scholarly journals A generalized method for deriving mass-loss rates: The first order moment of unsaturated P Cygni line profiles

1983 ◽  
Vol 90 (2) ◽  
pp. 299-311 ◽  
Author(s):  
J. Surdej
Keyword(s):  
Mass Loss ◽  
Order Moment ◽  
Line Profiles ◽  
First Order ◽  
Loss Rates

scholarly journals Revisited Mass-Loss Rates of Planetary Nebula Nuclei Observed with IUE

1989 ◽  
Vol 131 ◽  
pp. 317-317
Author(s):  
D. Hutsemékers ◽  
J. Surdej
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Order Moment ◽  
Line Profiles ◽  
Improved Method ◽  
Low Resolution ◽  
First Order ◽  
Average Value ◽  
Resonance Doublet ◽  
Loss Rates

The first order moment of P Cygni line profiles has been computed for the case of resonance doublet and subordinate line transitions, using realistic velocity and opacity distributions. This improved method has allowed us to rederive mass-loss rates for a sample of 17 PNN observed in the low resolution mode with IUE. The average value of our mass-loss rates amounts to 10−7 M⊙/yr.

scholarly journals Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive

2014 ◽  
Vol 439 (1) ◽  
pp. 908-923 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger ◽  
Jon O. Sundqvist ◽  
Alex W. Fullerton ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Profiles ◽  
Shock Physics ◽  
X Ray ◽  
Loss Rates

scholarly journals Stellar Winds and Mass-Loss Rates from Be Stars

1982 ◽  
Vol 98 ◽  
pp. 377-385 ◽  
Author(s):  
Theodore P. Snow
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Stellar Winds ◽  
Be Stars ◽  
Line Profiles ◽  
Sample Group ◽  
Show Evidence ◽  
Acceleration Zone ◽  
Low Levels ◽  
Loss Rates

Resonance-line profiles of SiIII and SiIV lines in 22 B and Be stars have been analyzed in the derivation of mass-loss rates. Of the 19 known Be or shell stars in the sample group, all but one show evidence of winds. It is argued that for stars of spectral type B1.5 and later, SiIII and SiIV are the dominant stages of ionization, and this conclusion, together with theoretical fits to the line profiles, leads to mass-loss rates between 10-11 and 3 × 10-9 for the stars. The rate of mass loss does not correlate simply with stellar parameters, and probably is variable with time. The narrow FeIII shell lines often seen in the ultraviolet spectra of Be stars may arise at low levels in the wind, below the strong acceleration zone. The mass-loss rates from Be stars are apparently insufficient to affect stellar evolution.

scholarly journals Wind properties of variable B supergiants

2018 ◽  
Vol 614 ◽  
pp. A91 ◽  
Author(s):  
M. Haucke ◽  
L. S. Cidale ◽  
R. O. J. Venero ◽  
M. Curé ◽  
M. Kraus ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Empirical Relationship ◽  
Variable Stars ◽  
Stellar Winds ◽  
Radial Pulsation ◽  
Line Profiles ◽  
Stellar Radius ◽  
Wind Variability ◽  
Loss Rates

Context. Variable B supergiants (BSGs) constitute a heterogeneous group of stars with complex photometric and spectroscopic behaviours. They exhibit mass-loss variations and experience different types of oscillation modes, and there is growing evidence that variable stellar winds and photospheric pulsations are closely related. Aims. To discuss the wind properties and variability of evolved B-type stars, we derive new stellar and wind parameters for a sample of 19 Galactic BSGs by fitting theoretical line profiles of H, He, and Si to the observed ones and compare them with previous determinations. Methods. The synthetic line profiles are computed with the non-local thermodynamic equilibrium (NLTE) atmosphere code FASTWIND, with a β-law for hydrodynamics. Results. The mass-loss rate of three stars has been obtained for the first time. The global properties of stellar winds of mid/late B supergiants are well represented by a β-law with β > 2. All stars follow the known empirical wind momentum–luminosity relationships, and the late BSGs show the trend of the mid BSGs. HD 75149 and HD 99953 display significant changes in the shape and intensity of the Hα line (from a pure absorption to a P Cygni profile, and vice versa). These stars have mass-loss variations of almost a factor of 2.8. A comparison among mass-loss rates from the literature reveals discrepancies of a factor of 1 to 7. This large variation is a consequence of the uncertainties in the determination of the stellar radius. Therefore, for a reliable comparison of these values we used the invariant parameter Qr. Based on this parameter, we find an empirical relationship that associates the amplitude of mass-loss variations with photometric/spectroscopic variability on timescales of tens of days. We find that stars located on the cool side of the bi-stability jump show a decrease in the ratio V∞∕Vesc, while their corresponding mass-loss rates are similar to or lower than the values found for stars on the hot side. Particularly, for those variable stars a decrease in V∞∕Vesc is accompanied by a decrease in Ṁ. Conclusions. Our results also suggest that radial pulsation modes with periods longer than 6 days might be responsible for the wind variability in the mid/late-type. These radial modes might be identified with strange modes, which are known to facilitate (enhanced) mass loss. On the other hand, we propose that the wind behaviour of stars on the cool side of the bi-stability jump could fit with predictions of the δ−slow hydrodynamics solution for radiation-driven winds with highly variable ionization.

scholarly journals An APEX survey of outflow and infall toward the youngest protostars in Orion

2020 ◽  
Vol 642 ◽  
pp. A137
Author(s):  
Z. Nagy ◽  
A. Menechella ◽  
S. T. Megeath ◽  
J. J. Tobin ◽  
J. J. Booker ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Profiles ◽  
Space Observatory ◽  
Bolometric Luminosity ◽  
Line Intensities ◽  
Upper Limits ◽  
Molecular Lines ◽  
Low Mass ◽  
Loss Rates

Aims. We aim to characterize the outflow properties of a sample of early Class 0 phase low-mass protostars in Orion, which were first identified by the Herschel Space Observatory. We also look for signatures of infall in key molecular lines. Methods. Maps of CO J = 3–2 and J = 4–3 toward 16 very young Class 0 protostars were obtained using the Atacama Pathfinder EXperiment (APEX) telescope. We searched the data for line wings indicative of outflows and calculated masses, velocities, and dynamical times for the outflows. We used additional HCO+, H13CO+, and NH3 lines to look for infall signatures toward the protostars. Results. We estimate the outflow masses, forces, and mass-loss rates based on the CO J = 3–2 and J = 4–3 line intensities for eight sources with detected outflows. We derive upper limits for the outflow masses and forces of sources without clear outflow detections. The total outflow masses for the sources with clear outflow detections are in the range between 0.03 and 0.16 M⊙ for CO J = 3–2 and between 0.02 and 0.10 M⊙ for CO J = 4–3. The outflow forces are in the range between 1.57 × 10−4 and 1.16 × 10−3 M⊙ km s−1 yr−1 for CO J = 3–2 and between 1.14 × 10−4 and 6.92 × 10−4 M⊙ km s−1 yr−1 for CO J = 4–3. Nine protostars in our sample show asymmetric line profiles indicative of infall in HCO+, compared to H13CO+ or NH3. Conclusions. The outflow forces of the protostars in our sample show no correlation with the bolometric luminosity, unlike those found by some earlier studies for other Class 0 protostars. The derived outflow forces for the sources with detected outflows are similar to those found for other, more evolved, Class 0 protostars, suggesting that outflows develop quickly in the Class 0 phase.

scholarly journals A Powerful Method for Deriving Mass-Loss Rates from Planetary Nebulae and Other Objects: The First Order Moment W1 of Unsaturated P Cygni Line Profiles

1983 ◽  
Vol 103 ◽  
pp. 337-337
Author(s):  
Jean Surdej
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Rotational Velocity ◽  
Central Star ◽  
Order Moment ◽  
Sobolev Type ◽  
First Order ◽  
N Level ◽  
Fractional Abundance ◽  
Image Position

For the case of optically thin lines, we show that the relation existing between the first order moment of a P Cygni line profile and the quantity n (level) (cf. Castor, Lutz and Seaton, 1981), where is the mass-loss rate of the central star and n (level) the fractional abundance of the relevant ion, is in fact independent of any Sobolev-type approximations used for the transfer of line radiation. Consequently, all results established in the context of “very rapidly” expanding atmospheres (see Surdej, 1982) and mainly referring to the non-dependence of W1 on various physical (underlying photospheric absorption line, limb darkening, collisions, multiplet line transitions, etc.) and geometrical (radial and rotational velocity fields, size of the atmosphere, etc) effects remain unchanged for arbitrary (e.g. non-Sobolev type) outward-accelerating velocity laws.

scholarly journals Effects of X-rays on the ionization state of Be star winds

1994 ◽  
Vol 162 ◽  
pp. 202-203
Author(s):  
J. J. MacFarlane
Keyword(s):  
Mass Loss ◽  
Driving Force ◽  
X Rays ◽  
Line Profiles ◽  
Ionization State ◽  
Polarization Data ◽  
Radiation Line ◽  
Be Star ◽  
Loss Rates

It is important to understand the ionization state of Be star winds for several reasons, including: (1) if known, mass loss rates can be determined from UV P Cygni profiles; (2) the radiation line driving force which accelerates the winds depends on the ionization distribution; and (3) analysis of line profiles, in conjunction with polarization data, can help assess the credibility of various hypotheses for the assymetric nature of Be star winds.

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