On the Turbulent Flow Downstream of a Partly Opened Throttle Valve

Hu, Tieh-Feng; Hsu, Y.-Y.

doi:10.1243/pime_proc_1994_208_122_02

Cited by 11 publications

(19 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results indicate that this star is deficient in Fe which corroborates the results from Acke & Waelkens (2004). This star is photometrically constant within ∼1% in V, by comparing data in the literature (Hu et al 1989;Slawson et al 1992;Malfait et al 1998;de Winter et al 2001;Vieira et al 2003). We will therefore assume that the photometric variability will not affect our analysis of the RACs optical depth.…”

Section: Hd 100546supporting

confidence: 90%

Stellar parameters and evidence of circumstellar activity for a sample of Herbig Ae/Be stars

Guimarães

Alencar²,

Corradi³

et al. 2006

A&A

View full text Add to dashboard Cite

Aims. We investigate evidence of accretion in a sample of 15 Herbig Ae/Be stars to determine whether these events originate in a remnant gaseous structure from the primordial cloud (rich in hydrogen) or in a metal-rich body (like comets in our Solar System). During such analysis we also determine precise stellar parameters for this sample of stars. Methods. The stars were observed using high resolution spectroscopy (R = 48 000). A synthetic photospheric spectrum was constructed and then subtracted from the observed one to obtain the circumstellar component. An iterative procedure was applied to find the stellar parameters that were used to build the synthetic photospheric spectrum. Results. Evidence of circumstellar activity were found in four stars: HD 100546, HD 142666, HD 144432 and HD 145718. The presence of redshifted absorption features only in the Balmer lines implies that the accreting material is hydrogen-rich, excluding the possibility that the accretion events might have been created by comet-like bodies. We determined effective temperature, surface gravity, metallicity and the projected rotational velocity for the stars in our sample.

show abstract

Section: Hd 100546supporting

confidence: 90%

Stellar parameters and evidence of circumstellar activity for a sample of Herbig Ae/Be stars

Guimarães

Alencar²,

Corradi³

et al. 2006

A&A

View full text Add to dashboard Cite

show abstract

“…First of all, this star is among the brightest Herbig Ae stars of the southern hemisphere (m V = 6.6), which enables shortexposure high-resolution spectroscopy on an extended timebase with 2 m class telescopes. The membership of the group of Herbig Ae/Be stars has been established by Hu et al (1989). Donati et al (1997) observed this star in 1993 and 1995 in high resolution spectroscopy at AAT/UCLES; they reported that the spectrum of this A4V star features numerous spectral lines with relatively sharp profiles (v sin i = 12 ± 2 km s −1 ) and concluded that the star is either viewed pole-on or moderately rotating.…”

Section: Previous Related Workmentioning

confidence: 90%

Spectroscopic monitoring of the Herbig Ae star HD 104237

Böhm

Catala

Balona

et al. 2004

A&A

133

View full text Add to dashboard Cite

Abstract. We present the results of multisite observations spanning two years of the pre-main-sequence Herbig Ae star HD 104237. The star was observed in high resolution spectroscopy (R ≥ 35 000) for a total of 157.3 h of effective exposure time, over 42 nights, corresponding to a data base of 1888 individual echelle spectra. We confirm that the HD 104237 system includes a spectroscopic binary, whose primary component HD 104237 A is pulsating. The resulting high quality radial velocity curve allows us to detect for the first time by spectroscopic means multiperiodic oscillations in a pre-main sequence star. Five different modes are detected with very high confidence, with frequencies ranging between 28.5 and 35.6 d −1 , typical of δ Scuti pulsations; an additional 3 frequencies have been extracted from the data, but with a lower level of confidence. The pattern of frequencies indicates that at least some of the detected modes are non-radial. The precise orbit determination and the measurement of the double line spectroscopic binary observed around periastron enabled us to determine a mass ratio of 1.29 ± 0.02 between the primary and the secondary; based on the primary mass of 2.2 ± 0.1 M we conclude that the spectroscopic secondary HD 104237 b should have a mass of 1.7 ± 0.1 M and lie outside the pre-main sequence instability strip towards later spectral types. A search for pulsations in the radial velocity curve of the much weaker secondary component was not conclusive at this stage. The location of the primary in the HR diagram and its position with respect to recent pre-main sequence evolutionary tracks and isochrones implies a location of the secondary indicative of spectral type K3.

show abstract

“…It is located in the Chamaeleon star forming complex, but outside the boundaries of the molecular clouds. Although showing signatures typical of HAeBe stars (emission lines, IR excess from a dust shell) HD 104237 is not surrounded by a reflection nebula (Hu et al 1989) that would indicate association with a star forming cloud.…”

Section: A9 Hd 104237mentioning

confidence: 99%

“…HD 100546 is a B9.5 Ve HAeBe star (Hu et al 1989), and with an age of >10 Myr one of the most evolved objects of this class (van den Ancker et al 1997). Evidence for its rather high age comes from the λ Boo like abundance anomalies that hint at gas-dust separation and ensuing metal depletion of the accreted material, thought to take place in the late pre-MS phase (Acke & Waelkens 2004b).…”

Section: A8 Hd 100546mentioning

confidence: 99%

On the origin of the X-ray emission from Herbig Ae/Be stars

Stelzer

Micela

Hamaguchi

et al. 2006

A&A

100

107

View full text Add to dashboard Cite

Context. Herbig Ae/Be stars are fully radiative and not expected to support dynamo action analogous to their convective lower-mass counterparts, the T Tauri stars. Alternative X-ray production mechanisms, related to stellar winds or star-disk magnetospheres have been proposed, but their X-ray emission has remained a mystery. Aims. A study of Herbig Ae/Be stars' global X-ray properties (such as detection rate, luminosity, temperature, variability), helps to constrain the emission mechanism by comparison to other types of stars, e.g. similar-age but lower-mass T Tauri stars, similar-mass but more evolved main-sequence A-and B-type stars, and with respect to model predictions. Methods. We performed a systematic search for Chandra archival observations of Herbig Ae/Be stars. The superior spatial resolution of this satellite with respect to previous X-ray instrumentation has allowed us to also examine the possible role of late-type companions in generating the observed X-rays. Results. In the total sample of 17 Herbig Ae/Be stars, 8 are resolved from X-ray emitting faint companions or other unrelated X-ray bright objects within 10 . The detection fraction of Herbig Ae/Be stars is 76%, but decreases to 35% if all emission is attributed to further known and unresolved companions. The spectral analysis confirms the high X-ray temperatures (∼20 MK) and large range of fractional X-ray luminosities (log L x /L * ) of this class derived from earlier studies of individual objects. Conclusions. Radiative winds are ruled out as an emission mechanism on the basis of the high temperatures. The X-ray properties of Herbig Ae/Be stars are not vastly different from those of their late-type companion stars (if such are known), nor from other young late-type stars used for comparison. Therefore, either a similar kind of process takes place in both classes of objects, or there must be as yet undiscovered companion stars.

show abstract

On the Turbulent Flow Downstream of a Partly Opened Throttle Valve

Cited by 11 publications

References 8 publications

Stellar parameters and evidence of circumstellar activity for a sample of Herbig Ae/Be stars

Stellar parameters and evidence of circumstellar activity for a sample of Herbig Ae/Be stars

Spectroscopic monitoring of the Herbig Ae star HD 104237

On the origin of the X-ray emission from Herbig Ae/Be stars

Contact Info

Product

Resources

About