scholarly journals A ‘head/tail’ plasmon model with a Hubble law velocity profile

2020 ◽  
Vol 499 (1) ◽  
pp. L91-L95
Author(s):  
A C Raga ◽  
A Rodríguez-González ◽  
L Hernández-Martínez ◽  
J Cantó ◽  
A Castellanos-Ramírez
Keyword(s):  
Velocity Profile ◽  
Mass Loss ◽  
Finite Time ◽  
High Velocity ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Single Pulse ◽  
Time Variability ◽  
Velocity Versus ◽  
Ejection Velocity

ABSTRACT We present a model of a hypersonic, collimated, ‘single pulse’ outflow, produced by an event with an ejection velocity that first grows, reaches a peak, and then decreases again to zero velocity in a finite time (simultaneously, the ejection density can have an arbitrary time-variability). We obtain a flow with a leading ‘head’ and a trailing ‘tail’ that for times greater than the width of the pulse develops a linear, ‘Hubble law’ velocity versus position. We present an analytical model for a simple pulse with a parabolic ejection velocity versus time and time-independent mass-loss rate, and compare it to an axisymmetric gasdynamic simulation with parameters appropriate for fast knots in planetary nebulae. This ‘head/tail plasmon’ flow might be applicable to other high-velocity clumps with ‘Hubble law’ tails.

scholarly journals ASYMPTOTIC INTERNAL WORKING SURFACES OF PERIODICALLY VARIABLE JETS

2021 ◽  
Vol 57 (1) ◽  
pp. 147-155
Author(s):  
A. C. Raga ◽  
J. Cantó ◽  
A. Castellanos-Ramírez
Keyword(s):  
General Solution ◽  
Asymptotic Solution ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Center Of Mass ◽  
Time Variability ◽  
Ejection Time ◽  
Internal Working ◽  
Functional Forms

We present a derivation based on the “center of mass formalism”; of the asymptotic behaviour of internal working surfaces produced in a variable HerbigHaro (HH) jet. We obtain the general solution for an arbitrary periodic ejection time-variability, and then show examples for a limited set of functional forms for the velocity and density time-evolutions. Finally, we derive a prescription for obtaining the time-averaged mass loss rate from observations of knots along an HH jet (based on the asymptotic solution), and apply it to derive the mass loss rate of the HH 1 jet.

scholarly journals SN 2009ip: CONSTRAINTS ON THE PROGENITOR MASS-LOSS RATE

2013 ◽  
Vol 768 (1) ◽  
pp. 47 ◽  
Author(s):  
E. O. Ofek ◽  
L. Lin ◽  
C. Kouveliotou ◽  
G. Younes ◽  
E. Göğüş ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate

Effect of Sample Width on Downward Flame Spread over Typical Energy Conservation Material at a High Elevation Area

2014 ◽  
Vol 664 ◽  
pp. 199-203 ◽  
Author(s):  
Wei Guang An ◽  
Lin Jiang ◽  
Jin Hua Sun ◽  
K.M. Liew
Keyword(s):  
Mass Loss ◽  
Flame Spread ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
High Elevation ◽  
Flame Height ◽  
Spread Rate ◽  
Flame Spread Rate ◽  
Sample Width ◽  
Downward Flame Spread

An experimental study on downward flame spread over extruded polystyrene (XPS) foam at a high elevation is presented. The flame shape, flame height, mass loss rate and flame spread rate were measured. The influences of width and high altitude were investigated. The flame fronts are approximately horizontal. Both the intensity of flame pulsation and the average flame height increase with the rise of sample width. The flame spread rate first drops and then rises with an increase in width. The average flame height, mass loss rate and flame spread rate at the higher elevation is smaller than that at a low elevation, which demonstrates that the XPS fire risk at the higher elevation area is lower. The experimental results agree well with the theoretical analysis. This work is vital to the fire safety design of building energy conservation system.

scholarly journals Radio Supernovae as Direct Evidence of Stellar Evolution in Real Time

1998 ◽  
Vol 11 (1) ◽  
pp. 367-367
Author(s):  
S.D. Van Dyk ◽  
M.J. Montes ◽  
K.W. Weiler ◽  
R.A. Sramek ◽  
N. Panagia
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Direct Evidence ◽  
Mass Loss Rate ◽  
X Ray ◽  
Stringent Constraint ◽  
Clear Change ◽  
Late Stages ◽  
Circumstellar Environment

The radio emission from supernovae provides a direct probe of a supernova’s circumstellar environment, which presumably was established by mass-loss episodes in the late stages of the progenitor’s presupernova evolution. The observed synchrotron emission is generated by the SN shock interacting with the relatively high-density circumstellar medium which has been fully ionized and heated by the initial UV/X-ray flash. The study of radio supernovae therefore provides many clues to and constraints on stellar evolution. We will present the recent results on several cases, including SN 1980K, whose recent abrupt decline provides us with a stringent constraint on the progenitor’s initial mass; SN 1993J, for which the profile of the wind matter supports the picture of the progenitor’s evolution in an interacting binary system; and SN 1979C, where a clear change in presupernova mass-loss rate occurred about 104 years before explosion. Other examples, such as SNe 19941 and 1996cb, will also be discussed.

scholarly journals Evolution of the mass-loss rate during atmospheric and pressurized slow pyrolysis of wheat straw in a bench-scale reactor

2018 ◽  
Vol 136 ◽  
pp. 18-26 ◽  
Author(s):  
Gianluca Greco ◽  
María Videgain ◽  
Christian Di Stasi ◽  
Belén González ◽  
Joan J. Manyà
Keyword(s):  
Mass Loss ◽  
Wheat Straw ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Slow Pyrolysis ◽  
Bench Scale ◽  
Scale Reactor

scholarly journals Environmental Influence on Stellar Evolution: The Horizontal Branch of NGC 1851

1996 ◽  
Vol 174 ◽  
pp. 357-358
Author(s):  
I. Saviane ◽  
G. Piotto ◽  
M. Capaccioli ◽  
F. Fagotto
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Environmental Influence ◽  
Mass Loss Rate ◽  
Bimodal Distribution ◽  
Age Difference ◽  
Horizontal Branch ◽  
Cluster Area ◽  
The Difference ◽  
Red Clump

The bimodal nature of the horizontal branch (HB) of NGC 1851 is known since Stetson (1981). In order to better understand the properties of its HB, we collected a set of data at the ESO-NTT telescope, which provides a full coverage of the cluster area. Additional archive images from the HST-WFPC camera have been used in order to study the central region. The resulting c-m diagram (CMD) for 20500 stars is presented in Fig. 1 (left). Despite its metallicity ([Fe/H]=−1.3), NGC 1851 presents a well defined blue HB tail, besides the expected red clump. The observed CMD has been compared with the synthetic ones. The bimodal HB can be reproduced assuming that there are two stellar populations in the cluster, with an age difference of ∼ 4 Gyr, hypothesis not supported by other properties of the CMD. On the other side, if we assume that the stars in NGC 1851 are 15 Gyr old (as suggested by the difference between the HB and the TO luminosities), only a bimodal mass loss can reproduce the HB morphology: only stars with higher than standard mass loss rate are able to populate the blue-HB (BHB) tail (Fig. 1,left). There are no observational evidences for a bimodal distribution of other parameters (He, CNO, etc.).

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