Lastly, we discuss a scenario in which a common mechanism can explain the long-lasting dimming in RW Aur and recently in AA Tau.

The nature of the 2014-2015 dim state of RW Aurigae revealed by X-ray, optical, and near-IR observations / P.C. Schneider, H.M. Gunther, J. Robrade, S. Facchini, K.W. Hodapp, C.F. Manara, V. Perdelwitz, J.H.M.M. Schmitt, S. Skinner, S.J. Wolk. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 584(2015), pp. L9.1-L9.5. [10.1051/0004-6361/201527237]

The nature of the 2014-2015 dim state of RW Aurigae revealed by X-ray, optical, and near-IR observations

S. Facchini;
2015

Abstract

The binary system RW Aur consists of two classical T Tauri stars (CTTSs). The primary recently underwent its second observed major dimming event (ΔV ∼ 2 mag). We present new, resolved Chandra X-ray and UKIRT near-IR (NIR) data as well as unresolved optical photometry obtained in the dim state to study the gas and dust content of the absorber causing the dimming. The X-ray data show that the absorbing column density increased from NH < 0.1 × 1022 cm-2 during the bright state to ≈2 × 1022cm-2 in the dim state. The brightness ratio between dim and bright state at optical to NIR wavelengths shows only a moderate wavelength dependence and the NIR color-color diagram suggests no substantial reddening. Taken together, this indicates gray absorption by large grains (≳ 1 μm) with a dust mass column density of ≳ 2 × 10-4 g cm-2. Comparison with NH shows that an absorber responsible for the optical/NIR dimming and the X-ray absorption is compatible with the ISM's gas-to-dust ratio, i.e., that grains grow in the disk surface layers without largely altering the gas-to-dust ratio. Lastly, we discuss a scenario in which a common mechanism can explain the long-lasting dimming in RW Aur and recently in AA Tau.
Stars: individual: RW Aur; Stars: low-mass; Stars: pre-main sequence; Stars: variables: T Tauri, Herbig Ae/Be; X-rays: stars
Settore FIS/05 - Astronomia e Astrofisica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/866645
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