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1.
《New Astronomy》2007,12(7):590-596
We assume that the helium-I lines emitted by the massive binary system η Carinae are formed in the acceleration zone of the less-massive secondary star. We calculate the Doppler shift of the lines as a function of orbital phase and of several parameters of the binary system. We find that a good fit is obtained if the helium lines are formed in the region where the secondary wind speed is vzone = 430 km s−1. The acceptable binary eccentricity is in the range 0.90 ≲ e ≲ 0.95, and the inclination angle (the angle between a line perpendicular to the orbital plane and the line of sight) is in the range 40° ≲ i ≲ 55°. Lower values of e require higher values of i, and vice versa. The binary system is oriented such that the secondary star is in our direction (closer to us) during periastron passage. The orbital motion can account in part to the Doppler shift of the peak in X-ray emission.  相似文献   

2.
Ultraviolet spectra from the International Ultraviolet Explorer (IUE) and from the Hubble Space Telescope (HST) of the symbiotic novae AG Peg during the period 1978–1996 are analyzed. Some spectra showing the modulations of spectral lines at different times are presented. We determined the reddening from the 2200 Å feature, finding that E(B−V) = 0.10 ± 0.02. We studied N IV] at 1486 Å, C IV 1550 Å, and O III] at 1660 Å, produced in the fast wind from the hot white dwarf. The mean wind velocity of the three emission lines is 1300 km s−1 (FWHM). The mean wind mass loss rate is ∼6 × 10−7 M⊙ yr−1. The mean temperature is ∼6.5 × 105 K. The mean ultraviolet luminosity is ∼5 × 1033 erg s−1. The modulations of line fluxes in the emitting region at different times are attributed to the variations of density and temperature of the ejected matter as a result of variations in the rate of mass loss.  相似文献   

3.
《New Astronomy》2007,12(6):435-440
A detailed analysis of emission lines of carbon-like silicon reveals that some ratios of n = 3 → 2 line intensities are sensitive to the electron density, ne. The ratio between two groups of 3d → 2p transition lines of 55.246 Å and 55.346 Å provides a good diagnostic of ne because of the combined characteristic of sensitivity to electron density and relative insensitivity to temperature. From this ratio, a lower limit of the electron density of 0.6 × 108 cm−3 was set for Procyon, which is consistent with the values constrained by C V and Si X emission lines. Significant discrepancies were found between theoretical predictions and observations for the 3s → 2p lines relative to 3d → 2p lines in Procyon, recently measured using the Chandra high-resolution transmission grating instrument. The difference of more than a factor of 3, cannot be explained by uncertainties of atomic data. Ness and co-workers also suggested that the effect of opacity appeared not to be a major factor for the discrepancy. For the 3s → 2p line at 61.611 Å, present work indicates that the large discrepancy may be from the contamination of a S VIII line at 61.645 Å. For lines at 61.702 and 61.846 Å, we suggest that the discrepancies may be attributed to contaminations by currently yet-unknown spectral lines.  相似文献   

4.
Phase reddening is an effect that produces an increase of the spectral slope and variations in the strength of the absorption bands as the phase angle increases. In order to understand its effect on spectroscopic observations of asteroids, we have analyzed the visible and near-infrared spectra (0.45–2.5 μm) of 12 near-Earth asteroids observed at different phase angles. All these asteroids are classified as either S-complex or Q-type asteroids. In addition, we have acquired laboratory spectra of three different types of ordinary chondrites at phase angles ranging from 13° to 120°. We have found that both, asteroid and meteorite spectra show an increase in band depths with increasing phase angle. In the case of the asteroids the Band I depth increases in the range of ～2° < g < 70° and the Band II depth increases in the range of ～2° < g < 55°. Using this information we have derived equations that can be used to correct the effect of phase reddening in the band depths. Of the three meteorite samples, the (olivine-rich) LL6 ordinary chondrite is the most affected by phase reddening. The studied ordinary chondrites have their maximum spectral contrast of Band I depths at a phase angle of ～60°, followed by a decrease between 60° and 120° phase angle. The Band II depths of these samples have their maximum spectral contrast at phase angles of 30–60° which then gradually decreases to 120° phase angle. The spectral slope of the ordinary chondrites spectra shows a significant increase with increasing phase angle for g > 30°. Variations in band centers and band area ratio (BAR) values were also found, however they seems to have no significant impact on the mineralogical analysis. Our study showed that the increase in spectral slope caused by phase reddening is comparable to certain degree of space weathering. In particular, an increase in phase angle in the range of 30–120° will produce a reddening of the reflectance spectra equivalent to exposure times of ～0.1 × 106–1.3 × 106 years at about 1 AU from the Sun. This increase in spectral slope due to phase reddening is also comparable to the effects caused by the addition of different fractions of SMFe. Furthermore, we found that under some circumstances phase reddening could lead to an ambiguous taxonomic classification of asteroids.  相似文献   

5.
We examine spectral properties of the SDSS quasar J093201.60 + 031858.7, in particular the presence of strong blue peaks in the Balmer emission lines offset from the narrow lines by approximately 4200 km s?1. Asymmetry in the broad central component of the Hβ line indicates the presence of a double-peaked emitter. However, the strength and sharpness of the blue Hβ and blue Hγ peaks make this quasar spectrum unique among double-peaked emitters identified from SDSS spectra. We fit a disk model to the Hβ line and compare this object with other unusual double-peaked quasar spectra, particularly candidate binary supermassive black holes (SMBHs). Under the binary SMBH scenario, we test the applicability of a model in which a second SMBH may produce the strong blue peak in the Balmer lines of a double-peaked emitter. If there were only one SMBH, a circular, Keplerian disk model fit would be insufficient, indicating some sort of asymmetry is required to produce the strength of the blue peak. In either case, understanding the nature of the complex line emission in this object will aid in further discrimination between a single SMBH with a complex accretion disk and the actual case of a binary SMBH.  相似文献   

6.
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7.
I. Vince  O. Vince 《New Astronomy》2010,15(8):669-677
The spectral region in the vicinity of 5394 Å contains three prominent photospheric spectral lines, which can be used as a solar plasma diagnostic tool. The occurrence of telluric lines in this region is a potential source of systematic and random errors in these solar spectral lines. The goal of our investigation was to determine the telluric line contamination of this interesting spectral region. Several series of high-resolution solar spectra within an interval of about 4 Å around the 5394 Å wavelength were observed at different zenith distances of the Sun. Comparison of these spectra has permitted identification of telluric lines in this spectral interval. The observations were carried out with the horizontal solar spectrograph of the Heliophysical Observatory in Debrecen. Telluric feature blending was identified in the blue and red wings of the Fe I 5393.2 Å line, and in the local continuum of the Mn I 5394.7 Å line. The blue wing of the Fe I 5395.2 Å line is contaminated by a weak telluric feature too. The red continuum of this line has a more prominent telluric contamination. A dozen of water vapor telluric lines that determined the observed telluric features were identified in this spectral interval. The profiles of three telluric lines that have a significant influence on both the profiles of solar spectral lines and the level of local continuum were derived, and the variation of their parameters (equivalent width and central depth) with air mass were analyzed.  相似文献   

8.
The ZrO molecule has been detected in sunspot umbrae through the identification of following laboratory molecular transitions: 1Σ+ ? X1Σ+ (0, 0), A3Φ2 ? X2Δ1 (0, 0), A3Φ3 ? X2Δ2 (0, 0), A3Φ4 ? X2Δ3 (0, 0), B3Π2 ? X3Δ3 (0, 0), B3Π1 ? X3Δ2 (0, 0) and B3Π0 ? X3Δ1 (0, 0) in red – infrared region using high resolution, visible range Fourier Transform Spectrum of sunspot umbra observed at the National Solar Observatory in Kitt Peak (NSO/KP). Much new identification has been made in the searched spectral wavenumber region from 16650 cm?1 to 18007 cm?1 of sunspot spectrum. Equivalent widths of well resolved lines, versus rotational quantum number J have been used to determine the effective rotational temperature for seven bands of the ZrO molecule. This result agrees well with the temperatures derived for other molecules’ presence in sunspot umbrae. It is evident that ZrO molecular lines are formed in higher layers of the atmosphere of relatively “cold” sunspots.  相似文献   

9.
《New Astronomy》2007,12(3):187-191
Using the modified semiempirical approach, we have considered Stark widths for 6 Cu III, 6 Zn III and 3 Se III transitions where the full semiclassical perturbation approach is not applicable in an adequate way due to the lack of reliable atomic data. Results are obtained as a function of temperature, for perturber density of 1017 cm−3. Calculated results have been used to consider the influence of Stark broadening for A type star and DB white dwarf atmospheric conditions.  相似文献   

10.
The Huygens Probe provided a wealth of data concerning the atmosphere of Titan. It also provided tantalizing evidence of a small amount of surface liquid. We have developed a detailed surface energy balance for the Probe landing site. We find that the daily averaged non-radiative fluxes at the surface are 0.7 W m?2, much larger than the global average value predicted by McKay et al. (1991) of 0.037 W m?2. Considering the moist surface, the methane and ethane detected by the Probe from the surface is consistent with a ternary liquid of ethane, methane, and nitrogen present on the surface with mole fractions of methane, ethane, and nitrogen of 0.44, 0.34, and 0.22, respectively, and a total mass load of ～0.05 kg m?2. If this liquid is included in the surface energy balance, only a small fraction of the non-radiative energy is due to latent heat release (～10?3 W m?2). If the amount of atmospheric ethane is less than 0.6×10?5, the surface liquid is most likely evaporating over timescales of 5 Titan days, and the moist surface is probably a remnant of a recent precipitation event. If the surface liquid mass loading is increased to 0.5 kg m?2, then the liquid lifetime increases to ～56 Titan days. Our modeling results indicate a dew cycle is unlikely, given that even when the diurnal variation of liquid is in equilibrium, the diurnal mass variation is only 3% of the total liquid. If we assume a high atmospheric mixing ratio of ethane (>0.6×10?5), the precipitation of liquid is large (38 cm/Titan year for an ethane mixing ratio of 2×10?5). Such a flux is many orders of magnitude in excess of the photochemical production rate of ethane.  相似文献   

11.
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12.
We present spectral and spatial information for major volatile species in Comet 10P/Tempel 2, based on high-dispersion infrared spectra acquired on UT 2010 July 26 (heliocentric distance Rh = 1.44 AU) and September 18 (Rh = 1.62 AU), following the comet’s perihelion passage on UT 2010 July 04. The total production rate for water on July 26 was (1.90 ± 0.12) × 1028 molecules s?1, and abundances of six trace gases (relative to water) were: CH3OH (1.58% ± 0.23%), C2H6 (0.39% ± 0.04%), NH3 (0.83% ± 0.20%), and HCN (0.13% ± 0.02%). A detailed analysis of intensities for water emission lines provided a rotational temperature of 35 ± 3 K. The mean OPR is consistent with nuclear spin populations in statistical equilibrium (OPR = 3.01 ± 0.18), and the (1σ) lower bound corresponds to a spin temperature >38 K. Our measurements were contemporaneous with a jet-like feature observed at optical wavelengths. The spatial profiles of four primary volatiles display strong enhancements in the jet direction, which favors release from a localized vent on the nucleus. The measured IR continuum is much more sharply peaked and is consistent with a dominant contribution from the nucleus itself. The peak intensities for H2O, CH3OH, and C2H6 are offset by ～200 km in the jet direction, suggesting the possible existence of a distributed source, such as the release of icy grains that subsequently sublimed in the coma. On UT September 18, no obvious emission lines were present in our spectra, nevertheless we obtained a 3σ upper limit Q(H2O) < 2.86 × 1027 molecules s?1.  相似文献   

13.
A heliopause spectrum at 122 AU from the Sun is presented for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The focus of this work is on the spectral shape of the LIS below ∼1.0 GeV. The study is done by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations at ∼112 AU from the Sun and PAMELA data at Earth. Below ∼1.0 GeV, this LIS exhibits a power law with E−(1.55 ± 0.05), where E is the kinetic energy of these electrons. However, reproducing the PAMELA electron spectrum averaged for 2009, requires a LIS with a different power law of the form E−(3.15 ± 0.05) above ∼5 GeV. Combining the two power laws with a smooth transition from low to high energies yields a LIS over the full energy range that is relevant and applicable to the modulation of cosmic ray electrons in the heliosphere. The break occurs between ∼800 MeV and ∼2 GeV as a characteristic feature of this LIS. The power-law form below ∼1 GeV produces a challenge to the origin of these low energy galactic electrons. On the other hand, the results of this study can be used as a gauge for astrophysical modeling of the local interstellar spectrum for electrons.  相似文献   

14.
《New Astronomy》2007,12(3):215-223
We compare the results of two calibration methods for deriving a photospheric vector magnetogram, as applied to the Fei 5324.19 Å line. The first method ignores the dependence of its calibration coefficients on the inclination angle. The second method is a multi-iteration, nonlinear calibration technique developed by [M.J. Hagyard, J.I. Kineke, Solar Phys. 158 (1995) 11], which allows the polarization signals to depend on both field strength and inclination angle. We compare the relationship between the derived solar magnetic field and the Stokes parameters under both methods. We find that the circular polarization signal of the Fei 5324.19 Å line is linearly proportional to the longitudinal strength, BL, when the field strength ranges from 0 to 1000 Gauss. For BL > 1000 G and inclination angles ranging from 30° to 90°, deviation from linearity is significant. For the transverse field, BT, the assumption of linearity only holds for 0 < BT < 300 G. In contrast to the former method of calibration, the improved calibration method accounts for the nonlinear relationship between polarization signals and the magnetic field strength. Using [A. Skumanich, in: J.H. Thomas and N.O. Weiss (Eds.), Sunspots: Theory and Observations. Kluwer, Dordrecht, 1992, p. 121] dipole field model, we show that the Fei 5324.19 Å line has more linear property than the Fei 6302.5 Å line.  相似文献   

15.
We report sensitive Chandra X-ray non-detections of two unusual, luminous Iron Low-Ionization Broad Absorption Line Quasars (FeLoBALs). The observations do detect a non-BAL, wide-binary companion quasar to one of the FeLoBAL quasars. We combine X-ray-derived column density lower limits (assuming solar metallicity) with column densities measured from ultraviolet spectra and CLOUDY photoionization simulations to explore whether constant-density slabs at broad-line region densities can match the physical parameters of these two BAL outflows, and find that they cannot. In the “overlapping-trough” object SDSS J0300+0048, we measure the column density of the X-ray absorbing gas to be NH ? 1.8 × 1024 cm?2. From the presence of Fe ii UV78 absorption but lack of Fe ii UV195/UV196 absorption, we infer the density in that part of the absorbing region to be ne ? 106 cm?3. We do find that a slab of gas at that density might be able to explain this object’s absorption. In the Fe iii-dominant object SDSS J2215–0045, the X-ray absorbing column density of NH ? 3.4 × 1024 cm?2 is consistent with the Fe iii-derived NH ? 2 × 1022 cm?2 provided the ionization parameter is log U > 1.0 for both the ne = 1011 cm?3 and ne = 1012 cm?3 scenarios considered (such densities are required to produce Fe iii absorption without Fe iiabsorption). However, the velocity width of the absorption rules out its being concentrated in a single slab at these densities. Instead, this object’s spectrum can be explained by a low density, high ionization and high temperature disk wind that encounters and ablates higher density, lower ionization Fe iii-emitting clumps.  相似文献   

16.
Vertical distributions and spectral characteristics of Titan’s photochemical aerosol and stratospheric ices are determined between 20 and 560 cm?1 (500–18 μm) from the Cassini Composite Infrared Spectrometer (CIRS). Results are obtained for latitudes of 15°N, 15°S, and 58°S, where accurate temperature profiles can be independently determined.In addition, estimates of aerosol and ice abundances at 62°N relative to those at 15°S are derived. Aerosol abundances are comparable at the two latitudes, but stratospheric ices are ～3 times more abundant at 62°N than at 15°S. Generally, nitrile ice clouds (probably HCN and HC3N), as inferred from a composite emission feature at ～160 cm?1, appear to be located over a narrow altitude range in the stratosphere centered at ～90 km. Although most abundant at high northern latitudes, these nitrile ice clouds extend down through low latitudes and into mid southern latitudes, at least as far as 58°S.There is some evidence of a second ice cloud layer at ～60 km altitude at 58°S associated with an emission feature at ～80 cm?1. We speculate that the identify of this cloud may be due to C2H6 ice, which in the vapor phase is the most abundant hydrocarbon (next to CH4) in the stratosphere of Titan.Unlike the highly restricted range of altitudes (50–100 km) associated with organic condensate clouds, Titan’s photochemical aerosol appears to be well-mixed from the surface to the top of the stratosphere near an altitude of 300 km, and the spectral shape does not appear to change between 15°N and 58°S latitude. The ratio of aerosol-to-gas scale heights range from 1.3–2.4 at about 160 km to 1.1–1.4 at 300 km, although there is considerable variability with latitude. The aerosol exhibits a very broad emission feature peaking at ～140 cm?1. Due to its extreme breadth and low wavenumber, we speculate that this feature may be caused by low-energy vibrations of two-dimensional lattice structures of large molecules. Examples of such molecules include polycyclic aromatic hydrocarbons (PAHs) and nitrogenated aromatics.Finally, volume extinction coefficients NχE derived from 15°S CIRS data at a wavelength of λ = 62.5 μm are compared with those derived from the 10°S Huygens Descent Imager/Spectral Radiometer (DISR) data at 1.583 μm. This comparison yields volume extinction coefficient ratios NχE(1.583 μm)/NχE(62.5 μm) of roughly 70 and 20, respectively, for Titan’s aerosol and stratospheric ices. The inferred particle cross-section ratios χE(1.583 μm)/χE(62.5 μm) appear to be consistent with sub-micron size aerosol particles, and effective radii of only a few microns for stratospheric ice cloud particles.  相似文献   

17.
Determining the optical constants of Titan aerosol analogues, or tholins, has been a major concern for the last three decades because they are essential to constrain the numerical models used to analyze Titan’s observational data (albedo, radiative transfer, haze vertical profile, surface contribution, etc.). Here we present the optical constant characterization of tholins produced with an RF plasma discharge in a (95%N2–5%CH4) gas mixture simulating Titan’s main atmospheric composition, and deposited as a thin film on an Al–SiO2 substrate. The real and imaginary parts, n and k, of the tholin complex refractive index have been determined from 370 nm to 900 nm wavelength using spectroscopic ellipsometry. The values of n decrease from n = 1.64 (at 370 nm) to n = 1.57 (at 900 nm) as well as the values of k which feature two behaviors: an exponential decay from 370 nm to 500 nm, with k = 12.4 × e?0.018λ (where λ is expressed in nm), followed by a plateau, with k = (1.8 ± 0.2) × 10?3. The trends observed for the PAMPRE tholins optical constants are compared to those determined for other Titan tholins, as well as to the optical constants of Titan’s aerosols retrieved from observational data.  相似文献   

18.
《New Astronomy》2007,12(6):446-453
Using reliable trigonometric measurements, we find that the absolute magnitude of cataclysmic variables depends on the orbital period and de-reddened (J − H)0 and (H − K s)0 colours of 2MASS (Two Micron All Sky Survey) photometric system. The calibration equation covers the ranges 0.032d < Porb ⩽ 0.454d, −0.08 < (J − H)0 ⩽ 1.54, −0.03 < (H − Ks)0 ⩽ 0.56 and 2.0 < MJ < 11.7; It is based on trigonometric parallaxes with relative errors of (σπ/π) ⩽ 0.4. By using the period-luminosity-colours (PLCs) relation, we estimated the distances of cataclysmic variables with orbital periods and 2MASS observations and compared them with distances found from other methods. We suggest that the PLCs relation can be a useful statistical tool to estimate the distances of cataclysmic variables.  相似文献   

19.
《Astroparticle Physics》2007,26(6):402-411
We constrain the possibility of a non-trivial refractive index in free space corresponding to an energy-dependent velocity of light: c(E) ≃ c0(1 − E/M), where M is a mass scale that might represent effect of quantum-gravitational space-time foam, using the arrival times of sharp features observed in the intensities of radiation with different energies from a large sample of gamma-ray bursters (GRBs) with known redshifts. We use wavelet techniques to identify genuine features, which we confirm in simulations with artificial added noise. Using the weighted averages of the time-lags calculated using correlated features in all the GRB light curves, we find a systematic tendency for more energetic photons to arrive earlier. However, there is a very strong correlation between the parameters characterizing an intrinsic time-lag at the source and a distance-dependent propagation effect. Moreover, the significance of the earlier arrival times is less evident for a subsample of more robust spectral structures. Allowing for intrinsic stochastic time-lags in these features, we establish a statistically robust lower limit: M > 0.9 × 1016 GeV on the scale of violation of Lorentz invariance.  相似文献   

20.
M.R. Sanad 《New Astronomy》2010,15(1):113-118
We analyze both long and short high resolution ultraviolet spectrum of Beta Lyrae eclipsing binary system observed with the International Ultraviolet Explorer (IUE) between 1980 and 1989. The main spectral features are P Cygni profiles originating from different environments of Beta Lyrae. A set of 23 Mg II k&h spectral lines at 2800 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H], have been identified and measured to determine their fluxes and widths. We found that there is spectral variability for these physical parameters with phase, similar to that found for the light curve [Kondo, Y., McCluskey, G.E., Jeffery, M.M.S., Ronald, S.P., Carolina, P.S. McCluskey, Joel, A.E., 1994. ApJ, 421, 787], which we attribute to the eclipse effects [Ak, H., Chadima, P., Harmanec, P., Demircan, O., Yang, S., Koubský, P., ?koda, P., ?lechta, M., Wolf, M., Bo?i?, H., 2007. A&A, 463, 233], in addition to the changes of density and temperature of the region from which these lines are coming, as a result of the variability of mass loss from the primary star to the secondary [Hoffman, J.L., Nordsieck, K.H., Fox, G.K., 1998. AJ, 115, 1576; Linnell, A.P., Hubeny, I., Harmanec, P., 1998. ApJ, 509, 379]. Also we present a study of Fe II spectral line at 2600 Å, originating from the atmosphere of the primary star [Hack, M., 1980. IAUS, 88, 271H]. We found spectral variability of line fluxes and line widths with phase similar to that found for Mg II k&h lines. Finally we present a study of Si IV spectral line at 1394 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H]. A set of 52 Si IV spectral line at 1394 Å have been identified and measured to determine their fluxes and widths. Also we found spectral variability of these physical parameters with phase similar to that found for Mg II k&h and Fe II spectral lines.  相似文献   

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