An Interesting Episode of Accretion Activity in UX Orionis

Natta, A.; Гринин, В. П.; Тамбовцева, Л. В.

doi:10.1086/309526

Cited by 31 publications

(42 citation statements)

References 17 publications

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“…The structure and parameters of the magnetosphere in HAEBEs are still not fully understood. Natta et al (2000) presented direct evidence of the gas infall in HAEs. Using a non-LTE analysis of the line optical depths, they showed that the infalling gas cannot be heavily hydrogen depleted, which suggests a similarity between HAEs and classical T Tauri stars, where gas infall occurs in an analogous fashion.…”

Section: Hybrid Model: Disk Wind X-wind and Magnetospherementioning

confidence: 99%

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Тамбовцева

Гринин

Weigelt

2014

A&A

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Infrared interferometric observations with high spatial and spectral resolution and their quantitative modeling provide us with a unique opportunity to improve our understanding of the circumstellar environment of young stars and the accretion-ejection process. The goal of this paper is to investigate various models of the emitting regions in young Herbig Ae/Be stars that consist of (i) a compact rotating magnetosphere; (ii) an X-wind; and (iii) a disk wind. These models can be used, for example, to quantitatively interpret line profile measurements and infrared interferometric observations with the AMBER instrument of the Very Large Telescope Interferometer (VLTI) in the high spectral resolution mode (R = 12 000). VLTI/AMBER observations allow us to resolve the disk wind region and study the flux contribution of the unresolved magnetosphere and X-wind region to the total line flux. Analyzing the results of our non-LTE calculations, we conclude that the mechanisms of the different broadening of emission lines of different series include (1) the kinematic expansion due to the motion of the outflowing, accelerating gas in the magneto-centrifugal disk wind; (2) the Stark effect; and (3) the rotation of the magnetosphere. We also investigated extinction effects that can influence the shape of the line profiles. We considered the obscuration of the outer disk wind by an opaque dust and gas disk, the obscuration of the disk wind by a flared disk or by dust in the disk wind itself, and absorption of the star and disk continuum radiation in the disk wind along the line of sight. We show that due to extinction effects, the line profiles can change from double-peaked to single-peaked and P Cygni profiles. We studied the contribution of the different components of the stellar environment to different hydrogen emission lines and investigated how this contribution is dependent on the model parameters. The results of this study can be used for the detailed modeling of the emitting regions of individual young stars.

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Section: Hybrid Model: Disk Wind X-wind and Magnetospherementioning

confidence: 99%

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Тамбовцева

Гринин

Weigelt

2014

A&A

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“…Thus, the analysis of the CS contribution to the observed spectra requires a careful subtraction of the stellar photospheric spectrum and a method to characterize the blended kinematical components. In this section we describe the procedure we have followed, which is the one used in Natta et al (2000), although we have improved it by considering all detected TACs simultaneously.…”

Section: Analysis Of the Spectramentioning

confidence: 99%

“…As a more convenient way to represent this contribution we define the R parameter (normalized residual absorption): R = 1 − F obs /F syn R = 0 means no CS absorption, and R = 1 denotes complete stellar light occultation, i.e. R quantifies the CS absorption strength and could be directly compared to the models in Natta et al (2000). R is also plotted in Fig.…”

Section: Subtraction Of the Ux Ori Photospheric Spectrummentioning

confidence: 99%

“…Based on spectra qualitatively similar to those discussed here, Natta et al (2000) analysed the chemical composition of one infalling event in UX Ori. Non-LTE models were used to estimate the ionization and excitation of Balmer (up to Hδ), Ca II and NaI lines.…”

Section: Origin Of the Circumstellar Gasmentioning

confidence: 99%

“…A strong observational requirement is set by the time scale of monitoring of the TACs. In Natta et al (2000) spectra were taken 3 days apart. Since UX Ori is a highly variable star, there is some ambiguity in identifying transient spectral components of different velocities detected over this time interval as having the same physical origin.…”

Section: Introductionmentioning

confidence: 99%

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A dynamical study of the circumstellar gas in UX Orionis

Mora

Natta²,

Eiroa³

et al. 2002

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Abstract. We present the results of a high spectral resolution (λ/∆λ = 49 000) study of the circumstellar (CS) gas around the intermediate mass, pre-main sequence star UX Ori. The results are based on a set of 10échelle spectra covering the spectral range 3800-5900 Å, monitoring the star on time scales of months, days and hours. A large number of transient blueshifted and redshifted absorption features are detected in the Balmer and in many metallic lines. A multigaussian fit is applied to determine for each transient absorption the velocity, v, dispersion velocity, ∆v, and the parameter R, which provides a measure of the absorption strength of the CS gas. The time evolution of those parameters is presented and discussed. A comparison of intensity ratios among the transient absorptions suggests a solar-like composition of the CS gas. This confirms previous results and excludes a very metal-rich environment as the cause of the transient features in UX Ori. The features can be grouped by their similar velocities into 24 groups, of which 17 are redshifted and 7 blueshifted. An analysis of the velocity of the groups allows us to identify them as signatures of the dynamical evolution of 7 clumps of gas, of which 4 represent accretion events and 3 outflow events. Most of the events decelerate at a rate of tenths of m s −2 , while 2 events accelerate at approximately the same rate; one event is seen experiencing both an acceleration and a deceleration phase and lasts for a period of few days. This time scale seems to be the typical duration of outflowing and infalling events in UX Ori. The dispersion velocity and the relative aborption strength of the features do not show drastic changes during the lifetime of the events, which suggests they are gaseous blobs preserving their geometrical and physical identity. These data are a very useful tool for constraining and validating theoretical models of the chemical and physical conditions of CS gas around young stars; in particular, we suggest that the simultaneous presence of infalling and outflowing gas should be investigated in the context of detailed magnetospheric accretion models, similar to those proposed for the lower mass T Tauri stars.

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