Hamilton Echelle Spectra of Young Stars. II. Time Series Analysis of H(alpha) Variations

Johns, Christopher; Basri, Gibor

doi:10.1086/117487

Cited by 102 publications

(130 citation statements)

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“…This is likely a consequence of the small magnetosphere size used for the models (constrained by the large adopted rotation velocity), as well as the uncertain temperature structure at the outer part of the magnetosphere. Deviations from a dipole geometry and/or axisymmetry, as has been suggested from profile variability studies of SU Aur (e.g., Johns & Basri 1995;Oliveira et al 2000), could also explain the discrepancies. Such details are beyond the scope of this paper.…”

Section: Optical Line Profiles: Magg Netospheric Accretionmentioning

confidence: 80%

The Mass Accretion Rates of Intermediate-Mass T Tauri Stars

Calvet¹,

Muzerolle²,

Briceño³

et al. 2004

411

537

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We present Hubble Space Telescope ultraviolet spectra and supporting ground-based data for a sample of nine intermediate-mass T Tauri stars (IMTTSs; 1.5-4 M ). The targets belong to three star-forming regions: T Tau, SU Aur, and RY Tau in the Taurus clouds; EZ Ori, P2441, and V1044 Ori in the Ori OB1c association surrounding the Orion Nebula cluster; and CO Ori, GW Ori, and GX Ori in the ring around k Ori. The supporting groundbased observations include nearly simultaneous UBV(R I ) C photometry, 6 8 resolution spectra covering the range 3900-7000 8, optical echelle observations in the range 5800-8600 8, and K-band near-infrared spectra. We use these data to determine improved spectral types and reddening corrections and to obtain physical parameters of the targets. We find that an extinction law with a weak 2175 8 feature but high values of A UV =A V is required to explain the simultaneous optical-UV data; the reddening laws for two B-type stars located behind the Taurus clouds, HD 29647 and HD 283809, meet these properties. We argue that reddening laws with these characteristics may well be representative of cold, dense molecular clouds. Spectral energy distributions and emission-line profiles of the IMTTSs are consistent with expectations from magnetospheric accretion models. We compare our simultaneous optical-UV data with predictions from accretion shock models to get accretion luminosities and mass accretion rates (Ṁ ) for the targets. We find that the average mass accretion rate for IMTTSs is $3 ; 10 À8 M yr À1 , a factor of $5 higher than that for their low-mass counterparts. The new data extend the correlation betweenṀ and stellar mass to the intermediate-mass range. Since the IMTTSs are evolutionary descendants of the Herbig Ae/ Be stars, our results put limits to the mass accretion rates of their disks. We present luminosities of the UV lines of highly ionized metals and show that they are well above the saturation limit for magnetically active cool stars but correlate strongly with accretion luminosity, indicating that they are powered by accretion, in agreement with previous claims but using a sample in which reddening and accretion luminosities have been determined self-consistently. Finally, we find that the relation between accretion luminosity and Br luminosity found for low-mass T Tauri stars extends to the intermediate-mass regime.

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Section: Optical Line Profiles: Magg Netospheric Accretionmentioning

confidence: 80%

The Mass Accretion Rates of Intermediate-Mass T Tauri Stars

Calvet¹,

Muzerolle²,

Briceño³

et al. 2004

411

537

View full text Add to dashboard Cite

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“…9 and 10, we show the average residual profiles of Hα and Hβ lines with the normalized variance profiles, as calculated with the data observed during 2009 Jan. 1-14, and all the observations. The variance profiles, as defined in Johns & Basri (1995a), are measurements of variability in each velocity bin within the lines. The variance profiles of Hα and Hβ show blue-shifted peaks, corresponding to the variable absorption features (see Fig.…”

Section: Line Variancementioning

confidence: 99%

GW Orionis: Inner disk readjustments in a triple system

Fang

Sicilia‐Aguilar

Roccatagliata

et al. 2014

A&A

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Context. Disks are expected to dissipate quickly in binary or multiple systems. Investigating such systems can improve our knowledge of the disk dispersal. The triple system GW Ori, still harboring a massive disk, is an excellent target. Aims. We study the young stellar system GW Ori, concentrating on its accretion, wind activity and disk properties. Methods. We use high-resolution optical spectra of GW Ori to do spectral classification and derive the radial velocities (RV). We analyze the wind and accretion activity using the emission lines in the spectra. We also use U-band photometry, which has been collected from the literature, to study the accretion variability of GW Ori. We characterize the disk properties of GW Ori by modeling its spectral energy distribution (SED).Results. By comparing our data to the synthetical spectra, we classify GW Ori as a G8 star. Based on the RVs derived from the optical spectra, we confirm the previous result as a close companion in GW Ori with a period of ∼242 days and an orbital semi-major axis of ∼1 AU. The RV residuals after the subtraction of the orbital solution with the equivalent widths (EW) of accretion-related emission lines vary with periods of 5−6.7 days during short-time intervals, which are caused by the rotational modulation. The Hα and Hβ line profiles of GW Ori can be decomposed in two central-peaked emission components and one blue-shifted absorption component. The blue-shifted absorption components are due to a disk wind modulated by the orbital motion of the close companion. Therefore, the systems like GW Ori can be used to study the extent of disk winds. We find that the accretion rates of GW Ori are rather constant but can occasionally be enhanced by a factor of 2−3. We reproduce the SED of GW Ori by using disk models with gaps ∼25−55 AU in size. A small population of tiny dust particles within the gap produces the excess emission at near-infrared bands and the strong and sharp silicate feature at 10 μm. The SED of GW Ori exhibits dramatic changes on timescales of ∼20 yr in the near-infrared bands, which can be explained as the change in the amount and distribution of small dust grains in the gap. We collect a sample of binary/multiple systems with disks in the literature and find a strong positive correlation between their gap sizes and separations from the primaries to companions, which is generally consistent with the prediction from the theory.

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“…The relative variability plots provide information on the strength and wavelength position of the changes in the line intensity (Johns & Basri 1995). …”

Section: Appendix A: Tables With Multi-epoch Line Ews and Fluxesmentioning

confidence: 99%

Optical spectroscopic variability of Herbig Ae/Be stars

Mendigutía

Eiroa

Montesinos

et al. 2011

A&A

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Aims. In order to gain insights into the variability behaviour of the circumstellar (CS) atomic gas, we have analysed 337 multi-epoch optical spectra of 38 Herbig Ae/Be (HAeBe) stars. Methods. Equivalent widths (EWs) and line fluxes of the Hα, [O i]6300, He i5876 and Na iD lines were obtained for each spectrum; the Hα line width at 10% of peak intensity (W 10 ) and profile shapes were also measured and classified. The mean line strengths and relative variabilities were quantified for each star. Simultaneous optical photometry was used to estimate the line fluxes.Results. We present a homogeneous spectroscopic database of HAeBe stars. The lines are variable in practically all stars and timescales, although 30% of the objects show a constant EW in [O i]6300, which is also the only line that shows no variability on timescales of hours. The He i5876 and Na iD EW relative variabilities are typically the largest, followed by those in [O i]6300 and Hα. The EW changes can be larger than one order of magnitude for the He i5876 line, and up to a factor 4 for Hα. The [O i]6300 and Hα EW relative variabilities are correlated for most stars in the sample. The Hα mean EW and W 10 are uncorrelated, as are their relative variabilities. The Hα profile changes in ∼70% of the objects. The massive stars in the sample (M * > 3 M ) usually show more stable Hα profiles with blueshifted self-absorptions and less variable 10% widths. Conclusions. Our data suggest multiple causes for the different line variations, but the [O i]6300 and Hα variability must share a similar origin in many objects. The physical mechanism responsible for the Hα line broadening does not depend on the amount of emission; unlike in lower-mass stars, physical properties based on the Hα luminosity and W 10 would significantly differ. Our results provide additional support to previous works that reported different physical mechanisms in Herbig Ae and Herbig Be stars. The multi-epoch observations we present are a useful tool for understanding the origin of the CS lines and their variability, and to establish distinctions in the physical processes operating in pre-main sequence stars.

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Hamilton Echelle Spectra of Young Stars. II. Time Series Analysis of H(alpha) Variations

Cited by 102 publications

References 0 publications

The Mass Accretion Rates of Intermediate-Mass T Tauri Stars

The Mass Accretion Rates of Intermediate-Mass T Tauri Stars

GW Orionis: Inner disk readjustments in a triple system

Optical spectroscopic variability of Herbig Ae/Be stars

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