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1.
The paper presents the results of the spectral observations of comet C/2001 Q4 (NEAT) acquired with the Zeiss-600 telescope of the Andrushevka astronomical observatory in May 2004. The spectrum of the comet was obtained in the range of 3600–8200 Å. We identified a number of emission features in the spectrum of comet C/2001 Q4 (NEAT). The emission bands of C2, C3, CN, CH, NH2, H2O+ were detected in the spectrum of the comet, and their intensities were determined. The ratios of gas-production rates Q(C2)/Q(CN) = 0.23, Q(C3)/Q(CN) = ?0.79, and Q(NH2)/Q(CN) = ?0.029 were determined with the Haser model.  相似文献   

2.
The HCN emission features near 3 μm recently detected by Geballe et al. (2003, Astrophys. J. 583, L39) are analyzed with a model for fluorescence of sunlight in the ν3 band of HCN. The emission spectrum is consistent with current knowledge of the atmospheric temperature profile and the HCN distribution inferred from millimeter-wave observations. The spectrum is insensitive to the abundance of HCN in the thermosphere and the thousand-fold enhancement relative to photochemical models suggested by Geballe et al. (2003, Astrophys. J. 583, L39) is not required to explain the observations. We find that the spectrum can be matched with temperatures from 130 to 200 K, with slightly better fits at high temperature, contrary to the temperature determination of 130±10 K of Geballe et al. (2003, Astrophys. J. 583, L39). The HCN emission spectrum is sensitive to the collisional de-excitation probability, P10, for the ν3 state and we determine a value of 10−5 with an accuracy of about a factor of two. Analysis of absorption lines in the C2H2ν3 band near 3 μm, detected in the same spectrum, indicate a C2H2 mole fraction near 0.01 μbar of 10−5 for P10=10−4. The derived mole fraction, however, is dependent upon the value adopted for P10 and lower values are required if P10 at Titan temperatures is less than its room temperature value.  相似文献   

3.
《New Astronomy》2007,12(7):597-604
We investigate the effect on the U, B, V, RC and RJ magnitudes of the removal of emission lines from a spectrum. We determined Δm corrections from the ratio of fluxes with and without emission lines, transmitted from the object through a photometric filter. An exact and simplified approach for operative use was applied. The effect was demonstrated for classical symbiotic stars, symbiotic novae and the classical nova V1974 Cyg. It was found that about 20–30%, 30–40%, 10% and 26/20% of the observed flux in the U, B, V and RC/RJ filters, respectively, are radiated in the emission lines of the investigated classical symbiotic stars. The largest effect was found for symbiotic novae (RR Tel and V1016 Cyg) and the classical nova V1974 Cyg at 210 days (an average of 74%, 79%, 56% and 66/60%), because of their very strong emission line spectrum. In all cases, the line corrected flux points fit the theoretical continuum well. The difference between Δm corrections obtained by the accurate calculation and that given by our approximate formula is less than 10%. Deviations up to 30% can exist only in the U passband. Examples for practical applications are suggested.  相似文献   

4.
Soft X-ray emission from the X-ray source Per X-1 was observed in the 0.4–2 keV energy interval from a rocket borne X-ray detector. Spectral analysis of the data indicates that in the 0.4–2 keV band the X-ray emission from Per X-1 can be fitted either with a power law of slope-(4.8±1.2) or a thermal bremsstrahlung spectrum with akT value of (0.26 ?0.08 +0.12 ) keV. Such a steep spectrum is inconsistent with the spectrum measured above 2 keV. The measured flux in 0.4–2 keV band corresponds to X-ray luminosity of 3×1045 ergs s?1 for Per X-1.  相似文献   

5.
We report observation and analysis of a high-resolution 2.87-3.54 μm spectrum of the southern temperate region of Saturn obtained with NIRSPEC at Keck II. The spectrum reveals absorption and emission lines of five molecular species as well as spectral features of haze particles. The ν2+ν3 band of CH3D is detected in absorption between 2.87 and 2.92 μm; and we derived from it a mixing ratio approximately consistent with the Infrared Space Observatory result. The ν3 band of C2H2 also is detected in absorption between 2.95 and 3.05 μm; analysis indicates a sudden drop in the C2H2 mixing ratio at 15 mbar (130 km above the 1 bar level), probably due to condensation in the low stratosphere. The presence of the ν3+ν9+ν11 band of C2H6 near 3.07 μm, first reported by Bjoraker et al. [Bjoraker, G.L., Larson, H.P., Fink, U., 1981. Astrophys. J. 248, 856-862], is confirmed, and a C2H6 condensation altitude of 10 mbar (140 km) in the low stratosphere is determined. We assign weak emission lines within the 3.3 μm band of CH4 to the ν7 band of C2H6, and derive a mixing ratio of 9±4×10−6 for this species. Most of the C2H6 3.3 μm line emission arises in the altitude range 460-620 km (at ∼μbar pressure levels), much higher than the 160-370 km range where the 12 μm thermal molecular line emission of this species arises. At 2.87-2.90 μm the major absorber is tropospheric PH3. The cloud level determined here and at 3.22-3.54 is 390-460 mbar (∼30 km), somewhat higher than found by Kim and Geballe [Kim, S.J., Geballe, T.R., 2005. Icarus 179, 449-458] from analysis of a low resolution spectrum. A broad absorption feature at 2.96 μm, which might be due to NH3 ice particles in saturnian clouds, is also present. The effect of a haze layer at about 125 km (∼12 mbar level) on the 3.20-3.54 μm spectrum, which was not apparent in the low resolution spectrum, is clearly evident in the high resolution data, and the spectral properties of the haze particles suggest that they are composed of hydrocarbons.  相似文献   

6.
The T Tauri variable V1331 Cyg is characterized by an intensive emission spectrum, by signatures of a high rate of mass loss, and also by presence of a circular reflection nebula. According to these characteristics, the star can be considered as a possible pre-FUor star. Up to the present the photospheric spectrum of the star has not been recorded. In this work we analyze the high-resolution spectra of V1331 Cyg that were obtained by G.H. Herbig with the HIRES spectrograph at the Keck-1 telescope in 2004 and 2007. For the first time the numerous photospheric lines of the star have been detected and the spectral class has been estimated, viz., G7-K0 IV. It is revealed that the projection of the rotation velocity is lower than the width of instrumental profile (vsini < 6 km/s); this means that the angle between the stellar axis of rotation and the line of sight is small. The radial velocity of the star derived from the photospheric lines is RV = ?15.0 ± 0.3 km/s. The difference in radial velocities for 2004 and 2007 is lower than the measurement error. The photospheric spectrum is veiled considerably, but the amount of veiling is not the same in different lines. This depends on the line strength in the template spectrum of the G7 IV star: in the weakest lines (EW = 5–10 mÅ in the template spectrum) VF ≈ 1 and it increases up to 4–5 in stronger lines. The Hα and Hβ lines demonstrate classical P Cyg profiles, which testifies to an intensive wind with a maximal velocity of about 400 km/s. In addition, the emission lines of Fe II, Mg I and K I and of several other elements are accompanied by a narrow blue-shifted absorption at ?150...?250 km/s. The emission spectrum of V1331 Cyg is rich in the narrow (FWHM = 30–50 km/s) lines of neutral and ionized metals showing the excitation temperature T exc = 3800 ± 300 K. The stellar mass M* ≈ 2.8M ⊙ and radius R* ≈ 5R ⊙ are estimated.  相似文献   

7.
A spectrum of Mars of unprecedented quality was obtained in the range of 904-1183 Å with a spectral resolution of 0.2 Å using the Far Ultraviolet Spectroscopic Explorer. Besides marking the first detection of molecular hydrogen on Mars (Krasnopolsky and Feldman, Science 2001 294, 1914-1917), the spectrum also revealed many emission lines of H, O, N, C, Ar, He, N+, C+, and Ar+ and the bands of N2 and CO. The spectrum makes it possible to study the emission multiplet structures and the component ratios and to separate many of the blended lines. From the argon lines, we retrieved Ar mixing ratios of 1.5 and 1.3% at 150 and 130 km, respectively, in excellent agreement with the Viking mass spectrometric measurements of 1.6% in the lower atmosphere. The He 584-Å emission observed in second order also agrees with the Extreme Ultraviolet Explorer detection of He on Mars. The observed spectrum may be used as a database to study specific problems such as the dayglow excitation, radiative transfer, and composition in Mars' upper atmosphere.  相似文献   

8.
Kirsch  E.  Münch  J. W. 《Solar physics》1974,36(2):459-472
The NRL SOLRAD 10 satellite carries six ionization chambers to measure solar X-radiation in the 0.5 to 60 Å wavelength band. The X-ray emission spectrum in this range is determined by the derivative of the coronal emission measure (∫ N e 2 dV) with respect to temperature when the thermal processes of bremsstrahlung, radiative recombination and line radiation are considered. If a simple model for this differential emission measure is used and detector responses to the calculated spectra are fitted to the SOLRAD data by a least squares method, the differential emission measure can be obtained for temperatures between 2 × 106K and 64 × 106K. Data during quiet and flaring periods are analyzed and the general behavior of the differential emission measure during flares is presented. This analysis is based on experimental measurements of the efficiencies of the SOLRAD detectors.  相似文献   

9.
Results of photometric and spectroscopic studies for the new eclipsing cataclysmic variable star HBHA 4705-03 with an orbital period of 0.1718 days are presented. Its spectrum exhibits hydrogen and helium emission lines. The Doppler maps constructed from hydrogen lines and the He II λ 4686 line show that the regions near the inner Lagrangian point are the main source of emission in these lines, while the maps constructed from He I lines suggest the presence of an accretion disk around the primary. The masses of the components (M WD = 0.54 ± 0.10M ⊙ andM RD = 0.45 ± 0.05 M ⊙) and the orbital inclination of the system (i = 71.8° ± 0.7°) have been determined from observational data using well-known relations for close binaries and cataclysmic variable stars.  相似文献   

10.
Observations at Godhavn, Greenland show that the intersection of the polar cleft with the ionosphere can be recognized by simultaneous occurrence of hydrogen emissions (Hα, Hβ>) and enhanced OI 6300 Å emission. The Hα-line reveals a characteristic narrow and symmetric Doppler profile which is interpreted as indicating that the solar wind protons retain their typical flux and energy spectrum all the way down to the ionosphere. The cleft intersection seems to cover the sector 04:00–22:00 geomagnetic time.  相似文献   

11.
GRBs are the most energetic combination of jets and disks in the Universe. Observations made using Swift reveal a complex temporal and spectral behaviour. We propose that this behaviour can be used to refine the GRB classification scheme and align it better with progenitor types. The early (prompt) X-ray light curve can be well described by an exponential which relaxes into a power law. The transition time between the exponential and the power law gives a well-defined timescale, T p , for the burst duration which we use with the spectral index of the prompt emission, β p , and the prompt power law decay index, α p to define four classes of burst: short, slow, fast and soft. Short bursts tend to decline more gradually than long bursts. Most GRBs display a second “afterglow” component which can be fitted in a similar way to the early emission. During the decay of this second component, few GRBs show jet breaks in accord with pre-Swift predictions. However, the start time of the final afterglow decay, T a , correlates with the peak of the prompt γ-ray emission spectrum, E peak, in an analogous way to the Ghirlanda relation found between optical “jet-break” times, t j , and E peak. These data are inconsistent with simple achromatic jet-break models casting doubt on the reliability of using late temporal breaks to determine the jet collimation.  相似文献   

12.
Sang J. Kim  T.R. Geballe 《Icarus》2005,179(2):449-458
We have used synthetic spectra to analyze a medium resolution 2.9-4.2 μm spectrum of Saturn's temperate region observed at UKIRT using CGS4. The synthetic spectra include CH4, PH3, and NH3 lines, for which mixing ratios were adopted from recent Cassini results. The observed absorption features in the spectrum are well accounted for by lines of these molecular species formed 22 +/− 8 km above the 1 bar pressure level at ∼610 mbar. The influence of optically thin haze particles at higher altitudes on the spectrum is not pronounced, with higher spectral resolution probably required to constrain the effects of haze in this wavelength region. Fluorescent line emission by CH4 in its ν3 and ν3+ν4−ν4 bands, detected in the 3.2-3.5 μm region, originates between 400 km (∼0.06 mbar) and 800 km (∼0.01 μbar) above the 1 bar level, with peak contributions from the two major contributing bands at 550 km (∼3 μbar) and 700 km (∼0.1 μbar), respectively.  相似文献   

13.
Investigations in the line Hα of the spectrum of UX Ori WW Vul are presented. Comparison with the data of other researchers has shown that the regime of variable matter ejection of the star WW Vul is retained for a long time. The spectra of two nights (July 18 and 23, 2006) showed an increased intensity of red emission component without noticeable change in the radial velocity. On the other hand, radial velocity of the central absorption considerably changed to negative values with decreasing V/R. During the night on July 8, 2006, we found doubling of the blue emission component for these two spectra.  相似文献   

14.
《New Astronomy Reviews》2000,44(7-9):443-445
To explain the broad-band spectral energy distributions (SED) of Seyfert nuclei and QSOs, we study the emission spectrum emerging from a vertical disk–corona structure composed of a two-temperature plasma by solving hydrostatic equilibrium and radiative transfer self-consistently. Our model can nicely reproduce the soft X-ray excess with α (Lν ∝ ν−α) of about 1.5 and the hard tail extending to ∼50 keV with α∼0.5. The different spectral slopes (α∼1.5 below 2 keV and ∼0.5 above) are the results of different emission mechanisms: unsaturated Comptonization in the former and a combination of Comptonization, bremsstrahlung, and reflection of the coronal radiation at the disk–corona boundary in the latter.  相似文献   

15.
Statistical analyses of solar radio observations have shown that proton events are likely to occur when the flux at 3 cm, S3, of the SVC is greater than 25 sfu and when S3/S8 is grater than 1. A theoretical explanation of this fact is attempted in this paper. I calculated the spectrum of the SVC using the gyro-radiation emission and found that the main reason for S3 >; 25sfu is a ten-fold increase in the conductive energy flux in the active region over the quiet region, raising the height of the gyro-resonance layer for the 3 cm emission, and that the main reason for S3/S8 ? 1 is an increase in the coronal magnetic field gradient in the active region, causing a decrease in the optical thickness for the gyro-resonance absorption at 3 cm. It is precisely these active regions that are most favourable for the production of proton events.  相似文献   

16.
We have analyzed the Hubble Space Telescope spectrum of the young star FU Ori in the range 2300–3100 Å. The long-wavelength part of the spectrum is similar to the spectrum of a supergiant with T eff ? 5000–6000 K, but the range of wavelengths shorter than ?2600 Å is dominated by radiation from a region with T eff ? 9000 K. We discuss the possibility of explaining these peculiarities of the spectrum, the Al II] 2669.2 emission line profile, and the results of X-ray observations for FU Ori in terms of an accretion disk model whose thickness increases as the star is approached starting from distances ?1012 cm. Near the star, the disk has the shape of a cone in which only the part of its surface on the far (from the observer) side is visible. The suggested model is a kind of a compromise between the models of a thin α-disk and a supergiant: basically, this is an accretion model, but it resembles a supergiant in observational manifestations. Numerous absorption lines originating in the disk wind are superimposed on the disk spectrum. The wind is a cold (T ? 5000 K), dense (N e ? 1011 cm?3) gas. The number of wind absorption lines in the ultraviolet spectrum of FU Ori increases with decreasing wavelength. This causes a rapid decline in intensity in the short-wavelength part of the spectrum. As a result, the maximum temperature in the disk estimated from low-resolution IUE spectra has been underestimated.  相似文献   

17.
A new spectrum of Jupiter from 700 to 1600 cm?1 was obtained with an interferometric experiment using the 91.5 cm telescope of the NASA Airborne Infrared Observatory. The spectral resolution is 10 cm?1 and the signal-to-noise ratio is 30 at 900 cm?1. NH3 absorption lines are observed between 820 and 1020 cm?1. The 1306 cm?1ν4CH4 band strongly appears in emission at a temperature of at least 145° K. The Jovian brightness temperature between 1400 and 1600 cm?1, according to our measurement, is lower than 170° K.  相似文献   

18.
It is generally believed that the synchrotron radiation of electrons from the internal shock is the main radiation mechanism of the prompt GRB (gamma-ray burst) emission. However, what this model predicts can not explain observations well. In this paper, we confirm that electrons are quickly cooled due to radiation losses and also point out that the synchrotron radiation spectrum presented in previous papers is a relatively rough estimation. We get the precise synchrotron radiation spectrum of fast-cooling electrons by carrying out a numerical calculation, and thereby reasonably explain the observed distribution of low-energy spectral index (α) of long GRBs based on a unified model. In addition, we fit the correlation between α and the peak energy of the νFν spectrum (Ep).  相似文献   

19.
We investigate the dissociative recombination contribution to I(5577) and I(6300) of [OI] as a function of low energy cutoff for two measured solar proton spectra. The volume ionization rate profiles used in the calculation are obtained using a detailed atomic cross section approach in the continuous slowing down approximation. The ratio of the dissociative recombination contribution to the direct impact contribution for both the 5577 Å and 6300 Å [OI] emissions is found to be dependent upon the low energy cutoff. This ratio has a nominal value of ～2.0 for the 5577 Å [OI] emission and ～0.25 for the 6300 Å [OI] emission. The I(5577)/I(3914) and I(6300)/I(3914) ratios including the direct and dissociative recombination contributions are strongly dependent upon the low energy cutoff of the spectrum. We have also investigated F-layer enhancements resulting from the low energy spectrum component. For the Mizera et al. (1972) spectrum with a low energy cutoff of 12.4 keV, we find an NmF2 of ～4.5 × 103 electrons/cm3 or about 10 per cent of the ionization required to maintain the dip pole at a value of 5 × 104 electrons/cm3. Extension of the cutoff to 1 keV results in ～1 × 104 electrons/cm3, or about 20 per cent of the required maintenance ionization.  相似文献   

20.
In the homogeneous model of solar radio burst model, the spectral index of the optically thick part of the spectrum is almost independent of the spectral index of the electron energy, while from the optically thin part, the derived electron index δR is far smaller than that derived from the X-ray emission, δX. An inhomogeneous model is proposed, in which, by adjusting two parameters within reasonable limits, we can make δR, derived from both the optically thick and thin parts, to equal δX. The model is exemplified by the 1981 April 27 0800 UT burst.  相似文献   

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