scholarly journals Properties of Thorne–Żytkow object explosions

2021 ◽  
Vol 508 (1) ◽  
pp. 74-78
Author(s):  
Takashi J Moriya ◽  
Sergei I Blinnikov
Keyword(s):  
Neutron Star ◽  
Nuclear Reactions ◽  
Accretion Disc ◽  
Long Duration ◽  
Long Time ◽  
Bright Phase

ABSTRACT Thorne–Żytkow objects are stars that have a neutron star core with an extended hydrogen-rich envelope. Massive Thorne–Żytkow objects are proposed to explode when the nuclear reactions sustaining their structure are terminated by the exhaustion of the seed elements. In this paper, we investigate the observational properties of the possible Thorne–Żytkow object explosions. We find that Thorne–Żytkow object explosions are observed as long-duration transients lasting for several years. If the accretion disc triggering the explosions does not last for a long time, Thorne–Żytkow object explosions have a luminosity plateau with about $10^{39}\, \mathrm{erg\, s^{-1}}$ lasting for a few years, and then they suddenly become faint. They would be observed as vanished stars after a bright phase lasting for a few years. If the accretion disc is sustained for long time, the Thorne–Żytkow object explosions become as bright as supernovae. They would be observed as supernovae with rise times of several hundred days. We found that their photospheric velocities are $2000\, \mathrm{km\, s^{-1}}$ at most, much smaller than those found in supernovae. Supernovae with extremely long rise times such as HSC16aayt and SN 2008iy may be related to the explosions of Thorne–Żytkow objects.

scholarly journals Developing an end-to-end simulation framework of supernova neutrino detection

2020 ◽  
Author(s):  
Masamitsu Mori ◽  
Yudai Suwa ◽  
Ken’ichiro Nakazato ◽  
Kohsuke Sumiyoshi ◽  
Masayuki Harada ◽  
...  
Keyword(s):  
Neutron Star ◽  
Neutrino Emission ◽  
Neutrino Detectors ◽  
Sn 1987A ◽  
Neutrino Detection ◽  
Time Simulation ◽  
Consistent Manner ◽  
Long Time ◽  
Neutron Star Cooling ◽  
Proto Neutron Star

Abstract Massive stars can explode as supernovae at the end of their life cycle, releasing neutrinos whose total energy reaches 1053erg. Moreover, neutrinos play key roles in supernovae, heating and reviving the shock wave as well as cooling the resulting proto-neutron star. Therefore, neutrino detectors are waiting to observe the next galactic supernova and several theoretical simulations of supernova neutrinos are underway. While these simulation concentrate mainly on only the first one second after the supernova bounce, the only observation of a supernova with neutrinos, SN 1987A, revealed that neutrino emission lasts for more than 10 seconds. For this reason, long-time simulation and analysis tools are needed to compare theories with the next observation. Our study is to develop an integrated supernova analysis framework to prepare an analysis pipeline for treating galactic supernovae observations in the near future. This framework deals with the core-collapse, bounce and proto-neutron star cooling processes, as well as with neutrino detection on earth in a consistent manner. We have developed a new long-time supernova simulation in one dimension that explodes successfully and computes the neutrino emission for up to 20 seconds. Using this model we estimate the resulting neutrino signal in the Super-Kamiokande detector to be about 1,800 events for an explosion at 10 kpc and discuss its implications in this paper. We compare this result with the SN 1987A observation to test its reliability.

scholarly journals 1. On Galvanic Polarisation

1882 ◽  
Vol 11 ◽  
pp. 202-204
Author(s):  
Helmholtz
Keyword(s):  
Electrolytic Cell ◽  
Motive Force ◽  
Long Duration ◽  
Long Time ◽  
Electro Motive Force ◽  
A Current

In 1872 I wrote a paper on galvanic currents, which continue for a long time in an electrolytic cell, under the influence of an electro-motive force, too feeble to effect electrolytic decomposition. I tried at that time to prove that the long duration of these currents was caused by oxygen dissolved in the water of the electrolyte, combining with the hydrogen, which is carried by the electrolytic motion to the cathode. So the oxygen, which existed formerly near the surface of the cathode, is taken away, and instead of it the same amount of oxygen is liberated at the anode. This can return by diffusion to the cathode, and so the same action can go on without end. It appears as a current producing no electrolytic action. I called it “Electrolytic convection.”

Deep Donor and Acceptor Levels Induced by High Temperature and long time Annealing in LEC Gallium Arsenide

1991 ◽  
Vol 240 ◽  
Author(s):  
G. Marrakchi ◽  
A. Kalboussi ◽  
G. Guillot ◽  
M. Ben Salem ◽  
H. Maaref ◽  
...  
Keyword(s):  
High Temperature ◽  
Cold Water ◽  
Deep Level ◽  
Electron Trap ◽  
Single Donor ◽  
Long Duration ◽  
Donor And Acceptor ◽  
Deep Donor ◽  
Long Time ◽  
Lec Gaas

ABSTRACTThe effects of high temperature isothermal annealing on the electrical properties of donor and acceptor defects in n-type LEC GaAs are investigated. The annealing experiments are performed under As-rich atmosphere at 1000°C for 1–4 and 16 hours followed by a very quick quenching into cold water of the quartz ampoules containing the samples. The donor and acceptor levels are detected respectively by standard (DLTS) and optical (ODLTS) deep level spectroscopy. DLTS results show the presence of one single donor level present in unannealed and annealed samples at Ec - 0.79eV which is identified as the well known electron trap EL2 Only the sample annealed for 16 hs exhibits the presence of a new electron trap named TAI at Ec - 0.32eV. The appearance of TAI is correlated in one hand with the evolution of EL2 concentration and in the other hand to the effect of long duration (16 hs) of the treatment. For acceptor levels, two hole traps HT1 and HT2 are detected respectively at EV + 0.18 eV and EV+ 0.28 eV. HT1 is detected only in samples annealed for 4 and 16 hs and HT2 is detected in all studied samples. Photoluminescence (PL) measurements show the presence of the 1.44 eV band corresponding to gallium antisite GaAs defect. This band observed in unannealed and annealed samples shows that GaAs remains stable even after thermal annealing at lOOO°C for 16 hs and it is correlated with the presence of HT2.

scholarly journals Thermal evolution and quiescent emission of transiently accreting neutron stars

2019 ◽  
Vol 629 ◽  
pp. A88 ◽  
Author(s):  
A. Y. Potekhin ◽  
A. I. Chugunov ◽  
G. Chabrier
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Reactions ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Equilibrium Temperature ◽  
Theoretical Interpretation ◽  
Quasi Equilibrium ◽  
Accretion Rates

Aims. We study the long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. Methods. We performed simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We also tested and compared results for different modern theoretical models. We updated a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compared the observational estimates with the theoretical results. Results. The long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave the previous conclusions unchanged, namely that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.

scholarly journals Production of56Ni in black hole-neutron star merger accretion disc outflows

2014 ◽  
Vol 41 (4) ◽  
pp. 044006 ◽  
Author(s):  
R Surman ◽  
O L Caballero ◽  
G C McLaughlin ◽  
O Just ◽  
H-Th Janka
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Accretion Disc

scholarly journals A hospital based cross sectional study on comorbid psychiatric problems in persons with epilepsy from north eastern part of India

2017 ◽  
Vol 04 (01) ◽  
pp. 031-035 ◽  
Author(s):  
Sajjadur Rehman ◽  
Kamal Kalita ◽  
Aparajeeta Baruah
Keyword(s):  
Psychiatric Comorbidity ◽  
Tertiary Care ◽  
Cross Sectional Study ◽  
Clinical Factors ◽  
Cross Sectional ◽  
Psychiatric Comorbidities ◽  
Psychiatric Disturbances ◽  
Long Duration ◽  
North Eastern ◽  
Long Time

Abstract Context The relationship between epilepsy and psychiatric disorders has been recognized for a long time. Psychiatric disturbances like depression, anxiety disorder, psychosis, panic disorder, suicidal behavior etc are associated with epilepsy. Different demographic and clinical factors are associated with the onset of these psychiatric disturbances. Aims To study the prevalence of psychiatric comorbidity in persons with epilepsy. Also assess the different demographic and clinical factors and its relation with the presence of psychiatric comorbidity in persons with epilepsy. Settings and design It was a cross sectional observational study. Methods and material Diagnosed cases of epilepsy, attending Epilepsy Clinic, fulfilling the inclusion and exclusion criteria were recruited for the study. Patients were evaluated with Mini International Neuropsychiatric Interview (MINI) to see their psychiatric comorbidities and also the socio-demographic and clinical factors were assessed Statistical analysis used SPSS version 23.0 for Windows and Graph Pad InStat software trial version 3.1 was used for analysis. Results Psychiatric comorbidity was seen in 50% subjects with comorbid with epilepsy. Depression 18%, Psychosis 14% and Anxiety Disorders 11%, were the most commonly found psychiatric morbidities. Presence of partial seizures, frequent seizures, long duration of epilepsy and poor compliance to antiepileptic drug were significantly associated with presence of psychiatric comorbidity in persons with epilepsy. Conclusions Psychiatric comorbidities are very common in epilepsy. Psychosis associated with epilepsy is seen more in hospital settings. Depression and anxiety though commonly reported in studies are less commonly presented to tertiary care settings.

scholarly journals Early neutron star evolution in high-mass X-ray binaries

2020 ◽  
Vol 494 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Wynn C G Ho ◽  
M J P Wijngaarden ◽  
Nils Andersson ◽  
Thomas M Tauris ◽  
F Haberl
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Thermal Emission ◽  
Equilibrium Phase ◽  
High Mass ◽  
X Ray ◽  
Spin Period ◽  
Long Duration ◽  
X Ray Binaries ◽  
The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

Nuclear reactions on accreting neutron star surface

1985 ◽  
Vol 116 (1) ◽  
pp. 97-106
Author(s):  
K. Duorah ◽  
H. L. Duorah
Keyword(s):  
Neutron Star ◽  
Nuclear Reactions ◽  
Star Surface
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