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Littérature scientifique sur le sujet « X-rays: star »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 11 mars 2023

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Articles de revues sur le sujet "X-rays: star"

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Vilhu, O., T. R. Kallman, K. I. I. Koljonen et D. C. Hannikainen. « Wind suppression by X-rays in Cygnus X-3 ». Astronomy & ; Astrophysics 649 (mai 2021) : A176. http://dx.doi.org/10.1051/0004-6361/202140620.

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Context. The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star. Aims. We aim to estimate how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3. Methods. We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott & Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. We solved the wind equations at different orbital angles from the line joining the stars and took the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We compared them to those obtained from observations. Results. We found that the ionization potentials of the ions contributing the most to the line force fall in the extreme-UV region (100–230 Å). If the flux in this region is high, the line force is weak, and consequently, the wind velocity is low. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping, this correlation disappears. We compared the XSTAR method used here with the comoving frame method and found that they agree reasonably well with each other. Conclusions. We show that soft X-rays in the extreme-UV region from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2–3) solar masses.
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Brorby, M., et P. Kaaret. « X-rays from Green Pea analogues ». Monthly Notices of the Royal Astronomical Society 470, no 1 (24 mai 2017) : 606–11. http://dx.doi.org/10.1093/mnras/stx1286.

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Abstract X-ray observations of two metal-deficient luminous compact galaxies (LCG; SHOC 486 and SDSS J084220.94+115000.2) with properties similar to the so-called Green Pea galaxies were obtained using the Chandra X-ray Observatory. Green Pea galaxies are relatively small, compact (a few kpc across) galaxies that get their green colour from strong [O iii] λ5007 Å emission, an indicator of intense, recent star formation. These two galaxies were predicted to have the highest observed count rates, using the X-ray luminosity–star formation rate (LX–SFR) relation for X-ray binaries, from a statistically complete sample drawn from optical criteria. We determine the X-ray luminosity relative to SFR and metallicity for these two galaxies. Neither exhibits any evidence of active galactic nuclei, and we suspect that the X-ray emission originates from unresolved populations of high-mass X-ray binaries. We discuss the LX–SFR–metallicity plane for star-forming galaxies and show that the two LCGs are consistent with the prediction of this relation. This is the first detection of Green Pea analogues in X-rays.
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Nagase, Fumiaki. « Photoionized Plasmas in X-Ray Binary Pulsars : ASCA Observations ». Symposium - International Astronomical Union 188 (1998) : 101–4. http://dx.doi.org/10.1017/s0074180900114524.

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Massive X-ray binary pulsars have often evolved early-type companion stars which emanate strong stellar winds. X-rays emitted from the accreting neutron star irradiate and ionize the surrounding stellar wind, thus forming a photoionized sphere surrounding the neutron star. The photoionization structure of matter surrounding the neutron star was calculated by Hatchett and McCray (1977) and McCray et al. (1984), for Cen X-3 and Vela X-1 respectively.
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Watson, A. « ASTROPHYSICS:Z Mimics X-rays From Neutron Star ». Science 286, no 5447 (10 décembre 1999) : 2059. http://dx.doi.org/10.1126/science.286.5447.2059.

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Ruderman, M. « Neutron Star Powered Accelerators ». Symposium - International Astronomical Union 195 (2000) : 463–71. http://dx.doi.org/10.1017/s0074180900163508.

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Neutron stars can be the underlying source of energetic particle acceleration in several ways. The huge gravitational-collapse energy released in their birth, or the violent fusion at the end of the life of a neutron-star binary, is the energy source for an accelerator in the surrounding medium far from the star. This would be the case for: (a) cosmic rays from supernova explosions with neutron-star remnants; (b) energetic radiation from “plerions” around young neutron stars (e.g., the Crab Nebula, see Pacini 2000); and (c) “afterglow” and γ-rays of cosmic Gamma-Ray Burst (GRB) sources with possible neutron-star central engines. Particles can also be energetically accelerated if a neutron star's gravitational pull sustains an accretion disk fed by a companion. Examples are accretion-powered X-ray pulsars and low-mass X-ray binaries. A third family of “neutron-star powered” accelerators consists of those which do not depend on the surrounding environment. These are the accelerators which must exist in the magnetospheres of many solitary, spinning-down, magnetized neutron stars (“spinsters”) when they are observed as radio pulsars or γ-ray pulsars. (There are probably ~ 103 dead radio pulsars for each one in our Galaxy that is still active; the ratio for γ-ray pulsars may well exceed 105.)
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Fabian, A. C., et P. A. Thomas. « X-Rays from Elliptical Galaxies ». Symposium - International Astronomical Union 127 (1987) : 155–65. http://dx.doi.org/10.1017/s0074180900185146.

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X-ray observations have shown that early-type galaxies contain a hot interstellar medium. This implies that the galaxies have a) a low supernova rate; b) high total gravitational binding masses and c) continuous star formation. Much of the gas in isolated galaxies is probably due to stellar mass-loss. The details of its behaviour are complex.
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Babel, J. « Diffusion, Winds and X-Rays from Magnetic Stars ». Highlights of Astronomy 11, no 2 (1998) : 674–75. http://dx.doi.org/10.1017/s1539299600018426.

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AbstractWe propose a self-consistent approach of the CP star phenomenon and try to solve simultaneously the problems of abundance spots, wind and X-ray emission from these stars. We also discuss the periodic X-ray emission from the 07V star θ1 Orionis C and its link with Bp stars.
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Oskinova, L. M., R. Ignace et D. P. Huenemoerder. « X-ray diagnostics of massive star winds ». Proceedings of the International Astronomical Union 12, S329 (novembre 2016) : 151–55. http://dx.doi.org/10.1017/s1743921317002952.

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AbstractObservations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.
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Kumagai, S. « X-Rays and γ-Rays from SN 1987A ». International Astronomical Union Colloquium 145 (1996) : 173–81. http://dx.doi.org/10.1017/s0252921100008046.

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Theoretical light curves and spectra of X-rays and γ-rays from SN 1987A are calculated by the Monte Carlo method, based on a model built up from the early observations of neutrinos and optical light. Comparison of the predicted radiation with observational results obtained later confirms the radiation mechanism of supernovae: γ-rays are emitted in the decays of radioactive 56Co and X-rays are generated by the Compton degradation of these γ-rays. It also suggests that large scale mixing occurred and clumpy structure was formed inside the ejecta. These findings lead us to construct the model with a new distribution of elements, which is determined through comparisons of observations of X-rays and γ-rays with numerical simulations based on the assumed distribution. Using this model, the subsequent X-ray and γ-ray emission is predicted: the light curves of X-rays and γ-rays as well as their spectral evolution are in very good agreement with that expected from the radioactive decays of 56Co and 57Co. The mass of newly synthesized 44Ti and the emission from the neutron star will be determined by future satellite and balloon-borne observations.
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Bogdanov, Slavko. « X-rays from Radio Millisecond Pulsars ». Proceedings of the International Astronomical Union 13, S337 (septembre 2017) : 116–19. http://dx.doi.org/10.1017/s1743921317011553.

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AbstractThe Galactic population of rotation-powered (aka radio) millisecond pulsars (MSPs) exhibits diverse X-ray properties. Energetic MSPs show pulsed non-thermal radiation from their magnetospheres. Eclipsing binary MSPs predominantly have X-ray emission from a pulsar wind driven intra-binary shock. Typical radio MSPs emit X-rays from their heated magnetic polar caps. These thermally emitting MSPs offer the opportunity to place interesting constraints on the long sought after dense matter equation of state, making them important targets of investigation of the recently deployed Neutron Star Interior Composition Explorer (NICER) X-ray mission.
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Thèses sur le sujet "X-rays: star"

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Sasaki, Manami. « X-rays tracing the star formation history of the Magellanic clouds ». [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964798824.

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Sasaki, Manami. « X-rays tracing the star formation history of the Magellanic clouds ». Diss., lmu, 2002. http://nbn-resolving.de/urn:nbn:de:bvb:19-4438.

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Güver, Tolga, Feryal Özel, Herman Marshall, Dimitrios Psaltis, Matteo Guainazzi et Maria Díaz-Trigo. « SYSTEMATIC UNCERTAINTIES IN THE SPECTROSCOPIC MEASUREMENTS OF NEUTRON STAR MASSES AND RADII FROM THERMONUCLEAR X-RAY BURSTS. III. ABSOLUTE FLUX CALIBRATION ». IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621974.

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Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HETG/ACIS-S and RXTE/PCA as well as by XMM-Newton EPIC-pn and RXTE/PCA, we quantify the degree of uncertainty in the flux calibration by assessing the differences between the measured fluxes during bursts. We find that the RXTE/PCA and the Chandra gratings measurements agree with each other within their formal uncertainties, increasing our confidence in these flux measurements. In contrast, XMM-Newton EPIC-pn measures 14.0 +/- 0.3% less flux than the RXTE/PCA. This is consistent with the previously reported discrepancy with the flux measurements of EPIC-pn, compared with EPIC MOS1, MOS2, and ACIS-S detectors. We also show that any intrinsic time-dependent systematic uncertainty that may exist in the calibration of the satellites has already been implicity taken into account in the neutron star radius measurements.
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Gregory, Scott G. « T Tauri stars : mass accretion and X-ray emission ». Thesis, St Andrews, 2007. http://hdl.handle.net/10023/336.

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Igance, Richard. « Modeling X-ray Emission Line Profiles from Massive Star Winds - A Review ». Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2686.

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The Chandra and XMM-Newton X-ray telescopes have led to numerous advances in the study and understanding of astrophysical X-ray sources. Particularly important has been the much increased spectral resolution of modern X-ray instrumentation. Wind-broadened emission lines have been spectroscopically resolved for many massive stars. This contribution reviews approaches to the modeling of X-ray emission line profile shapes from single stars, including smooth winds, winds with clumping, optically thin versus thick lines, and the effect of a radius-dependent photoabsorption coefficient.
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Hubrig, S., M. Schöller, A. Kholtygin, H. Tsumura, A. Hoshino, S. Kitamoto, L. Oskinova, Richard Ignace, H. Todt et I. Ilyin. « New Multiwavelength Observations of the Of?p Star CPD -28◦ 2561 ». Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/6241.

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A rather strong mean longitudinal magnetic field of the order of a few hundred gauss was detected a few years ago in the Of?p star CPD −28° 2561 using FORS2 (FOcal Reducer low dispersion Spectrograph 2) low-resolution spectropolarimetric observations. In this work, we present additional low-resolution spectropolarimetric observations obtained during several weeks in 2013 December using FORS 2 mounted at the 8-m Antu telescope of the Very Large Telescope (VLT). These observations cover a little less than half of the stellar rotation period of 73.41 d mentioned in the literature. The behaviour of the mean longitudinal magnetic field is consistent with the assumption of a single-wave variation during the stellar rotation cycle, indicating a dominant dipolar contribution to the magnetic field topology. The estimated polar strength of the surface dipole Bd is larger than 1.15 kG. Further, we compared the behaviour of the line profiles of various elements at different rotation phases associated with different magnetic field strengths. The strongest contribution of the emission component is observed at the phases when the magnetic field shows a negative or positive extremum. The comparison of the spectral behaviour of CPD −28° 2561 with that of another Of?p star, HD 148937 of similar spectral type, reveals remarkable differences in the degree of variability between both stars. Finally, we present new X-ray observations obtained with the Suzaku X-ray Observatory. We report that the star is X-ray bright with log LX/Lbol ≈ −5.7. The low-resolution X-ray spectra reveal the presence of a plasma heated up to 24 MK. We associate the 24 MK plasma in CPD −28° 2561 with the presence of a kG strong magnetic field capable to confine stellar wind.
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RIGOSELLI, MICHELA. « X-ray emission from the magnetic polar caps of old rotation-powered pulsars ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/277373.

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Le stelle di neutroni sono il risultato dell'evoluzione di stelle massive dopo l'esplosione di supernova. Il progetto di questa Tesi di PhD consiste nello studio dell'emissione di raggi X da parte di stelle di neutroni isolate di età superiore a 100000 anni. Sono stati analizzati dati provenienti dal satellite XMM-Newton (ESA). Per estrarre la miglior informazione possibile dai dati, ho implementato un metodo di maximum likelihood (ML) e l'ho utilizzato per estrarre spettri e profili pulsati di pulsar vecchie in banda X, che poi sono stati analizzati con raffinati di emissione. La Tesi è strutturata come segue: nei primi tre capitoli illustro le proprietà principali delle stelle di neutroni, con particolare attenzione ai processi termici e non termici che producono raggi X. I raggi X non termici sono prodotti da particelle relativistiche accelerate da campi elettromagnetici; una frazione di queste particelle viene accelerata verso la superficie della stella, e riscalda le zone delle calotte polari magnetiche. La componente termica, che può essere prodotta dall'intera superficie o da una parte, viene solitamente descritta come un corpo nero; tuttavia, la presenza di intensi campi magnetici superficiali influenza le proprietà della materia, e la radiazione emessa è ampiamente anisotropa. Nel Capitolo 4 descrivo come ho generato spettri e profili pulsati sintetici, utilizzando modelli di emissione che considerano calotte polari ricoperte di un'atmosfera di idrogeno magnetizzata. Mi sono basata su un software esistente che, dato un certo set di parametri relativi alle proprietà fisiche della stella, stima l'intensità della radiazione prodotta. Successivamente, esso somma i contributi degli elementi di superficie che sono visibili all'osservatore alle differenti fasi di rotazione. Quindi, nel Capitolo 5 descrivo come ho implementato un software di analisi che si basa sul metodo di ML. Dato un certo modello, esso stima i parametri più probabili che ricostruiscono i dati osservati, nella fattispecie il numero di conteggi relativo alla sorgente e al background. Ho validato il metodo e dimostrato che esso è particolarmente efficace per sorgenti deboli, quali sono la maggior parte delle pulsar vecchie. Successivamente, ho applicato i metodi finora descritti ad alcune pulsar vecchie. Nel Capitolo 6 riporto l'analisi di PSR J0726-2612, una pulsar radio che ha alcune delle caratteristiche delle XDINSs: un periodo di rotazione lungo, un intenso campo magnetico, ed emissione X termica. Grazie ad un'analisi congiunta dello spettro e del profilo pulsato, ho mostrato che la presenza di impulsi radio in PSR J0726-2612, così come la loro assenza nelle XDINSs, potrebbe essere dovuta ad un'orientazione differente rispetto all'osservatore. Nel Capitolo 7 presento il caso di PSR B0943+10, una pulsar con emissione X sia termica sia non termica ma che, nonostante sia un rotatore allineato, ha una grande frazione pulsata. Sono riuscita a riappacificare i due diversi aspetti grazie ad un'attenta analisi di ML e all'intrinseca anisotropia dell'emissione termica prodotta da un'atmosfera magnetizzata. Nel Capitolo 8 ho invece applicato il metodo di ML su sette pulsar poco brillanti, delle quali quattro avevano diverse analisi già pubblicate in letteratura, ma con risultati discordanti, mentre le altre tre non erano ancora state rivelate in banda X. Ho trovato tracce evidenti di emissione termica solo in due oggetti, più un accenno nello spettro pulsato di un terzo oggetto. Infine, ho considerato tutte le pulsar vecchie che emettono raggi X termici e ho confrontato le misure di temperatura, raggio e luminosità alle aspettative dei modelli teorici. In particolare, ho scoperto che le aree di emissione sono generalmente in accordo con quelle previste dal modello di dipolo magnetico rotante, purché vengano considerati anche effetti di proiezione geometrica e modelli di emissione realistici, quali appunto i modelli di atmosfera magnetizzata.
Neutron stars are the remnants of massive stars whose cores collapse during the supernova explosions. The project of this PhD Thesis consisted in the study of the X-ray emission from isolated neutron stars older than about 100000 years. The work was based mainly on data obtained with the XMM-Newton satellite (ESA). To extract the best possible information from the data, I implemented a maximum likelihood (ML) technique and used it to derive the X-ray spectra and pulse profiles of several old pulsars, that were then studied with state-of-the-art models of X-ray emission. The Thesis is structured as follows: in the first three chapters I outline the main properties of neutron stars, with a major focus on the thermal and nonthermal processes that produce X-rays. The nonthermal X-rays are produced by relativistic particles accelerated by rotation-induced electric fields and moving along the magnetic field lines. A fraction of these particles is accelerated backward and returns on the stellar surface, heating the magnetic polar caps. The thermal component, that can be produced by the whole stellar surface or by small hot spots, can be described, in a first approximation, by a blackbody. However, the presence of intense surface magnetic fields strongly affects the properties of matter, and the emergent radiation is widely anisotropic. In Chapter 4, I describe how I generated synthetic spectra and pulse profiles using thermal emission models that consider polar caps covered by a magnetized hydrogen atmosphere or with a condensed iron surface. I relied on an existing software that, given a set of stellar parameters, evaluates the emerging intensity of the radiation. A second software, which I adapted on the sources I analyzed in the Thesis, collects the contribution of surface elements which are in view at different rotation phases from a stationary observer. Then, in Chapter 5, I describe how I implemented an analysis software that relies on the ML method. It estimates the most probable number of source and background counts by comparing the spatial distribution of the observed counts with the expected distribution for a point source plus an uniform background. I demonstrated that the ML method is particularly effective for dim sources, as most old pulsars are. Subsequently, I applied the methods described above to some old pulsars. In Chapter 6, I report the analysis of PSR J0726-2612, a radio pulsars that shares some properties with the radio-silent XDINSs, as the long period, the high magnetic field, and the thermal X-ray emission from the cooling surface. Thanks to an in-depth analysis of the combined spectrum and pulse profile, I showed that the presence of radio pulses from PSR J0726-2612, as well as the absence from the XDINSs, might simply be due to different viewing geometries. In Chapter 7, I present the case of PSR B0943+10, a pulsar with a nonthermal and thermal X-ray spectrum but that, despite being an aligned rotator, has a large pulsed fraction. I could reconcile the two opposite properties analyzing with the ML the spectrum and the pulse profile, and considering the magnetic beaming of a magnetized atmosphere model, that well fits the thermal component. In Chapter 8, I applied the ML method to seven old and dim pulsars, of which four had controversial published results, and three were so far undetected. I found convincing evidence of thermal emission only in the phase-averaged spectrum of two of them, plus a hint for a thermal pulsed spectrum in a third object. Finally, I considered all the old thermal emitters and I compared their observed temperatures, radii and luminosities to the expectations of the current theoretical models for these objects. In particular, I found that the emitting area are generally in agreement with the polar cap regions evaluated in a dipole approximation, if the combined effects of geometry projections plus realistic thermal models (as the magnetic atmosphere) are taken into account.
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Leto, P., Corrado Trigilio, Lidia M. Oskinova, Richard Ignace, C. S. Buemi, G. Umana, A. Ingallinera, H. Todt et F. Leone. « The Detection of Variable Radio Emission from the Fast Rotating Magnetic Hot B-Star HR 7355 and Evidence for Its X-Ray Aurorae ». Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/2695.

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In this paper we investigate the multiwavelengths properties of the magnetic early B-type star HR7355. We present its radio light curves at several frequencies, taken with the Jansky Very Large Array, and X-ray spectra, taken with the XMM X-ray telescope. Modeling of the radio light curves for the Stokes I and V provides a quantitative analysis of the HR7355 magnetosphere. A comparison between HR7355 and a similar analysis for the Ap star CUVir, allows us to study how the different physical parameters of the two stars affect the structure of the respective magnetospheres where the non-thermal electrons originate. Our model includes a cold thermal plasma component that accumulates at high magnetic latitudes that influences the radio regime, but does not give rise to X-ray emission. Instead, the thermal X-ray emission arises from shocks generated by wind stream collisions close to the magnetic equatorial plane. The analysis of the X-ray spectrum of HR7355 also suggests the presence of a non-thermal radiation. Comparison between the spectral index of the power-law X-ray energy distribution with the non-thermal electron energy distribution indicates that the non-thermal X-ray component could be the auroral signature of the non-thermal electrons that impact the stellar surface, the same non-thermal electrons that are responsible for the observed radio emission. On the basis of our analysis, we suggest a novel model that simultaneously explains the X-ray and the radio features of HR7355 and is likely relevant for magnetospheres of other magnetic early type stars.
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Leto, P., Courtney Trigilio, Lidia M. Oskinova, Richard Ignace, C. S. Buemi, G. Umana, A. Ingallinera et al. « A Combined Multiwavelength VLA/ALMA/Chandra Study Unveils the Complex Magnetosphere of the B-Type Star HR5907 ». Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/2682.

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We present new radio/millimeter measurements of the hot magnetic star HR 5907 obtained with the VLA and ALMA interferometers. We find that HR 5907 is the most radio luminous early type star in the cm–mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast-rotating magnetic star. We classify HR 5907 as another member of the growing class of strongly magnetic fast-rotating hot stars where the gyro-synchrotron emission mechanism efficiently operates in their magnetospheres. The new radio observations of HR 5907 are combined with archival X-ray data to study the physical condition of its magnetosphere. The X-ray spectra of HR 5907 show tentative evidence for the presence of non-thermal spectral component. We suggest that non-thermal X-rays originate a stellar X-ray aurora due to streams of non-thermal electrons impacting on the stellar surface. Taking advantage of the relation between the spectral indices of the X-ray power-law spectrum and the non-thermal electron energy distributions, we perform 3-D modelling of the radio emission for HR 5907. The wavelength-dependent radio light curves probe magnetospheric layers at different heights above the stellar surface. A detailed comparison between simulated and observed radio light curves leads us to conclude that the stellar magnetic field of HR 5907 is likely non-dipolar, providing further indirect evidence of the complex magnetic field topology of HR 5907.
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Oskinova, Lidia M., Richard Ignace et D. P. Huenemoerder. « X-ray Diagnostics of Massive Star Winds ». Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2703.

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Observations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.
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Livres sur le sujet "X-rays: star"

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United States. National Aeronautics and Space Administration., dir. X-rays from the youngest stars. [Washington, DC : National Aeronautics and Space Administration, 1994.

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United States. National Aeronautics and Space Administration., dir. X-rays from the youngest stars. [Washington, DC : National Aeronautics and Space Administration, 1994.

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United States. National Aeronautics and Space Administration., dir. X-rays from the youngest stars. [Washington, DC : National Aeronautics and Space Administration, 1994.

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United States. National Aeronautics and Space Administration., dir. A deep PSPC observation of the Cyg OB2 association : Final report. [Washington, D.C : National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., dir. A deep PSPC observation of the Cyg OB2 association : Final report. [Washington, DC : National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., dir. A deep PSPC observation of the Cyg OB2 association : Final report. [Washington, DC : National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., dir. A deep PSPC observation of the Cyg OB2 association : Final report. [Washington, D.C : National Aeronautics and Space Administration, 1995.

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Masayuki, Itoh, Nagase F. 1941- et United States. National Aeronautics and Space Administration., dir. A search for X-ray evidence of a compact companion to the unusual Wolf-Rayet star HD 50896 (EZ CMa). [Amsterdam, The Netherlands] : Elsevier, 1998.

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Masayuki, Itoh, Nagase F. 1941- et United States. National Aeronautics and Space Administration., dir. A search for X-ray evidence of a compact companion to the unusual Wolf-Rayet star HD 50896 (EZ CMa). [Amsterdam, The Netherlands] : Elsevier, 1998.

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United States. National Aeronautics and Space Administration., dir. An investigation of the largest flares in active cool star binaries with ALEXIS : Final report. [Washington, DC : National Aeronautics and Space Administration, 1998.

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Chapitres de livres sur le sujet "X-rays: star"

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White, Richard L., et Wan Chen. « Particle Acceleration, X-Rays, and Gamma-Rays from Winds ». Dans Instability and Variability of Hot-Star Winds, 295–307. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0315-2_23.

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Tatischeff, V., A. Decourchelle et G. Maurin. « Nonthermal X-Rays from Low-Energy Cosmic Rays in the Arches Cluster Region ». Dans Cosmic Rays in Star-Forming Environments, 433–38. Berlin, Heidelberg : Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-35410-6_31.

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Feigelson, Eric D. « MYStIX : Massive Young Stellar Cluster Study in Infrared and X-Rays ». Dans The Labyrinth of Star Formation, 485–87. Cham : Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03041-8_97.

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Montmerle, Thierry, et Nicolas Grosso. « X-Rays from Star-Forming Regions in the VLT Era ». Dans The Origins of Stars and Planets : The VLT View, 452–60. Berlin, Heidelberg : Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-40277-1_59.

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Macfarlane, J. J. « Effects of X-rays on the Ionization State of Be Star Winds ». Dans Pulsation, Rotation and Mass Loss in Early-Type Stars, 202–3. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1030-3_51.

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Pollock, A. M. T., G. Tagliaferri et R. Pallavicini. « X-rays from both components of the flare star binary Gliese 867 ». Dans Surface Inhomogeneities on Late-Type Stars, 331–33. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/3-540-55310-x_186.

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Bourke, T. L., S. J. Wolk, M. Vigil et J. Alves. « The Massive Star Forming Region RCW 38 — from X-Rays to Molecular Gas ». Dans Springer Proceedings in Physics, 637–40. Berlin, Heidelberg : Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-18902-9_111.

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Schmitt, J. H. M. M., et B. Stelzer. « Nuclear Burning Stars ». Dans The Universe in X-Rays, 97–131. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-34412-4_10.

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Staubert, R. « Accreting Neutron Stars ». Dans The Universe in X-Rays, 217–36. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-34412-4_15.

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Sciortino, Salvatore. « Star-Forming Regions ». Dans Handbook of X-ray and Gamma-ray Astrophysics, 1–42. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-4544-0_82-1.

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Actes de conférences sur le sujet "X-rays: star"

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Robrade, J., J. H. M. M. Schmitt et Eric Stempels. « Altair—the hottest ‘cool’ star in X-rays ». Dans COOL STARS, STELLAR SYSTEMS AND THE SUN : Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099190.

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Spaans, Marco, Aycin Aykutalp, John H. Wise et Rowin Meijerink. « The effects of x-rays on star formation and black hole growth in young galaxies ». Dans FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754342.

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Demina, Natalya. « DEVELOPMENT OF NEW METHODS OF AUTO- AND CROSS-CORRELATION ANALYSIS OF QUASI-STAR OBJECTS� X-RAYS INTENSITY ». Dans 18th International Multidisciplinary Scientific GeoConference SGEM2018. Stef92 Technology, 2018. http://dx.doi.org/10.5593/sgem2018/6.1/s28.074.

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Trushkin, S., A. Shevchenko, N. Bursov, P. Tsybulev et N. Nizhelsky. « Long-term multi-frequency studies of flaring activity from microquasars ». Dans ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.196.

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The long-term monitoring at RATAN-600 of studies of bright X-ray binary stars in various ranges of the electromagneticspectrum, a search and detailed study of correlations between variable X-ray, radio and gamma radiation was carried out.It is a key point for understanding the formation of jet emissions from accreting matter onto a black hole (or neutron star).From April 2019 For a year, we began to use the multi-azimuth measurement mode on the Southern Sector antenna systemwith a flat reflector, when 31 measurements of flux densities at frequencies 4.7, 8.6, 15 and 30 GHz of several giant CygnusX-3 flares, SS433 [1] and GRS1915+105 bright flashes were carried out for 5–6 hours around the culmination of the source.In January 2020, Cyg X-3 switched to a hyper-soft X-ray state, the exit from which in early February led to the brightest theradio flash for the all history of its observations. The Cygnus X-3 flow density increased from 5 mJy to 20 Jy at a frequencyof 4.7 GHz and up to 22 Jy at 2.3 GHz in 2–3 days. In multi-azimuthal observations in the beginning phase, we registered alinear law of increase in the flux at times from 1 to 5 hours. Comparing the data of the space Gamma-ray telescopes (Swift,AGILE and Fermi) and the MAXI and NICER X-ray monitors on board the ISS, we found that flaring events from the radioto the Gamma-rays are interrelated, which is a reflection of the causal relationship of physical processes in the accretiondisk and in jet emissions. The spectral and time dependence of the evolution of flares allow us to model the synchrotronradiation of microquasars based on changes in the volume of jet emissions, the strength of their magnetic field and the modeof generation and absorption of radio radiation from relativistic electrons. Radio flares of the microquasar GRS1915+105,as a clear manifestation of a new jet activity, always have the character of a reaction to changes in the conditions forgenerating X-rays in the accretion disk (MAXI) and in the corona (Swift). We have studied in details periodic radio flaresfrom the X-ray binary with bright Gamma-ray radiation LSI+61d303 for more than 60 orbital periods. Undoubtedly, thenature of these flares changes dramatically depending on the known super-orbital 4.6-year period.
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Ryspaeva, E. B. « X-ray emission fromHerbig stars ». Dans Всероссийская с международным участием научная конференция студентов и молодых ученых, посвященная памяти Полины Евгеньевны Захаровой «Астрономия и исследование космического пространства». Ural University Press, 2021. http://dx.doi.org/10.15826/b978-5-7996-3229-8.42.

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The archived X-ray observations of 9 Ae/Be Herbig stars obtained on the XMM-Newton space observatory are analysed for checking the hypotheses of their X-rays formation. An analysis of the dependences of the X-ray radiation characteristics for Herbig stars on the parameters of the stars revealed a close relationship between the magnetic activity and the processes of generation of X-ray radiation from Herbig stars, as well as the possible presence of a non-thermal component of the X-ray spectra.
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Nagase, F. « Transient Be star binary systems ». Dans X-RAY ASTRONOMY : Stellar Endpoints,AGN, and the Diffuse X-ray Background. AIP, 2001. http://dx.doi.org/10.1063/1.1434639.

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Blaes, Omer. « Coalescence of neutron star binaries ». Dans The evolution of X-ray binaries. AIP, 1994. http://dx.doi.org/10.1063/1.46017.

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Postnov, K., A. Kuranov, L. Yungelson et M. Gil’fanov. « X-ray luminosity function of accreting neutron stars and black holes ». Dans ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.114.

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We model X-ray luminosity functions (XLF) of accreting neutron stars and black holes in 10 35 ≤ L X ≤ 10 41 erg s −1range in star-forming galaxies and galaxies with the initial star formation burst. XLFs are obtained by combining a fastgeneration of compact object+normal star population using the binary population synthesis code BSE and calculation ofthe subsequent detailed binary evolution by the MESA code.
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Guainazzi, M. « Comptonization in X-ray bright neutron star globular cluster systems ». Dans X-RAY ASTRONOMY : Stellar Endpoints,AGN, and the Diffuse X-ray Background. AIP, 2001. http://dx.doi.org/10.1063/1.1434705.

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Wijers, Ralph A. M. J. « Evolution versus variability in neutron star binaries ». Dans The evolution of X-ray binaries. AIP, 1994. http://dx.doi.org/10.1063/1.45977.

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Rapports d'organisations sur le sujet "X-rays: star"

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Nilsen, Joseph. X-ray Lasers : The evolution from Star Wars to the table-top. Office of Scientific and Technical Information (OSTI), décembre 2020. http://dx.doi.org/10.2172/1759988.

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Tournear, Derek M. Non-Quiescent X-ray Emission from Neutron Stars and Black Holes. Office of Scientific and Technical Information (OSTI), août 2003. http://dx.doi.org/10.2172/815297.

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Tournear, Derek M. X-ray Bursts in Neutron Star and Black Hole Binaries from USA Data : Detections and Upper Limits. Office of Scientific and Technical Information (OSTI), février 2003. http://dx.doi.org/10.2172/813180.

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Sun, Yipeng. Design and Start-to-End Simulation of an X-Band RF Driven Hard X-Ray FEL with LCLS Injector. Office of Scientific and Technical Information (OSTI), août 2012. http://dx.doi.org/10.2172/1049749.

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in't Zand, J. J. M., Christopher M. Malone, D. Altamirano, D. R. Ballantyne, S. Bhattacharyya, E. F. Brown, Y. Cavecchi et al. The LOFT perspective on neutron star thermonuclear bursts : White paper in support of the mission concept of the large observatory for X-ray timing. Office of Scientific and Technical Information (OSTI), janvier 2015. http://dx.doi.org/10.2172/1167485.

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X-ray diffraction analysis of cuttings from Happy Valley A-10, Happy Valley B-12, Kenai Beluga Unit 31-18, Ninilchik Unit G Oskolkoff 1, Ninilchik Unit G Oskolkoff 2, Ninilchik Unit G Oskolkoff 3, Ninilchik Unit G Oskolkoff 5, Ninilchik Unit G Oskolkoff 8, Star 1, Swanson River Unit 24-15, Swanson River Unit 32C-15, Swanson River Unit 34-10, and Swanson River Unit 34-16 wells. Alaska Division of Geological & Geophysical Surveys, novembre 2017. http://dx.doi.org/10.14509/29810.

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