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 500 毫秒
1.
We describe Bayesian probabilistic approach to estimating the properties of stars and the interstellar extinction law based on photometric observations and using prior data about the parameters of the stars. The accuracy of the resulting estimates is analyzed in the case of SDSS and 2MASS surveys. We found that our estimates have no systematic deviations in the case of photometric accuracy typical of the surveys considered and errors of prior data of ΔT eff = ±150 K and Δlog g = ±0.5. Note that the error of the estimated interstellar extinction A 0 is of about 0. m 3, and the error of the R 0 estimate depends on extinction and is close 0.2 for moderate A0 values. The fractional error of the estimated stellar angular diameters is close to 10%. A possible application of our approach is to determine the dependence of interstellar extinction on distance using stars closely located in the same sky area.  相似文献   

2.
We have measured the interstellar extinction in the region of ultradeep Galactic-field observations by the Chandra telescope (l II, b II) ≈ 0.1–1.42 using photometric data from the 2MASS infrared allsky survey. The angular resolution of our interstellar extinction map is 1′.8. We show that the interstellar extinction has a minimum, A V ～ 3.4, near the center of the Chandra field of view and increases to A V ～ 5.8–6 at the edge of the field of view. In addition, we show that the bulk of the extinction is gained in the Galactic disk and is approximately the same for all bulge stars. Our results will be subsequently used to process the Chandra data and to estimate the properties of the stellar population in this region.  相似文献   

3.
We determine the color excesses, photometric distances, ages, astrometric parallaxes and proper motions for 94 open clusters in the northern part of the Milky Way. We estimate the color excesses and photometric distances based on the data from IPHAS photometric survey of the northern Galactic plane using individual total-to-selective extinction ratios Rr = Ar/Er?i for each cluster computed via the color-difference method based on IPHAS r, i, and Hα-band, 2MASS J-, H-, and Ks-band, WISE W1-band, and Pan-STARRS i-, z-, and y-band data. The inferred Rr values vary significantly from cluster to cluster spanning the Rr = 3.1–5.2 interval with a mean and standard deviation equal to 〈Rr〉 = 3.99 and σRr = 0.34, respectively.We identified cluster members using (1) absolute proper motions determined from individual-epoch positions of stars retrieved from IPHAS, 2MASS,URAT1, ALLWISE,UCAC5, and Gaia DR1 catalogs and positions of stars on individual Palomar Sky Survey plates reconstructed based on the data provided in USNO-B1.0 catalog and (2) absolute proper motions provided in Gaia DR2 catalog, and computed the averageGaia DR2 trigonometric parallaxes and propermotions of the clusters. Themean formal error of the inferred astrometric parallaxes of clusters is of about 7 μas, however, a comparison of astrometric and photometric parallaxes of our cluster sample implies that Gaia DR2 parallaxes are, on the average, systematically underestimated by 45 ± 9 μas. This result agrees with estimates obtained by other authors using other objects. At the same time, we find our photometric distance scale to be correct within the quoted errors (the inferred correction factor is equal to unity to within a standard error of 0.025).  相似文献   

4.
Based on the Gaia DR1 TGAS parallaxes and photometry from the Tycho-2, Gaia, 2MASS, andWISE catalogues, we have produced a sample of ~100 000 clump red giants within ~800 pc of the Sun. The systematic variations of the mode of their absolute magnitude as a function of the distance, magnitude, and other parameters have been analyzed. We show that these variations reach 0.7 mag and cannot be explained by variations in the interstellar extinction or intrinsic properties of stars and by selection. The only explanation seems to be a systematic error of the Gaia DR1 TGAS parallax dependent on the square of the observed distance in kpc: 0.18R 2 mas. Allowance for this error reduces significantly the systematic dependences of the absolute magnitude mode on all parameters. This error reaches 0.1 mas within 800 pc of the Sun and allows an upper limit for the accuracy of the TGAS parallaxes to be estimated as 0.2 mas. A careful allowance for such errors is needed to use clump red giants as “standard candles.” This eliminates all discrepancies between the theoretical and empirical estimates of the characteristics of these stars and allows us to obtain the first estimates of the modes of their absolute magnitudes from the Gaia parallaxes: mode(M H ) = ?1.49 m ± 0.04 m , mode(M Ks ) = ?1.63 m ± 0.03 m , mode(M W1) = ?1.67 m ± 0.05 m mode(M W2) = ?1.67 m ± 0.05 m , mode(M W3) = ?1.66 m ± 0.02 m , mode(M W4) = ?1.73 m ± 0.03 m , as well as the corresponding estimates of their de-reddened colors.  相似文献   

5.
We present the results of spectroscopic and photometric studies of a new polar CRTS CSS130604 J 215427+155714, conducted at the telescopes of the SAO RAS. Analysis of the photometric series of observations allowed to clarify the orbital period of the system, P o = 0. d 0672879 (±0.0000003). We build radial velocity curves and trace the intensity variations in the Hβ and Hγ hydrogen lines and He II λ 4686 ?A ionized heliumline. Based on the Hβ and He II lines we build Doppler maps. It is shown that the line formation region is localized near the Lagrange point. The following parameter estimates of the system are obtained:M 1 = 0.83 ± 0.10M ⊙, M 2 = 0.15 ± 0.01M ⊙, q = M 2/M 1 = 0.18 ± 0.03, i = 53? ± 5?. Based on the results of spectral, photometric and previously published polarimetric observations the possible geometric model of the system is discussed.  相似文献   

6.
Parallaxes with an accuracy better than 10% and proper motions from the Gaia DR1 TGAS catalogue, radial velocities from the Pulkovo Compilation of Radial Velocities (PCRV), accurate Tycho-2 photometry, theoretical PARSEC, MIST, YaPSI, BaSTI isochrones, and the most accurate reddening and interstellar extinction estimates have been used to analyze the kinematics of 9543 thin-disk B-F stars as a function of their dereddened color. The stars under consideration are located on the Hertzsprung–Russell diagram relative to the isochrones with an accuracy of a few hundredths of a magnitude, i.e., at the level of uncertainty in the parallax, photometry, reddening, extinction, and the isochrones themselves. This has allowed us to choose the most plausible reddening and extinction estimates and to conclude that the reddening and extinction were significantly underestimated in some kinematic studies of other authors. Owing to the higher accuracy of TGAS parallaxes than that of Hipparcos ones, the median accuracy of the velocity components U, V, W in this study has improved to 1.7 km s?1, although outside the range ?0.1 m < (B T ? V T )0 < 0.5 m the kinematic characteristics are noticeably biased due to the incompleteness of the sample. We have confirmed the variations in the mean velocity of stars relative to the Sun and the stellar velocity dispersion as a function of their dereddened color known from the Hipparcos data. Given the age estimates for the stars under consideration from the TRILEGAL model and the Geneva–Copenhagen survey, these variations may be considered as variations as a function of the stellar age. A comparison of our results with the results of other studies of the stellar kinematics near the Sun has shown that selection and reddening underestimation explain almost completely the discrepancies between the results. The dispersions and mean velocities from the results of reliable studies fit into a ±2 km s?1 corridor, while the ratios σ V /σ U and σ W /σ U fit into ±0.05. Based on all reliable studies in the range ?0.1 m < (B T ? V T )0 < 0.5m, i.e., for an age from 0.23 to 2.4 Gyr, we have found: W⊙ = 7.15 km s?1, \({\sigma _U} = 16.0{e^{1.29({B_T} - {V_T})o}}\), \({\sigma _V} = 10.9{e^{1.11({B_T} - {V_T})o}}\), \({\sigma _W} = 6.8{e^{1.46({B_T} - {V_T})o}}\), the stellar velocity dispersions in km s?1 are proportional to the age in Gyr raised to the power β U = 0.33, β V = 0.285, and β W = 0.37.  相似文献   

7.
We present the results of our photometric UBV JHKL observations for the symbiotic star V1413 Aql obtained in 2012–2018. An analysis of the data has shown that inMay 2017 the system passed to a quiescent state with B ? V ≈ 0? 6 for the first time since 1993. It lasted no more than five months. The J ? K color at the primary minimum of 2012 reached 1? 5, which, given the interstellar reddening, corresponds to spectral type M5-M6 III of the cool component. A secondary minimum has been detected at φ ≈ 0.5 on the JK phase light curves constructed for the dates of observations with B ≥ 13.  相似文献   

8.
We used high-resolution echelle spectra with high signal-to-noise ratio to determine with a high degree of accuracy some atmospheric parameters (T eff, log g and [Fe/H]) for 68 non-variable supergiants of types F, G, and K and 26 classical Cepheids in 302 pulsation phases. Very accurate effective temperatures, with errors of only 10–30 K, were determined by the line-depth ratio method. We found that the observed intrinsic color indices (B ? V)0 can be related to these parameters: (B ? V)0 = 57.984? 10.3587(log T eff)2 + 1.67572(log T eff)3 ? 3.356 log g+ 0.321 V t + 0.2615[Fe/H] + 0.8833log g(log T eff). With this empirical relation, the intrinsic colors of individual supergiants and classical Cepheids of spectral types F0-K0 and of luminosity classes I and II can be estimated with an accuracy as high as 0.05 m , which is comparable to the accuracy of the most elaborate photometric procedures. In view of large distances to supergiants, the method we propose here allows a large-scale mapping of interstellar extinction with an accuracy of 0.1–0.2 m in a quite large region of the Galaxy.  相似文献   

9.
ASTRONIRCAM is a cryogenic-cooled slit camera-spectrograph for the spectral range 1–2.5 μm installed at the Nasmyth focus of the 2.5-meter telescope of the Caucasian observatory of the Sternberg Astronomical Institute of Lomonosov Moscow State University. The instrument is equipped with a HAWAII-2RG 2048×2048 HgCdTe array. Grisms are used as dispersive elements. In the photometric mode ASTRONIRCAM allows for extended astronomical object imaging in a 4.′6 × 4.′6 field of view with a 0.269 arcsec/pixel scale in standard photometric bands J, H, K, and K s as well as in the narrow-band filters centered on the lines CH4, [Fe II], H2 v=1-0 S(1), Br γ , and CO. In the spectroscopic mode, ASTRONIRCAM takes spectra of extended or point-like sources with a spectral resolution of R = λ/Δλ ≤ 1200. The general design, optical system, detector electronics and readout, amplification and digitization schemes are considered. The GAIN conversion factor measurement results are described as well as its dependence on the accumulated signal (nonlinearity).The full transmission of the atmosphere-to-detector train ranges from 40 to 50% in the wide-band photometry mode. The ASTRONIRCAMsensitivity at the 2.5-m telescope is characterized by the limiting J = 20, K = 19 stellar magnitudes measured with a 10% precision and 15 minute integration for 1″ atmospheric seeing conditions. References to the first results based on ASTRONIRCAM observations are given.  相似文献   

10.
The properties of red clump giants in the central regions of the Galactic bulge are investigated in the photometric Z and Y bands of the infrared VVV (VISTA/ESO) survey and the [3.6], [4.5], [5.8], and [8.0] μm bands of the GLIMPSE (Spitzer/IRAC) Galactic plane survey. The absolute magnitudes for objects of this class have been determined in these bands for the first time: M Z = ?0.20 ± 0.04, M Y = ?0.470 ± 0.045, M[3.6] = ?1.70 ± 0.03, M[4.5] = ?1.60 ± 0.03, M[5.8] = ?1.67 ± 0.03, and M[8.0] = ?1.70 ± 0.03. A comparison of the measured magnitudes with the predictions of theoretical models for the spectra of the objects under study has demonstrated good mutual agreement and has allowed some important constraints to be obtained for the properties of bulge red clump giants. In particular, a comparison with evolutionary tracks has shown that we are dealing predominantly with the high-metallicity subgroup of bulge red clump giants. Their metallicity is slightly higher than has been thought previously, [M/H] ? 0.40 (Z ? 0.038) with an error of [M/H] ? 0.1 dex, while the effective temperature is 4250± 150 K. Stars with an age of 9–10 Gyr are shown to dominate among the red clump giants, although some number of younger objects with an age of ~8 Gyr can also be present. In addition, the distances to several Galactic bulge regions have been measured, as D = 8200–8500 pc, and the extinction law in these directions is shown to differ noticeably from the standard one.  相似文献   

11.
The Tycho-2 proper motions and five-band Tycho-2 and 2MASS photometry for approximately 2.5 million common stars have been used to select OB stars and to determine the extinction and photometric distance for each of them. We have selected 37 485 stars and calculated their reddenings based on their positions in the two-color V T -H, J-Ks diagrams relative to the zero-age main sequence and the theoretical reddening line for B5 stars. Tests confirm that the selected stars belong to the spectral types O-B with a small admixture of later types. We calculate the extinction coefficient R and its variations with Galactic longitude based on the positions of the selected stars in the two-color B T -V T , V T -Ks diagram. The interstellar extinction for each star is calculated as the product of the reddening found and the coefficient R. The extinction and its variations with Galactic longitude agree well with the extinction based on the model by Arenou et al. (1992). Calibration of the relation between the absolute magnitude and reduced proper motion V T − + 5 + 5 log μ for Hipparcos stars has allowed us to calculate the absolute magnitudes and photometric distances for the selected stars. The distances found agree with those derived from the Hipparcos parallaxes within 500 pc. The distribution of the stars and the extinction variations with distance found show that the selected stars form an almost complete sample of stars with spectral types earlier than B5 within about 750 pc of the Sun. The sample includes many noticeably reddened stars in the first and second Galactic quadrants that are absent from the Hipparcos and Tycho Spectral Types Catalogues. This slightly changes the pattern of the distribution of OB stars compared to the classical pattern based on Hipparcos. Original Russian Text ? G.A. Goncharov, 2008, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2008, Vol. 34, No. 1, pp. 10–20.  相似文献   

12.
We present the results of our long-term photometric and spectroscopic observations at the Russian–Turkish RTT-150 telescope for the optical counterpart to one of the best-known sources, representatives of the class of fast X-ray transients, IGR J17544-2619. Based on our optical data, we have determined for the first time the orbital and physical parameters of the binary system by the methods of Doppler spectroscopy.We have calculated theoretical spectra of the optical counterpart by applying non- LTE corrections for selected lines and obtained the parameters of the stellar atmosphere (T eff = 33 000 K, log g = 3.85, R = 9.5 R ⊙, and M = 23 M ⊙). The latter suggest that the optical star is not a supergiant as has been thought previously.  相似文献   

13.
High-resolution spectra of nine yellow nonvariable supergiants (NVSs) located within the canonical Cepheid instability strip from Sandage and Tammann (1969) (α Aqr, ? Leo, μ Per, ω Gem, BD+60 2532, HD 172365, HD 187299, HD 190113, and HD 200102) were taken with the 1-m Zeiss and 6-m BTA telescopes at the Special Astrophysical Observatory of the Russian Academy of Sciences in the 1990s. These have been used to determine the atmospheric parameters, chemical composition, radial velocities, reddenings, luminosities, distances, and radii. The spectroscopic estimates of T eff and the luminosities determined from the Hipparcos parallaxes have shown eight of the nine program NVSs on the T eff?log(L/L ⊙) diagram to be outside the canonical Cepheid instability strip. When the edges of the Cepheid instability strip from Bono et al. (2000) are used, out of the NVSs from the list on the diagram one is within the Cepheid instability strip but closer to the red edge, two are at the red edge, three are beyond the red edge, two are at the blue edge, and one is beyond the blue edge. The evolutionary masses of the objects have been estimated. The abundances of α-elements, r- and s-process elements for all program objects have turned out to be nearly solar. The СNO, Na, Mg, and Al abundance estimates have shown that eight of the nine NVSs from the list have already passed the first dredge-up. Judging by the abundances of the key elements and its position on the T eff?log(L/L ⊙) diagram, the lithium-rich supergiant HD 172365 is at the post-main-sequence evolutionary stage of gravitational helium core contraction and moves toward the first crossing of the Cepheid instability strip. The star ? Leo should be assigned to bright supergiants, while HD 187299 and HD 190113 may have already passed the second dredge-up and move to the asymptotic branch.  相似文献   

14.
We present the results of multicolor (UBV JHKLM) photometry (2009–2017) and low-resolution spectroscopy (2016–2017) of the semi-regular variable V1427 Aql = HD 179821, a yellow supergiant with gas-dust envelope. The star displays low-amplitude (ΔV<0 . m 2) semi-periodic brightness variations superimposed on a long-term trend. The light curve shape and timescale change from cycle to cycle. There are temperature variations characteristic for pulsations; brightness oscillations with no significant change of color are also observed. The UBV data for the 2009–2011 interval are well reproduced by a superposition of two periodic components with P = 170d and 141d (or P = 217d—the one year alias of P = 141d). The variation became less regular after 2011, the timescale increased and exceeded 250d. Unusual photometric behavior was seen in 2015 when the star brightness increased by 0 . m 25 in the V filter in 130 days and reached the maximum value ever observed in the course of our monitoring since 1990. In 2009–2016 the annual average brightness monotonically increased in V, J, K, whereas it decreased in U and B. The annual average U ? B, B ? V, and J ? K colors grew, the star was getting redder. The cooling and expanding of the star photosphere along with the increasing of luminosity may explain the long-term trend in brightness and colors. Based on our photometric data we suppose that the photosphere temperature decreased by ~400 K in the 2008–2016 interval, the radius increased by ~24%, and the luminosity grew by ~19%. We review the change of annual average photometric data for almost 30 years of observations. Low-resolution spectra in the λ4000?9000 Å wavelength range obtained in 2016–2017 indicate significant changes in the spectrum of V1427 Aql as compared with the 1994–2008 interval, i.e., the Ba II and near-infraredCa II triplet absorptions have gotten stronger while the OI λ7771-4 triplet blend has weakened that points out the decrease of temperature in the region where the absorptions are formed. The evolutionary stage of the star is discussed. We also compare V1427 Aql with post-AGB stars and yellow hypergiants.  相似文献   

15.
R. Misawa  J-Ph. Bernard  Y. Longval  I. Ristorcelli  P. Ade  D. Alina  Y. André  J. Aumont  L. Bautista  P. de Bernardis  O. Boulade  F. Bousqet  M. Bouzit  V. Buttice  A. Caillat  M. Chaigneau  M. Charra  B. Crane  F. Douchin  E. Doumayrou  J. P. Dubois  C. Engel  M. Griffin  G. Foenard  S. Grabarnik  P. Hargrave  A. Hughes  R. Laureijs  B. Leriche  S. Maestre  B. Maffei  C. Marty  W. Marty  S. Masi  J. Montel  L. Montier  B. Mot  J. Narbonne  F. Pajot  E. Pérot  J. Pimentao  G. Pisano  N. Ponthieu  L. Rodriguez  G. Roudil  M. Salatino  G. Savini  O. Simonella  M. Saccoccio  J. Tauber  C. Tucker 《Experimental Astronomy》2017,43(3):211-235
The Polarized Instrument for Long-wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon-borne astronomy experiment designed to study the linear polarization of thermal dust emission in two photometric bands centred at wavelengths 240 μm (1.2 THz) and 550 μm (545 GHz), with an angular resolution of a few arcminutes. Several end-to-end tests of the instrument were performed on the ground between 2012 and 2014, in order to prepare for the first scientific flight of the experiment that took place in September 2015 from Timmins, Ontario, Canada. This paper presents the results of those tests, focussing on an evaluation of the instrument’s optical performance. We quantify image quality across the extent of the focal plane, and describe the tests that we conducted to determine the focal plane geometry, the optimal focus position, and sources of internal straylight. We present estimates of the detector response, obtained using an internal calibration source, and estimates of the background intensity and background polarization.  相似文献   

16.
The results of long-term photometric and spectroscopic observations of the young compact planetary nebula Vy 2-2 (PNG 045.4-02.7) are presented. The UBV photometry in 1990–2016 has revealed a slight brightness trend in the yearly averaged data, most pronounced in the V band. We have measured the relative fluxes of optical emission lines on the spectrograms taken with the 1.25-m telescope at the Southern Station of the SAI MSU in 1999–2016, estimated the absolute flux in the Hβ line to be F(Hβ) = (2.1 ± 0.4) × 10?12 erg cm?2 s?1, and determined the interstellar extinction constant c(Hβ) = 1.8. The electron temperature and density in the nebula have been estimated from diagnostic line ratios: Te = (10?12) × 103 K and Ne ≥ 105 cm?3. To detect any possible evolutionary changes, we have compared the new observations with the archival data obtained over the entire history of spectroscopic observations of Vy 2-2. No significant changes in the relative intensities of the strongest emission lines and the integrated flux in the Hβ line exceeding the observational errors have been found. We have revealed a tendency for the intensity ratio F(λ4363)/F(λ4959) to decrease with time, which may be related to a decrease in the electron density in the nebula. Based on our photometric and spectroscopic data, we have estimated the luminosity of the central star of Vy 2-2, which corresponds to the evolutionary tracks for the most massive post-AGB stars of the O-rich sequence.  相似文献   

17.
We present a catalogue of galaxy clusters detected in the Planck all-sky Compton parameter maps and identified using data from the WISE and SDSS surveys. The catalogue comprises about 3000 clusters in the SDSS fields. We expect the completeness of this catalogue to be high for clusters with masses larger than M 500 ≈ 3 × 1014 M ⊙, located at redshifts z < 0.7. At redshifts above z ≈ 0.4, the catalogue contains approximately an order of magnitude more clusters than the 2nd Planck Catalogue of Sunyaev-Zeldovich sources in the same fields of the sky. This catalogue can be used for identification of massive galaxy clusters in future large cluster surveys, such as the SRG/eROSITA all-sky X-ray survey.  相似文献   

18.
We consider two samples of OB stars with different distance scales that we have studied previously. The first and second samples consist of massive spectroscopic binaries with photometric distances and distances determined from interstellar calcium lines, respectively. The OB stars are located at heliocentric distances up to 7 kpc. We have identified them with the Gaia DR1 catalogue. Using the proper motions taken from the Gaia DR1 catalogue is shown to reduce the random errors in the Galactic rotation parameters compared to the previously known results. By analyzing the proper motions and parallaxes of 208 OB stars from the Gaia DR1 catalogue with a relative parallax error of less than 200%, we have found the following kinematic parameters: (U, V)⊙ = (8.67, 6.63)± (0.88, 0.98) km s?1, Ω0 = 27.35 ± 0.77 km s?1 kpc?1, Ω′0 = ?4.13 ± 0.13 km s?1 kpc?2, and Ω″0 = 0.672 ± 0.070 km s?1 kpc?3, the Oort constants are A = ?16.53 ± 0.52 km s?1 kpc?1 and B = 10.82 ± 0.93 km s?1 kpc?1, and the linear circular rotation velocity of the local standard of rest around the Galactic rotation axis is V 0 = 219 ± 8 km s?1 for the adopted R 0 = 8.0 ± 0.2 kpc. Based on the same stars, we have derived the rotation parameters only from their line-of-sight velocities. By comparing the estimated values of Ω′0, we have found the distance scale factor for the Gaia DR1 catalogue to be close to unity: 0.96. Based on 238 OB stars of the combined sample with photometric distances for the stars of the first sample and distances in the calcium distance scale for the stars of the second sample, line-of-sight velocities, and proper motions from the Gaia DR1 catalogue, we have found the following kinematic parameters: (U, V, W)⊙ = (8.19, 9.28, 8.79)± (0.74, 0.92, 0.74) km s?1, Ω0 = 31.53 ± 0.54 km s?1 kpc?1, Ω′0 = ?4.44 ± 0.12 km s?1 kpc?2, and Ω″0 = 0.706 ± 0.100 km s?1 kpc?3; here, A = ?17.77 ± 0.46 km s?1 kpc?1, B = 13.76 ± 0.71 km s?1 kpc?1, and V 0 = 252 ± 8 km s?1.  相似文献   

19.
Stellar evolution calculations were carried out from the main sequence to the final stage of the asymptotic giant branch for stars with initial masses 1 M⊙ ≤ MZAMS ≤ 2 M⊙ and metallicity Z = 0.01. Selected models of evolutionary sequences were used as initial conditions for solution of the equations of radiation hydrodynamics and time–dependent convection describing radial stellar pulsations. The study was aimed to construct the hydrodynamic models of Mira–type stars that show the secular decrease in the pulsation period Π commenced in 1970th at Π = 315 day. We show that such a condition for the period change is satisfied with evolutionary sequences 1 M⊙ ≤ MZAMS ≤ 1.2 M⊙ and the best agreement with observations is obtained for MZAMS = 1.2 M⊙. The pulsation period reduction is due to both the stellar radius decrease during the thermal pulse of the helium burning shell and mode switch from the fundamental mode to the first overtone. Theoretical estimates of the fundament parameters of the star at the onset of pulsation period reduction are as follows: the mass is M = 0.93 M⊙, the luminosity is L = 4080 L⊙, and the radius is R = 220 R⊙. The mode switch occurs 35 years after the onset of period reduction.  相似文献   

20.
Speckle-interferometric observations of FU Ori are performed with the 6-m telescope of the Special Astrophysical Observatory with 600/40 nm and 800/100 nm (central bandwidth/halfwidth) filters. The companion star FU Ori S that was recently discovered at λ >-1.25µm was recorded in observations with the λ/Δλ==800/100 nm filter. The positional parameters and magnitude difference of the companion in the filter considered are found to be θ = (163.9 ± 1.0)°, ρ = (0.493 ± 0.007)″, Δm = 3.96 ± 0.28. An analysis of the spectral energy distribution of the companion implies that for the extinction A V toward FU Ori to be greater than about 1.6 m , i.e., the minimum value required by the available models of the fuor, the spectral type of the companion star must be no later than K3. The reliability of this conclusion and the possible ways for obtaining more accurate estimates of A V are discussed.  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