Context. V1184 Tau is a young variable that for a long time has been monitored at optical wavelengths. Its variability has been ascribed to a sudden and repetitive increase of the circumstellar extinction (UXor-type variable), but the physical origin of this kind of variation, although hypothesized, has not been fully supported on an observational basis. Aims. With the aim of getting a new insight into the variability of V1184 Tau, we present here new photometric and spectroscopicobservations that were taken in the period 2008−2015. During that time, the source reached the same high brightness level that it had before the remarkable fading of about 5 mag, which happened in 2004. The optical spectrum is the first to be obtained when the continuum was at its maximum level. Methods.All the observational data are interpreted in the framework of extinction-driven variability. In particular, we analyze light curves, optical and near-infrared colors, spectral energy distribution, and optical spectrum. Results. The emerging picture indicates that the source fading is due to an extinction increase of ΔAv∼5 mag, which is associated with the appearance of a strong infrared excess, attributable to a thermal component a T∼1000 K. From the flux of Hα, we derive a mass accretion rate in the range 10^{−11}–5×10^{−10} Msun/yr, which is marginally consistent with what is expected for a classical T Tauri star of similar mass. The source spectral energy distribution was fitted for both the high- and low- level of brightness. Remarkably, a scenario that is consistent with the known stellar properties (such as spectral type, mass, and radius) is obtained only if the distance to the source is of few hundreds of parsecs, in contrast with the commonly assumed value of ∼1.5 kpc. Conclusions. Our analysis partially supports a previous model, according to which the circumstellar disk undergoes a periodic puffing, the observational effects of which both shield the central star and provide evidence of disk wind activity. However, since the mass accretion rate remains almost constant with time, the source is likely not subject to accretion bursts.

A new insight into the variability of V1184 Tauri

STRAFELLA, Francesco;
2016

Abstract

Context. V1184 Tau is a young variable that for a long time has been monitored at optical wavelengths. Its variability has been ascribed to a sudden and repetitive increase of the circumstellar extinction (UXor-type variable), but the physical origin of this kind of variation, although hypothesized, has not been fully supported on an observational basis. Aims. With the aim of getting a new insight into the variability of V1184 Tau, we present here new photometric and spectroscopicobservations that were taken in the period 2008−2015. During that time, the source reached the same high brightness level that it had before the remarkable fading of about 5 mag, which happened in 2004. The optical spectrum is the first to be obtained when the continuum was at its maximum level. Methods.All the observational data are interpreted in the framework of extinction-driven variability. In particular, we analyze light curves, optical and near-infrared colors, spectral energy distribution, and optical spectrum. Results. The emerging picture indicates that the source fading is due to an extinction increase of ΔAv∼5 mag, which is associated with the appearance of a strong infrared excess, attributable to a thermal component a T∼1000 K. From the flux of Hα, we derive a mass accretion rate in the range 10^{−11}–5×10^{−10} Msun/yr, which is marginally consistent with what is expected for a classical T Tauri star of similar mass. The source spectral energy distribution was fitted for both the high- and low- level of brightness. Remarkably, a scenario that is consistent with the known stellar properties (such as spectral type, mass, and radius) is obtained only if the distance to the source is of few hundreds of parsecs, in contrast with the commonly assumed value of ∼1.5 kpc. Conclusions. Our analysis partially supports a previous model, according to which the circumstellar disk undergoes a periodic puffing, the observational effects of which both shield the central star and provide evidence of disk wind activity. However, since the mass accretion rate remains almost constant with time, the source is likely not subject to accretion bursts.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11587/408419
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