scholarly journals Optical and near-infrared observations of the Fried Egg Nebula

2020 ◽  
Vol 635 ◽  
pp. A183 ◽  
Author(s):  
E. Koumpia ◽  
R. D. Oudmaijer ◽  
V. Graham ◽  
G. Banyard ◽  
J. H. Black ◽  
...  
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Continuum Emission ◽  
Large Set ◽  
Depth Effect ◽  
Good Opportunity ◽  
Fast Wind

Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate and geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is crucial. Aims. We aim to provide insight into the nature (i.e. geometry, rates) of mass-loss episodes, and in particular, the connection between the observed asymmetries due to the mass lost in a fast wind or during a previous, prodigious mass-losing phase. In this context, yellow hypergiants offer a good opportunity to study mass-loss events. Methods. We analysed a large set of optical and near-infrared data in spectroscopic and photometric, spectropolarimetric, and interferometric (GRAVITY/VLTI) modes, towards the yellow hypergiant IRAS 17163−3907. We used X-shooter optical observations to determine the spectral type of this yellow hypergiant and we present the first model-independent, reconstructed images of IRAS 17163−3907 at these wavelengths tracing milli-arcsecond scales. Lastly, we applied a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published diffraction-limited VISIR images at 8.59 μm, 11.85 μm, and 12.81 μm simultaneously, adopting a revised distance determination using Gaia Data Release 2 measurements. Results. We constrain the spectral type of IRAS 17163−3907 to be slightly earlier than A6Ia (Teff ∼ 8500 K). The interferometric observables around the 2 μm window towards IRAS 17163−3907 show that the Brγ emission appears to be more extended and asymmetric than the Na I and the continuum emission. Interestingly, the spectrum of IRAS 17163−3907 around 2 μm shows Mg II emission that is not previously seen in other objects of its class. In addition, Brγ shows variability in a time interval of four months that is not seen towards Na I. Lastly, in addition to the two known shells surrounding IRAS 17163−3907, we report on the existence of a third hot inner shell with a maximum dynamical age of only 30 yr. Conclusions. The 2 μm continuum originates directly from the star and not from hot dust surrounding the stellar object. The observed spectroscopic variability of Brγ could be a result of variability in the mass-loss rate. The interpretation of the presence of Na I emission at closer distances to the star compared to Brγ has been a challenge in various studies. To address this, we examine several scenarios. We argue that the presence of a pseudo-photosphere, which was traditionally considered to be the prominent explanation, is not needed and that it is rather an optical depth effect. The three observed distinct mass-loss episodes are characterised by different mass-loss rates and can inform theories of mass-loss mechanisms, which is a topic still under debate both in theory and observations. We discuss these in the context of photospheric pulsations and wind bi-stability mechanisms.

scholarly journals The theory of winds in early type stars

1981 ◽  
Vol 59 ◽  
pp. 125-130 ◽  
Author(s):  
A.G. Hearn
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Optical Measurements ◽  
Early Type ◽  
Large Uncertainty ◽  
Early Type Stars ◽  
Loss Rates

I assume that the purpose of this review of the theory of winds from early type stars is to summarize the way in which the mass loss rate of a star may be included in a calculation of stellar evolution. Let me summarize my conclusions. It is not possible. One can only use estimates of mass loss rates obtained from the observations. Even these give a large uncertainty. The observed mass loss rates for different stars of the same spectral type vary. Further the mass loss rates obtained by different methods for the same star differ. An extreme example of this is 9 Sgr. The mass loss rate derived from the radio observations is forty times greater than that derived from the U.V. and optical measurements (Abbott et al. 1980).

scholarly journals The Properties of Planetary Nebulae Nuclei: Stellar Winds

1993 ◽  
Vol 155 ◽  
pp. 85-85 ◽  
Author(s):  
L. Bianchi ◽  
G. De Francesco
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Forthcoming Paper ◽  
Continuum Emission ◽  
Stellar Winds ◽  
High Gravity ◽  
Wind Characteristics

We present IUE observations of some nuclei of Planetary Nebulae. From these data we derive the stellar photospheric parameters (Teff Lbol, log g), and the wind characteristics (velocity, mass loss rate). Teff, R∗, Lbol are derived from UV low resolution spectra, combining optical and radio data, from Bianchi (1988) or from new IUE data, with the same method (fit of the UV continuum with model atmospheres for high gravity stars, after correcting for reddening and for the contribution of continuum emission by the nebular gas). P Cygni profiles from IUE high resolution spectra are fitted with the SEI method and V∞ is derived. The non-LTE ionisation in the wind and the mass loss rate are computed as in Bianchi et al. (1986). Details are given in a forthcoming paper. The results for a first group of objects are given in the Table below.

scholarly journals The Influence of the Ratio of Total to Selective Extinction on the Determination of the Mass Loss Rate of Wolf Rayet Stars from Infrared Excess Measurements

1982 ◽  
Vol 99 ◽  
pp. 197-201
Author(s):  
P.S. The ◽  
K.A. van der Hucht ◽  
M. Arens
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Infrared Excess ◽  
Photometric Observations ◽  
Order Of Magnitude ◽  
Selective Extinction ◽  
Loss Rates

It is shown that the mass loss rate of the WN7 star HD 93162 decreases with larger values of the ratio of total to selective extinction R. for HD 93162 the mass loss rate will change one order of magnitude, only if ΔR ∼ 2. Mass loss rates are derived for nine other WR stars of which visual, red and near-infrared photometric observations were obtained.

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 Wind characteristics of the 07 n star HD 217086 in the Cep OB 3 association

1981 ◽  
Vol 59 ◽  
pp. 41-44
Author(s):  
Mario Perinotto ◽  
Nino Panagia
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Terminal Velocity ◽  
Uv Spectra ◽  
H Ii Region ◽  
Wind Characteristics

AbstractThe 07 n star HD 217086 which provides the ionization of the H II region S 155 A and is the brightest member of the Cep OB 3 association, has been observed in the ultraviolet with IUE. From an analysis of the UV spectra we determine a terminal velocity of 3560 ± 100 km s-1 and a mass loss rate of . A comparison is made with the stars of similar spectral type.

scholarly journals Sub-millimeter detection of a Galactic center cool star IRS 7 by ALMA

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Takahiro Tsutsumi ◽  
Ryosuke Miyawaki ◽  
Makoto Miyoshi ◽  
...  
Keyword(s):  
Mass Loss ◽  
Flux Density ◽  
Loss Rate ◽  
Galactic Center ◽  
Mass Loss Rate ◽  
Continuum Emission ◽  
Cool Star ◽  
Sagittarius A ◽  
Tail Structure ◽  
Supergiant Star

Abstract IRS 7 is an M red supergiant star which is located at ${5{^{\prime \prime}_{.}}5}$ north of Sagittarius A$^\ast$. We detected firstly the continuum emission at $340\:$GHz of IRS 7 using the Atacama Large Millimeter/submillimeter Array (ALMA). The total flux density of IRS 7 is $S_{\, \nu} =448\pm 45\, \mu$Jy. The flux density indicates that IRS 7 has a photosphere radius of $R=1170\pm 60\, R_{\odot }$, which is roughly consistent with the previous Very Large Telescope Interferometer measurement. We also detected a shell-like feature with a northern extension in the H30α recombination line using ALMA. The electron temperature and electron density of the shell-like structure are estimated to be $\bar{T}^\ast _\mathrm{e}=4650\pm 500\:$K and $\bar{n}_\mathrm{e}=(6.1\pm 0.6)\times 10^4\:$cm$^{-3}$, respectively. The mass loss rate is estimated to be $\dot{m}\,\, \sim 1\times 10^{-4}\, M_{\odot }\:$yr$^{-1}$, which is consistent with a typical mass loss rate of a pulsating red supergiant star with $M = 20$–$25\, M_{\odot }$. The kinematics of the ionized gas would support the hypothesis that the shell-like structure made by the mass loss of IRS 7 is supersonically traveling in the ambient matter towards the south. The brightened southern half of the structure and the northern extension would be a bow shock and a cometary-like tail structure, respectively.

scholarly journals A Unified Formula For Mass Loss Rate of 0 to M Stars and its Effect on Stellar Evolution

1989 ◽  
Vol 106 ◽  
pp. 382-382
Author(s):  
S.P. Tarafdar
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Be Stars ◽  
Conservation Equations ◽  
Special Groups ◽  
Continuous Radiation ◽  
M Stars

A formula for stellar mass-loss rate has been derived using conservation equations of mass and momentum for coronal and continuous radiation driven wind. The derived mass-loss rate formula has been found to be consistent with the observed mass-loss rates for stars from 0 to M spectral type. Two constant parameters appearing in the mass-loss rate formula have been found to have values for special groups of stars like Be-stars and Wolf-Rayet stars different from each other and from the majority of stars. The effect of mass-loss according to the formula for the majority of stars on stellar evolution has been examined.

scholarly journals Is AS 431 a Superluminous WR Star?

1986 ◽  
Vol 116 ◽  
pp. 229-230
Author(s):  
D. J. Stickland ◽  
C. Lloyd ◽  
A. J. Willis
Keyword(s):  
Point Source ◽  
Mass Loss ◽  
Emission Line ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
X Ray ◽  
Radio Data ◽  
General Properties ◽  
Order Of Magnitude

The recent study by Caillault et al. (1985) has shown the emission-line star AS 431 (= WR 147) to be a strong X-ray source and moderately strong radio emitter. Combining optical, near-infrared and radio data, they deduced that its mass loss rate was ∼ 4 × 10−4 M⊙yr−1, an order of magnitude greater than is normal for WR stars. They also suggested that it would show up in the IRAS survey and that such data would help to elucidate whether its extreme reddening had a significant circumstellar component. To investigate this possibility and to study the general properties of the object, we have raided the IRAS Point Source Catalogue.

scholarly journals Axially Symmetric Dynamics of PNe

1993 ◽  
Vol 155 ◽  
pp. 351-351
Author(s):  
Lifan Wang
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
Axially Symmetric ◽  
Fast Wind ◽  
Interaction Scheme ◽  
Time Variations ◽  
Red Giant ◽  
Slow Wind

Following Kahn & West (1985), we investigate the formation of PNe in the slow and fast wind interaction scheme by assuming the slow wind axially symmetric. We have further assumed that the mass loss rate for the slow wind is not steady. It is found that the final morphology of the nebula depends not only upon the initial degrees of the seed asymmetry in the slow wind, but also upon the time variations of the mass loss rate. As an example, we show in some detail the case where the central star first blows an axially symmetric slow wind during its red giant stage, this wind is followed by a superwind while the star is on the AGB, these slow wind is later overtaken and shaped by the fast wind during the post-AGB branch. It is found that a small initial asymmetry can be amplified and reproduces the various observed morphologies of the PNe.

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