We discuss the infrared (IR) (1.25–5 µm) photometry of eight planetary nebulae performed in 1999–2006. For all of the nebulae under study, we have firmly established IR brightness and color variations on time scales shorter than one year and up to 6–8 years. The greatest IR brightness variations were observed in IC 2149, IC 4997, and NGC 7662. Their J magnitudes varied within 0.m2–0.m25. In the remaining objects, the J magnitude variations did not exceed 0.m15. All of the planetary nebulae under study exhibited IR color variations. Based on the IR photometry, we have classified the central regions of the planetary nebula NGC 1514 and of the northern part of NGC 7635 seen through a 12″ aperture as a B(3–7) main-sequence star (NGC 1514) and a ～O9.5 upper-main-sequence star (NGC 7635). The nebulae IC 4997 and NGC 7027 exhibited an excess emission (with respect to the emission from a hot source) at λ > 2.5 µm. 相似文献
An intense outburst of hard radiation (with a peak flux of ～50 mCrab) was detected from the X-ray transient AX J1749.1-2733 by the IBIS/ISGRI gamma-ray telescope onboard the INTEGRAL observatory when the Galactic center field was monitored on September 8–10, 2003. Previously, this source had never been observed in a bright X-ray state. During the outburst, the source’s radiation spectrum was gently sloping and hard (extended to ～100 keV), followed a power law in the standard X-ray energy range, and had an exponential cutoff above 40–50 keV. The spectral hardness decreased with increasing flux. These and other properties described here and the shortness of the outburst (<2 days) allow the source to be attributed to the group of fast X-ray transients many representatives of which have an early O-B supergiant as their optical counterpart. Possible causes of the outbursts of fast transients are discussed. We show that accretion from the supergiant’s stellar wind should have led to intense persistent radiation from transients. The absence of radiation can be explained by the ejection of accreting matter from the system (propeller effect) during its contact with the magnetosphere of a rapidly rotating neutron star. Transient outbursts could originate in sources of this type if the spin period of their neutron star Ps differed only slightly from the critical period Ps* ? 3 s at which the propeller effect is still possible. The outburst is triggered by an insignificant rise in the local stellar wind density, by a factor of (Ps*/Ps)7/3. The entire outburst profile cannot be explained by an individual inhomogeneity in the wind, but is the reflection of a long-term (～2 days for AX J1749.1-2733) change in the rate of wind outflow from the supergiant’s surface facing the compact source. The rate of wind outflow could be enhanced through X-ray heating of the supergiant’s surface. 相似文献
The results of a cross-correlation analysis of the optical and X-ray light curves for eight Seyfert galaxies, NGC 5548, NGC 7469, NGC 3227, NGC 4051, NGC 4151, Mrk 509, Mrk 79, and Akn 564 and for the optical spectra of the quasar 1E 0754 are presented. In the case of the galaxies NGC 5548 and NGC 7469, the maximum values of cross-correlation coefficients for optical and X-ray variations proved to be high (0.73 and 0.79, respectively). The lag time, determined from the maximum of cross-correlation function, is 2.800?1.58+3.12 days for NGC 5548 and 0.6?4.3+0.9 days for NGC 7469. This result favors downscattering of the X-ray emission into the optical range (direct Compton effect) for NGC 5548 and NGC 7469. In addition to the main maximum, which corresponds to the lag of the optical flux variations behind the X-ray flux, six objects (excluding Akn 564 and NGC 4151) show the wings in the intervals of cross-correlation functions that correspond to the time lags of X-ray emission behind the optical emission of approximately 10 days. A method of determining the masses of central black holes in AGNs through spectral line widths is presented; with this method the mass of the central black hole in the quasar 1E 0754 was found (MBH = 1.01 × 108Msun). The position of the quasar 1E 0754 in the mass-luminosity diagram meets the position of other NLS 1 galaxies. 相似文献
Based on our UBV RI observations and X-ray data from the RXTE satellite, we have investigated the variability of the galaxy 3C 120 over the period 1996–2008. The relative variability amplitude in the U and B bands without any subtraction of the contribution from the underlying galaxy is 23 and 22%, respectively, against 21% in the X-ray band. The autocorrelation function based on the B-band data is considerably wider than that based on the X-ray data. The structure functions on a time scale from 1 to ～100–300 days in the X-ray and optical spectral ranges have the form of a power law (SF ～ τb). However, their indices differ significantly: b = 0.42 in the X-ray band and b = 1.36 in the B band. Considering the X-ray and optical variabilities as a superposition of independent flares in a wide range of durations, we may conclude that the amplitudes of short flares in the X-ray band are higher than those in the optical one and, conversely, the relative amplitudes of long flares in the X-ray band are slightly lower than those in the optical one, i.e., short events dominate in the X-ray band. The optical flux variations in the Rc and Ic bands lag significantly behind those in the B band, by 3.9?0.7+1.0 and 6.2?0.6+1.1 days, respectively, if the lag is estimated from the centroid of the cross-correlation function. The X-ray variability on a time scale of about 1800 days (～5 yr) lags behind the B-band variations by 5.3?3.3+2.7 days, but the confidence level of this estimate is only 87%. A more detailed analysis of the correlation between the X-ray and optical emissions has revealed a fairly complex picture: different degrees of correlation between the optical and X-ray fluxes are observed at different times. 相似文献
We present the results of our UBV and JHKLM photometry for the semiregular pulsating variable V1027 Cyg, a supergiant with an infrared excess, over the period from 1997 to 2015 (UBV) and in 2009–2015 (JHKLM). Together with the new data, we analyze the photometric observations of V1027 Cyg that we have obtained and published previously. Our search for a periodicity in the UBV brightness variations has led to several periods from P = 212d to 320d in different time intervals. We have found the period P = 237d based on our infrared photometry. The variability amplitude, the lightcurve shape, and themagnitude of V1027 Cyg atmaximum light change noticeably from cycle to cycle. The deepest minimum was observed in 2011, when the amplitudes of brightness variations in the star reached the following values: ΔU = 1.m28, ΔB = 1.m10, ΔV = 1.m05, ΔJ = 0.m30, ΔH = 0.m35, ΔK = 0.m32, ΔL = 0.m26, and ΔM = 0.m10. An ambiguous correlation of the B ? V and U ? B colors with the brightness has been revealed. For example, a noticeable bluing of the star was observed during the deep 1992, 2008, and 2011 minima, while the variations with smaller amplitudes show an increase in B ? V at the photometric minima. The spectral energy distribution for V1027 Cyg from our photometry in the range 0.36 (U)–5.0 (M) μm corresponds to spectral types from G8I to K3I at different phases of the pulsation cycle. Low-resolution spectra of V1027 Cyg in the range λ4400–9200 ?A were taken during 16 nights over the period 1995–2015. At the 1995 and 2011 photometric minima the star’s spectrum exhibited molecular TiO bands whose intensity corresponded to spectral types M0–M1, while the photometric data point to a considerably earlier spectral type. We hypothesize that the TiO bands are formed in the upper layers of the extended stellar atmosphere. We have measured the equivalent widths of the strongest absorption lines, in particular, the infrared Ca II triplet in the spectrum of V1027 Cyg. The calcium triplet (Ca T) with Wλ(Ca T) = 20.3 ± 1.8 ?A as a luminosity indicator for supergiants places V1027 Cyg in the region of the brightest G–K supergiants. V1027 Cyg has been identified with the infrared source IRAS 20004+2955 and is currently believed to be a candidate for post-AGB stars. The evolutionary status of the star and its difference from other post-AGB objects are discussed. 相似文献
We analyze the spectroscopic and photometric observations of the active galactic nucleus (AGN) 1E 0754.6+3928 performed at Crimean Astrophysical Observatory in 1998–2004. Based on formal spectroscopic criteria for the optical wavelength range, we can classify this object as a narrow-line Seyfert 1 (NLS1) galaxy. Over the period of its observations, the AGN 1E 0754.6+3928 showed a very low rms flux variability amplitude in both continuum and Hβ (～3%). The Hβ time lag relative to the continuum has been found from the cross-correlation function centroid to be τcent = 112?67+215 days. This result and the Hβ line dispersion estimate have allowed us to determine the central black hole mass by the reverberation method: 1.05 × 108M⊙. The position of 1E 0754.6+3928 in the black hole mass-luminosity diagram agrees with the positions of other NLS1 galaxies and can be explained by an enhanced mass accretion rate in the central source. 相似文献
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 (nHL>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
Coolingflows, cluster mergers, and the motions of galaxies through cluster gas with supersonic and sonic velocities must lead to large scale motions of the intracluster medium (ICM). A high-resolution numerical simulation of X-ray cluster formation by Norman and Bryan (1999) predicts cluster-wide turbulence with νturb ≈300–600 km s?1 and eddy scales louter ≈100–500 kpc, the larger numbers being characteristic of turbulence near the virial radius, while the smaller numbers pertain to the core. The simulation also predicts the existence of ordered bulk flows in the core with v≈400 km s?1 on scales of several hundred kpc. In this paper, we consider the observability of such fluid motions via the distortions they induce in the CMB via the kinematic SZ effect, as well as via Doppler broadening and shifting of metal lines in the X-ray spectrum. We estimate |ΔT/T|kinematic?6—at or below current limits of detectability. However, we find that an energy resolution of a few eV is sufficient to detect several Doppler shifted components in the 6.7 keV Fe line in the cluster core. 相似文献
We present the results of our photometric (BV R) and spectroscopic CCD observations of NGC 304 and NGC 7625, candidate polar-ring galaxies, performed with the 6-m Special Astrophysical Observatory telescope. For NGC 304, such a study has been carried out for the first time. We have obtained basic integrated characteristics of the galaxies and determined their morphological types (S0 for NGC 304 and Sa for NGC 7625). The absolute magnitudes of the galaxies, MB = ?20m.81 for NGC 304 and MB = ?19m.34 for NGC7625, are indicative of their fairly high luminosities. The disk and bulge parameters have been determined forNGC 304 (µ0 = 20m.60, h = 3.86 kpc, µe = 21m.59, re = 1.26 kpc in the B band); these correspond to the parameters of S0-type objects. The rotation velocity for NGC 304 (200 km s?1) reaches its maximum at a galactocentric distance of 3.1 kpc, which yields a mass estimate for the galaxy of 2.8 × 1010\(\mathcal{M}_ \odot \). The observed photometric features at the center of NGC 304 indicate that it may have an inner ring structure, although we have failed to confirm the existence of two kinematic systems based on our spectroscopic observations. In NGC 7625, the disk makes a dominant contribution to the total brightness. The derived integrated color indices (B-V = 0m.81 and V-R = 0m.61) agree with previous determinations of other authors. We have estimated the учештсешщт in the inner galactic regions. In the outer regions, we have detected structures with bluer colors (B-V = 0m.60), which may be indicative of a polar ring with a minor stellar component. 相似文献
In 2003–2008, highly accurate photoelectric and CCD observations of the close binary system DI Her were performed in the V band. The light curves of three primary and three secondary eclipses were constructed. These observations, along with the highly accurate photoelectric observations of other authors obtained in different years from 1963 to 1986, have confirmed the difference between the observed (1.o3 ± 0.o1/100 yr) and theoretical (4.o3/100 yr) rates of apsidal motion. Our photometric data are indicative of a possible variability in the system with period P′ = 1.175 days and amplitude A′ = 0.m011, which is probably related to the pulsations of one of the components. There may be a third body in the system that produces in-phase variations in the times of primary and secondary minima with a period of 10.5 yr and an amplitude of 1.m5. 相似文献
Long-term photometric and spectroscopic observations of the yellow symbiotic star LT Del are analyzed. UBV light curves are presented. Based on the observations of 20 cycles, we have refined the orbital period of the star, P = 476·d0 ± 1·d0. The brightness has been found to be unstable at some orbital phases with an amplitude up to 0·m 3. We have measured the fluxes in hydrogen and helium emission lines and in continuum and investigated their relationship to the orbital period. The fluxes in hydrogen and HeI lines follow the UBV light curves in phase; the He II 4686 Å flux does not depend on the phase and is constant within the accuracy of our measurements. The intensity ratio of the 4686 Å andHβ lines changes from 0.2 to 0.9 over the period. We interpret the spectroscopic observations based on the hypothesis of heating and ionization of the stellar wind from a cool component by high-frequency radiation from a hot star with a temperature of 105 K. We have estimated the spectral type of the cool star from our photometry and its continuum energy distribution as a bright K2–4 red giant branch halo star. The bolometric luminosity and mass loss rate have been estimated for the K component to be Lbol ～ 700L⊙ and \(\dot{M}\) ～ 10?8M⊙ yr?1, respectively. 相似文献
We present our long-term photometric and spectroscopic observations of a high-latitude B supergiant with an infrared excess—the protoplanetary nebula IRAS 18062+2410. OurUBV observations in 2000–2006 have confirmed the rapid irregular photometric variability of the star with a maximum amplitude as high as 0.m4 in V that we found previously. The B—V and U—B color indices vary with amplitudes as high as 0.m10 and 0.m25, respectively, and show no clear correlation with the brightness. Our V-band CCD observations on 11 nights in 2006 have revealed brightness trends during the night. The variability of IRAS18062+2410 is similar in pattern to the light variations in other hot post-AGB objects and some of the nuclei of young planetary nebulae. We assume that pulsations and a variable stellar wind can be responsible for the variability of these stars. In addition to the rapid variability, our 12-year-long observations have revealed a systematic decline in the mean brightness of IRAS 18062+2410. This may be related to a rise in the temperature of the star at constant luminosity as a result of its evolution. Low-resolution spectroscopic observations have shown a systematic increase in the equivalent widths of the Hα, Hβ, [NII]λ6584 Å, OI λ8446 Å, and [OII] λ7320–7330 Å emission lines. The changes in the star’s emission line spectrum are probably caused by an increase in the degree of ionization of the gas shell due to a rise in the temperature of the ionizing star. Our photometric and spectroscopic observations of IRAS 18062+2410 confirm the previously made assumptions that the star evolves very rapidly to the region of planetary nebulae. 相似文献
We have analyzed the optical (U BV) and ultraviolet (λ1000–2700 Å) observations of the nuclear variability of the Seyfert galaxy NGC 4151 in the period 1987–2001 (the second cycle of activity). The fast (tens of days) and slow (～10 years) components of the nuclear variability, F and S, respectively, are shown to be completely different, but thermal in nature. We associate the S component with the formation and evolution of an accretion disk and the F component (flares) with instabilities in the accretion disk and their propagation over the disk in the form of a shock wave. The S component is present not only in the optical, but also in the ultraviolet range, with its amplitude being comparable over the entire range λ1000–5500 Å under study. The amplitude of the average flare (the F component) doubles as the wavelength decreases from 5500 to 1000 Å, while the rise time of the brightness to its maximum Δt (the variability time scale) decreases from
to 6d ± 2d. The brightness decline (flare decay) time decreases by a factor of 16. The extinction in the ultraviolet is shown to have been grossly underestimated: beginning from the first IUE data, only the extinction in our Galaxy,
leads to a large increase in the luminosity of the variable source in the nucleus of NGC 4151: L = (6–8) × 1046 erg s?1. The spectral energy distribution for the variable source (λ950–5500 Å) agrees well with two Planck distributions: Te = 65 000 (λmax = 450 Å) and 8000 K. The radiation with Te = 8000 K is the reprocessing of the bulk of the ultraviolet radiation by the accretion disk with a lag of 0.5–0.6 days in the V band. The lag in the U-B variability of the slow component revealed the existence of an extended broad line region (EBLR) at an effective distance of 1.5 lt-years, as confirmed by spectroscopic data obtained at the Crimean Astrophysical Observatory. This yields the following mass of the central object in NGC 4151: Mc = (1–3) × 109M⊙. The luminosity of the variable source then accounts for 50–60% of LEdd rather than 1–2%, as has been thought previously. In general, the pattern of ultraviolet and optical variability in NGC 4151 agrees excellently with the theory of disk accretion instability for a supermassive black hole suggested by N. Shakura and R. Sunyaev 30 years ago: the energy release is at a maximumin the ultraviolet (in the case under consideration, at λ450 Å), the luminosity is ～1047 erg s?1 for Mc ～ 109M⊙ (several tens of percent of LEdd), and the variability time scale ranges from several days to many years.
We present the results of our multicolor UBV RI observations of NGC 7469, a type 1 Seyfert galaxy (SyG 1), in 2008–2014 at the Maidanak Observatory. Analysis of the long-term variability of NGC 7469 for two observing periods, 1990–2007 and 2008–2014, has shown the existence of yet another activity cycle of the slow component in 2009–2014 with an activity maximum in 2011–2012. We have studied the slow variability component in 2009–2014 and constructed the color–color (U ? B), (B ? V) diagrams for the variability maxima and minima of NGC 7469 in various apertures and for the blackbody gas radiation modeling the accretion disk radiation. It can be seen from the color–color diagram that the color of the nuclear part of NGC 7469 becomes bluer at maximum brightness, suggesting a higher temperature of the accretion disk. We have analyzed the X-ray variability of NGC 7469 in 2008 and 2009 in comparison with the activity minimum in 2003. The optical–X ray correlation coefficient in 2008 is close to 0.5. The weak correlation is explained by the influence of an SN 1a explosion in the circumnuclear part of NGC 7469, which manifests itself in the optical band but does not change the pattern of X-ray variability. Comparison of the variability data for 2009 shows an optical–X ray (U band–7–10 keV) correlation with a correlation coefficient of about 0.93. The correlation coefficient and the lag depend on the wavelength in the optical and X-ray bands. The lag between the X-ray and optical fluxes in 2009 is observed to a lesser extent in 2003. 相似文献
During the GRIF experiment onboard the Mir orbiting station, the sky was monitored with a PX-2 wide-field (～1 sr) scintillation X-ray spectrometer to detect bursts in the photon energy range 10–300 keV. Because of the comprehensive instrumentation, which, apart from the X-ray and gamma-ray instruments, also included charged-particle detectors, the imitations of astrophysical bursts by magnetospheric electron precipitations and strongly ionizing nuclei were effectively filtered out. It was also possible to separate solar and atmospheric events. Several tens of bursts interpreted as being astrophysical were detected in the experiment at sensitivity levels S～10?7 erg cm?2 (for bursts whose spectra were characterized by effective temperatures kT～100 keV) and S～3×10?8 erg cm?2 (for bursts with kT～25 keV). Some of the soft gamma-ray or hard X-ray bursts with kT～10–50 keV were identified with the bursting pulsar GRO J1744-28. Our estimate of the detection rate for cosmological soft gamma-ray or hard X-ray bursts from the entire sky suggests that the distributions of long-duration (>1 s) gamma-ray bursts (GRBs) in characteristic energy kT and duration are inconsistent with the steady-state cosmological model in which the evolution of burst sources is disregarded. Based on GRIF and BATSE/CGRO data, we conclude that most of the GRB sources originate at redshifts 1<z<5. 相似文献
Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto–Nagai expressions. The Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen–Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ⊙ = 0.1 M⊙ pc?3 and the force Kz=1.1/2πG = 77 M⊙ pc?2 acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, MG(R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 1012M⊙, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, MG(R ≤ 200 kpc) = (1.45 ±0.30)× 1012M⊙, MG(R ≤ 200 kpc) = (1.29± 0.14)× 1012M⊙ at γ = 6.3, and the smallest value has been found in model II, MG(R ≤ 200 kpc) = (0.61 ± 0.12) × 1012M⊙. In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is MG(R ≤ 200 kpc) = (0.75 ± 0.19) × 1012M⊙. A comparative analysis with the models by Irrgang et al. (2013), including those using the integration of orbits for the two globular clusters NGC 104 and NGC 1851 as an example, has been performed. The third model is shown to have subjected to a significant improvement. 相似文献
We present the results of our analysis of the observations of the intermediate polar V2400 Oph by the INTEGRAL and RXTE observatories. We reconstructed the spectrum of the source over a wide (3–100 keV) energy range. The spectrum obtained can be fitted by a computed theoretical model of the post-shock emitting region with Tmax～22 keV. As a result, we estimated the mass (0.59M⊙) and radius (8.8×108 cm) of the white dwarf in the system V2400 Oph. 相似文献
We present the results of the reduction of our photometric and spectroscopic observations for the eclipsing binary SZ Cam performed with the telescopes at the Astronomical Observatory of the Ural Federal University and the Special Astrophysical Observatory of the Russian Academy of Sciences in 1996–2014. Based on an 11-year-long photometric monitoring of SZ Cam, we have obtained new elements of its photometric orbit and parameters of its components. We have detected low-amplitude periodic light variations in SZ Cam that are possibly related to the ellipsoidal shape of the components of the spectroscopic binary third body. Based on published data and our new spectroscopy, we have found new values for the mass ratio, q = 0.72 ± 0.01, and parameters of the radial velocity curves of the components, V0 = ?3.6 ± 1.7 km s?1, K1 = 190.2 ± 1.9 km s?1, and K2 = 263.0 ± 2.4 km s?1. The component masses have been estimated to be M1 = 16.1 M⊙ and M2 = 11.6 M⊙. We have obtained new light elements and parameters of the radial velocity curves for the third body, V03b = 4.2 ± 0.6 km s?1 and K13b = 26.6 ± 0.8 km s?1. We have improved the period of the relative orbit of SZ Cam and the third body, Porb = 55.6 ± 1.5 yr. 相似文献
We report the results of our optical speckle interferometric observations of the nearby triple system GJ 795 performed with the 6 m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with diffraction-limited angular resolution. The three components of the system were optically resolved for the first time. Position measurements allowed us to determine the elements of the inner orbit of the triple system. We use the measured magnitude differences to estimate the absolute magnitudes and spectral types of the components of the triple: MVAa=7.31±0.08, MVAb=8.66±0.10, MVB=8.42±0.10, SpAa≈K5, SpAb≈K9, SpB≈K8. The total mass of the system is equal to ΣMAB=1.69±0.27M⊙. We show GJ795 to be a hierarchical triple system which satisfies the empirical stability criteria. 相似文献
We obtained constraints on the luminosity of the central source in SNR 1987 A using XMM-Newton and INTEGRAL data. XMM-Newton yields an upper limit on the SNR luminosity in the 2–10 keV energy band, LX ? 5 × 1034 erg s?1. Since the optical depth of the envelope is still large in the XMM-Newton energy band, this constraint carries no useful information about the luminosity of the central source. The optical depth is expected to be small in the hard (20–200 keV) X-ray band of the IBIS telescope aboard the INTEGRAL observatory. We detected no statistically significant emission from SNR 1987 A in the INTEGRAL data and obtained an upper limit of LX ? 1.1 × 1036 erg s?1 on the luminosity of the central source in the 20–60 keV band. We also obtained an upper limit on the mass of radioactive 44Ti, M(44Ti) ? 10?3M⊙. 相似文献
