Effects of Nuclear Burning on X-Ray and UV Emission from Accreting Degenerate Dwarfs

The energy liberated by nuclear burning of matter accreting onto degenerate dwarfs can be more than an order of magnitude greater than that available from the release of gravitational potential energy. Nuclear burning therefore significantly alters the characteristics of X radiation from such stars. Here we report the results of two-fluid calculations in which steady burning occurs at various rates, and compare them with our earlier calculations which assumed no burning. If the star has a weak or no magnetic field, we find that nuclear burning enhances the soft X-ray flux emitted from the stellar surface, increases Compton cooling of the emission region and therefore reduces the hard X-ray luminosity and softens the hard X-ray spectrum. On the other hand, if the star has a strong magnetic field we find that nuclear burning enhances the soft X-ray flux emitted from the stellar surface but has little effect on the hard X-ray luminosity and spectrum. We apply the results of our calculations to the AM Her sources and to cataclysmic variables such as SS Cyg and U Gem, and discuss the evidence for and against nuclear burning of accreted material in these objects.

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Effects of Nuclear Burning on X-Ray and UV Emission from Accreting Nonmagnetic Degenerate Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100075850 ◽

1979 ◽

Vol 53 ◽

pp. 140-144 ◽

Cited By ~ 1

Author(s):

G. J. Weast ◽

R. H. Durisen ◽

J. N Imamura ◽

N. D. Kylafis ◽

D. Q. Lamb

Keyword(s):

Potential Energy ◽

Gravitational Potential ◽

Accretion Rate ◽

Gravitational Potential Energy ◽

X Ray ◽

Uv Emission ◽

Order Of Magnitude ◽

Nuclear Burning ◽

Burning Rates

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Detection of TeV Gamma Rays from SN1006

Symposium - International Astronomical Union ◽

10.1017/s0074180900114585 ◽

1998 ◽

Vol 188 ◽

pp. 121-124 ◽

Cited By ~ 1

Author(s):

Toru Tanimori

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Gamma Rays ◽

High Energy ◽

Shock Acceleration ◽

Emission Region ◽

X Ray ◽

High Energy Electrons ◽

Tev Gamma Rays ◽

The Magnetic Field

In spite of the recent progress of high energy gamma-ray astronomy, there still remains quite unclear and important problem about the origin of cosmic rays. Supernova remnants (SNRs) are the favoured site for cosmic rays up to 1016 eV, as they satisfy the requirements such as an energy input rate. But direct supporting evidence is sparse. Recently intense non-thermal X-ray emission from the rims of the Type Ia SNR SN1006 (G327.6+14.6) has been observed by ASCA (Koyama et al. 1995)and ROSAT (Willingale et al. 1996), which is considered, by attributing the emission to synchrotron radiation, to be strong evidence of shock acceleration of high energy electrons up to ~100 TeV. If so, TeV gamma rays would also be expected from inverse Compton scattering (IC) of low energy photons (mostly attributable to the 2.7 K cosmic background photons) by these electrons. By assuming the magnetic field strength (B) in the emission region of the SNR, several theorists (Pohl 1996; Mastichiadis 1996; Mastichiadis & de Jager 1996; Yoshida & Yanagita 1997) calculated the expected spectra of TeV gamma rays using the observed radio/X-ray spectra. Observation of TeV gamma rays would thus provide not only the further direct evidence of the existence of very high energy electrons but also the another important information such as the strength of the magnetic field and diffusion coefficient of the shock acceleration. With this motivation, SN1006 was observed by the CANGAROO imaging air Cerenkov telescope in 1996 March and June, also 1997 March and April.

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Understanding the coexistence of spin-up and spin-down behaviours in long-period X-ray pulsars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3459 ◽

2020 ◽

Vol 492 (1) ◽

pp. 762-769

Author(s):

W Wang ◽

H Tong

Keyword(s):

Magnetic Field ◽

Binary Systems ◽

Accretion Rate ◽

Constant Mass ◽

X Ray ◽

Spin Period ◽

Long Period ◽

Rotational Evolution ◽

Order Of Magnitude ◽

Field Decay

ABSTRACT Assuming wind-fed accretion magnetars in long-period X-ray pulsars, we calculated the rotational evolution of neutron stars. Our calculations considered the effects of magnetic field decay in magnetars. The results show that wind-fed accretion magnetars can evolve to long-period X-ray pulsars with a spin period much longer than 1000 s. The spin-down trend observed in 4U 2206+54-like sources is expected when young X-ray binary systems are on the way to their equilibrium period. Detailed calculations showed that the spin-down may be affected by accretion with outflows or accretion while spinning down. Due to magnetic field decay in magnetars, wind-fed accretion magnetars will have a decreasing equilibrium period for a constant mass accretion rate. For 2S 0114+65, the spin-up rate due to magnetic field decay is one order of magnitude smaller than observations. The spin-up rate of 2S 0114+65 may be attributed to the formation of a transient disc during wind accretion. The slowest X-ray pulsar AX J1910.7+0917 would be a link source between 4U 2206+54 and 2S 0114+65.

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Physical inference from the γ-ray, X-ray, and optical time variability of a large sample of Fermi blazars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2557 ◽

2019 ◽

Vol 490 (1) ◽

pp. 124-134

Author(s):

Anwesh Majumder ◽

Kaustav Mitra ◽

Ritaban Chatterjee ◽

C M Urry ◽

C D Bailyn ◽

...

Keyword(s):

Magnetic Field ◽

Cross Correlation ◽

Time Lag ◽

Monitoring Program ◽

Emission Region ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region ◽

Γ Ray

ABSTRACT We present cross-correlation studies of γ-ray (0.1–300 GeV), X-ray (0.2–10 keV), and optical (R band) variability of a sample of 26 blazars during 2008–2016. The light curves are from Fermi-LAT, Swift-XRT, and the Yale-SMARTS blazar monitoring program. We stack the discrete cross-correlation functions of the blazars such that the features that are consistently present in a large fraction of the sample become more prominent in the final result. We repeat the same analysis for two subgroups, namely, low synchrotron peaked (LSP) and high synchrotron peaked (HSP) blazars. We find that, on average, the variability at multiple bands is correlated, with a time lag consistent with zero in both subgroups. We describe this correlation with a leptonic model of non-thermal emission from blazar jets. By comparing the model results with those from the actual data, we find that the inter-band cross-correlations are consistent with an emission region of size 0.1 pc within the broad-line region for LSP blazars. We rule out large changes of magnetic field (>0.5 Gauss) across the emission region or small values of magnetic field (e.g., 0.2 Gauss) for this population. We also find that the observed variability of the HSP blazars can be explained if the emission region is much larger than the distance to the broad-line region from the central black hole.

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The Cyclotron Lines in the Optical Spectra of the Stars of AM Herculis Group: Observations and Interpretation

Symposium - International Astronomical Union ◽

10.1017/s0074180900065311 ◽

1980 ◽

Vol 88 ◽

pp. 453-465 ◽

Cited By ~ 1

Author(s):

I. G. Mitrofanov

Keyword(s):

Magnetic Field ◽

Cataclysmic Variables ◽

Magnetized Plasma ◽

Close Binaries ◽

X Rays ◽

Observational Method ◽

Ultraviolet Continuum ◽

X Ray ◽

Optical Continuum ◽

Basic Prediction

The stars of the AM Herculis group (AM Her, VV Pup, AN UMa and 2A 0311-227) are close binaries containing a mass losing, nondegenerate star and an accreting degenerate dwarf. Their main properties are: the large linear and circular polarization of the optical light, high and low luminosity states, the variable emission line, spectra of H, He and other elements and the identification of these objects with X-ray sources. It is generally accepted that the strong magnetic field of the degenerate dwarf is responsible for these peculiar properties and for the distinction between these objects and the cataclysmic variables (Mitrofanov 1978, 1979a). The polarized optical continuum may be emitted by the accreted magnetized plasma (e.g. Chanmugam and Wagner, 1979), by the magnetized photosphere of the degenerate dwarf (Mitrofanov et al. 1977), or by both sources (Mitrofanov, 1979b). To explain the observed X-rays, Lamb and Masters (1979) showed that a magnetic field about 108 gs is necessary. Unfortunately, the basic prediction of their model - the strong ultraviolet continuum in the spectrum of AM Herculis - appears to be absent (Raymond et al. 1979). Chanmugam and Wagner (1979) proposed a rather different estimate for B of 2 · 108/m*gs (m* = 5 ÷ 25). For further investigations of the AM Herculis-type stars it seems useful to find a direct observational method for measuring the dwarfs′ magnetic fields.

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THE WEBT CAMPAIGN ON 3C279 IN 2006

International Journal of Modern Physics D ◽

10.1142/s021827180801308x ◽

2008 ◽

Vol 17 (09) ◽

pp. 1503-1513

Author(s):

M. BÖTTCHER

Keyword(s):

Magnetic Field ◽

Time Scale ◽

High Energy ◽

Field Configuration ◽

Characteristic Time Scale ◽

X Ray ◽

Very High Energy ◽

Order Of Magnitude ◽

Γ Ray ◽

Optical Flux

The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from January through April 2006, including an optical-IR-radio Whole Earth Blazar Telescope (WEBT) campaign and Target of Opportunity X-ray and soft γ-ray observations with Chandra and INTEGRAL in mid-January 2006, with additional X-ray coverage by RXTE and Swift XRT as well as independent very-high-energy (VHE) γ-ray observations by MAGIC, which led to the first-ever reported tentative detection of a quasar at VHE γ-rays. In this paper we summarize the results of the WEBT campaign. The source exhibited substantial variability of optical flux and spectral shape, with a characteristic time scale of a few days. The variability patterns throughout the optical BVRI bands were very closely correlated with each other, while there was no obvious correlation between the optical and radio variability. In intriguing contrast to other (in particular, BL Lac type) blazars, we find a lag of shorter-wavelength behind longer-wavelength variability throughout the RVB wavelength ranges, with a time delay increasing with increasing frequency. Spectral hardening during flares appears delayed with respect to a rising optical flux. This, in combination with the very steep IR-optical continuum spectral index of αo ~ 1.5 – 2.0, may indicate a highly oblique magnetic field configuration near the base of the jet, leading to inefficient particle acceleration and a very steep electron injection spectrum. An alternative explanation through a slow (time scale of several days) acceleration mechanism would require an unusually low magnetic field of B < 0.2 G , about an order of magnitude lower than inferred from previous analyses of simultaneous SEDs of 3C 279 and other FSRQs with similar properties.

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X-Ray Bursts

Highlights of Astronomy ◽

10.1017/s1539299600002446 ◽

1977 ◽

Vol 4 (1) ◽

pp. 101-110 ◽

Cited By ~ 1

Author(s):

George W. Clark

Keyword(s):

Neutron Star ◽

Compact Star ◽

Compact Object ◽

Gravitational Potential Energy ◽

X Rays ◽

High Luminosity ◽

Emission Pattern ◽

X Ray ◽

Accretion Rates ◽

Nuclear Burning

Most of the variable phenomena of high-luminosity (≳1036erg s−1) stellar X-ray sources can be explained, at least qualitatively, within the general framework of binary accretion models in which thermal X-rays are emitted in the vicinity of a neutron star or blackhole by plasma that has flowed downhill from the surface of a nuclear burning companion and been heated by conversion of its gravitational potential energy. The yield of X-ray energy in this process is so high, exceeding in some cases 0.1c2per unit mass, that X-ray luminosities in excess of 104L⊙can be generated with accretion rates of only ˜10−BM⊙per year. Since the transfer process depends strongly on many parameters that specify the relevant properties of two stars and their interaction, one finds a remarkable variety and range of X-ray phenomena. If the compact object is a magnetized neutron star, rotation will cause its X-ray emission pattern to sweep over a distant observer and thereby produce regular pulsations like those observed with periods in the range from 1 to 103seconds. Orbital motions can cause regular eclipses and absorption dips like those observed with periods in the range from hours to days. Changes in the rate of mass loss by the nuclear burning star or in the transfer efficiency can account for the variations in intrinsic X-ray luminosities that appear as flares, novae and on-off transitions. Irregularities in the flow of plasma near the compact star can also affect the intrinsic luminosity and appear as erratic fluctuations, spikes and shot-noise in the observed intensity.

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Convergence of Numbers of Synapses and Quantum Foci within Human Brain Space: Quantitative Implications of the Photon as the Source of Cognition

International Letters of Chemistry Physics and Astronomy ◽

10.18052/www.scipress.com/ilcpa.30.59 ◽

2014 ◽

Vol 30 ◽

pp. 59-66 ◽

Cited By ~ 2

Author(s):

Michael A. Persinger

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Rest Mass ◽

Recoil Energy ◽

Photon Flux ◽

Gravitational Potential Energy ◽

Geomagnetic Variations ◽

Intrinsic Nature ◽

Order Of Magnitude ◽

Intrinsic Energy

Quantitative solutions involving classical methods indicated that the numbers of quantum foci within the human cerebrum are the same order of magnitude as the numbers of synapses in the cerebral cortices. The Bohr frequency for the magnitude of the quantum associated with the removal of one nucleus from another is within the range of the width of synapse (~1 µm) while the recoil energy from a rest mass photon is equivalent to the energy produced by the entire field of dynamic neurons per second. The intrinsic energy (10-20 J) associated with each action potential is similar to the gravitational potential energy from Planck’s mass applied across 1 µm. Both the endogenous cerebral magnetic field strength which is similar in magnitude to intergalactic intensities and the interaction between weak geomagnetic variations and the cerebrum’s electric dipole current are associated with photon flux densities in the order (10-11 W∙m-2) that have been measured in the laboratory. The perspective of the human cerebral volume as a field of foci of photon quanta offers different perspectives for the intrinsic nature of consciousness and cognition and their influence by phenomena from astronomical origins.

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Reflection of positron radiation from star surface and shift of inter pulse position in Crab pulsar

Advances in Astronomy and Space Physics ◽

10.17721/2227-1481.7.30-35 ◽

2017 ◽

Vol 7 (1-2) ◽

pp. 30-35 ◽

Cited By ~ 1

Author(s):

V. Kontorovich ◽

S. Trofymenko

Keyword(s):

Magnetic Field ◽

High Frequency ◽

Main Pulse ◽

Stellar Surface ◽

Crab Pulsar ◽

X Ray ◽

Unique Information ◽

Radio Frequencies ◽

Star Surface ◽

The Magnetic Field

The pulsed radiation from the Crab pulsar consists of the main pulse (MP) and inter pulse (IP), as well as of the extra pulse components appearing at certain frequencies. It has been studied in many frequencies and contains unique information, which is not available for the majority of the pulsars. One of the mysteries of these data, found by Moffett and Hankins twenty years ago, is the shift of the IP at high radio frequencies compared to lower ones and return to its previous position in the more high-frequency optical and X-ray range. We propose the explanation of these mysterious changes with the frequency as a reflection of radiation by relativistic positrons from the stellar surface. The magnetic field of the pulsar in the pole must be inclined to the surface of the star and affects on the discussed processes.

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The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa991 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5350-5359 ◽

Cited By ~ 4

Author(s):

G Vasilopoulos ◽

P S Ray ◽

K C Gendreau ◽

P A Jenke ◽

G K Jaisawal ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Broad Band ◽

Accurate Estimate ◽

X Ray ◽

Bolometric Luminosity ◽

Order Of Magnitude ◽

Moderate Magnetic Field ◽

Eddington Limit

ABSTRACT In 2019 November, MAXI detected an X-ray outburst from the known Be X-ray binary system RX J0209.6−7427 located in the outer wing of the Small Magellanic Cloud. We followed the outburst of the system with NICER, which led to the discovery of X-ray pulsations with a period of 9.3 s. We analysed simultaneous X-ray data obtained with NuSTAR and NICER, allowing us to characterize the spectrum and provide an accurate estimate of its bolometric luminosity. During the outburst, the maximum broad-band X-ray luminosity of the system reached (1–2) × 1039 erg s−1, thus exceeding by about one order of magnitude the Eddington limit for a typical 1.4 M⊙ mass neutron star (NS). Monitoring observations with Fermi/GBM and NICER allowed us to study the spin evolution of the NS and compare it with standard accretion torque models. We found that the NS magnetic field should be of the order of 3 × 1012 G. We conclude that RX J0209.6−7427 exhibited one of the brightest outbursts observed from a Be X-ray binary pulsar in the Magellanic Clouds, reaching similar luminosity level to the 2016 outburst of SMC X-3. Despite the super-Eddington luminosity of RX J0209.6−7427, the NS appears to have only a moderate magnetic field strength.

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