Three years of photometry of IM pegasi = HR8703     

J. A. Eaton  D. S. Hall  G. W. Henry  L. P. Lovell  C. A. Stephan  C. R. Chambliss  P. K. Detterline  H. J. Landis  H. Louth  T. R. Renner  D. R. Skillman 《Astrophysics and Space Science》1983,89(1):53-60

Differential photometry of this K1 IV–III p RS VNn-type binary in 1978–79, 1979–80, and 1980–81 at eight different observatories shows that the variability, discovered orignally by Herbst, is periodic. The mean of three different determinations of the photometric period was 24^d.39±-0^d.03, about 1% shorter than the orbital period of 24^d.649 determined spectroscopically by Harper. The total range observed during these three years was 5 ^m .60<V<5 ^m .85. The light curve was nearly sinusoidal but always noticeably asymmetric, with the sense reversing sometime between 1979–80 and 1980–81.  相似文献   

Evolution of starspot regions in DM UMa     

S. Mohin  A. V. Raveendran  M. V. Mekkaden  D. S. Hall  G. W. Henry  R. D. Lines  R. E. Fried  H. Louth  H. J. Stelzer 《Astrophysics and Space Science》1985,115(2):353-368

B andV photometry of DM UMa obtained between January, 1980 and June, 1984 is presented. Analysis yields a mean photometric period 7^d.478±0^d.010, compared to the known oribital period of 7^d.492±0^d.009. Light curves obtained during any two seasons do not agree in any of the following: shape, amplitude, phases of the light maxima and minima, mean light level, or brightness at the light maxima and minima. From the change inB-V over the photometric period, we concludethat the hemisphere visible during the light minimum is cooler than that seen during light maximum. The mean colorB-V=1^m.065±0^m.002 is consistent with K1 III or K2 IV. Phases of light minima lie on two well-separated groups with different slopes; the corresponding periods are 7^d.471±0^d.002 and 7^d.481±0^d.001, in dicating that both migrate linearly towards decreasing orbital phase. In terms of the starspot model this indicates that two respective centers of activity were situated at different longitudes and latitudes on a differentially rotating star. From circumstantial evidence we infer that the dark region seen from 1979 onwards disintegrated sometime between the 1982 and 1983 observing seasons, leaving behind an area of relatively high surface brightness. We can put a lower limit of about four years on the lifetime of a center of activity.  相似文献   

Comparative analysis of photometric variability of TT ARI in the years 1994–1995 and 2001, 2004     

A. I. Belova  V. F. Suleimanov  I. F. Bikmaev  I. M. Khamitov  G. V. Zhukov  D. S. Senio  I. Yu. Belov  N. A. Sakhibullin 《Astronomy Letters》2013,39(2):111-125

We present the results of photometric observations of a bright cataclysmic variable TT Ari with an orbital period of 0.13755 days. CCD observations were carried out with the Russian-Turkish RTT 150 telescope in 2001 and 2004 (13 nights). Multi-color photoelectric observations of the system were obtained with the Zeiss 600 telescope of SAO RAS in 1994–1995 (6 nights). In 1994–1995, the photometric period of the system was smaller than the orbital one (0 _. ^d 132 and 0 _. ^d 134), whereas it exceeded the latter (0 _. ^d 150 and 0 _. ^d 148) in 2001, 2004. An additional period exceeding the orbital one (0 _. ^d 144) is detected in 1995 modulations. We interpret it as indicating the elliptic disc precession in the direction of the orbital motion. In 1994, the variability in colors shows periods close to the orbital one (0 _. ^d 136, b-v), as well as to the period indicating the elliptic disk precession (0 _. ^d 146, w-b). We confirm that during the epochs characterized by photometric periods shorter than the orbital one, the quasi-periodic variability of TT Ari at time scales about 20 min is stronger than during epochs with long photometric periods. In general, the variability of the system can be described as a “red” noise with increased amplitudes of modulations at characteristic time scales of 10–40 min.  相似文献   

Photometric lightcurves and pole determination of 433 Eros     

F. Scaltriti  V. Zappalà 《Icarus》1976,28(1):29-35

Fourteen photometric lightcurves of 433 Eros were made at the Astronomical Observatory of Torino during the 1974–75 close passage. The absolute magnitude of the primary maximum (10^m78), the phase coefficient (0.023 mag/degree), the synodic and sidereal period of rotation (0^d.21956 and 0^d.21959, respectively) and the ecliptic coordinates of the pole (λ = 17°, β = 10°) were deduced.  相似文献   

Photometric and spectroscopic study of the supergiant with an infrared excess V1027 Cygni     

V. P. Arkhipova  O. G. Taranova  N. P. Ikonnikova  V. F. Esipov  G. V. Komissarova  V. I. Shenavrin  M. A. Burlak 《Astronomy Letters》2016,42(11):756-773

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 = 212^d to 320^d in different time intervals. We have found the period P = 237^d 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 _. ^m 28, ΔB = 1 _. ^m 10, ΔV = 1 _. ^m 05, ΔJ = 0 _. ^m 30, ΔH = 0 _. ^m 35, ΔK = 0 _. ^m 32, ΔL = 0 _. ^m 26, and ΔM = 0 _. ^m 10. 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 W _λ(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   

Five years of photometry of λ andromedae     

R. W. Boyd  J. A. Eaton  D. S. Hall  G. W. Henry  R. M. Genet  L. P. Lovell  J. L. Hopkins  J. D. Sabia  K. Krisciunas  C. R. Chambliss  P. K. Detterline  H. J. Landis  H. Louth  T. R. Renner  D. R. Skillman  R. E. Montle 《Astrophysics and Space Science》1983,90(1):197-206

We present photoelectric photometry of this bright long-period RS CVn binary and use it, along with earlier photometry, to derive the photometric period and discuss the changing light curve shape. The best ephemeris for times of minimum light is 2443829.2+53.^d95E. Because times of minimum and maximum extending back to those of Calder in 1933–37 can be phased together properly, the principal dark region must have maintained its identify for almost 50 yr. Over the last five years the brightness range has been 3 ^m .70<V<4 ^m .05. During 1980–81 shallow secondary minima developed at phases where maxima occurred in previous years. λ And remains the only wellestablished case of non synchronous rotation among the known RS CVn binaries.  相似文献   

Pole orientation of asteroid 44 Nysa via photometric astrometry,including a discussion of the method's application and its limitations     

R.C. Taylor  Edward F. Tedesco 《Icarus》1983,54(1):13-22

The results of photometric astrometry, a method of determining the orientation of a rotation axis, as applied to asteroid 44 Nysa are presented. The pole orientation of Nysa was found to be λ₀ = 100°, β₀ = +60° with an uncertainty of 10°. The sidereal period is 0^d.26755902 ± 0.00000006, and the rotation prograde. Refinements to, and limitations of, the application of the method of photometric astrometry are discussed. In light of the results presented herein, we believe that all photometric astrometry pole determinations of the past should be redone.  相似文献   

Five years of photometry ofσ geminorum     

R. E. Fried  J. A. Eaton  D. S. Hall  G. W. Henry  C. A. Vaucher  J. L. Hopkins  J. D. Sabia  K. Krisciunas  C. R. Chambliss  H. J. Landis  H. Louth  T. G. McFaul  D. R. Skillman  T. R. Renner 《Astrophysics and Space Science》1983,93(2):305-311

Five years of photoelectric photometry of this bright K1 III RS CVn binary has been obtained at thirteen different observatories. Except for one year, the light curve has shown two minima, separated by roughly a half cycle. At the epoch of discovery (1977.2) one minimum was shallower but as of 1980.2 the two became comparable in depth. During the 1979–80 season the light curve changed shape rapidly, the shallower minimum becoming as deep as the other within about 80 days or perhaps less. Times of both minima can be fit with a photometric period of 19 ^d .423, which is 0.9% shorter than the 19 ^d .603 orbital period. The overall brightness range during the five years has been 4 ^m .13<V<4 ^m .29.Guest Observer, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.  相似文献   

Four years of photometry of DK draconis=HR 4665     

J. A. Eaton  D. S. Hall  G. W. Henry  C. A. Vaucher  C. R. Chambliss  P. K. Detterline  H. J. Landis  R. P. Wasatonic  H. Louth  T. R. Renner  A. M. Bloschak  J. S. Gillman  A. C. Krahnert  B. B. McGuinness 《Astrophysics and Space Science》1982,87(1-2):305-312

Differential BV photometry of the K0III+K0III long-period RS CVn-type binary DK Dra=HR 4665 in 1977, 1978, 1979, and 1980 at eight different observatories is presented. A least squares fit to times of maximum and minimum light yields the ephemeris JD=2 443 219.5+63 _. ^d 75E for times of minimum. This photometric period is 1% shorter than the spectroscopically determined orbital period 64 _. ^d 44. The light curve was symmetrical and roughly sinusoidal in 1979 and 1980 but was asymmetrical in 1977 and 1978, with a faster rise to maximum. During these four years DK Dra varied between V=6 _. ^m 07 and 6 _. ^m 35.Of the AAVSO.Amateur Astronomers, Inc.  相似文献   

Search for and study of photometric variability in magnetic white dwarfs     

A. F. Valeev  K. A. Antonyuk  N. V. Pit  A. S. Moskvitin  A. O. Grauzhanina  D. R. Gadelshin  S. V. Kolesnikov  E. A. Zhuzhulina  T. E. Burlakova  G. A. Galazutdinov  A. G. Gutaev  R. Ya. Zhuchkov  A. I. Ikhsanova  D. G. Zhukov  Arti Joshi  J. C. Pandey  A. F. Kholtygin  G. G. Valyavin 《Astrophysical Bulletin》2017,72(1):44-50

We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70?8247 with a likely period from several days to several dozen days and a half-amplitude of about 0_. ^m 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0_. ^m 005, and the likely period of this degenerate star lies in the 10–20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated “magnetic field–rotation period” diagram for the white dwarfs.  相似文献   

Multicolor Photometry and Spectroscopy of the Yellow Supergiant with Dust Envelope HD 179821 = V1427 Aquilae     

N.?P.?IkonnikovaEmail author  O.?G.?Taranova  V.?P.?Arkhipova  G.?V.?Komissarova  V.?I.?Shenavrin  V.?F.?Esipov  M.?A.?Burlak  V.?G.?Metlov 《Astronomy Letters》2018,44(7):457-473

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 = 170^d and 141^d (or P = 217^d—the one year alias of P = 141^d). The variation became less regular after 2011, the timescale increased and exceeded 250^d. 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   

Photometric and spectroscopic variability of the pre‐main sequence star V1184 Tauri (CB 34V)     

E. H. Semkov 《Astronomische Nachrichten》2006,327(4):328-334

We present recent results from optical photometric and spectroscopic observations of the pre‐main sequence star V1184 Tau (CB 34V). The star is associated with the Bok globule CB 34 and was considered as a FUOR candidate in previous studies. Our photometric data obtained from October 2000 to April 2003 show that the stellar brightness varies with an amplitude of about 0.m 5 (I ), but from August 2003 the photometric behavior of the star has changed dramatically. Three deep brightness minima (ΔI ∼ 4^m.2) were observed during the past two years. The analysis of available photometric data suggests that V1184 Tau shows two types of variability produced (1) by rotation of large cool spotted surface and (2) by occultation from circumstellar clouds of dust or from features of a circumstellar disk. The behavior of the V – I index indicates that the star becomes redder towards minimum light, but from a certain turning point (V ∼ 18^m.2) it gets bluer and is fading further. Five medium dispersion optical spectra of V1184 Tau were obtained in the period 2001–2004. Signi.cant changes in the profile and strength of the emission lines in the spectrum of V1184 Tau were found. During minimum light the equivalent width of the Hα emission line increases from 4 Å to 9 Å. The [O I] lines (λλ 6003, 6363 Å) are also seen in emission while the sodium doublet keeps its absorption strength and equivalent width. The possibility to reconstruct the historical light curve of V1184 Tau using photographical plate archives is brie.y discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

VR c photometry of dwarf cepheids (I)     

Chulhee Kim  Michael D. Joner 《Astrophysics and Space Science》1994,218(1):113-135

In this paper, we present VRc photometric observations of four dwarf cepheids: YZ Boo (P = 0 _. ^d 104, V = 0 _. ^m 5), AD CMi (P = 0 _. ^d 123, V = 0 _. ^m 5), XX Cyg (P = 0 _. ^d 135, V = 0 _. ^m 5), EH Lib (P = 0 _. ^d 088, V = 0 _. ^m 7). The light curves were obtained at West Mountain Observatory, Provo, Utah on 14 nights from 1983 through 1986 and contain 589 data points in each of theV andR bands in the Cousin photometric system. A detailed study of these stars, based on the present light curves, will be published separately.  相似文献   

HR 7275: A new variable star     

R. E. Fried  Joel A. Eaton  D. S. Hall  G. W. Henry  L. P. Lovell  K. Krisciunas  C. R. Chambliss  P. K. Detterline  H. J. Landis  H. Louth  D. R. Skillman 《Astrophysics and Space Science》1982,83(1-2):181-188

Differential photometry of the KI IV-III RS CVn-type binary HR 7275 in 1978, 1979, and 1980 at nine different observatories shows it definitely to be variable, thus confirming the suspicion of Herbst. The photometric period determined two ways was 27 _. ^d 91 or 27 _. ^d 65, thus about 3% shorter than the spectroscopically determined orbital period of 28 _. ^d 59. The total variation observed during the three years was 0 _. ^m 22 in theV. The light curve was always asymmetrical, with a stillstand on the rising branch in 1978 but on the falling branch in 1980.Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.Of the AAVSO.  相似文献   

Pulsations and apsidal motion in the eclipsing variable system DI Herculis     

V. S. Kozyreva  L. A. Bagaev 《Astronomy Letters》2009,35(7):483-493

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 _. ^o 3 ± 0 _. ^o 1/100 yr) and theoretical (4 _. ^o 3/100 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 _. ^m 011, 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 _. ^m 5.  相似文献   

On the possible binarity of asteroid 21 Lutetia from analysis of simultaneous BVR observations     

V. V. Prokof’eva  V. V. Bochkov  V. V. Busarev 《Solar System Research》2006,40(6):468-476

We obtained ～1000 B, V, and R magnitude measurements for asteroid 21 Lutetia quasi-simultaneously with the digital TV system of a 0.5-m MTM-500 meniscus telescope from November 3 through November 11, 2004. We performed a frequency analysis of the B-V and V-R color indices and the V magnitudes based on data averaged over five measurements, which provided an accuracy of the mean color indices and magnitudes of ～0. ^m 005 and 0. ^m 08, respectively. Our analysis of the color indices showed the absence of the known period, 0.^d3405 (8.^h172), and the presence of several periods at a confidence level of 7–10 σ, including P ₀ = 2.^h93 (1/P = 8.17c/d) and its alias 2.^h64 (1/P = 9.17c/d). Our analysis of the V-band data revealed the periods P ₁ = 0.^d70 and P ₂ = 3.^d20; both periods yielded double-peaked light curves with amplitudes of 0. ^m 12 and 0. ^m 10. The first period is probably the rotation period of the main component, while the second period may be equal to the orbital period of the satellite with one side facing the main body. Another model of the asteroid is also possible: P ₀ = 2.^h93 is the rotation period of the main body, P ₁ = 0.^d70 is the orbital period of the synchronous satellite, and P ₂ = 3.^d20 is the precession period.  相似文献   

New 1982 — 1990 photometry of λ Andromedae and its 11-year cycle     

Douglas S. Hall  Gregory W. Henry  Dietmar Böhme  Peter A. Brooks  Sandy Chang  Ales Dolzan  George L. Fortier  Robert E. Fried  Russell M. Genet  Bruce S. Grim  James Hannon  Darrel B. Hoff  Kevin Krisciunas  Howard J. Landis  Howard P. Louth  Larry P. Lovell  Paul Nielsen  Bobby E. Powell  Harry D. Powell  Don Pray  Thomas R. Renner  Charles W. Rogers  Stephen Shervais  Douglas M. Slauson  Samuel Slote  Harold J. Stelzer  Arthur J. Stokes  Jack C. Troeger  Louis C. Turner  Norman F. Wasson  Kenneth W. Zeigler 《Journal of Astrophysics and Astronomy》1991,12(4):281-287

We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29 different observatories. Then we combine it with all other photometry available to us (previously published, contained in the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0^m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season, we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0^m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0^m.09 down almost to 0^m.03. The spot rotation periods were 55^d.9 ± 0^d.6 and 520^d.8 ± 1^d.0, respectively.  相似文献   

HD 52721 - A close binary system among the Ae/Be Herbig stars     

M. A. Pogodin  N. G. Beskrovnaya  I. S. Guseva  S. E. Pavlovskiy  N. Rusomarov 《Astrophysics》2011,54(2):214-230

Photometric and high resolution spectroscopic data for the Herbig star HD 52721 obtained from October 2009 through October 2010 are presented. We confirm the cyclical character of the photometric variability of HD 52721 discovered previously by others. The variability shows up as minima in the light curve of this star which repeat with a period P = 0^d.805 and are typical of eclipsing binary systems. ASAS data covering an observation period from September 2003 through December 2009 show that two neighboring photometric minima differ from one another, and the actual orbital period of the system must be twice as high (P = 1^d.610). This is confirmed by the spectroscopic data. These show that the center of gravity of the emission Hα line and the profile of the HeI 6678 line with a distinct, bright circumstellar component have a clear correlation with a period of 1^d.610. To all appearances, HD 52721 is a close binary system consisting of two class B2 stars with quite similar parameters. We propose that the observed cyclical variations in the circumstellar parameters may be related to the existence of a global azimuthal inhomogeneity within the shell which rotates synchronously with the orbital motion of the system components.  相似文献   

Photometric and Colorimetric Observations of Asteroid 423 Diotima and Their Analysis     

Prokof'eva  V. V.  Karachkina  L. G. 《Solar System Research》2004,38(2):108-119

Series of photometric and colorimetric observations of the Main-Belt asteroid 423 Diotima during its five oppositions were obtained at the Crimean Astrophysical Observatory. It was concluded, based on the results of a frequency analysis of the V-band photometry obtained in 1990, that the asteroid is a binary system: the rotation period of the primary component is equal to 4_. ^h56, and the period of rotation and the orbital period of the satellite are equal to 14_. ^h90. An analysis of simultaneous BV and BVR observations made in 1993 and 1998–1999 yielded a rotation period of 4_. ^h54 ± 0_. ^h01 for the primary component. An analysis of the sets of V-band observations of the asteroid made from 1982 through 2000 allowed us to find the period of forced precession, which was equal to 113^d (or 226^d). It was suggested that the axis of the primary component of the binary asteroid precesses and the large amplitude of brightness variations (about 1 ^m ) is due to its lenticular shape.  相似文献   

54 Cam: A new variable star     

J. A. Eaton  D. S. Hall  G. W. Henry  C. A. Vaucher  H. Louth  D. R. Skillman 《Astrophysics and Space Science》1981,80(2):405-410

Differential photometry of the RS CVn-type binary 54 Cam in 1978, 1979, and 1980 shows its light to be variable with a period of 10 _. ^d 163±0 _. ^d 009 and an amplitude inV (max. to min.) which increased from 0 _. ^m 03 to 0 _. ^m 06 between 1979.19 and 1980.82. An epoch of light minimum was JD 2444529.7. The 9% difference betweenP(phtm.)=10 _. ^d 163 andP(orb.)=11 _. ^d 0764,a much larger difference than is characteristic of other RS CVn binaries, is suggested as an explanation for the radio emission.Guest Investigator, Kitt Peak National Observatory,which is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.Of the AAVSO.  相似文献