Showing papers in "Chinese Journal of Astronomy and Astrophysics in 2003"
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TL;DR: In this article, the authors summarize some of the relevant results obtained with the Italian satellite BeppoSAX on the prompt and afterglow emission of Gamma Ray Bursts and discuss the most relevant open issues on these events.
Abstract: In this review paper I will summarize some of the relevant results obtained with the Italian satellite BeppoSAX on the prompt and afterglow emission of Gamma Ray Bursts. I will also discuss the most relevant open issues on these events.
251 citations
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TL;DR: In this article, an extensive non-LTE analysis of the neutral sodium lines of Na i 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars was performed.
Abstract: We performed an extensive non-LTE analysis of the neutral sodium lines of Na i 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range ( 4 < (Fe/H) < +0.4), using our own data as well as data collected from the literature. For comparatively metal- rich disk stars ( 1 < (Fe/H) < +0.4) where the weaker 6154/6161 lines are the best abundance indicators, we confirmed (Na/Fe) 0 with an "upturn" (i.e., a shallow/broad dip around 0.5 < (Fe/H) < 0) as already reported in previous studies. For the metal-deficient halo stars, where the much stronger 5890/5896 or 8183/8195 lines subject to considerable (negative) non-LTE corrections amounting to 0.5 dex have to be used, our analysis suggests mildly "subsolar" (Na/Fe) values down to 0.4 (with a somewhat large scatter of ± 0.2 dex) on the average at the typical halo metallicity of (Fe/H) 2, followed by a rise again to a near-solar ratio of (Na/Fe) 0 at the very metal-poor regime (Fe/H) 3 to 4. These results are discussed in comparison with the previous observational studies along with the theoretical predictions from the available chemical evolution models.
82 citations
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TL;DR: In this article, the effect of strong magnetic fields on the structure of a neutron star was studied and it was shown that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star's mass and radius are negligible; if the field is as large as that estimated from the scalar virial theorem, then considerable effects will be induced.
Abstract: We study the effect of strong magnetic fields on the structure of neutronstar. We find that if the interior field is on the same order as the surface fieldcurrently observed, then the influences of the field on the star's mass and radius arenegligible; if the field is as large as that estimated from the scalar virial theorem,then considerable effects will be induced. The maximum mass of the star will beincreased substantially while the central density is greatly reduced. The radius ofa magnetic star can be larger by about 10% ~ 20% than a nonmagnetic star of thesame mass.
75 citations
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TL;DR: In this paper, the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002 was investigated and it was shown that the amplitude of the 53-yr period was much higher than that of the 11yr period.
Abstract: We investigate the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002. The curve of the global wavelet power spectrum peaks at 11-yr, 53-yr and 101-yr periods. The evolution of the amplitudes of the three periods is studied. The results show that around 1750 and 1800, the amplitude of the 53-yr period was much higher than that of the the 11-yr period, that the ca. 53-yr period was apparent only for the interval from 1725 to 1850, and was very low after 1850, that around 1750, 1800 and 1900, the amplitude of the 101-yr period was higher than that of the 11-yr period and that, from 1940 to 2000, the 11-yr period greatly dominates over the other two periods.
45 citations
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TL;DR: In this paper, the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789 were presented, and a total of 28 new variable stars were discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified).
Abstract: We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified). In addition, we recovered 11 old variables previously discovered by other authors. Preliminary parameters are given for some of these variables.
44 citations
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TL;DR: In this article, a statistical analysis of 482 6.7 GHz methanol maser sources from the available literature, on their maser emission and the characteristics of their associated infrared sources is presented.
Abstract: We present a statistical analysis of 482 6.7 GHz methanol maser sources from the available literature, on their maser emission and the characteristics of their associated infrared sources. On the color-color diagram, more than 70% of the objects fall within a very small region (0.57 ≤ [25-12] ≤ 1.30 and 1.30 ≤ [60-12] ≤ 2.50). This suggests that 6.7 GHz methanol maser emission occurs only within a very short evolutionary phase during the earliest stage of star formation. The velocity ranges of the masers belong to two main groups: one from 1 to 10 km s−1, and one from about 11 to 20 km s−1. These velocity ranges indicate that the masers are probably associated with both disks and outflows. The correlations between the maser and infrared flux densities, and between the maser and infrared luminosities, suggest that far-infrared radiation is a possible pumping mechanism for the masers which most probably originate from some outer molecular envelopes or disks.
31 citations
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TL;DR: In this article, a theoretical model for explaining the O'Connell effect of close binary stars is given based on the hypothesis that the circumstellar material of a binary system is captured by its components.
Abstract: A theoretical model for explaining the O'Connell effect of close binary stars is given based on the hypothesis that the circumstellar material of a binary system is captured by its components. The results inferred from the model suggest that late-type and/or short-period binaries can easily produce obvious O'Connell effect and that the occurrence of O'Connell effect has no relation with the type of binaries. These conclusions are in agreement with the observed results. The observed O'Connell effects of six binary systems are examined by the model. For three W-subtype W UMa binaries (YY Eri, BX Per and SW Lac), the densities of the materials captured by the two components are assumed to be equal, and the calculated O'Connell effect is found to be almost equal to the observed effect. For three A-subtype W UMa systems (CN And, FG Hya and AU Ser), the two densities are assumed to be different, and are calculated separately. The calculated O'Connell effect turns out to agree better with the observed effect than that was formerly obtained.
27 citations
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TL;DR: In this paper, a binary black hole model was proposed to explain the long term radio light curve of the extremely variable BL Lacertae object AO 0235+16 by Raiteri et al.
Abstract: Recent analysis of the long term radio light curve of the extremely variable BL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outbursts with a period of 5.7 ± 0.5yr. Periodicity analysis of the optical light curve also shows evidence for a shorter period. Here we discuss whether such a behavior can be explained by a binary black hole model where the accretion disk of one of the supermassive black holes is precessing due to the tidal eects of the companion. We estimate the mass of the accreting hole and analyze constraints on the secondary mass and the orbital parameters of the system. It is possible to provide a viable interpretation of the available multiwavelength data.
26 citations
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TL;DR: In this paper, the authors analyzed the magnetic configurations of three super active regions, NOAA 10484, 10486 and 10488, observed by the Huairou Multi-Channel Solar Tele-scope (MCST) from 2003 October 18 to November 4.
Abstract: We analyze the magnetic configurations of three super active regions, NOAA 10484, 10486 and 10488, observed by the Huairou Multi-Channel Solar Tele- scope (MCST) from 2003 October 18 to November 4. Many energetic phenomena, such as flares (including a X-28 flare) and coronal mass ejections (CMEs), occurred during this period. We think that strong shear and fast emergence of magnetic flux are the main causes of these events. The question is also of great interest why these dramatic eruptions occurred so close together in the descending phase of the solar cycle.
24 citations
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TL;DR: In this paper, the mass-radius relations for bare and crusted strange stars are calcu- lated with the bag model, and the authors come to the conclusion that it is incorrect to say that EXO 0748-676 cannot be a strange star.
Abstract: The mass-radius relations for bare and crusted strange stars are calcu- lated with the bag model. Comparing these relations with the observed one derived from the redshift of EXO 0748-676, we come to the conclusion that it is incorrect to say that EXO 0748-676 cannot be a strange star. Various strange star models can show that EXO 0748-676 could have a mass of (1.3 1.7)M and a radius of (8.4 11.4)km. It is proposed that a proportion of nascent strange stars could be bare and have masses 0.1M , and their masses increased over a long period of accretion.
24 citations
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TL;DR: Wang et al. as mentioned in this paper presented a new automatic method of star/(normal) galaxy separation based on Statistical Mixture Modeling with Radial Basis Function Neural Networks (SMM-RBFNN), which is a continuation of our previous one, where active and non-active celestial objects were successfully segregated.
Abstract: For LAMOST, the largest sky survey program in China, the solution of the problem of automatic discrimination of stars from galaxies by spectra has shown that the results of the PSF test can be significantly refined. However, the problem is made worse when the redshifts of galaxies are not available. We present a new automatic method of star/(normal) galaxy separation, which is based on Statistical Mixture Modeling with Radial Basis Function Neural Networks (SMM-RBFNN). This work is a continuation of our previous one, where active and non-active celestial objects were successfully segregated. By combining the method in this paper and the previous one, stars can now be eectively separated from galaxies and AGNs by their spectra—a major goal of LAMOST, and an indispensable step in any automatic spectrum classification system. In our work, the training set includes standard stellar spectra from Jacoby's spectrum library and simulated galaxy spectra of E0, S0, Sa, Sb types with redshift ranging from 0 to 1.2, and the test set of stellar spectra from Pickles' atlas and SDSS spectra of normal galaxies with SNR of 13. Experiments show that our SMM-RBFNN is more ecient in both the training and testing stages than the BPNN (back propagation neural networks), and more importantly, it can achieve a good classification accuracy of 99.22% and 96.52%, respectively for stars and normal galaxies.
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TL;DR: In this paper, the intrinsic spectral properties and energy properties of GRBs with known redshift based on 12 BeppoSAX events were extended by including in the sample a total of 10 more events detected either by BATSE, BEPOSAX or HETE-2.
Abstract: We extend a previous work on the intrinsic spectral properties and energetics of GRBs with known redshift based on 12 BeppoSAX events by including in the sample a total of 10 more events detected either by BATSE, BeppoSAX or HETE-2. An indication of a trend of the total isotropic equivalent radiated energy, Erad, with redshift is found and, remarkably, the previously found relationship between the peak energy of the rest-frame vFv spectrum, Eprest and Erad is confirmed and its significance increased. The implications of these results are briefly discussed in the framework of standard models for the prompt emission of GRBs.
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TL;DR: A tilt-correction adaptive optical system installed on the 430 mm solar telescope of Nanjing University has been put in operation as discussed by the authors. But the system is not suitable for large-scale observations.
Abstract: A tilt-correction adaptive optical system installed on the 430 mm Solar Telescope of Nanjing University has been put in operation. It consists of a tip-tilt mirror, a correlation tracker and an imaging CCD camera. An absolute difference algorithm is used for detecting image motion in the correlation tracker. The sampling frequency of the system is 419 Hz. We give a description of the system's configuration, an analysis of its performance and a report of our observational results. A residual jitter of 0.14 arcsec has been achieved. The error rejection bandwidth of the system can be adjusted in the range 5–28 Hz according to the beacon size and the strength of atmospheric turbulence.
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TL;DR: In this paper, the status of the knowledge about magnetic fields of neutron stars in accreting X-ray binaries through the measurement of cyclotron lines (Cyclotron Resonance Scattering Features -- CRSF) is reviewed.
Abstract: The status of the knowledge about magnetic fields of neutron stars in accreting X-ray binaries through the measurement of cyclotron lines (Cyclotron Resonance Scattering Features -- CRSF) is reviewed. A systematic search for cyclotron lines through observations with the Rossi X-ray Timing Explorer (RXTE) and a uniform analysis have led to a list of 10 objects showing one or more line feature(s) in phase averaged spectra (Coburn 2001, Coburn et al. 2002a). Another 3 objects are known from observations by Ginga, HEXE and OSSE, but were not observed by RXTE. For 12 further objects upper limits have been set from RXTE observations (Coburn et al. 2002b). Four objects show more than one line, with 4U 0115+63 showing up to five lines. The range of magnetic fields in these objects is ∼ (1l 5) 10 12 Gauss. There are a number of significant correlations between parameters describing the line and the continuum spectrum, as well as among the line parameters themselves. The physics of these correlations is not well understood.
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TL;DR: In this paper, the authors present a numerical study of magnetic configurations characterized by a levitating flux rope embedded in a bipolar background field whose normal field at the solar surface is the same or very close to that of a central dipole.
Abstract: Using an axisymmetrical ideal MHD model in spherical coordinates, we present a numerical study of magnetic configurations characterized by a levitating flux rope embedded in a bipolar background field whose normal field at the solar surface is the same or very close to that of a central dipole. The characteristic plasma (the ratio between gas pressure and magnetic pressure) is taken to be so small ( = 10 4 ) that the magnetic field is close to being force-free. The system as a whole is then let evolve quasi-statically with a slow increase of either the annular magnetic flux or the axial magnetic flux of the rope, and the total magnetic energy of the system grows accordingly. It is found that there exists an energy threshold: the flux rope sticks to the solar surface in equilibrium if the magnetic energy of the system is below the threshold, whereas it loses equilibrium if the threshold is exceeded. The energy threshold is found to be larger than that of the corresponding fully-open magnetic field by a factor of nearly 1.08 irrespective as to whether the background field is completely closed or partly open, or whether the magnetic energy is enhanced by an increase of annular or axial flux of the rope. This gives an example showing that a force-free magnetic field may have an energy larger than the corresponding open field energy if part of the field lines is allowed to be detached from the solar surface. The implication of such a conclusion in coronal mass ejections is briefly discussed and some comments are made on the maximum energy of force-free magnetic fields.
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TL;DR: In this paper, an expanding anisotropic universe is found to isotropize during its expansion, but a static universe cannot isotropise, and the cosmological constant decreases with time as ⁄ / t i2.
Abstract: Exact solutions for a model with variable G, ⁄ and bulk viscosity are obtained. Inflationary solutions with constant (de Sitter-type) and variable energy density are found. An expanding anisotropic universe is found to isotropize during its expansion but a static universe cannot isotropize. The gravitational constant is found to increase with time and the cosmological constant decreases with time as ⁄ / t i2 .
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TL;DR: In this article, the authors performed a study of the X-ray binary population in the Milky Way and compared the results with the binary populations of other galaxies, including the galaxies observed by CHANDRA.
Abstract: We performed a study of the X-ray binary population in the Milky Way. The results of this study, spatial distribution and in particular luminosity function, can be used for comparison with the X-ray binary populations of other galaxies. In the second part we give an example by investigating the connection between the star formation rate and the high mass X-ray binary population in galaxies observed by CHANDRA.
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TL;DR: The most important characteristics and multi-frequency behaviour of the active RS CVn binaries are reviewed in this paper, where new long-term photometric and spectroscopic observations of several short-period active RSCVn binaries were presented.
Abstract: The most important characteristics and multi-frequency behaviour of the active RS CVn binaries are reviewed. New long-term photometric and spectroscopic observations of several short-period active RS CVn binaries are presented. The results for RT And, XY UMa and preliminary analysis of SV Cam and ER Vul are given. New prospects for research in the field are outlined.
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TL;DR: In this paper, the standard model of the post-shock accretion flow in mCVs is discussed and some results of the current study of two-temperature flows are presented.
Abstract: The standard model of the post-shock accretion flow in mCVs is discussed. We present some results of the current study of two-temperature flows in mCVs. New observations supporting the standard model are presented. Recent developments in the studies of the global properties of the accretion stream are briefly discussed.
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Istituto Nazionale di Fisica Nucleare1, Autonomous University of Barcelona2, University of Łódź3, École Polytechnique Fédérale de Lausanne4, Max Planck Society5, University of Würzburg6, Yerevan Physics Institute7, Complutense University of Madrid8, University of Udine9, University of California, Davis10, University of Siena11
TL;DR: MAGIC as discussed by the authors is the largest ground-based gamma ray telescope with an energy threshold as low as 30 GeV, and it is scheduled to reach full operation by the end of 2003.
Abstract: The MAGIC telescope, presently at its commissioning phase, will become fully operative by the end of 2003. Placed at the Roque de los Muchachos Observatory (ORM) on the island of La Palma, MAGIC is the largest among new generation ground-based gamma ray telescopes, and will reach an energy threshold as low as 30 GeV. The range of the electromagnetic spectrum between 10 and 250 GeV remains to date mostly unexplored. Observations in this energy region are expected to provide key data for the understanding of a wide variety of astrophysical phenomena belonging to the so-called ``non thermal Universe'', like the processes in the nuclei of active galaxies, the radiation mechanisms of pulsars and supernova remnants, and the enigmatic gamma-ray bursts. An overview of the telescope and its physics goals is presented.
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TL;DR: In this article, the authors summarize studies of helical properties of solar magnetic fields such as current helicity and twist of magnetic fields in solar active regions (ARs), that are observational tracers of the alpha-eect in the solar convective zone (SCZ).
Abstract: We summarize studies of helical properties of solar magnetic fields such as current helicity and twist of magnetic fields in solar active regions (ARs), that are observational tracers of the alpha-eect in the solar convective zone (SCZ). Information on their spatial distribution is obtained by analysis of systematic mag- netographic observations of active regions taken at Huairou Solar Observing Station of National Astronomical Observatories of Chinese Academy of Sciences. The main property is that the tracers of the alpha-eect are antisymmetric about the solar equator. Identifying longitudinal migration of active regions with their individual rotation rates and taking into account the internal dierential rotation law within the SCZ known from helioseismology, we deduce the distribution of the eect over depth. We have found evidence that the alpha-eect changes its value and sign near the bottom of the SCZ, and this is in accord with the theoretical studies and numerical simulations. We discuss other regularities which can be revealed by fur- ther analysis such as possible dependence on longitude, time, and magnetic field strength, etc.
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TL;DR: In this article, the authors summarize the physics of the fluorescent line formation and show that Fe Kα line profile observations can be used to probe relativistic effects in the vicinity of the black hole, concentrating on recent results from XMM-Newton.
Abstract: The Fe Kα lines seen in many Active Galactic Nuclei (AGN) are thought to originate close to the central supermassive black hole. In this review we summarize the physics of the fluorescent line formation and show that Fe Kα line profile observations can be used to probe relativistic effects in the vicinity of the black hole, concentrating on recent results from XMM-Newton.
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TL;DR: In this paper, the authors summarize information about multiwavelength emission of the large-scale extragalactic jets, and point out several modifications of the standard jet radiation models (connected with relativistic bulk velocities, jet radial stratification and particle energization all the way along the jet), which can possibly explain some of the mentioned puzzling observations.
Abstract: Large-scale extragalactic jets, observed to extend from a few to a few hundred kiloparsecs from active galactic nuclei, are now studied over many decades in frequency of electromagnetic spectrum, from radio until (possibly) TeV γ rays. For hundreds of known radio jets, only about 30 are observed at optical frequencies. Most of them are relatively short and faint, with only a few exceptions, like 3C 273 or M 87, allowing for detailed spectroscopic and morphological studies. Somewhat surprisingly, the large-scale jets can be very prominent in X-rays. Up to now, about 30 jets were detected within the 1 - 10 keV energy range, although the nature of this emission is still under debate. In general, both optical and X-ray jet observations present serious problems for standard radiation models for the considered objects. Recent TeV observations of M 87 suggest the possibility of generating large photon fluxes at these high energies by its extended jet. In this paper we summarize information about multiwavelength emission of the large-scale jets, and we point out several modifications of the standard jet radiation models (connected with relativistic bulk velocities, jet radial stratification and particle energization all the way along the jet), which can possibly explain some of the mentioned puzzling observations. We also comment on γ-ray emission of the discussed objects.
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TL;DR: In this article, the performance of learning vector quantization (LVQ) in classifying multi-wavelength data was explored for separating active sources from non-active ones, where different classes of X-ray emitters populate distinct regions of a multidimensional parameter space.
Abstract: The sizes of astronomical surveys in different wavebands are increasing rapidly. Therefore, automatic classification of objects is becoming ever more important. We explore the performance of learning vector quantization (LVQ) in classifying multi-wavelength data. Our analysis concentrates on separating active sources from non-active ones. Different classes of X-ray emitters populate distinct regions of a multidimensional parameter space. In order to explore the distribution of various objects in a multidimensional parameter space, we positionally cross-correlate the data of quasars, BL Lacs, active galaxies, stars and normal galaxies in the optical, X-ray and infrared bands. We then apply LVQ to classify them with the obtained data. Our results show that LVQ is an effective method for separating AGNs from stars and normal galaxies with multi-wavelength data.
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TL;DR: A short review of recent studies of the X-ray source populations of nearby galaxies can be found in Fabbiano & White (2003), from where this talk was partially extracted as discussed by the authors.
Abstract: This paper gives a short review of recent studies of the X-ray source populations of nearby galaxies. A more complete review of this subject can be found in Fabbiano & White (2003), from where this talk was partially extracted.
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TL;DR: In this article, the authors discuss the origin of these jets and the likely consequences of their interactions with the intracluster medium in clusters of galaxies, and discuss the potential consequences of these interactions.
Abstract: Clusters of galaxies contain large ellipticals near their cores. Elliptical galaxies in the centers of these clusters are often found to be the source of large-scale jets that propagate outward into the intracluster medium. These jets are thought to be produced by accretion-powered processes in the active galactic nuclei (AGN) at the centers of some giant ellipticals. In this paper, we discuss the origin of these jets and the likely consequences of their interactions with the intracluster medium in clusters of galaxies.
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TL;DR: In this paper, the central black hole mass to the bulge mass (M bh /M bulge ) for 15 Narrow Line Seyfert I galaxies (NLS1s) was estimated.
Abstract: We present estimated ratios of the central black hole mass to the bulge mass ( M bh / M bulge ) for 15 Narrow Line Seyfert I galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio is about 1×10 -4 with a spread of 2, which is one order of magnitude lower than for Broad Line AGNs and quiescent galaxies. This lower value, as compared to that established essentially for all other types of galaxies, can be accounted for by an underestimation of the black hole masses and an overestimation of the bulge masses in the NLS1s.
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TL;DR: In this paper, a model based on the fast blazing of very collimated thin gamma jets was proposed to explain the GRB-Pulsar power connection and the apparent huge GRBs output.
Abstract: Old and recent puzzles of GRBs and SGRs find a solution with a model based on the fast blazing of very collimated thin gamma Jets. Damped oscillating afterglows in GRB 030329 find a natural explanation assuming a very thin Jet - - whose persistent activity and different angle of view maybe combined at once with the Supernovae power and the apparent huge GRBs output: . This leads to a better understanding of the remarkable GRB-Supernovae connection discovered in the GRB 980425/SN 1998bw and in the most recent GRB 030329/SN 2003dh events. The same thin beaming offer an understanding of the apparent SGR-Pulsar power connection: . A thin collimated precessing Gamma Jet model for both GRBs and SGRs, at their different scaled luminosity (1038-1044 erg s−1), explains the existence of few identical energy spectra and time evolution of these sources leading to a unified model. Their similarity with the huge precessing Jets in AGN, QSRs and Radio-Galaxies inspires this smaller scale SGR-GRB model. The spinning-precessing Jet explains the rare (≈ 6%) mysterious X-Ray precursors in GRBs and SGRs events. Any large Gamma Jet off-axis beaming to the observer might lead to the X-Flash events without any GRB signals, as the most recent XRF 030723. Its possible re-brightening would confirm the evidence of the variable pointing of the jet in or off line towards the observer. Indeed a multi-precessing Jet at peak activity in all bands may explain the puzzling X or optical re-brightening bumps found in the GRB 021004, GRB 030329 and the SGR 1900+ 14 on 27 August 1998 and once again on the 18 April 2001. Rarest micro-quasars neutron star in our galaxy as SS433, and Herbig Haro objects and Cir-X-1 describe these thin precessing Jet imprints in the spectacular shapes of their relic nebulae.
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TL;DR: In this article, the authors present a study of the beta Cephei instability strip based on a sample of 49 stars of this type and derive their effective temperatures and luminosities from their observed (B - V), (U - B) colors and parallaxes.
Abstract: We present a study of the beta Cephei instability strip based on a sample of 49 stars of this type. After deriving their effective temperatures and luminosities from their observed (B - V), (U - B) colors and parallaxes we find their positions in the HR diagram to be mostly confined to the main sequence, and their masses to lie between 7M(circle dot) and 30 M-circle dot. Their distribution on the HR diagram matches well with our previous theoretical instability strip which has an upper bound in the luminosity and rather tight boundaries in the effective temperature.
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TL;DR: In this paper, the authors discuss the behavior of X-ray binary systems, in order to present to the readers an updated panorama of this important class of Xray sources.
Abstract: The goal of this paper is to discuss the behaviour of the X-ray binary systems, in order to present to the readers an updated panorama of this important class of X-ray sources. They have in common the binary nature, but rather different characteristics: millisecond pulsations in low mass binary systems, seconds-hundreds seconds pulsations in transient high mass X-ray systems, pulsations limited in a narrow ∼6-12s band in the enigmatic class of systems named anomalous X-ray pulsars. However, all these systems are characterized by a neutron star as collapsed object. A few words will be devoted also to those systems having a black hole as collapsed object. Some comments on radio pulsars-SNRs and X-ray pulsars-SNRs associations will be given too.