首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Estimates of relative line intensities available in the literature and integrated Hβ fluxes of the planetary nebula NGC 6572 during the time covered by optical observations (1938–2013) are compared to search for possible variations. Line intensities measured from observations obtained at the Crimean Station of the Sternberg Astronomical Institute in 2013 are presented, as well as previously unpublished photographic spectroscopic data obtained 1972–2005. Our analysis of all the available data shows that the line intensities do not vary within the observational uncertainties, with the possible exception of the [OIII] 4959 and 5007 Å lines, which show a tendency for their intensity increase with time. This can be interpreted as a manifestation of a temperature increase of the central star, or radial stratification of the [OIII] emission in the nebula, with the latter explanation being less probable. However, stratification is clearly visible in the [OII] and [NII] line intensities. The integrated Hβ flux is most probably constant at F(Hβ) = (1.50 ± 0.03) × 10?10 erg cm?2 s?1. A refined estimate of the interstellar extinction toward NGC 6572 has been obtained from radio and optical data, c(Hβ) = 0.42 ± 0.03. The MAST spectroscopy data were used to derive the central star’s UBV magnitudes in 2004. Integrated photoelectric UBV observations of the nebula and central star for 1971–2005 are presented.  相似文献   

2.
We have determined the realistic seeing of the 1.5-m AZT-22 telescope of the Mt. Maidanak Observatory (Astronomical Institute, Uzbek Academy of Sciences) using more than 20 000 CCD frames with stellar images in the UBV RI bands acquired in 1996–2005: ε = 1.065″ in the V band. The characteristic seeing reduced to unit air mass, ε med V (M(z) = 1), is 0.945″. We derived color equations for the CCD detectors used with the telescope. Atmospheric-extinction coefficients in different photometric bands were also determined. The mean V -band atmospheric extinction is 0.20 m ± 0.04 m . The time needed for the conditions to settle, in the free atmosphere as well as inside the telescope dome, is 2–2.5 hours after the end of astronomical twilight. For nights with ε med V > 0.9″, we find a persistent difference between the seeing found at this telescope and measured simultaneously with a differential image motion monitor, amounting to ∼0.1 m .  相似文献   

3.
An empirical relation H=K(1?2/3α4) has been derived between the hardness H of A m B n-like crystals, as obtained by smoothing the Mohs hardness scale, and the bond-ionicity α, where K is a constant determined by the number of the rows to which the atoms A and B belong in the periodic classification of elements. The applicability of the above relation is extended to crystals in which B is a polyatomic anion. Electron charges in some crystals have also been calculated with help of the proposed relation.  相似文献   

4.
Between 1994 and 2006, we obtained uniform spectroscopic observations of SS 433 in the region of Hα. We determined Doppler shifts of the moving emission lines, Hα + and Hα ?, and studied various irregularities in the profiles for the moving emission lines. The total number of Doppler shifts measured in these 13 years is 488 for Hα ? and 389 for Hα +. We have also used published data to study possible long-term variations of the SS 433 system, based on 755 Doppler shifts for Hα ? and 630 for Hα + obtained over 28 years. We have derived improved kinematic model parameters for the precessing relativistic jets of S S 433 using five-and eight-parameter models. On average, the precession period was stable during the 28 years of observations (60 precession cycles), at 162.250d ± 0.003d. Phase jumps of the precession period and random variations of its length with amplitudes of ≈6% and ≈1%, respectively, were observed, but no secular changes in the precession period were detected. The nutation period, P nut = 6.2876d ± 0.00035d, and its phase were stable during 28 years (more than 1600 nutation cycles). We find no secular variations of the nutation cycle. The ejection speed of the relativistic jets, v, was, on average, constant during the 28 years, β = v/c = 0.2561 ± 0.0157. No secular variation of β is detected. In general, S S 433 demonstrates remarkably stable long-term characteristics of its precession and nutation, as well as of the central “engine” near the relativistic object that collimates the plasma in the jets and accelerates it to v = 0.2561c. Our results support a model with a “slaved” accretion disk in S S 433, which follows the precession of the optical star’s rotation axis.  相似文献   

5.
We have used 46 high-resolution echelle spectra of the Wolf-Rayet star HD 192163 taken in 2005–2009 at the Cassegrain focus of the 2-m Zeiss-2000 telescope of the Shamakha Astrophysical Observatory to study profiles of the five strongest emission lines (HeII 4859, HeII 5411, CIV 5808, HeI 5875, (HeII + Hα) 6560). We also obtained four echelle spectrograms of the Wolf-Rayet star HD 191765 for a comparative study of the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines. The echelle spectrograms were reduced using the DECH20 code. We determined the equivalent widths, radial velocities, central intensities, and half-widths of the emission lines. We detected variations in the violetwing of the (HeII + Hα) 6560 emission band (between λ ～ 6496 Å and λ ～ 6532 Å). Our statistical analysis of the radial velocities available for the (HeII + Hα) 6560 emission band reveals a peak at the ～1% level at the frequency ν = 0.195 d?1, corresponding to the period P = 5.128d. We also studied the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines, which are important for understanding the nature of the nebula NGC 6888, whose origin is related to HD 192163. Asymmetric profiles were found for the NaI 5890 and NaI 5896 interstellar absorption lines, interpreted as reflecting a contribution from NGC 6888 to these lines. We suggest that the detected profile variations of the (HeII + Hα) 6560 emission band and the periodic variations of its Doppler shifts (P = 5.128d) are due to the existence of a low-mass K-M star companion to the Wolf-Rayet star. HD 192163 is a possible evolutionary progenitor of a low-mass X-ray binary.  相似文献   

6.
We have carried out photometry and spectroscopy of the star V1327 Aql (R = 16 m ) as part of our program of observations of poorly studied cataclysmic variables using the 1.5-m optical Russian—Turkish telescope (RTT-150, Turkey) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. After analyzing our photometry, we have re-classified the variable as an RR Lyrae star. Our BV R photometry during 10 nights reveals brightness variations with the period 12h49m, with the B, V, and R amplitudes being 1.36 m , 1.13 m , and 1.11 m , respectively. We derived the first estimates of the star’s atmospheric parameters from our moderate-resolution spectra: T eff = 6280 K, log g = 3.3, [M/H] = ?1.05. The extremely high radial velocity of the star’s motion (V R = ?470 km/s) and the star’s large distances to the Galactic center (13.1 kpc) and disk (4.2 kpc) testify to a probable extragalactic origin of this object.  相似文献   

7.
Activity-composition relations are derived for ideal substitutional solid solutions through the Helmholtz free energy expressed in terms of the partition function. For solutions of the type (A, B)uZw involving mixing on one type of atom site, ideal activities of end-member components are expressed by: aAuZw = (XAuZw)u, and aBuZw = (XBuZw)u. With multi-site mixing excluding charge balance restrictions, as in (A, B)αu (C, D)βvZw, the ideal activity of an end-member component such as AuCvZw is calculated as: aAuCvZw = (XαA)u (Xβc)v. These expressions support the ‘ionic solid solution model for the activities of components in ideal solid solutions. Ideal solution models for coupled substitutions involving charge balance are considered using plagioclase as an example. Ideal activity expressions for solid solution of albite and anorthite are derived with and without adherence to the Al avoidance principle. Mixing models involving local electrostatic balance are contrasted with those involving independent, random mixing of Na-Ca and Al-Si. Of several possible ideal solution models for plagioclase, only that specifying complete Al-Si ordering and local electrostatic neutrality yields activities conforming to Raoult's Law.  相似文献   

8.
We present new spectroscopic observations of the peculiar supergiant IRC+10420. In 1997–2000, we obtained three high signal-to-noise ratio spectra of the object at 4300–8000 Å with a spectral resolution of 15 000 (20 km/ s) using the 6-m telescope of the Special Astrophysical Observatory. From our 2000 spectrum, we estimate the spectral type of IRC+10420 to be A2, corresponding to a temperature of ～9200 K. Many emission lines were detected, identified with lines of Fe I; Fe II, Ti II, Cr II, and Sc II ions; and [O I], [Fe II], and [Ca II] forbidden lines. The radial velocity derived from absorption lines without obvious emission components (He I λ5876, O I, N I, Si II) and from absorption components of the Balmer lines is 93±1 km/s. The redshift of photospheric lines relative to the star’s center-of-mass velocity is interpreted as a consequence of scattering in the expanding, optically thick dust envelope. Both emission and absorption lines show a correlation between radial velocity and oscillator strength. We found variability in the relative intensities of the H α and H β emission components. We conclude that IRC+10420 is rapidly evolving towards a Wolf-Rayet stage; the current rate of the photospheric temperature increase is ～120 K per year. Based on the intensity of the O I (λ7773) triplet, we estimate the star’s luminosity to be M bol=?9.5m. In all 1997–2000 spectra of IRC+10420, the He I λ5876 line has a significant equivalent width of at least 200 mÅ; this may be possible in the presence of such a low temperature due to the star’s high luminosity and the enhanced helium abundance in the supergiant’s atmosphere.  相似文献   

9.
Mass absorption coefficients (A2) for a series of standard rocks, have been calculated in the wavelength region 0.492–3.03 a?. Plots of these data against the intensity of the Compton scattered peak [(I) Compton] give an excellent correlation for the wavelengths 0.429 a? to the Fe-absorption edge (1.74 a?); the data confirm the observations of Reynolds. Hence, routine measurement of one peak will give the mass absorption coefficient of a sample in an analytically important region (Sn/1bKα to Ni/1bKα). A2 has also been directly measured on three of the samples and systematic differences between calculated and measured are attributed to the measuring technique. At wavelengths longer than the Fe-absorption edge, (up to 3.03 a?) A2 can be estimated using a combination of (I) Compton and Fe/1bKα c.p.s. This technique enables meaningful matrix corrections to be carried out on the elements Co, Mn, Cr, V, Ti, Sc (K spectra) and Ba (L spectra). Cr and Ba results are presented for some standard rocks.  相似文献   

10.
An analysis of spectroscopic and photometric data for the young pre-cataclysmic variable (PCV) PN G068.1+11.0, which passed through its common-envelope stage relatively recently, is presented. The spectroscopic and photometric data were obtained with the 6-m telescope and Zeiss-1000 telescope of the Special Astrophysical Observatory. The light curves show sinusoidal brightness variations with the orbital-period time scale and brightness-variation amplitudes of Δm = 1.m41, 1.m62, and 1.m57 in the B, V, and R bands, respectively. The system’s spectrum exhibits weak HI (Hβ–Hδ) andHeII λλ4541, 4686, 5411 Å absorption lines during the phases of minimum brightness, as well as HI, HeII, CIII, CIV, NIII, and OII emission lines whose intensity variations are synchronized with variations of the integrated brightness of the system. The emission-line formation in the spectra can be fully explained by the effects of fluorescence of the ultraviolet light from the primary at the surface of the cool star. All the characteristics of the optical light of PN G068.1+11.0 confirm that it is a young PCV containing sdO subdwarf. The radial velocities were measured from a blend of lines of moderately light elements, CIII+NIII λ4640 Å, which is formed at the surface of the secondary due to reflection effects. The ephemeris of the system has been improved through a joint analysis of the radial-velocity curves and light curves of pre-cataclysmic variable, using modelling of the reflection effects. The fundamental parameters of PN G068.1+11.0 have been determined using two evolutionary tracks for planetary-nebula nuclei of different masses (0.7 M⊙and 0.78M⊙). The model spectra for the system and a comparison with the observations demonstrate the possibility of refining the components’ effective temperatures if the quality of the spectra used is improved.  相似文献   

11.
《Applied Geochemistry》2003,18(10):1653-1662
The through- and out-diffusion of HTO, 36Cl− and 125I− in Opalinus Clay, an argillaceous rock from the northern part of Switzerland, was studied under different confining pressures between 4 and 15 MPa. The direction of diffusion and the confining pressure were perpendicular to the bedding. Confining pressure had only a small effect on diffusion. An increase in pressure from 4 to 15 MPa resulted in a decrease of the effective diffusion coefficient of ∼20%. Diffusion accessible porosities were not measurably affected. The values of the effective diffusion coefficients, De, ranged between (5.6±0.4)×10−12 and (6.7±0.4)×10−12 m2 s−1 for HTO, (7.1±0.5)×10−13 and (9.1±0.6)×10−13 m2 s−1 for 36Cl− and (4.5±0.3)×10−13 and (6.6±0.4)×10−13 m2 s−1 for 125I−. The rock capacity factors, α, measured were circa 0.14 for HTO, 0.040 for 36Cl− and 0.080 for 125I−. Because of anion exclusion effects, anions diffuse slower and exhibit smaller diffusion accessible porosities than the uncharged HTO. Unlike 36Cl−, 125I− sorbs weakly on Opalinus Clay resulting in a larger rock capacity factor. The sorption coefficient, Kd, for 125I− is of the order of 1–2×10−5 m3 kg−1. The effective diffusion coefficient for HTO is in good agreement with values measured in other sedimentary rocks and can be related to the porosity using Archie's Law with exponent m=2.5.  相似文献   

12.
Twenty-eight CS molecular clouds toward HII regions with Galactocentric distances from ～ 4 to 20 kpc have been studied based on observations obtained in the J=2→1 lines of CS and C34S on the 20-meter radio telescope of the Onsala Space Observatory (Sweden) in March 2001. All 28 clouds have been mapped with an angular resolution of ～40″. The peak intensity in the C34S line has been measured for 20 objects. An LTE analysis has been performed and the parameters of the molecular cloud cores derived. The core sizes are dA=0.3–4.8 pc, with a median value of ～1.6 pc. The mean hydrogen densities in the cloud cores are nH2=3.5×102–3.7 × 104 cm?3, with a median value of ～7.2×103 cm?3. The value of nH2 ends to decrease with increasing Galactocentric distance of the cloud. The masses of most clouds are 102?6×103M⊙, with the most probable value being MCS～103M⊙. The data follow the dependence MCS ∝d A (2.4–3.2) . As a rule, the cloud masses are lower than the virial masses for MCS<103M⊙.  相似文献   

13.
We present the results of spectroscopic observations of the X-ray binary V404 Cyg obtained on the 6-m telescope of the Special Astrophysical Observatory in 2001–2002. We have used a statistical approach to interpret the radial-velocity curve of V404 Cyg. We derived the dependence of the mass of the X-ray emitting component mx on the mass of the optical component mv via an analysis of the radial-velocity curve based on profiles of the CaI 6439.075 Å absorption line synthesized in a Roche model. Using the orbital inclination estimated from the ellipticity of the optical component, i=54°–64°, and the component-mass ratio q=mx/mv=16.7 found from the rotational broadening of the spectral lines, we obtain m s =10.65±1.95M⊙ for the mass of the black hole.  相似文献   

14.
Radio flux measurements of the Crab nebula have been performed over many years relative to Orion A at 927 MHz and relative to Cygnus A and Virgo A at 151.5 MHz. The inferred average secular rates of decrease in the radio flux of the Crab nebula are d 927 MHz = ?0.18 ± 0.10% yr?1 over 1977–2000 and d 151.5 MHz = ?0.3 ± 0.1% yr?1 over 1980–2003. The weighted mean flux-decrease rate averaged over several years of relative measurements at 86, 151.5, 927, and 8000 MHz is d mw = ?0.17 ± 0.02% yr?1. The secular flux decrease is frequency independent, with an upper limit of |dα/dt| < 3 × 10?4 yr?1 for the absolute value of the rate of change of the spectral index, and remains constant in time when averaged over long time intervals. The results of our measurements at 151.5 and 927 MHz combined with published absolute measurements at 81.5 and 8250 MHz are used to determine the radio spectrum of the Crab nebula for epoch 2010.0.  相似文献   

15.
The paper reports the results of BV RI surface photometry of the giant galaxy NGC 5351 based on CCD observations obtained on the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Analysis of the structure and radial brightness distribution in the galaxy shows that NGC 5351 has a complex and, in some places, asymmetric structure. The galaxy possesses a large quantity of dust. The average internal extinction due to dust is AV=1.2m±0.4m. After correcting for the effect of this dust, the parameters of the galaxy are typical of late-type spirals. The compositions of the stellar population in various parts of the galaxy are estimated using two-color diagrams. Star-forming regions in NGC 5351 are identified and studied. Most of the star-forming regions are located in the ring of the galaxy. Evolutionary modeling is used to estimate the ages of regions of violent star formation. An elliptical companion galaxy to NGC 5351 was found. The rotation curve of the galaxy is modeled and its mass estimated. The disk of NGC 5351 is self-gravitating within its optical radius.  相似文献   

16.
Two daily sets of monitoring data of the Galactic X-ray binary SS 433 (V1343 Aql) obtained on the RATAN-600 radio telescope (117 days in 1997 and 120 days in 1999) show variations in its quiescent radio emission with a period of 6.05±0.1 days at six frequencies from 0.96 to 22 GHz. This 10–15% modulation in the quiescent radio light curves differs significantly from the well-known 6.28-day periodicity in the emission of moving spectral features and in optical photometric data, which are related to nodding motions of the jets and accretion-disk wobble. This period coincides almost exactly with the theoretical value for the harmonic f=2(I o+I p), related to the orbital (T o=13.08 days) and precessional (T p=162.4 days) periods for slaved accretion-disk models. The 6.06-day period corresponds to the combined frequency. It is proved that the modulation of the radio flux of SS 433 may be associated with relativistic boosting of the jet emission due to periodic variation of the orientation of the jets, which are nodding with a period of six days. The synchrotron emission of the two jets contributes to the quiescent radio flux of SS 433, and the six-day harmonic has the same radio spectrum as the quiescent radio flux: S v ～v ?0.6.  相似文献   

17.
A generalized physicochemical model of the response of marine organisms’ calcifying fluids to CO2-induced ocean acidification is proposed. The model is based upon the hypothesis that some marine calcifiers induce calcification by elevating pH, and thus ΩA, of their calcifying fluid by removing protons (H+). The model is explored through two end-member scenarios: one in which a fixed number of H+ is removed from the calcifying fluid, regardless of atmospheric pCO2, and another in which a fixed external-internal H+ ratio ([H+]E/[H+]I) is maintained. The model is able to generate the full range of calcification response patterns observed in prior ocean acidification experiments and is consistent with the assertion that organisms’ calcification response to ocean acidification is more negative for marine calcifiers that exert weaker control over their calcifying fluid pH. The model is empirically evaluated for the temperate scleractinian coral Astrangia poculata with in situ pH microelectrode measurements of the coral’s calcifying fluid under control and acidified conditions. These measurements reveal that (1) the pH of the coral’s calcifying fluid is substantially elevated relative to its external seawater under both control and acidified conditions, (2) the coral’s [H+]E/[H+]I is approximately the same under control and acidified conditions, and (3) the coral removes fewer H+ from its calcifying fluid under acidified conditions than under control conditions. Thus, the carbonate system dynamics of A. poculata’s calcifying fluid appear to be most consistent with the fixed [H+]E/[H+]I end-member scenario. Similar microelectrode experiments performed on additional taxa are required to assess the model’s general applicability.  相似文献   

18.
We have obtained the first estimates of the masses of the components of the Her X-1/HZ Her X-ray binary system taking into account non-LTE effects in the formation of the H γ absorption line: m x = 1.8 M ⊙ and m v = 2.5 M ⊙. These mass estimates were made in a Roche model based on the observed radial-velocity curve of the optical star, HZ Her. The masses for the X-ray pulsar and optical star obtained for an LTE model lie are m x = 0.85 ± 0.15 M ⊙ and m v = 1.87 ± 0.13 M ⊙. These mass estimates for the components of Her X-1/HZ Her derived from the radial-velocity curve should be considered tentative. Further mass estimates from high-precision observations of the orbital variability of the absorption profiles in a non-LTE model for the atmosphere of the optical component should be made.  相似文献   

19.
We present a catalog of galaxies in and around the cluster A1367, together with the results of a spectroscopic study of eight faint galaxies projected onto the central part of the cluster. The observations were carried out with the Boller and Chivens spectrograph of the 2m telescope of the Guillermo Haro Observatory (Cananea, Mexico). Redshifts of eight galaxies were derived from both emission and absorption lines; the redshift for one of these, derived from Hα, SII, OIII, and Hβ emission lines, is z = 0.015. The spectrum of this galaxy displays no absorption lines at z = 0.026, testifying that it is located between the observer and A1367.  相似文献   

20.
Our measurements of the arrival-time delays of radio pulses from the Crab pulsar, PSR B0531+21, at low frequencies 111, 63, and 44 MHz revealed additional delays compared to the usual quadratic frequency relation, Δt(v) ∝ v ?2. These additional delays are 65 ms between 63 MHz and 111 MHz—i.e., a factor of two longer than the pulsar’s period, i.e., a factor of five longer than the pulsar period—and cannot be explained by the “twisting” of the magnetic-field lines by the rotation of the pulsar. We suggest the model in which a previously unknown high-density plasma layer with a high electron concentration is present along the line of sight in the Crab nebula, causing an additional frequency-dependent delay of the observed radio pulses at low frequencies due to the contribution of the n e 2 v ?4 term in the dispersion-delay formula. The parameters of this inferred layer have been derived: emission measure EM ? 4 × 106 pc/cm6, electron density n e ? 106 cm?3, depth along the line of sight d ? 4 × 10?6 pc, and electron temperature T e ≥ 2 × 106 K.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号