Infrared photometry of the symbiotic novae V1016 Cyg and HM Sge in 1978–1999     

O. G. Taranova  V. I. Shenavrin 《Astronomy Letters》2000,26(9):600-608

The photometric JHKLM observations of the symbiotic novae V1016 Cyg and HM Sge in 1978–1999 are presented. Parameters of the cool stars themselves and the dust envelopes are estimated. The periods of 470±5 days (for V1016 Cyg) and 535±5 days (for HM Sge) are reliably determined from the entire set of our photometric J data for V1016 Cyg and HM Sge. In addition, monotonic light and color variations are observed on a time scale of several thousand days, with the increase in infrared brightness occurring with the simultaneous decrease in infrared color indices; i.e., the dust envelopes in which both components of the systems were embedded before the outburst of their hot sources in 1964 and 1975, respectively, had continued to disperse until late 1999. The amplitudes of these variations for HM Sge are almost twice those for V1016 Cyg. For HM Sge, the dust envelope reached a maximum density near JD 2447500 and then began to disperse. In the case of V1016 Cyg, a maximum density of the dust envelope was probably reached near JD 2444800, and its dispersal has been continuing for about 20 years. Thus, in both symbiotic novae, their dust envelopes reached a maximum density approximately eight years after the outburst of the hot component and then began to disperse. An analysis of the color-magnitude (J–K, J) diagram reveals that grains in the dust envelopes of V1016 Cyg and HM Sge are similar in their optical properties to impure silicates. The observed [J–K, K–L] color variations for the symbiotic novae under study can be explained in terms of the simple model we chose by variations in the Mira's photospheric temperature from 2400 to 3000 K and in the dust-envelope optical depth from 1 to 3 at a wavelength of 1.25 µm for a constant grain temperature. The observed J–K and K–L color indices for both symbiotic novae, while decreasing, tend to the values typical of Miras. The dust envelopes of both symbiotic novae are optically thick. The dust envelope around HM Sge is, on the average, twice as dense as that around V1016 Cyg; the Mira in V1016 Cyg is slightly cooler (~2800–2900 K) than that in HM Sge (~2600–2700 K). The dust-envelope density decreases as the Mira's temperature increases. The absolute bolometric magnitudes are $ - 5\mathop .\limits^m 1 \pm 0\mathop .\limits^m 15$ for V 1016 Cyg and $5\mathop .\limits^m 27 \pm 0\mathop .\limits^m 17$ for HM Sge. Their distances are 2.8±0.6 and 1.8±0.4 kpc, respectively; the luminosities and radii of their cool components (Miras) are 8.6×10³ L _⊙, 1×10⁴ L _⊙, 500R _⊙, and 540R _⊙. The radii of their dust envelopes are 1400R _⊙ and 1500R _⊙; the masses are (3?3.3) × 10^?5M_⊙ and (4?8) × 10^?5M_⊙ The dust envelope of V1016 Cyg disperses slower than that of HM Sge by almost a factor of 25.  相似文献   

IR photometry results and dust envelope model for symbiotic Mira star candidate V 335 Vul     

M. B. Bogdanov  O. G. Taranova  V. I. Shenavrin 《Astrophysical Bulletin》2017,72(4):447-451

We present the results of JHKLM-photometry for the symbiotic Mira star candidate V 335 Vul. Based on the average flux data, supplemented by IRAS, MSX, AKARI, and WISE mid-IR observations, we calculated a model of a spherically symmetric dust envelope of the star, made up of amorphous carbon and silicon carbide particles. The optical depth of the envelope in the visible range with a dust temperature at the inner boundary of T₁ = 1300 K is τ _V = 0.58. For an envelope expansion velocity of 26.5 km s^?1, the estimated mass loss rate is equal to 5.7 × 10^?7M_⊙ yr^?1.  相似文献   

Photometric variability and spectral features of the protoplanetary nebula LSII + 34° 26 = V1853 Cyg     

V. P. Arkhipova  N. P. Ikonnikova  R. I. Noskova  G. V. Komissarova  V. G. Klochkova  V. F. Esipov 《Astronomy Letters》2001,27(11):719-727

We present photoelectric and spectroscopic observations of the protoplanetary object V 1853 Cyg, a B supergiant with an IR excess. Over two years of its observations, the star exhibited rapid irregular light variations with amplitudes $\Delta V = 0\mathop .\limits^m 3$ , $\Delta B = 0\mathop .\limits^m 3$ , $\Delta U = 0\mathop .\limits^m 4$ and no correlation between color and magnitude. Its mean magnitude has not changed since the first UBV observations in 1973 (Drilling 1975). Low-resolution spectroscopic observations show that the spectrum of V 1853 Cyg in 2000 corresponded to that of a B1–B2 star with T _eff ～ 20000 K. High-resolution spectroscopic observations confirm the conclusion that the profiles of absorption and emission lines are variable. We identified the star’s spectral lines and measured the equivalent widths of more than 40 lines. The star’s radial velocity is 〈V _r 〉= ?49 × 5 km s^?1, as measured from absorption lines, and ranges from–50 to–85 km s^–1 for different lines, as measured from shell emission lines. The velocity of the dust clouds on the line of sight determined from diffuse interstellar bands (DIBs) and from interstellar Na I lines is 〈V _r 〉= ?16 × 5 km s^?1. The P Cyg profiles of the He I λ5876 Å and λ6678 Å lines suggest an ongoing mass loss by the star. An analysis of the observational data confirms the conclusion that the star belongs to the class of intermediatemass protoplanetary objects.  相似文献   

Unusual infrared fading of CH Cygni in 2006     

O. G. Taranova  V. I. Shenavrin 《Astronomy Letters》2007,33(8):531-535

Infrared observations of the unique symbiotic system CH Cyg in 2003–2006 are presented. Analysis of the observations has shown that a fairly dense dust structure (a cloud or a shell) appeared on the line of sight in August–November 2006. The dust grains in the new shell are similar in optical properties to graphite ones and their sizes are mostly within the range 0.14–0.16 μm. The dust shell is optically thick and its optical depth at 2.2 μm is τ(2.2) ≈ 0.97. The dust shell mass is M _d(06) ≈ 8 × 10⁻⁶ M _⊙ and the rate of matter flow into the shell has reached ∼2 × 10⁻⁵ M _⊙ yr⁻¹. Original Russian Text ? O.G. Taranova, V.I. Shenavrin, 2007, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2007, Vol. 33, No. 8, pp. 598–603.  相似文献   

Infrared photometry of Sakurai’s object (V4334 Sgr) in 1996–1999     

A. M. Tatarnikov  V. I. Shenavrin  B. F. Yudin  P. A. Whitelock  M. W. Feast 《Astronomy Letters》2000,26(8):506-519

The infrared photometric observations of V4334 Sgr in 1996–1999 are presented. Together with optical data, they have allowed us to accurately estimate the bolometric flux from this star and to investigate the structure of its dust envelope over the above period. The star is shown to have passed through four well-defined stages in these four years as it moved backward along the post-AGB track, and it now appears to have started moving forward after a halt. At the first stage (1996), there was no dust in the star’s envelope. Its visual brightness slightly increased, and it reddened in the entire observed spectral range. The bolometric flux also gradually rose. At the second stage (1997), an optically thick dust envelope condensed around the star, which, however, essentially did not manifest itself at optical wavelengths. The bolometric flux continued to rise through an increase in the star’s infrared brightness alone; the rate of its rise also increased. At the third stage (1998–March 1999), V4334 Sgr entered the R CrB phase. First two shallow minima and then two deep minima were observed at optical wavelengths. The star appreciably reddened during the deep minima. The bolometric flux ceased to rise and began to gradually fall in the second half of 1998. At the fourth stage (since March 1999 up until now), V4334 Sgr has been at a protracted deep minimum, which is atypical of the R CrB stars. The bolometric flux between March and October underwent no significant variations. We describe the structure of the dust envelope around V4334 Sgr since its formation. From June 1997 until July 1998, the optical depth of the dust shell, its inner and outer radii, and its mass increased by factors of ～2.2, ～2.0, 2.3, and ～10, respectively. In July 1998, τ(V)≈2.3, R _{d, in}≈7.4×10¹⁴ cm, R _{d, in}/R _{d, out}≈0.7(R _{d, in}/R _*≈47), and M _dust≈1.6×10^?7 M _⊙.  相似文献   

Infrared photometry of Nova Delphini 2013 (=V339 Del) in the first sixty days after its outburst     

O. G. Taranova  A. M. Tatarnikov  V. I. Shenavrin  A. A. Tatarnikova 《Astronomy Letters》2014,40(2-3):120-124

The results of JHKLM photometry for Nova Delphini 2013 obtained in the first sixty days after its outburst are analyzed. Analysis of the energy distribution in a wide spectral range (0.36–5 µm) has shown that the source mimics the emission of normal supergiants of spectral types B5 and A0 for two dates near its optical brightness maximum, August 15.94 UT and August 16.86 UT, respectively. The distance to the nova has been estimated to be D ≈ 3 kpc. For these dates, the following parameters have been estimated: the source’s bolometric fluxes ～9 × 10^?7 and ～7.2 × 10^?7 erg s^?1 cm^?2, luminosities L ≈ 2.5 × 10⁵ L _⊙ and ≈2 × 10⁵ L _⊙, and radii R ≈ 6.3 × 10¹² and ≈1.2 × 10¹³ cm. The nova’s expansion velocity near its optical brightness maximum was ～700 km s^?1. An infrared (IR) excess associated with the formation of a dust shell is shown to have appeared in the energy distribution one month after the optical brightness maximum. The parameters of the dust component have been estimated for two dates of observations, JD2456557.28 (September 21, 2013) and JD2456577.18 (October 11, 2013). For these dates, the dust shell parameters have been estimated: the color temperatures ≈1500 and ≈1200 K, radii ≈6.5 × 10¹³ and 1.7 × 10¹⁴ cm, luminosities ～4 × 10³ L _⊙ and ～1.1 × 10⁴ L _⊙, and the dust mass ～1.6 × 10²⁴ and ～10²⁵ g. The total mass of the material ejected in twenty days (gas + dust) could reach ～1.1 × 10^?6 M _⊙. The rate of dust supply to the nova shell was ～8 × 10^?8 M _⊙ yr^?1. The expansion velocity of the dust shell was about 600 km s^?1.  相似文献   

Kinematics and parameters of the gas in the vicinity of TW Hya     

S. A. Lamzin  A. S. Kravtsova  M. M. Romanova  C. Batalha 《Astronomy Letters》2004,30(6):413-427

The following conclusions about the kinematics and parameters of the gas in the vicinity of TW Hya have been drawn from an analysis of optical and ultraviolet line profiles and intensities. The accreting matter rises in the magnetosphere to a distance z>R_* above the disk plane and falls to the star near its equator almost perpendicular to its plane. The matter outflows from a disk region with an outer radius of ≤0.5 AU. The [OI], [SII], and H2 lines originate in the disk atmosphere outside the outflow region, where the turbulent gas velocity is close to the local speed of sound. In the formation region of the forbidden lines, T?8500 K and N_e?5×10⁶ cm^?3, and the hydrogen is almost neutral: x_e<0.03. The absorption features observed in the blue wings of some of the ultraviolet lines originate in the part of the wind that moves almost perpendicular to the disk plane, i.e., in the jet of TW Hya. The V _z gas velocity component in the jet decreases with increasing distance from the jet axis from 200 to 30 km s^?1. The matter outflowing from the inner disk boundary, moves perpendicular to the disk plane in the formation region of blue absorption line components, at a distance of ～0.5 AU from the axis of symmetry of the disk. This region of the wind is collimated into the jet at a distance of <3 AU from the disk plane. The gas temperature in the formation region of absorption components is ?2×10⁴ K, and the gas density is <3×10⁶ cm^?3. This region of the jet is on the order of several AU away from the disk plane, while free recombination in the jet begins even farther from the disk. The mass-loss rate for TW Hya is \(\dot M_w < 7 \times 10^{ - 10} M_ \odot yr^{ - 1}\), which is a factor of 3lower than the mean accretion rate. The relative abundance of silicon and aluminum in the jet gas is at least an order of magnitude lower than its standard value.  相似文献   

Effects of boundary conditions and viscous energy dissipation on carbon burning in thermonuclear supernova models     

N. V. Dunina-Barkovskaya  V. S. Imshennik 《Astronomy Letters》2003,29(1):10-19

Based on a one-dimensional hydrodynamic model, we investigate carbon burning in a thermonuclear type-Ia supernova in the approximation of unsteady convection. The relatively broad range of convective parameters, 1×10^?3≤α_c≤2×10^?3, in which delayed detonation from the edge takes place was found to be preserved only for cases with a low boundary temperature at the presupernova stage, T _b ^(PS) = 6.4 × 10⁶ K, and with a high envelope mass, m_ex ? 2 × 10^?3M_⊙. In cases with a more realistic temperature, T _b ^(PS) = 2 × 10⁸ K, which corresponds to helium burning in the shell source, and with a lower mass m_ex, delayed detonation from the edge takes place only at α_c = 2 × 10^?3, while at α_c = 1 × 10^?3, numerous model pulsations occur during t?500 s. Artificial viscosity is shown to give a determining contribution to the increase in entropy in outer model shells, which is caused by the generation of weak shock waves during pulsations. We also show that the entropies calculated by two independent methods are equal.  相似文献   

Observations of the gamma-ray flux from the X-ray source Cyg X-3 in 1994–1995     

Yu. I. Neshpor  O. R. Kalekin  A. A. Stepanian  V. P. Fomin  N. N. Chalenko 《Astronomy Letters》2003,29(4):236-240

We present the observations of Cygnus X-3 carried out with the GT-48 gamma-ray telescope at the Crimean Astrophysical Observatory in 1994–1995. The mean gamma-ray flux at energy E>10¹² eV is shown to be approximately equal to 1.3×10^?11 cm^?2 s^?1. The flux in 1994 was much lower than that in 1995, being (6.2±2.6)×10^?12 cm^?2 s^?1; i.e., it was statistically insignificant. The flux in 1995 was (2.7±0.7)×10^?11 cm^?2 s^?1. Thus, the very high energy gamma-ray emission from Cyg X-3 is variable. These measurement results can be used to obtain upper limits on the flux from Cyg X-3 in 1994–1995.  相似文献   

Infrared photometry for two RV Tau stars and V1027 Cyg     

O. G. Taranova  V. I. Shenavrin  A. M. Tatarnikov 《Astronomy Letters》2009,35(7):472-482

We present and discuss the results of our long-term JHKLM photometry for two RV Tau stars (R Sge and RV Tau) and the yellow supergiant V1027 Cyg, a candidate for protoplanetary nebulae. The amplitude of the infrared brightness variations in R Sge and RV Tau over fourteen years of observations was 0 _. ^m 9?1 ^m ; the infrared brightness variations in V1027 Cyg over eighteen years did not exceed 0 _. ^m 25. The infrared brightness and color of R Sge fluctuated about their gradually changing mean values; the infrared brightness variations agree with a period of 70.77 days. The periodic J brightness and J-H color variations in R Sge can be explained by temperature pulsations with ΔT ≤ 200 K and radial pulsations with [ΔR/R] ≤ 0.2. From 1995 to 2008, the mean J brightness of RV Tau increased, while its mean J-H color index decreased; the variations in the mean J brightness can be associated mainly with stellar temperature variations; a periodic component with P = 78.73 days is observed in the infrared brightness and color fluctuations. The variations in the mean J brightness and J-H color index of the supergiant V1027 Cyg over eighteen years of observations did not exceed a few hundredths of a magnitude; both temperature and radial pulsations may be present in the observed J brightness variations. The most probable period of the infrared brightness fluctuations in V1027 Cyg is 237 ± 2 days. The dust shell of R Sge may consist of two layers with grain temperatures of ～1000 and ～700 K; the optical depth at 1.25 µm is ～0.02 and ～0.24, respectively. The grain temperatures in the circumstellar dust shells of the supergiants RV Tau and V1027 Cyg are ～600 K (RV Tau) and ～700 K (V1027 Cyg). Their optical depths at 1.25 µm are ～0.24 (RV Tau) and ～0.008 (V1027 Cyg).  相似文献   

A galactic model with a pulsating active nucleus     

Teruaki Ohnishi 《Astrophysics and Space Science》1974,28(1):3-16

The accumulation and distribution of rare-light elements in the Galaxy is investigated according to a model of the galaxy at which center there exists a pulsating active nucleus with decreasing activity with time. The abundances of rare-light elements rapidly decrease with approaching to the galactic center whereas the most abundant region of these elements is the annular region of the radial distance ofr=8～14 kpc from the galactic center. In the inner region ofr?8 kpc the abundances of these elements have varied by two to three orders of magnitude from the early days of the galactic history till now, but inr?8 kpc they have been almost constant within a factor of 2. It has become clear that if the nuclides D,³He,⁷Li,¹⁰B and¹¹B have been produced mainly by the shock process taking place in the outer envelope of type-II supernova, they must have been created by the mass fractions of the supernova of some 2.7×10^?3, 1.7×10^?4, 6.9×10^?8, 1.7×10^?7 and 7.9×10^?7, respectively, to account for the solar system abundances.  相似文献   

A study of the B[e] star AS 160     

A. S. Miroshnichenko  V. G. Klochkova  K. S. Bjorkman 《Astronomy Letters》2003,29(5):336-343

We present the results of our study of the poorly known B[e] star AS 160=IRAS 07370-2438. The high-resolution spectrum obtained with the 6-m BTA telescope exhibits strong emission in the Hα line with a two-component profile, indicating that the gaseous envelope of the star is nonspherical. Previously nonanalyzed photometric data suggest the presence of a compact dust envelope. The fundamental parameters of the star (log L/L_⊙ = 4.4 ± 0.2, v sin i = 200 km s^?1 and its distance (3.5±0.5 kpc) have been determined for the first time and are in agreement with published estimates of the MK spectral type of the object (B1.5 V:). Analysis of the object's properties leads us to suggest that this is a binary system that belongs to our recently identified type of Be stars with warm dust.  相似文献   

Neutral hydrogen around the oxygen-sequence Wolf-Rayet star WR 102 and the nebula G2.4+1.4     

I. V. Gosachinskij  T. A. Lozinskaya 《Astronomy Letters》2002,28(10):701-712

We carried out the first 21-cm line observations of an extended region around the Wolf-Rayet star WR 102 and the associated nebula G2.4+1.4 with the RATAN-600 radio telescope. An irregular H I shell was identified. Its maximum expansion velocity reaches ～50 km s^?1, and its outer diameter (at a distance of 3 kpc) is 56 pc. The mechanical luminosity of the stellar wind required to produce the observed shell is estimated to be ～0.8×10³⁸ erg s^?1; the age of the shell is ～3.4×10⁵ yr. We compare the inferred parameters of the H I shell with the structure and kinematics of the ionized nebula and with the dust distribution in the region.  相似文献   

Searches for the shell swept up by the stellar wind from Cyg OB2     

T. A. Lozinskaya  V. V. Pravdikova  A. V. Finoguenov 《Astronomy Letters》2002,28(4):223-236

We investigated the kinematics of ionized gas in an extended (20°×15°) region containing the X-ray Superbubble in Cygnus with the aim of finding the shell swept up by a strong wind from Cyg OB2. Hα observations were carried out with high angular and spectral resolutions using a Fabry-Perot interferometer attached to the 125-cm telescope at the Crimean Observatory of the Sternberg Astronomical Institute. We detected high-velocity gas motions, which could result from the expansion of the hypothetical shell at a velocity of 25–50 km s^?1. Given the number of OB stars increased by Knödlseder (2000) by an order of magnitude, Cyg OB2 is shown to possess a wind that is strong enough [L _w ? (1–2) × 10³⁹ erg s^?1] to produce a shell comparable in size to the X-ray Superbubble and to a giant system of optical filaments. Based on our measurements and on X-ray and infrared observations, we discuss possible observational manifestations of the shell swept up by the wind.  相似文献   

Properties of Wolf-Rayet stars in eclipsing binary systems     

A. M. Cherepashchuk 《Astrophysics and Space Science》1982,86(2):299-319

The results of investigations of a number of eclipsing Wolf-Rayet binaries are presented. The ‘core’ radiuses, the ‘core’ temperatures and masses of WR stars in the eclipsing WR+OB binary systems V 444 Cyg, CX Cep, CQ Cep, and CV Ser are obtained (see Table I). The results obtained from the light curves analysis of the V 444 Cyg in the range λλ2460 Å-3.5μ give strong evidence for the Beals (1944) model of WR phenomenon. The chromospheric-coronal effects in the WN5 extended atmosphere are not observed up to a distance ofr?20R _⊙. In the Hertzsprung—Russell diagram all the WR stars lie on the left side from the main sequence between the main sequence and the sequence of uniform helium stars (see Figure 9). Their locations are close to those of the helium remnants formed as a result of mass exchange in massive close binary systems. The period variations in the systems V 444 Cyg and CQ Cep have been discovered and a reliable value of the mass loss rateM=10^?5 M _⊙yr^?1 is obtained, for the two WR stars. The results of the photometric and spectroscopic investigations of the WR stars with low mass companions (post X-ray binary stage?) are presented too (see Table II). The masses of the companions are (1–2)M _⊙, their optical luminosity is ～10³⁶, erg s^?1 which implies that these companions cannot be the normal stars. It is possible that these companions are neutron stars accreting from the stellar wind of the WR stars. Low values of the X-ray luminosities of such WR stars with low mass companions imply that the accretion of matter in such systems is distinct from the accretion process in classical X-ray binary systems. It is noted also that the parameters of low massive companions coupled with WR stars are close to those of helium stars.  相似文献   

On the change of the inner boundary of an optically thick accretion disk around white dwarfs using the dwarf nova SS Cyg as an example     

M. G. Revnivtsev  R. A. Burenin  A. Yu. Tkachenko  I. M. Khamitov  T. Ak  A. Merloni  M. N. Pavlinsky  R. A. Sunyaev 《Astronomy Letters》2012,38(4):238-248

We present the results of our studies of the aperiodic optical flux variability for SS Cyg, an accreting binary systemwith a white dwarf. The main set of observational data presented here was obtained with the ANDOR/iXon DU-888 photometer mounted on the RTT-150 telescope, which allowed a record (for CCD photometers) time resolution up to 8 ms to be achieved. The power spectra of the source’s flux variability have revealed that the aperiodic variability contains information about the inner boundary of the optically thick flow in the binary system. We show that the inner boundary of the optically thick accretion disk comes close to the white dwarf surface at the maximum of the source’s bolometric light curve, i.e., at the peak of the instantaneous accretion rate onto the white dwarf, while the optically thick accretion disk is truncated at distances 8.5 × 10⁹ cm ∼10R _WD in the low state. We suggest that the location of the inner boundary of the accretion disk in the binary can be traced by studying the parameters of the power spectra for accreting white dwarfs. In particular, this allows the mass of the accreting object to be estimated.  相似文献   

Venera 9, 10: Is there a dust ring around Venus?     

V.A. Krasnopolsky  A.A. Krysko 《Planetary and Space Science》1979,27(7):951-957

Four surveys in which the geometrical parameters were suitable for observations on weak scattering objects were carried out by the Venera 9, 10 orbiters using 3000–8000 Å spectrometers. The results of one survey can be explained by a dust layer at the height of sighting h = 100–700 km. Its absence in other sessions suggests a ring structure. The spectrum of dust scattering is a power function of the wavelength with the index varying from ?2.1 at 100km to ?1.3 at 500km. A method is proposed for obtaining the optical thickness, density and size distribution of dust particles from the scattering spectra. For m > 10^?14 g the number of dust particles with a mass higher than m is proportional to m^?1.3. The radial optical thickness τ is 0.7 × 10^?5 at 5000 Å assuming the geometric thickness δ to be 100 km. The maximum optical thickness along the normal to the plane of the ring is τ_n = 4 × 10^?6. The mass of the ring is 20 tons or 5 × 10^?3 g cm^?1 per unit circumference length; the maximum mass in a column normal to the ring plane is 10^?10g cm^?2; the maximum density (for δ = 100 km) is 10^?17 g cm^?3. A satellite of Venus gradually destroyed by temperature effects and by meteorite streams and plasma fluxes is suggested as the source of dust in the ring. One of 1 km radius could sustain such a ring for a billion years. The zodiacal light intensity near Venus is estimated.  相似文献   

Constraints on dark matter in the solar system     

N. P. Pitjev  E. V. Pitjeva 《Astronomy Letters》2013,39(3):141-149

We have searched for and estimated the possible gravitational influence of dark matter in the Solar system based on the EPM2011 planetary ephemerides using about 677 thousand positional observations of planets and spacecraft. Most of the observations belong to present-day ranging measurements. Our estimates of the dark matter density and mass at various distances from the Sun are generally overridden by their errors (σ). This suggests that the density of dark matter ρ _dm, if present, is very low and is much less than the currently achieved error of these parameters. We have found that ρ _dm is less than 1.1 × 10^?20 g cm^?3 at the orbital distance of Saturn, ρ _dm < 1.4 × 10^?20 g cm^?3 at the orbital distance of Mars, and ρ _dm < 1.4 × 10^?19 g cm^?3 at the orbital distance of the Earth. We also have considered the case of a possible concentration of dark matter to the Solar system center. The dark matter mass in the sphere within Saturn’s orbit should be less than 1.7 × 10^?10 M _⊙ even if its possible concentration is taken into account.  相似文献   

New in the optical spectrum and kinematic state of the atmosphere of the variable V1027 Cyg (=IRAS 20004+2955)     

V. G. Klochkova  V. E. Panchuk  N. S. Tavolzhanskaya 《Astronomy Letters》2016,42(12):815-824

Based on our high-spectral-resolution observations performed with the NES echelle spectrograph of the 6-m telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the cool supergiant V1027 Cyg, the optical counterpart of the infrared source IRAS 20004+2955. A splitting of the cores of strong absorptions of metals and their ions (Si II, Ni I, Ti I, Ti II, Sc II, Cr I, Fe I, Fe II, BaII) has been detected in the stellar spectrum for the first time. The broad profile of these lines contains a stable weak emission in the core whose position may be considered as the systematic velocity V _sys = 5.5 km s^?1. Small radial velocity variations with an amplitude of 5–6 km s^?1 due to pulsations have been revealed by symmetric low- and moderate-intensity absorptions. A long-wavelength shift of the Hα profile due to line core distortion is observed in the stellar spectrum. Numerous weak CN molecular lines and the KI 7696 Å line with a P Cyg profile have been identified in the red spectral region. The coincidence of the radial velocities measured from symmetric metal absorptions and CN lines suggests that the CN spectrum is formed in the stellar atmosphere. We have identified numerous diffuse interstellar bands (DIBs) whose positions in the spectrum, V _r (DIBs) = ?12.0 km s^?1, correspond to the velocity of the interstellar medium in the Local Arm of the Galaxy.  相似文献   

The photometric evolution of FU Orionis objects: disc instability and wind–envelope interaction     

C. Clarke  G. Lodato  S. Y. Melnikov  M. A. Ibrahimov 《Monthly notices of the Royal Astronomical Society》2005,361(3):942-954

We present the results of a photometric monitoring campaign of three well-studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken at Maidanak Observatory between 1981 and 2003. When combined with photometric data in the literature, this data base provides a valuable resource for searching for short time-scale variability – both periodic and aperiodic – as well as for studying the secular evolution of these systems. In the case of V1057 Cyg (which is the system exhibiting the largest changes in brightness since it went into outburst) we compare the photometric data with time-dependent models. We show that prior to the end of the 'plateau' stage in 1996, the evolution of V1057 Cyg in the V –( B − V ) colour–magnitude diagram is well represented by disc instability models in which the outburst is triggered by some agent – such as an orbiting planet – in the inner disc. Following the end of the plateau phase in 1996, the dimming and irregular variations are consistent with occultation of the source by a variable dust screen, which has previously been interpreted in terms of dust condensation events in the observed disc wind. Here we instead suggest that this effect results from the interaction between the wind and an infalling dusty envelope, the existence of this envelope having been previously invoked in order to explain the mid-infrared emission of FU Orionis systems. We discuss how this model may explain some of the photometric and spectroscopic characteristics of FU Orionis systems in general.  相似文献