The Spectral Energy Distribution and Mass‐Loss Rate of the A‐Type Supergiant Deneb

2002 ◽  
Vol 570 (1) ◽  
pp. 344-368 ◽  
Author(s):  
J. P. Aufdenberg ◽  
P. H. Hauschildt ◽  
E. Baron ◽  
T. E. Nordgren ◽  
A. W. Burnley ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy

scholarly journals Are the silicate crystallinities of oxygen-rich evolved stars related to their mass loss rates?

2018 ◽  
Vol 14 (S343) ◽  
pp. 425-426
Author(s):  
Biwei Jiang ◽  
Jiaming Liu ◽  
Aigen Li
Keyword(s):  
Energy Distribution ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Evolved Stars ◽  
Loss Rates

AbstractA sample of 28 oxygen-rich evolved stars is selected based on the presence of crystalline silicate emission features in their ISO/SWS spectra. The crystallinity, measured as the flux fraction of crystalline silicate features, is found not to be related to mass loss rate that is derived from fitting the spectral energy distribution.

scholarly journals Long-term evolution of AGB wind envelopes: Insights from hydrodynamical models

1999 ◽  
Vol 191 ◽  
pp. 379-388
Author(s):  
M. Steffen ◽  
D. Schönberner ◽  
R. Szczerba
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Alternative Mechanism ◽  
Agb Stars ◽  
Hydrodynamical Simulations ◽  
Thermal Pulses

Up to now, hydrodynamical models of dust-driven AGB winds do not generally take into account the ‘long-term’ changes of the stellar parameters (on stellar evolution time scales of 103 to 105 yrs), although it is well known that the luminosity and (very likely) the mass loss rate undergo significant variations when so called ‘thermal pulses’ occur on the upper AGB. In this review we demonstrate that time-dependent radiation hydrodynamics calculations are needed to understand the formation, structure, and spectral energy distribution of detached dust shells detected by IRAS and ISO. Combined with appropriate models, these observations can reveal part of the previous mass loss history on the AGB and allow an empirical check of presently adopted mass loss laws.Based on insights from hydrodynamical simulations, we discuss the two competing scenarios that have been put forward to explain the origin of the very thin molecular shells recently discovered around some carbon stars. We find that the signature of a short mass loss ‘eruption’ broadens quickly with time due to the related velocity gradient across the shell. Hence, this scenario is not considered a likely explanation of detached CO shells. On the other hand, the alternative mechanism, interaction of winds, is shown to be capable of producing very thin shells of greatly enhanced gas density in the dusty outflows from AGB stars by sweeping up matter at the interface between both type of winds.

scholarly journals ISO Observations of AGB Stars in the Small Magellanic Cloud

1999 ◽  
Vol 192 ◽  
pp. 95-99
Author(s):  
J.A.D.L. Blommaert ◽  
M.A.T. Groenewegen ◽  
M. R. Cioni ◽  
H. J. Habing ◽  
J.Th. van Loon ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Magellanic Cloud ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Agb Stars ◽  
Small Magellanic Cloud

We used ISOCAM and ISOPHOT to observe the spectral energy distribution between 3.6 and 60 μm of AGB stars in the Small Magellanic Cloud detected by IRAS. CAM-CVF spectra are made which enable us to establish the carbon- or oxygen-rich nature of the stars.We are in the process of analysing this data using a radiative transfer model. This will provide us with accurate determinations of luminosity and mass loss rate. Combining the results on the SMC, LMC and Galaxy we hope to address the open question of the metallicity dependencies of the mass loss rate. This in turn is important in the ejection of matter by AGB stars into the interstellar medium.

STUDY OF THE OBJECT HD 87643

2012 ◽  
Vol 18 ◽  
pp. 53-57
Author(s):  
EDUARDO LENHO COELHO ◽  
DALTON DE FARIA LOPES
Keyword(s):  
Energy Distribution ◽  
Mass Loss ◽  
Transfer Equation ◽  
Spectral Energy Distribution ◽  
Astronomical Observatory ◽  
Spectral Energy ◽  
Spherically Symmetric ◽  
Balmer Series ◽  
Exact Integration ◽  
Different Time Scales

HD 87643 is one of the B[e] stars that still defy our understanding to better classify it. The spectroscopic observations of HD 87643 performed in the Astronomical Observatory of La Silla (ESO) between December 1998 and April 2000 show an object far more complex than was already known, with profiles of the Balmer series showing variability on different time scales. This work examine the formation of Hα and Hβ profiles with the SEI method (Sobolev approximation with Exact Integration of the transfer equation), as well as their spectral energy distribution by means of codes Cloudy and Dusty. For a homogeneous and spherically symmetric nebula around a star with T ef ~ 15, 000 K and log L/L⊙ > 4.2, the reproduction of the profiles mentioned was only achieved for Hβ and to some extent, considering two distinct regions with different laws for the expansion of the wind and with different rates of mass loss.

scholarly journals X-ray spectral diagnostics of activity in massive stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 348-353 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Broad Band ◽  
Variable Structure ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Spectral Diagnostics ◽  
Loss Rates

AbstractX-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption signatures. In some cases, the degree of wind absorption is so high, that the hardening of the X-ray SED can be quite significant. We discuss these results as applied to the early O stars ζ Pup (O4 If), 9 Sgr (O4 V((f))), and HD 93129A (O2 If*).

scholarly journals The spectral energy distribution and mass-loss history of IRC + 10420

1996 ◽  
Vol 280 (4) ◽  
pp. 1062-1070 ◽  
Author(s):  
René D. Oudmaijer ◽  
M. A. T. Groenewegen ◽  
H. E. Matthews ◽  
J. A. D. L. Blommaert ◽  
K. C. Sahu
Keyword(s):  
Energy Distribution ◽  
Mass Loss ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
History Of

scholarly journals The Carnegie Supernova Project II

2020 ◽  
Vol 638 ◽  
pp. A92 ◽  
Author(s):  
F. Taddia ◽  
M. D. Stritzinger ◽  
C. Fransson ◽  
P. J. Brown ◽  
C. Contreras ◽  
...  
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Line Profile ◽  
Electron Scattering ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Shock Velocity ◽  
Spectral Energy ◽  
Model Calculations

We present ultra-violet (UV) to mid-infrared (MIR) observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II beginning two days after discovery and extending until +887 days (d). The SN reached a peak r-band absolute magnitude of ≈−19 mag and an even brighter UV peak, and its light curve evolution resembles that of SN 1988Z. The spectra of SN 2013L are dominated by hydrogen emission features, characterized by three components attributed to different emission regions. A unique feature of this Type IIn SN is that, apart from the first epochs, the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from ∼4800 km s−1 at +48 d, decreasing as t−0.23 to ∼2700 km s−1 after a year. We performed spectral modeling of both the broad- and intermediate-velocity components of the Hα line profile. The high-velocity component is consistent with emission from a radially thin, spherical shell located behind the expanding shock with emission wings broadened by electron scattering. We propose that the intermediate component originates from preionized gas from the unshocked dense CSM with the same velocity as the narrow component, ∼100 km s−1, but also that it is broadened by electron scattering. These features provide direct information about the shock structure, which is consistent with model calculations. The spectra exhibit broad O I and [O I] lines that emerge at ≳+144 d and broad Ca II features. The spectral continua and the spectral energy distributions (SEDs) of SN 2013L after +132 d are well reproduced by a two-component black-body (BB) model; one component represents emitting material with a temperature between 5 × 103 and 1.5 × 104 K (hot component) and the second component is characterized by a temperature around 1–1.5 × 103 K (warm component). The warm component dominates the emission at very late epochs (≳+400 d), as is evident from both the last near infrared (NIR) spectrum and MIR observations obtained with the Spitzer Space Telescope. Using the BB fit to the SEDs, we constructed a bolometric light curve that was modeled together with the unshocked CSM velocity and the shock velocity derived from the Hα line modeling. The circumstellar-interaction model of the bolometric light curve reveals a mass-loss rate history with large values (1.7 × 10−2 − 0.15 M⊙ yr−1) over the ∼25−40 years before explosion, depending on the radiative efficiency and anisotropies in the CSM. The drop in the light curve at ∼350 days and the presence of electron scattering wings at late epochs indicate an anisotropic CSM. The mass-loss rate values and the unshocked-CSM velocity are consistent with the characteristics of a massive star, such as a luminous blue variable (LBV) undergoing strong eruptions, similar to η Carinae. Our analysis also suggests a scenario where pre-existing dust grains have a distribution that is characterized by a small covering factor.

scholarly journals How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions

2020 ◽  
Vol 642 ◽  
pp. A142 ◽  
Author(s):  
J. Wiegert ◽  
M. A. T. Groenewegen ◽  
A. Jorissen ◽  
L. Decin ◽  
T. Danilovich
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
The Impact

Context. High-angular-resolution observations of asymptotic giant branch (AGB) stars often reveal non-spherical morphologies for the gas and dust envelopes. Aims. We aim to make a pilot study to quantify the impact of different geometries (spherically symmetric, spiral-shaped, and disc-shaped) of the dust component of AGB envelopes on spectral energy distributions (SEDs), mass estimates, and subsequent mass-loss rate (MLR) estimates. We also estimate the error made on the MLR if the SED is fitted by an inappropriate geometrical model. Methods. We use the three-dimensional Monte-Carlo-based radiative-transfer code RADMC-3D to simulate emission from dusty envelopes with different geometries (but fixed spatial extension). We compare these predictions with each other, and with the SED of the AGB star EP Aqr that we use as a benchmark since its envelope is disc-like and known to harbour spiral arms, as seen in CO. Results. The SEDs involving the most massive envelopes are those for which the different geometries have the largest impact, primarily on the silicate features at 10 and 18 μm. These different shapes originate from large differences in optical depths. Massive spirals and discs appear akin to black bodies. Optically thick edge-on spirals and discs (with dust masses of 10−4 and 10−5 M⊙) exhibit black-body SEDs that appear cooler than those from face-on structures and spheres of the same mass, while optically thick face-on distributions appear as warmer emission. We find that our more realistic models, combined spherical and spiral distributions, are 0.1 to 0.5 times less massive than spheres with similar SEDs. More extreme, less realistic scenarios give that spirals and discs are 0.01 to 0.05 times less massive than corresponding spheres. This means that adopting the wrong geometry for an AGB circumstellar envelope may result in a MLR that is incorrect by as much as one to two orders of magnitude when derived from SED fitting.

The dust production rate of carbon-rich stars in the Magellanic Clouds

2018 ◽  
Vol 14 (S343) ◽  
pp. 478-479
Author(s):  
Ambra Nanni ◽  
Martin A. T. Groenewegen ◽  
Bernhard Aringer ◽  
Paola Marigo ◽  
Stefano Rubele ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Energy Distribution ◽  
Mass Loss ◽  
Optical Constants ◽  
Spectral Energy Distribution ◽  
Magellanic Clouds ◽  
The Other ◽  
Spectral Energy ◽  
Circumstellar Envelopes ◽  
Dust Production

AbstractWe present our new investigation aimed to estimate the mass-loss and dust production rates of carbon-rich stars (C-stars) in the Magellanic Clouds (MCs). We compute dust growth and radiative transfer in circumstellar envelopes of C-stars for a grid of stellar parameters and for selected optical constants that simultaneously reproduce the main colour–colour diagrams in the infrared. We employ these grids of spectra to fit the spectral energy distribution of C-stars in the MCs. We find that our estimates can be significantly different from the other ones in the literature.

scholarly journals Dust in the Wolf–Rayet nebula M 1-67

2020 ◽  
Vol 497 (4) ◽  
pp. 4128-4142
Author(s):  
P Jiménez-Hernández ◽  
S J Arthur ◽  
J A Toalá
Keyword(s):  
Mass Loss ◽  
Galactic Plane ◽  
Spectral Synthesis ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Optical Data ◽  
Spectral Energy ◽  
Wide Field ◽  
Power Law Distribution ◽  
Massive Star Evolution

ABSTRACT The Wolf–Rayet nebula M 1-67 around WR 124 is located above the Galactic plane in a region mostly empty of interstellar medium, which makes it the perfect target to study the mass-loss episodes associated with the late stages of massive star evolution. Archive photometric observations from Wide-field Infrared Survey Explorer(WISE), Spitzer (MIPS), and Herschel (PACS and SPIRE) are used to construct the spectral energy distribution (SED) of the nebula in the wavelength range of 12–500 μm. The infrared (photometric and spectroscopic) data and nebular optical data from the literature are modelled simultaneously using the spectral synthesis code cloudy, where the free parameters are the gas density distribution and the dust grain-sized distribution. The infrared SED can be reproduced by dust grains with two size distributions: an MRN power-law distribution with grain sizes between 0.005 and 0.05 μm and a population of large grains with representative size of 0.9 μm. The latter points towards an eruptive origin for the formation of M 1-67. The model predicts a nebular ionized gas mass of $M_\mathrm{ion} = 9.2^{+1.6}_{-1.5}~\mathrm{M}_\odot$ and the estimated mass-loss rate during the dust formation period is $\dot{M} \approx 6 \times 10^{-4}~ \mathrm{M}_\odot$ yr−1. We discuss the implications of our results in the context of single and binary stellar evolution and propose that M 1-67 represents the best candidate for a post-common envelope scenario in massive stars.

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