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1.
An overview of the results of observations for the transient X-ray pulsar 4U 0115+63, amember of a binary system with a Be star, since its discovery to the present day (～40 years) based on data from more than dozen observatories and instruments is presented. An overall light curve and the history of change in the spin frequency of the neutron star over the entire history of its observations, which also includes the results of recent measurements made by the INTEGRAL observatory during the 2004, 2008, and 2011 outbursts, are provided. The source’s energy spectra have also been constructed from the INTEGRAL data obtained during the 2011 outburst for a dynamic range of its luminosities 1037?7 × 1037 erg s?1. We show that apart from the fundamental harmonic of the cyclotron absorption line at energy～11 keV, its four higher harmonics at energies ?24, 35.6, 48.8, and 60.7 keV are detected in the spectrum. We have performed a detailed analysis of the source’s spectra in the 4–28 keV energy band based on all of the available RXTE archival data obtained during bright outbursts in 1995–2011. We have confirmed that modifying the source’s continuum model can lead to the disappearance of the observed anticorrelation between the energy of the fundamental harmonic of the cyclotron absorption line and the source’s luminosity. Thus, the question about the evolution of the cyclotron absorption line energy with the luminosity of the X-ray pulsar 4U 0115+63 remains open and a physically justified radiation model for X-ray pulsars is needed to answer it.  相似文献   

2.
We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the RXTE and INTEGRAL observatories in a wide X-ray (3–100 keV) energy band during its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic of the cyclotron resonance absorption line near the maximum of the X-ray flux from the source (luminosity range 5 × 1037–2 × 1038 erg s?1) is ～11 keV. When the pulsar luminosity falls below ～5 × 1037 erg s?1, the energy of the fundamental harmonic is displaced sharply toward the high energies, up to ～16 keV. Under the assumption of a dipole magnetic field configuration, this change in cyclotron harmonic energy corresponds to a decrease in the height of the emitting region by ～2 km, while other spectral parameters, in particular, the cutoff energy, remain essentially constant. At a luminosity ～7 × 1037 erg s?1, four almost equidistant cyclotron line harmonics are recorded in the spectrum. This suggests that either the region where the emission originates is compact or the emergent spectrum from different (in height) segments of the accretion column is uniform. We have found significant pulse profile variations with energy, luminosity, and time. In particular, we show that the profile variations from pulse to pulse are not reduced to a simple modulation of the accretion rate specified by external conditions.  相似文献   

3.
We review the properties of the hard transient 4U 0115+63 in outburst as well as during quiescence. 4U 0115+63 is one of the few sources in which a sharp decrease of the X-ray flux at the end of an outburst has been observed, testifying to the action of the centrifugal barrier. Here we discuss explicitly the available upper limit on the X-ray luminosity during the quiescent phase to suggest that 4U 0115+63 is likely in the propeller regime.  相似文献   

4.
We present the results of measurements of the total X-ray flux from the Andromeda galaxy (M31) in the 3-100 keV band based on data from the RXTE/PCA, INTEGRAL/ISGRI, and SWIFT/BAT space experiments. We show that the total emission from the galaxy has a multicomponent spectrum whose main characteristics are specified by binaries emitting in the optically thick and optically thin regimes. The galaxy’s luminosity at energies 20–100 keV gives about 6% of its total luminosity in the 3–100 keV band. The emissivity of the stellar population in M31 is L 2–20 keV ～ 1.1 × 1029 erg s?1 M ⊙ ?1 in the 2–20 keV band and L 20–100 keV ～ 8 × 1027 erg s?1 M ⊙ ?1 in the 20–100 keV band. Since low-mass X-ray binaries at high luminosities pass into a soft state with a small fraction of hard X-ray emission, the detection of individual hard X-ray sources in M31 requires a sensitivity that is tens of times better (up to 10?13 erg s?1 cm?2) than is needed to detect the total hard X-ray emission from the entire galaxy. Allowance for the contribution from the hard spectral component of the galaxy changes the galaxy’s effective Compton temperature approximately by a factor of 2, from ～1.1 to ～2.1 keV.  相似文献   

5.
Using the observational data of hard X-ray emission lines of Her X-l, we make a preliminary study of the physics of the emission region. We found the emission region opaque to X-ray line radiation, with an excitation temperature sim;2.4 × 108K and a perpendicular cross section area ～2 × 107cm2. We predict that a third line will be 113 as intense as the first line and 3 times as wide.  相似文献   

6.
We present in this paper the results from a X-ray astronomy payload flown aboard a Centaur rocket on 30 July, 1977 from TERLS, Thumba. The rocket attained an apogee of 150 km and the experiment performed satisfactorily providing about 200 s of data above 105 km. A source at the position of recurrent transient 4U 0115+63 has been detected. Details of this source and other results are presented in this paper.  相似文献   

7.
X-ray binaries such as Cen X-3, Cyg X-1, Vela X-1, 2U1700-37, SMC X-1, Cir X-1, with periods ranging from 2d.087 to 12d.28, are probably evolution products of massive binary systems. The massive primary starts losing mass after core hydrogen burning and undergoes a supernova explosion. The evolution of binary systems consisting of a 20M⊙ primary and secondaries of respectively 14, 10, 8 and 6M⊙ was computed from Main Sequence stage through the X-ray phase, until the second mass transfer phase. Estimates were performed for the evolution of a secondary of 4M⊙. It may be seen that some of these systems during their X-ray phase match the observed mass ratios and periods.  相似文献   

8.
Thirty active regions were observed on the Sun during the period from October 19 to November 20, 2003. Hard X-ray and gamma-ray radiation was detected from four active regions (10484, 10486, 10488, and 10490): 14 solar flares stronger than M5.0 according to the GOES classification were recorded during this period by detectors onboard the Geostationary Operational Environmental Satellite (GOES), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and other satellites. Five of these flares (and also the M2.7 flare of October 27, 2003) were also observed by the AVS-F apparatus onboard the CORONAS-F satellite. This paper discusses the time profiles and energy spectra of the solar flares of October 26, 2003 (M7.6), and October 29, 2003 (X10), and of the initial phase of the flare of November 4, 2003 (X18), obtained by the AVS-F instrument during the passage of the satellite over the regions near the geomagnetic equator. The spectra of the M7.6 flare of October 26, 2003, and of the initial phase of the X18 flare of November 4, 2003, in the energy band from 0.1 to 17 MeV contain no lines, whereas the spectrum of the flare of October 29, 2003, exhibits nuclear lines and the 2.2-MeV line during the entire flare gamma-ray emission registration. We also report the time profiles of the flare of October 29, 2003, in the energy bands corresponding to the continuum in the energy band 0.3–0.6 MeV, the nuclear lines of 56Fe, 24Mg, 20Ne, 28Si, 12C, and 16O, and the 2.2-MeV neutron-capture line. The analysis of these temporal profile periodograms shows the presence of a thin structure with characteristic scales from 34 to 158 s at the 99% confidence level. The AVS-F apparatus analyzes temporal profiles of low-energy gamma-ray emission with a temporal resolution of 1 ms within the first 4.096 seconds of solar flares. The analysis of the data reveals no regularities in the time series on time scales ranging from 2 to 100 ms at a confidence level of 99% for these three solar flares.  相似文献   

9.
We present the results of the spectral and timing analysis of the X-ray pulsar LMC X-4 based on data from the NuSTAR observatory in the broad X-ray energy range 3–79 keV. Along with a detailed analysis of the source’s averaged spectrum, high-precision spectra corresponding to different phases of the neutron star spin cycle have been obtained for the first time. The Comptonization model is shown to describe best the source’s spectrum, and the evolution of its parameters as a function of the pulse phase has been traced. For all spectra (the averaged and phase-resolved ones) in the energy range 5–55 keV we have searched for the cyclotron absorption line. The derived upper limit on the optical depth of the cyclotron line τ ~ 0.15 (3σ) points to the absence of this feature in the given energy range, which provides a constraint on the magnetic field of the neutron star: B <3 × 1011 or >6.5 × 1012 G. The latter constraint is consistent with the magnetic field estimate obtained by analyzing the pulsar’s power spectrum, B ? 3 × 1013 G. Based on our analysis of the phase-resolved spectra, we have determined the delay between the emission peaks and the equivalent width of the fluorescent iron line. This delay depends on the orbital phase and is apparently associated with the travel time of photons between the emitting regions in the vicinity of the neutron star and the region where the flux is reflected (presumably in the inflowing stream or at the place of interaction between the stream and the outer edge of the accretion disk).  相似文献   

10.
The main results of the SPIRIT experiment on imaging spectroscopy of the Sun in the soft X-ray and extreme vacuum UV range are presented. The results were obtained onboard the CORONAS-F satellite, which has been operating since July 2001. More than 40 thousand observation sessions were performed during the experiment. About a million solar images and spectra (more than 250 Gb of information) were obtained, including monotemperature images of the solar atmosphere in six spectral regions, corresponding to temperatures from 0.05 to 2 MK; full-Sun spectral images (spectroheliograms) in more than 150 lines (177–207 Å and 285–335 Å, T from ～0.05 to 20 MK); images of the full Sun in the monochrome Mg XII line (8.42 Å, T ～ 10 MK); images of the solar corona at a distance of up to five solar radii; continuous series (up to 20 days long) of observations with high time resolution (40–100 s); observations of the flare dynamics, including the preflare, initial, and main phases, with a resolution of 7 s, and data on the absorption of X-ray and XUV solar radiation in the upper atmosphere of the Earth. The study was performed for the maximum of the 11-year solar activity cycle and for its decrease phase.  相似文献   

11.
Two CCD spectra of the star BM Ori were obtained with the echelle spectrograph of the 6-m telescope. In one of the spectra, a large proportion of lines are distorted by emission. The emission component is blueshifted by 50 km s?1, suggesting hot-gas outflow from the atmosphere. The equivalent-width ratio of measured lines in the spectra outside and during eclipse is consistent with the assumption that ～2/3 of the primary star’s area is obscured during eclipse, as follows from light curves. Measured line equivalent widths were used to estimate atmospheric parameters of the secondary star, T eff=7300 K, log g=5.2, and microturbulence ξt=6 km s?1, and to determine its chemical composition. The C, Na, Al, Si, S, Ca, Fe, Ni, and Zn abundances are solar, within the error limits. Li, Sc, Ti, V, Cr, Mn, Co, and Y are overabundant, while Mg, Cu, and Ba are underabundant. In general, the secondary is similar in chemical composition to the star V 1016 Ori. Based on the secondary’s mass determined by solving the radial-velocity curve and on log g estimated spectroscopically from iron ionization equilibrium, we calculated its photospheric radius, R 2 = 0.5R ⊙. However, the spectroscopic log g=5.2 disagrees with log g=3.5 calculated from the luminosity and effective temperature and with log g=3.0 calculated from light and radial-velocity curves. If the secondary’s photospheric radius is indeed small; this argues for the hypothesis that the eclipsing body is a dust envelope. The radial velocities measured from the two spectra are systematically higher than those calculated from the radial-velocity curve by +34 and +24 km s?1. It is likely that the secondary’s atmosphere occasionally shrinks.  相似文献   

12.
We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm?3 and T e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s−1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s−1. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s−1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm−3 and T e ∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = , ΔB = , and ΔU = and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A v = . Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M ⊙) protoplanetary nebula. Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747.  相似文献   

13.
J.S. Morgan 《Icarus》1985,62(3):389-414
Spectrographic data on the Io torus from 15 nights of observations spread over a 4-month period in 1981 are presented here. The [SII] λλ6716, 6731; [SII] λλ4069, 4076; [OII] λλ3726, 3729; and [SIII] λ3722 lines were simultaneously measured on each spectrogram. An east-west asymmetry was observed in the optical emissions, showing larger western intensities and a more diffuse and radially extensive nebula to the east. Two configurations of [SII] longitudinal asymmetry that were stable over at least 4 days were observed. The magnetic longitudes of ～ 180 and 300° are shown to be of particular interest. Longitudinal structure was not detected in either the [OII] intensity or the plasma density as measured by the [OII] and [SII] doublet ratios. Errors in the line ratios could mask density variations as large as a factor of ～ 1.5. A radial variation in the ratio of OII/SII was observed, with the ratio being largest near Io's orbit. Monthly variabilitywas detected in both the intensity and density of the tours. The [SII] line ratios indicated an increase in ne over the 4-month period that was accompanied by increased intensities. For single measurements, no correlation between the [SII] intensities and the [SII] λ6716/λ6731 line ratio was detected, but this could be a result of errors in the line ratio determinations. Extremely low values of this same ratio were measured. These appear to indicate errors in the presently accepted [SII] transition probabilities. These [SII] line ratios indicate that very-high-density regions are present in the torus, and it is shown how these regions could have significantly influenced these measurements.  相似文献   

14.
We present a broad range of complementary observations of the onset and impulsive phase of a fairly large (1B, M1.2) but simple two-ribbon flare. The observations consist of hard X-ray flux measured by the SMM HXRBS, high-sensitivity measurements of microwave flux at 22 GHz from Itapetinga Radio Observatory, sequences of spectroheliograms in UV emission lines from Ov (T ≈ 2 × 105 K) and Fexxi (T ≈ 1 × 107 K) from the SMM UVSP, Hα and Hei D3 cine-filtergrams from Big Bear Solar Observatory, and a magnetogram of the flare region from the MSFC Solar Observatory. From these data we conclude:
  1. The overall magnetic field configuration in which the flare occurred was a fairly simple, closed arch containing nonpotential substructure.
  2. The flare occurred spontaneously within the arch; it was not triggered by emerging magnetic flux.
  3. The impulsive energy release occurred in two major spikes. The second spike took place within the flare arch heated in the first spike, but was concentrated on a different subset of field lines. The ratio of Ov emission to hard X-ray emission decreased by at least a factor of 2 from the first spike to the second, probably because the plasma density in the flare arch had increased by chromospheric evaporation.
  4. The impulsive energy release most likely occurred in the upper part of the arch; it had three immediate products:
  1. An increase in the plasma pressure throughout the flare arch of at least a factor of 10. This is required because the Fexxi emission was confined to the feet of the flare arch for at least the first minute of the impulsive phase.
  2. Nonthermal energetic (～ 25 keV) electrons which impacted the feet of the arch to produce the hard X-ray burst and impulsive brightening in Ov and D3. The evidence for this is the simultaneity, within ± 2 s, of the peak Ov and hard X-ray emissions.
  3. Another population of high-energy (～100keV) electrons (decoupled from the population that produced the hard X-rays) that produced the impulsive microwave emission at 22 GHz. This conclusion is drawn because the microwave peak was 6 ± 3 s later than the hard X-ray peak.
  相似文献   

15.
We present our calculations of the spectrum and oscillator strengths for the 4f7?(4f65d+4f66s) Eu III transitions. The calculations were performed with Cowan's RCN-RCG-RCE codes in the single-configuration approximation. A comparison of computed level lifetimes with experimental data for three levels shows that the scale of theoretical oscillator strengths could be overestimated by a factor of 3. The theoretical oscillator strengths of red Eu III lines are two orders of magnitude smaller than their astrophysical oscillator strengths derived by Ryabchikova et al. (1999) from the condition of ionization balance. The new oscillator strengths were tested by analyzing the Eu abundance using Eu II and Eu III lines in the spectra of hot peculiar stars (α2 CVn is a typical representative) and cool peculiar stars (β CrB is a typical representative). First, we computed non-LTE corrections, which proved to be significant for α2 CVn. We also analyzed the Eu II λ6645.11-Å line as well as ultraviolet and optical Eu III lines. We show that the new oscillator strengths together with the non-LTE corrections allow the contradiction between the Eu abundances derived by Ryabchikova et al. (1999) separately from optical Eu II and Eu III lines in α2 CVn to be resolved. The new Eu abundance, log(Eu/N tot)=?6.5, also faithfully describes the blended near-ultraviolet resonance Eu III lines. Using the new Eu III oscillator strengths to analyze the spectrum of the cool Ap star β CrB, we found a significant deviation of the n(Eu II)/n(Eu III) ratio from its equilibrium value. For a chemically homogeneous model atmosphere, to obtain the observed intensity of the Eu III λ 6666.35-Å line, the Eu abundance must be increased by two orders of magnitude compared to that required to describe the Eu II λ 6645.11-Å line. We discuss the possibility of explaining the observed intensities of Eu II and Eu III lines in the spectrum of β CrB by the presence of an inhomogeneous atmosphere with Eu concentrated in its uppermost layers. In such atmospheres, the role of non-LTE effects becomes dominant.  相似文献   

16.
Presently seven nearby radio-quiet isolated neutron stars discovered in ROSAT data and characterized by thermal X-ray spectra are known. They exhibit very similar properties and despite intensive searches their number remained constant since 2001 which led to their name “The Magnificent Seven”. Five of the stars exhibit pulsations in their X-ray flux with periods in the range of 3.4 s to 11.4 s. XMM-Newton observations revealed broad absorption lines in the X-ray spectra which are interpreted as cyclotron resonance absorption lines by protons or heavy ions and/or atomic transitions shifted to X-ray energies by strong magnetic fields of the order of 1013 G. New XMM-Newton observations indicate more complex X-ray spectra with multiple absorption lines. Pulse-phase spectroscopy of the best studied pulsars RX J0720.4-3125 and RBS 1223 reveals variations in derived emission temperature and absorption line depth with pulse phase. Moreover, RX J0720.4-3125 shows long-term spectral changes which are interpreted as due to free precession of the neutron star. Modeling of the pulse profiles of RX J0720.4-3125 and RBS 1223 provides information about the surface temperature distribution of the neutron stars indicating hot polar caps which have different temperatures, different sizes and are probably not located in antipodal positions.  相似文献   

17.
The photometric UBV observations of AS 338 that we began after its outburst in 1983 are presented. They were accompanied by yearly spectroscopic observations and by occasional estimations of the star’s infrared JHKL magnitudes. In June 1993, the star’s optical spectrum was extended to the ultraviolet via IUE observations of AS 338. Collectively, the above observations make it possible to trace the evolution of stellar activity over a period of 15 years in various spectral ranges. In particular, a short-time return of the hot component of AS 338 to the state when He II lines reappeared in the star’s spectrum was noted in 1993. At this time, a blend of the C IV λλ5802 and 5812 lines, which is typical of Wolf-Rayet spectra, was detected in it. In June 1993, the temperature of the hot component was T h ≈ 8.8 × 104 K, and the ratio of its bolometric flux to that of the red giant was F h, bol/F g, bol ≈ 1.0. In August, its temperature increased to ～1.0×105 K, while the bolometric flux dropped by a factor of ～1.5(F h, bol/F g, bol ≈ 0.7). In the B-V, U diagram, the points referring to this so-called quiescent state form a separate group shifted in B-V from all the remaining ones located in a horizontal strip with $\Delta U \approx 3\mathop .\limits^m 5$ and $\Delta (B - V) \approx 0\mathop .\limits^m 4$ . This allows us to diagnose the state of the hot component without spectroscopic observations of the star. In October 1993, the hot component flared up again. The main brightness rise took no more than 19 days. The outburst occurred shortly before eclipse egress of the hot component, whose duration was ～0.01P orb. In December 1993, F h, bol/F g, bol≤1.5 at maximum light. During the recurrent, even stronger outburst in April 1995, F h, bol/F g, bol≤3.4. The Hαline during outbursts has a P Cyg profile and broad wings stretching to velocities of ±1500 km s?1. The color temperature of the active hot component at short optical wavelengths and in the ultraviolet lies in the range of effective temperatures for hot supergiants. Nevertheless, it always produces an H II region in the circumstellar envelope that is larger in size than this binary system.  相似文献   

18.
Two spectra of the star BM Ori were obtained with the 2.6-m Crimean Astrophysical Observatory telescope near its maximum eclipse phase. The light detector was a CCD array. The wavelength range 5305–5373 Å was chosen in such a way that it contained no strong primary lines. Optimum filtration of the spectra yielded a signal-to-noise ratio of ～300. Eighteen secondary lines are seen in the spectrum. Atmospheric parameters of the secondary star were determined: T eff=5740 K and logg=3.0; the secondary was classified by these parameters as being of spectral type G2 III. The best agreement between observed and synthetic spectra is achieved for metallicity [M/H]=?0.5 and microturbulence ξt=0 km s?1. The projected rotational velocity is Vsini=60 km s?, in agreement with the synchronous velocity in the hypothesis that assumes a total eclipse by the secondary star. Atmospheric elemental abundances in the secondary are estimated. Nickel, chromium, and iron exhibit an underabundance of ～1 dex.  相似文献   

19.
We analyze in detail the ASCA observations of the hard X-ray source IGR J16318-4848, which was recently discovered by the INTEGRAL observatory (Courvoisier et al. 2003). The source has an anomalously hard spectrum in the energy range 0.5–10 keV and is virtually undetectable below 4 keV because of strong photoabsorption (n H L>4×1023 cm?2). The Kα line of neutral or weakly ionized iron with an equivalent width of ～2.5 keV dominates in the energy range 4–10 keV. There is also evidence for the presence of a second line at energy ～7 keV. Our analysis of archival observational data for the infrared counterpart of IGR J16318-4848 that was discovered by Foschini et al. (2003) revealed the source in the wavelength range 1–15 µm. Available data suggest that the object can be an X-ray binary system surrounded by a dense envelope. The source may be a high-mass X-ray binary similar to GX 301-2. We believe that IGR J16318-4848 can be the first representative of a hitherto unknown population of strongly absorbed Galactic X-ray sources that could not be detected by previous X-ray observatories.  相似文献   

20.
The asteroid 133 Cyrene was observed photometrically on 17 nights during oppositions in 1979 and 1980. The synodic period of rotation was found to be 12.h708 ± 0.h001 with an amplitude of ～0.m30 during both oppositions. At large phase angles, the phase relation is quite ordinary (βv ≈ 0.025 mag/degree); however, the low phase angle observations reveal a dramatic opposition brightening, ～0.2 mag/degree near zero phase angle. The absolute magnitude, V(1,0), extrapolated with the above linear phase coefficient, is 8.40. The following color indicates were also measured: B- V = 0.90, U-B = 0.51.  相似文献   

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