scholarly journals Partial Stellar Explosions - Ejected Mass and Minimal Energy

2021 ◽  
Author(s):  
Itai Linial ◽  
Jim Fuller ◽  
Re’em Sari
Keyword(s):  
Compact Stars ◽  
Polytropic Index ◽  
Minimal Energy ◽  
Stellar Radius ◽  
Numerical Hydrodynamics ◽  
Wide Range ◽  
Wave Heating ◽  
Red Supergiants ◽  
Minimal Mass ◽  
Late Stages

Abstract Many massive stars appear to undergo enhanced mass loss during late stages of their evolution. In some cases, the ejected mass likely originates from non-terminal explosive outbursts, rather than continuous winds. Here we study the dependence of the ejecta mass, mej, on the energy budget E of an explosion deep within the star, using both analytical arguments and numerical hydrodynamics simulations. Focusing on polytropic stellar models, we find that for explosion energies smaller than the stellar binding energy, the ejected mass scales as $m_{\rm ej} \propto E^{\varepsilon _{m}}$, where ϵm = 2.4 − 3.0 depending on the polytropic index. The loss of energy due to shock breakout emission near the stellar edge leads to the existence of a minimal mass-shedding explosion energy, corresponding to a minimal ejecta mass. For a wide range of progenitors, from Wolf-Rayet stars to red supergiants, we find a similar limiting energy of $E_{\rm min} \approx 10^{46}-10^{47} \rm \, erg$, almost independent of the stellar radius. The corresponding minimal ejecta mass varies considerably across different progenitors, ranging from $\sim \! 10^{-8} \, \rm M_\odot$ in compact stars, up to $\sim \! 10^{-2} \, \rm M_\odot$ in red supergiants. We discuss implications of our results for pre-supernova outbursts driven by wave heating, and complications caused by the non-constant opacity and adiabatic index of realistic stars.

scholarly journals Emulating the global 21-cm signal from Cosmic Dawn and Reionization

2020 ◽  
Vol 495 (4) ◽  
pp. 4845-4859 ◽  
Author(s):  
Aviad Cohen ◽  
Anastasia Fialkov ◽  
Rennan Barkana ◽  
Raul A Monsalve
Keyword(s):  
Neutral Hydrogen ◽  
Mean Free Path ◽  
Microwave Background ◽  
Star Forming ◽  
Global Signal ◽  
Wide Range ◽  
The Mean ◽  
Rapid Generation ◽  
Minimal Mass ◽  
Formation Efficiency

ABSTRACT The 21-cm signal of neutral hydrogen is a sensitive probe of the Epoch of Reionization (EoR), Cosmic Dawn, and the Dark Ages. Currently, operating radio telescopes have ushered in a data-driven era of 21-cm cosmology, providing the first constraints on the astrophysical properties of sources that drive this signal. However, extracting astrophysical information from the data is highly non-trivial and requires the rapid generation of theoretical templates over a wide range of astrophysical parameters. To this end emulators are often employed, with previous efforts focused on predicting the power spectrum. In this work, we introduce 21cmgem– the first emulator of the global 21-cm signal from Cosmic Dawn and the EoR. The smoothness of the output signal is guaranteed by design. We train neural networks to predict the cosmological signal using a database of ∼30 000 simulated signals which were created by varying seven astrophysical parameters: the star formation efficiency and the minimal mass of star-forming haloes; the efficiency of the first X-ray sources and their spectrum parametrized by spectral index and the low-energy cut-off; the mean-free path of ionizing photons, and the cosmic microwave background optical depth. We test the performance with a set of ∼2000 simulated signals, showing that the relative error in the prediction has an rms of 0.0159. The algorithm is efficient, with a running time per parameter set of 0.16 s. Finally, we use the database of models to check the robustness of relations between the features of the global signal and the astrophysical parameters that we previously reported.

Petrogenesis of a rare Ediacaran tonalite–trondhjemite–granodiorite suite, Egypt, and implications for Neoproterozoic Gondwana assembly

2020 ◽  
pp. 1-22
Author(s):  
Abdel-Fattah M Abdel-Rahman
Keyword(s):  
Island Arc ◽  
Ionization Mass ◽  
East African ◽  
Wide Range ◽  
Mantle Sources ◽  
Nubian Shield ◽  
East African Orogen ◽  
Subducted Oceanic Crust ◽  
Late Stages ◽  
Arabian Nubian Shield

Abstract Most tonalite–trondhjemite–granodiorite (TTG) suites are Archean–Palaeoproterozoic in age, but those of Neoproterozoic–Phanerozoic age are scarce. A rare Ediacaran high-Al TTG suite has been identified at the Fannani Igneous Complex (FIC) in the northern Arabian–Nubian Shield, which is essentially composed of amalgamated Neoproterozoic island-arc Pan-African composite terranes that contain several ophiolitic sutures. The FIC exhibits a wide range of SiO2, Al2O3, Sr and Zr, shows moderate rare earth element (REE) enrichment, and K, Ti, Nb, Y and heavy REE depletion. It is a subsolvus suite with clear orogenic affinities and strong arc-geochemical signatures. The precise U–Pb zircon thermal ionization mass spectrometry age obtained (607.4 ± 1.95 Ma) indicates oceanic subduction extended to late stages of the East African Orogeny. The FIC exhibits 87Sr/86Sr compositions of 0.70346–0.71091 (Sr(i) ratio, 0.70284), and 143Nd/144Nd of 0.51254–0.51270 (ϵNd(t) = +5.12 to +7.16), typical of modern oceanic-arc rocks (as Japan-arc basalts), and suggestive of mantle sources and island-arc settings. The FIC possesses low values of Yb (1.55 ppm), Nb (14 ppm) and Y (24 ppm), and high ratios of Sr/Y (27), Zr/Sm (46) and Nb/Ta (11.8), typical of magmas produced by anatexis of a basaltic slab. Partial melting models show that the FIC magma was generated by melting (F = 0.25–0.50) of a subducted oceanic crust transformed into eclogite, leaving 10–25% garnet in the residue. The FIC and similar complexes produced via slab melting during the closure of the Mozambique Ocean formed large juvenile belts along the East African Orogen that sutured East and West Gondwana together into a united supercontinent.

scholarly journals The inner dust shell of Betelgeuse detected by polarimetric aperture-masking interferometry

2019 ◽  
Vol 628 ◽  
pp. A101 ◽  
Author(s):  
X. Haubois ◽  
B. Norris ◽  
P. G. Tuthill ◽  
C. Pinte ◽  
P. Kervella ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Mie Scattering ◽  
Parametric Models ◽  
Formation Mechanisms ◽  
Dust Shell ◽  
Stellar Radius ◽  
Fundamental Parameters ◽  
Red Supergiants ◽  
Visible Wavelengths

Context. Theory surrounding the origin of the dust-laden winds from evolved stars remains mired in controversy. Characterizing the formation loci and the dust distribution within approximately the first stellar radius above the surface is crucial for understanding the physics that underlie the mass-loss phenomenon. Aims. By exploiting interferometric polarimetry, we derive the fundamental parameters that govern the dust structure at the wind base of a red supergiant. Methods. We present near-infrared aperture-masking observations of Betelgeuse in polarimetric mode obtained with the NACO/SAMPol instrument. We used both parametric models and radiative transfer simulations to predict polarimetric differential visibility data and compared them to SPHERE/ZIMPOL measurements. Results. Using a thin dust shell model, we report the discovery of a dust halo that is located at only 0.5 R⋆ above the photosphere (i.e. an inner radius of the dust halo of 1.5 R⋆). By fitting the data under the assumption of Mie scattering, we estimate the grain size and density for various dust species. By extrapolating to the visible wavelengths using radiative transfer simulations, we compare our model with SPHERE/ZIMPOL data and find that models based on dust mixtures that are dominated by forsterite are most favored. Such a close dusty atmosphere has profound implications for the dust formation mechanisms around red supergiants.

scholarly journals Supernova Remnant Shocks in an Inhomogeneous Interstellar Medium

1988 ◽  
Vol 101 ◽  
pp. 205-222 ◽  
Author(s):  
Christopher F. McKee
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnant ◽  
Circumstellar Matter ◽  
Infrared Emission ◽  
Circumstellar Material ◽  
Hot Gas ◽  
Wide Range ◽  
Low Mass ◽  
Late Stages ◽  
Intercloud Medium

AbstractThe inhomogeneity of the interstellar medium (ISM) has a profound effect on the propagation of the interstellar shock generated by a supernova and on the appearance of the resulting supernova remnant (SNR). Low mass supernovae produce remnants that interact with the “pristine” ISM, which has density inhomogeneities (clouds) on a wide range of scales. The shock compresses and accelerates the clouds it encounters; inside the blast wave, the clouds are hydrodynamically unstable, and mass is injected from the clouds into the intercloud medium. Embedded clouds interact thermally with the shock also, adding mass to the hot intercloud medium via thermal evaporation or subtracting it via condensation and thermal instability. Mass injection into the hot intercloud medium, whether dynamical or thermal, leads to infrared emission as dust mixes with the hot gas and is thermally sputtered. The remnants of massive supernovae interact primarily with circumstellar matter and with interstellar material which has been processed by the ionizing radiation and wind of the progenitor star. After passing through any circumstellar material which may be present, the shock encounters a cavity which tends to “muffle” the SNR. The remnants of massive supernovae therefore tell us more about the late stages of the evolution of massive stars than about the ISM.

scholarly journals Maternal Hb during pregnancy and offspring's educational achievement: a prospective cohort study over 30 years

2010 ◽  
Vol 104 (9) ◽  
pp. 1363-1368 ◽  
Author(s):  
Mohammad Fararouei ◽  
Claire Robertson ◽  
John Whittaker ◽  
Ulla Sovio ◽  
Aimo Ruokonen ◽  
...  
Keyword(s):  
Cohort Study ◽  
Educational Achievement ◽  
Clinical Importance ◽  
Positive Association ◽  
Later Life ◽  
Birth Cohort Study ◽  
Level Of Education ◽  
Birth Month ◽  
Wide Range ◽  
Late Stages

The aim of the present study was to examine the association between maternal Hb levels during pregnancy and educational achievement of the offspring in later life. We analysed data obtained from the Northern Finnish Birth Cohort Study conducted in 1966, in which, data on mothers and offspring from pregnancy through to the age of 31 years were collected. The cohort comprised 11 656 individuals born from singleton births (51 % males and 49 % females). Maternal Hb levels were available from the third, seventh and ninth gestational months. Educational achievement was measured as school scores (range 4–10) taken at the ages of 14 (self-reported questionnaires) and 16 (school reports) years as well as the highest level of education at the age of 31 years. The present results showed a direct positive association between Hb levels and educational achievement in later life. After adjustment for sex, birth weight, birth month and a wide range of maternal factors (parity, smoking, mental status, whether pregnancy was wanted or not, education, social class and marital status), only maternal Hb levels that were measured at the ninth month were significantly associated with the offspring's school performance. If the levels were ≥ 110 g/l at all the three measurement points, offspring not only had better school scores at the ages of 14 and 16 years (β = 0·048, P = 0·04 and β = 0·68, P = 0·007, respectively), but also had an increased odds of having a higher level of education at the age of 31 years (OR = 1·14, P = 0·04). The present study suggests that low maternal Hb levels at the final stages of pregnancy are linked to the poorer educational achievement of the offspring. If our observation is confirmed, it would suggest that Fe prophylaxis even at fairly late stages of pregnancy may be beneficial for the subsequent health of the offspring. However, more studies are needed to fully establish the potential pathways and the clinical importance of the present findings.

Oxygen, hydrogen, and carbon isotopic studies of the Great Bear Lake silver deposits, Northwest Territories

1986 ◽  
Vol 23 (10) ◽  
pp. 1463-1469 ◽  
Author(s):  
A. Changkakoti ◽  
R. D. Morton ◽  
J. Gray ◽  
C. J. Yonge
Keyword(s):  
Meteoric Water ◽  
Carbon Isotopic ◽  
Bear Lake ◽  
Lake Region ◽  
Wide Range ◽  
Silver Deposits ◽  
Isotopic Studies ◽  
Native Silver ◽  
Host Rocks ◽  
Late Stages

The native-silver-bearing deposits of the Great Bear Lake region occur within two separate domains, namely the Echo Bay sector and the Camsell River sector. In all these deposits, native silver occurs in veins, associated with a wide range of Ni-, Co-, and Fe- arsenides, Cu-, Fe-, Ni-, and Co-sulfides, and pitchblende in gangues of quartz, calcite, dolomite, siderite, rhodochrosite, and fluorite. The host rocks of the veins are for the most part Aphebian volcano-sedimentary roof pendants within the Great Bear batholithic complex. The carbonates (calcite, dolomite, siderite, and rhodochrosite) show a wide range of δ18O (6.8 to 22.5‰, SMOW) and δ13C (−2.7 to −13.3‰, PDB) values. A single analysis of quartz gave a δ18O value of 16.54‰ (SMOW). The δD of water in fluid inclusions in quartz, dolomite, and calcite shows a range from −62.2 to −98.5‰ (SMOW). The δD of present-day meteoric waters from the region shows a range of −146.5 to −165.2‰ (SMOW). The δ18O of the hydrothermal fluids (0.47 to 9.12‰, SMOW) was calculated from the δ18O values of the quartz, calcite, and dolomite belonging to different paragenetic sequences. The δ13C of carbon (−2.8 to −8.6‰, PDB) in the hydrothermal fluid was calculated from the δ13C values of the calcites. The oxygen, carbon, and hydrogen isotopic values indicate that in the early stages of mineralization, magmatic water and carbon from a magmatic source were predominant. During the late stages of mineralization, the influence of meteoric water became more pronounced.

RELATIVISTIC EFFECTS IN POLYTROPIC COMPACT STARS

2007 ◽  
Vol 16 (09) ◽  
pp. 2834-2837 ◽  
Author(s):  
L. FERRARI ◽  
G. ESTRELA ◽  
M. MALHEIRO
Keyword(s):  
Equation Of State ◽  
Relativistic Effects ◽  
Fermi Gas ◽  
Matter Density ◽  
Compact Stars ◽  
Polytropic Index ◽  
First Order ◽  
Polytropic Equation ◽  
Relativistic Fermi ◽  
First Order Differential Equations

We solve numerically the two first order differential equations obtained by Tooper for polytropic compact stars. These equations depend on the polytropic index n related to the adiabatic index Γ = 1 + 1/n and on a parameter σ that manifests the relativistic content of the polytropic equation of state (EOS). In this work we investigate the effect of increasing σ for two polytropic EOS: the case of a nonrelativistic Fermi gas (n = 1.5) and the relativistic one (n = 3.0). We show that for large values of σ, where the sound velocity is not small in comparison to the velocity of light, the matter density is more concentrated in the center of the star and as a consequence the star mass also is: this effect is quite strong in the case of the relativistic fermi gas.

An anisotropic model for represent compact stars

2020 ◽  
Vol 35 (16) ◽  
pp. 2050132 ◽  
Author(s):  
Joaquin Estevez-Delgado ◽  
Jose Vega Cabrera ◽  
Joel Arturo Rodriguez Ceballos ◽  
Jorge Mauricio Paulin-Fuentes
Keyword(s):  
Speed Of Sound ◽  
Anisotropy Parameter ◽  
Compact Stars ◽  
Energy Conditions ◽  
Perfect Fluid Solution ◽  
Stellar Radius ◽  
Compactness Factor ◽  
The Stability ◽  
Decreasing Functions ◽  
Anisotropic Pressures

Starting from a perfect fluid solution we constructed a generalization with anisotropic pressures and regular geometry as well as the pressures, the density and the speed of sound, these are also positive and monotonic decreasing functions. The speed of sound is lower than the speed of light, that is to say, the condition of causality is not broken. The model satisfies all the energy conditions and the radial [Formula: see text] and tangential [Formula: see text] speeds and complies with [Formula: see text] because of this the solution is stable according to the stability criteria related with the concept of cracking. The maximum value of the compactness factor [Formula: see text] which is lower than the Buchdahl limit and associated to neutron stars. In a complementary manner, we realize an analysis of the behavior of a star with a mass of [Formula: see text], with a fixed value of the anisotropy parameter and different compactness values, giving as a result that their central density [Formula: see text] and the superficial density [Formula: see text], the maximum values match the value of greater compactness of the model with a stellar radius of 6506.921 m.

scholarly journals Resolving the mass loss from red supergiants by high angular resolution

2016 ◽  
Vol 12 (S329) ◽  
pp. 97-103
Author(s):  
Keiichi Ohnaka
Keyword(s):  
Mass Loss ◽  
Spatial Resolution ◽  
Angular Resolution ◽  
High Spatial Resolution ◽  
Spatial Scales ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Long Baseline ◽  
Red Supergiants ◽  
Late Stages

AbstractDespite its importance on late stages of the evolution of massive stars, the mass loss from red supergiants (RSGs) is a long-standing problem. To tackle this problem, it is essential to observe the wind acceleration region close to the star with high spatial resolution. While the mass loss from RSGs is often assumed to be spherically symmetric with a monotonically accelerating wind, there is mounting observational evidence that the reality is much more complex. I review the recent progress in high spatial resolution observations of RSGs, encompassing from the circumstellar envelope on rather large spatial scales (~100 stellar radii) to milliarcsecond-resolution aperture-synthesis imaging of the surface and the atmosphere of RSGs with optical and infrared long-baseline interferometers.

scholarly journals NEUTRINO EMISSIVITY OF DENSE STARS

1996 ◽  
Vol 05 (02) ◽  
pp. 385-401 ◽  
Author(s):  
SANJAY K. GHOSH ◽  
S.C. PHATAK ◽  
P.K. SAHU
Keyword(s):  
Quark Matter ◽  
Strong Dependence ◽  
Nuclear Interaction ◽  
Compact Stars ◽  
Hadronic Matter ◽  
Wide Range ◽  
Neutrino Emissivity ◽  
Relativistic Models ◽  
The Difference ◽  
Dense Stars

The neutrino emissivity of compact stars is investigated in this work. We consider stars consisting of nuclear as well as quark matter for this purpose. Different models are used to calculate the composition of nuclear and quark matter and the neutrino emissivity. Depending on the model under consideration, the neutrino emissivity of nuclear as well as quark matter varies over a wide range. We find that for nuclear matter, the direct URCA processes are allowed for most of the relativistic models without and with strange baryons, whereas for the nonrelativistic models this shows a strong dependence on the type of nuclear interaction employed. When the direct URCA processes are allowed, the neutrino emissivity of hadronic matter is larger than that of the quark matter by several orders of magnitude. We also find that the neutrino emissivity departs from T6 behavior when the temperature is larger than the difference in the Fermi momenta of the particles, participating in the neutrino-producing reactions.

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