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1.
Photoelectric observations of the RS CVn type non-eclipsing binary UX Arietis obtained at Nizamiah Observatory during the
observing seasons of 1975–76, 1981–82 and 1982–83 are presented. The light curve of UX Ari showed a distortion wave with an
amplitude inV varying from 0.02 mag during 1975–76 to 0.15 mag during 1982–83. An analysis of the available data shows that the light maximum
is almost constant. It is also evident that the light-curve minimum decreases as the wave amplitude increases. The constant
light at maximum,V = 6.51 ± 0.03 indicates the unspotted photospheric brightness. It is also suggested that the variation in meanV brightness is mainly due to spot activity and not due to intrinsic variation. 相似文献
2.
UBV photometry of HR 1099 obtained during the 1979-80 and 1980-81 observing seasons is presented. An analysis of the available
data shows that the brightness at the light curve maximum increases as the wave amplitude increases, while the brightness
at the light minimum remains almost the same. In terms of the starspot model it implies that there is always a hemisphere
of the active component that is nearly ’saturated’ with spots and that spots occupy a larger fraction of the stellar surface
when the wave amplitude is smaller. The continuous migration attributed to the photometric wave by various authors is far
from certain. The amplitude of the wave has a sharp rise followed by slow decay with a period around 5–6 yr. It is found that
the two-spot model proposed by Dorren and Guinan (1982) is inadequate to describe all the observed photometric peculiarities
of HR 1099. 相似文献
3.
We use the method of time – distance analysis to measure lifetimes of solar p modes in the range ℓ=100 − 600 and ν=3.0 − 4.5 mHz with data taken with the Taiwan Oscillation Network (TON). The lifetimes of p modes are determined by the changes in the amplitude and width of the cross-correlation function of a wave packet with the
number of skips. The amplitude of the cross-correlation function decreases exponentially with the number of skips as in previous
work. This decrease has been interpreted as the effect of the finite p-mode lifetime. In this study, we find that the width of the cross-correlation function increases with the number of skips.
We interpret this phenomenon as the effect of the dispersion of the wave packet. We include this effect in the determination
of the lifetime of the wave packet. The lifetime increases after the dispersion is taken into account. We also study the change
in lifetime between solar minimum and maximum. 相似文献
4.
We analyze long-term UBV observations and ASAS-3 photometry for five candidates for protoplanetary nebulae—F and G supergiants with infrared excesses
at highG alactic latitudes—V340 Ser, IRAS 05113+1347, V552 Pup, V448 Lac, and RV Col. These stars exhibit quasi-periodic multifrequency
light variations caused by pulsations with characteristic time scales from 83 to 139 days, depending on the stellar temperature.
Cooler stars undergo variations with larger amplitudes and periods. The variations at close frequencies with a period ratio
of 1.03–1.09 are responsible for the amplitude modulation revealed for most program stars. 相似文献
5.
We present new photometric data and analyze long-term UBV observations of three candidates for protoplanetary nebulae—F supergiants with infrared excesses at high Galactic latitudes—IRAS
18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All these stars exhibit quasi-periodic low-amplitude variations caused by
pulsations against the background of long-term brightness trends. For IRAS 18095+2704=V887 Her, we have found a pulsation
period of 109 days and revealed a linear brightness trend—the star brightens at constant (within the limits of the measurement
errors) yearly mean color indices. The light curve of IRAS 19386+0155=V1648 Aql in 2000–2008 is represented by a wave with
a fundamental period of 102 days whose modulation with a close period of 98 days leads to variations with a variable amplitude.
V1648 Aql also shows a systematic rise in V brightness along with a reddening. IRAS 19500–1709=V5112 Sgr exhibits irregular pulsations with periods of 39 and 47 days.
The long-term variability component of V5112 Sgr may indicate that the star is binary. 相似文献
6.
Chulhee Kim S.-L. Kim Y.-B. Jeon C.-H. Kim A. Gilmore 《Astrophysics and Space Science》2007,312(1-2):41-46
New differential time-series observations of KZ Hya were secured using the V filters, and 28 new times of light maximum were
identified. We collected 157 times of light maximum from the literature, unpublished data and open database, and proceeded
to investigate the variations of the O–C values for light maxima with the total of 185 times of light maximum. A quasi-sinusoidal
character of the O–C diagram was confirmed, and this was interpreted as a light travelling time effect due to a companion
moving in an eccentric (e=0.23) orbit with a period of about 24.77 years. The periods of KZ Hya were investigated and nine frequencies were determined
using the Fourier decomposition method. All nine were harmonic frequencies and no other frequency was identified. 相似文献
7.
V. P. Arkhipova N. P. Ikonnikova G. V. Komissarova V. F. Esipov 《Astronomy Letters》2006,32(9):594-603
We present the results of our photoelectric observations of HD 51585 (OY Gem), a B[e] star with an infrared excess and a candidate for protoplanetary nebulae, obtained with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in 1992–2005. The star exhibited rapid irregular brightness variations with amplitudes from We present the results of our photoelectric observations of HD 51585 (OY Gem), a B[e] star with an infrared excess and a candidate
for protoplanetary nebulae, obtained with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute
in 1992–2005. The star exhibited rapid irregular brightness variations with amplitudes from
in the V band to
in U band within the observing season as well as slow systematic variations with amplitudes from
in the V band to
in the U band and with a quasi-period of ∼2800 days. The B-V color index varied within
and did not follow the slow systematic brightness variations, while U-B correlated with the U brightness and varied between
at maximum light and
at minimum light. Our low-resolution spectroscopy performed in 1994–2005 has revealed significant variability of the Balmer
and Paschen hydrogen emission lines as well as the He I and O I lines. Equivalent widths are given for the H I, He I, O I,
and Fe II lines; a correlation has been found between the star’s photometric variability and the hydrogen line intensities.
Our joint analysis of the photometric and spectroscopic data suggests that variations in a strong stellar wind are responsible
for the variability of the star.
Original Russian Text ? V.P. Arkhipova, N.P. Ikonnikova, G. V. Komissarova, V. F. Esipo, 2006, published in Pis’ma v Astronomicheskiĭ
Zhurnal, 2006, Vol. 32, No. 9, pp. 662–671. 相似文献
8.
K. R. Anantharamaiah Pradeep Gothoskar T. J. Cornwell 《Journal of Astrophysics and Astronomy》1994,15(4):387-414
We present Very Large Array observations at wavelengths of 2, 3.5, 6, and 20 cm, of angular broadening of radio sources due
to the solar wind in the region 2–16 solar radii. Angular broadening is anisotropic with axial ratios in the range 2–16. Larger
axial ratios are observed preferentially at smaller solar distances. Assuming that anisotropy is due to scattering blobs elongated
along magnetic field lines, the distribution of position angles of the elliptically broadened images indicates that the field
lines are non-radial even at the largest heliocentric distances observed here. At 5R⊙, the major axis scattering angle is
∼ 0.7" atλ= 6 cm and it varies with heliocentric distance asR
-1.6. The level of turbulence, characterized by the wave structure function at a scale of 10 km along the major axis, normalized
toλ = 20 cm, has a value 20 ± 7 at 5R⊙and varies with heliocentric distance asR
-3. Comparison with earlier resu lts suggest that the level of turbulence is higher during solar maximum. Assuming a power-law
spectrum of electron density fluctuations, the fitted spectral exponents have values in the range 2.8–3.4 for scale sizes
between 2–35 km. The data suggests temporal fluctuations (of up to 10%) in the spectral exponent on a time scale of a few
tens of minutes. The observed structure functions at different solar distances do not show any evidence for an inner scale;
the upper limits are l k m at 2R⊙ and 4 km at 13R⊙. These upper limits are in conflict with earlier determinations and may suggest a reduced inner scale during solar maximum. 相似文献
9.
We study the evolution of the longitudinal asymmetry in solar activity through the wave packet technique applied to the period
domain of 25 – 31 days (centered at the 27-day solar rotation period) for the sunspot number and geomagnetic aa index. We observe the occurrence of alternating smaller and larger amplitudes of the 11-year cycle, resulting in a 22-year
periodicity in the 27-day signal. The evolution of the 22-year cycle shows a change of regime around the year 1912 when the
22-year period disappears from the sunspot number series and appears in the aa index. Other changes, such as a change in the correlation between solar and geomagnetic activity, took place at the same
time. Splitting the 27-day frequency domain of aa index shows an 11-year cycle for higher frequencies and a pure22-year cycle for lower frequencies, which we attribute to
higher latitude coronal holes. This evidence is particularly clear after 1940, which is another benchmark in the evolution
of the aa index. We discuss briefly the mechanisms that could account for the observed features of the 22-year cycle evolution. 相似文献
10.
O. N. Sholukhova S. N. Fabrika A. V. Zharova A. F. Valeev V. P. Goranskij 《Astrophysical Bulletin》2011,66(2):123-143
We present the results of studying the spectral and photometric variability of the luminous blue variable star V532 in M33.
The photometric variations are traced from 1960 to 2010, spectral variations—from 1992 to 2009. The star has revealed an absolute
maximum of visual brightness (1992–1994, high/cold state) and an absolute minimum (2007–2008, low/hot state) with a brightness
difference of ΔB ≈ 2.3
m
. The temperature estimates in the absolute maximum and absolute minimum were found to be T ∼ 22000 K and T ∼ 42000 K, respectively. The variability of the spectrum of V532 is fully consistent with the temperature variations in its
photosphere, while both permitted and forbidden lines are formed in an extended stellar atmosphere. Broad components of the
brightest lines were found, the broadening of these components is due to electron scattering in the wind parts closest to
the photosphere. We measured the wind velocity as a difference between the emission and absorption peaks in the PCyg type
profiles. The wind velocity clearly depends on the size of the stellar photosphere or on the visual brightness, when brightness
declines, the wind velocity increases. In the absolute minimum a kinematic profile of the V532 atmosphere was detected. The
wind velocity increases and its temperature declines with distance from the star. In the low/hot state, the spectral type
of the star corresponds to WN8.5h, in the high/cold state—to WN11. We studied the evolution of V532 along with the evolution
of AGCar and the massive WR binary HD5980 in SMC. During their visual minima, all the three stars perfectly fit with the WNL
star sequence by Crowther and Smith (1997). However, when visual brightness increases, all the three stars form a separate
sequence. It is possible that this reflects a new property of LBV stars, namely, in the high/cold states they do not pertain
to the bona fide WNL stars. 相似文献
11.
We report first evidence for a new unidentified and variable MeV source, located near the galactic plane at (l,b)∼(284.5°,
2.5°). The source, GRO J1036-55, is found at a significance level of ∼5.6σ by COMPTEL in its 3–10 MeV band. The energy spectrum indicates a spectral maximum at 3–4.3 MeV with a steep slope at higher
energies. Since the COMPTEL 3–4.3 MeV data contain contamination by an instrumental background line, we performed several
consistency checks, which all are consistent with an astrophysical nature of this emission feature. 相似文献
12.
The purpose of our work is to strongly constrain the mass to light ratio in the disk of the flocculent isolated Sc type spiral
NGC 4414 using a combined high resolution interferometric CO(1-0) and HI rotation curve, and deep HST B-V-I images of the
galaxy. To identify the mass contributions of the visible – stellar and gaseous – components, we observed the rotation curve
with high resolution in the optical disk. The M/L ratios we derive are low, about 1.5 in I band and 0.5 in K' band. The B
and V band M/L ratios vary greatly due to absorption by dust, reaching 4 in the molecular ring and decreasing to about 1.6
–1.8 at larger radii. This unequivocally shows that models, like most maximum disk models, assuming constant M/L ratios in
an optical waveband, simply are not appropriate. We illustrate this by making mock maximum disk models with a constant V band
M/L ratio. The key is having the central light distribution unobscured such that it can be used to trace the mass. The K'
band M/L ratio is virtually constant over the disk, suggesting that the intrinsic (unobscured) stellar M/L ratio is roughly
constant. We use our knowledge of the visible mass distribution to test disk and halo dark matter models. Fitting an NFW (Navarro
et al., 1996) halo to the rotation curve suggests that NGC 4414 is in a low mass concentrated halo typical of small galaxies
and early halo formation times.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Existence of compressive relativistic solitons is established in an arbitrary ξ-direction, inclining at an angle to the direction of the weak magnetic field (ω
pi
≫ω
Bi
) in this plasma compound with ions, relativistic electrons and relativistic electron beams. It is observed that the absolute
linear growth of amplitudes of compressive solitons is due to inactive role of the weak magnetic field and the initial streaming
speeds of relativistic electrons, electron beams, and Q
b
(ion mass to electron beam mass). Besides, the small initial streaming of electrons is found to be responsible to generate
relatively high amplitude compressive solitons. The non-relativistic ions in the background plasma, but in absence of electron-beam
drift and in presence of weak magnetic field are the causing effect of interest for the smooth growth of soliton amplitudes
in this model of plasma. 相似文献
14.
We study magnetic power spectra of active and quiet regions by using Big Bear Solar Observatory and SOHO/MDI measurements
of longitudinal magnetic fields. The MDI power spectra were corrected with Gaussian Modulation Transfer Function. We obtained
reliable magnetic power spectra in the high wave numbers range, up to k=4.6 Mm−1, which corresponds to a spatial scale l=1.4 Mm. We find that the occurrence of the spectral discontinuity at high wave numbers, k≥3 Mm−1, largely depends on the spatial resolution of the data and it appears at progressively higher wave numbers as the resolution
of the data improves. The spectral discontinuity in the raw spectra is located at wave numbers about 3 times smaller than
wave numbers, corresponding to the resolution of the data, and about 1.5–2.0 times smaller in the case of the noise- and-resolution
corrected spectra. The magnetic power spectra for active and quiet regions are different: active-region power spectra are
described as ∼k
−1.7, while in a quiet region the spectrum behaves as ∼k
−1.3. We suggest that the difference can be due to small-scale dynamo action in the quiet-Sun photosphere. Our estimations show
that the dynamo can generate more than 6% of the observed magnetic power. 相似文献
15.
V934 Her is a detached system, consisting of a cool giant and a neutron star. The neutron star accretes matter fromthe stellarwind
of the giant.Multicolor photoelectric observationsmade in 1997–2011 revealed a 415-day period, close to that, discovered spectroscopically
from radial velocities. This period is considered to be the orbital period of orbital motion of the neutron star around the
red giant. The wave with this period in the U-band has the largest amplitude 0m.12. We also detected multiperiodic pulsations of the red giant. The light curve in the V -band is dominated by a pulsation wave with the period of 28.82 days and the amplitude of 0m.10. 相似文献
16.
Jordanova V.K. Thorne R.M. Farrugia C.J. Dotan Y. Fennell J.F. Thomsen M.F. Reeves G.D. McComas D.J. 《Solar physics》2001,204(1-2):361-375
We study the development of the terrestrial ring current during the time interval of 13–18 July, 2000, which consisted of
two small to moderate geomagnetic storms followed by a great storm with indices Dst=−300 nT and Kp=9. This period of intense geomagnetic activity was caused by three interplanetary coronal mass ejecta (ICME) each driving
interplanetary shocks, the last shock being very strong and reaching Earth at ∼ 14 UT on 15 July. We note that (a) the sheath
region behind the third shock was characterized by B
z fluctuations of ∼35 nT peak-to-peak amplitude, and (b) the ICME contained a negative to positive B
z variation extending for about 1 day, with a ∼ 6-hour long negative phase and a minimum B
z of about −55 nT. Both of these interplanetary sources caused considerable geomagnetic activity (Kp=8 to 9) despite their disparity as interplanetary triggers. We used our global ring current-atmosphere interaction model
with initial and boundary conditions inferred from measurements from the hot plasma instruments on the Polar spacecraft and the geosynchronous Los Alamos satellites, and simulated the time evolution of H+, O+, and He+ ring current ion distributions. We found that the O+ content of the ring current increased after each shock and reached maximum values of ∼ 60% near minimum Dst of the great storm. We calculated the growth rate of electromagnetic ion cyclotron waves considering for the first time wave
excitation at frequencies below O+ gyrofrequency. We found that the wave gain of O+ band waves is greater and is located at larger L shells than that of the He+ band waves during this storm interval. Isotropic pitch angle distributions indicating strong plasma wave scattering were
observed by the imaging proton sensor (IPS) on Polar at the locations of maximum predicted wave gain, in good agreement with model simulations. 相似文献
17.
V andB observations of V711 Tauri (HR 1099) for the year 1982–1983 are presented. The light curves made with the data of this season are compared with those of the previous observations of the 1981–1982 season. The single-peaked maximum light had shifted slightly and the peak amplitude had decreased to 0.04 mag. inV. No clear sign of colour,B–V, variation in comparison with the low temperature dark-spot is detected.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
18.
Photoelectric aperture-photometry ofω Cen inU, B, V, R andI bands has established that the cluster is bluer between 2 arcmin and 4 arcmin from the centre, than it is elsewhere. The
difference inB - I colour between the centre and this blue zone is ≃ 0.45 mag. The core radius is found to be dependant on the wavelength band
chosen for observation, the smallest core radius being for theI band. Equidensitometry ofω Cen inB, V and infrared bands shows a wavelength dependence with the cluster being nearly spherical in the infrared band. It shows a
maximum ellipticity around 3 arcmin from the cluster centre. The blue contribution in this zone comes from both a diffuse
background of unresolved stars and an increase in the relative abundance of horizontal branch (HB) stars. The similarity between
the diffuse background and the HB stars has been demonstrated. A photographic subtraction technique is used to study the distribution
of HB stars in the cluster.
Results of equidensitometry of the cluster 47 Tuc, obtained in the present study, are compared with the earlier results of
photoelectric photometry. Here too an increase in ellipticity is associated with an increase in the blueness of the cluster.
All globular clusters studied so far for ellipticity show a similarity in the dependence of the ellipticity on the distance
from the centre. The ellipticity has small values near the centre and in the outer regions, with the maximum value in between.
We suggest that the red stars in globular clusters have a nearly spherical distribution. The blue stars form a bulge around
the core with a more elliptical distribution and a different orientation. A similarity between the ellipticity aspects of
both the globular clusters and rotation in the nucleus of M 31 is pointed out; the M 31 nucleus may thus show a bluer colour
and smaller UV excess around the region where the rotation curve shows a peak.
An erratum to this article is available at . 相似文献
19.
We have constructed the bolometric light curve of SN 1993J based on UBVRI(JHK) photometric data obtained from various sources
and assumingA
V = 0 and a distance modulus of 27.6. Effective temperatures and photosphere radius at various times have been obtained from
detailed blackbody fits. The bolometric light curve shows two maxima. The short rise time to the second maximum, and the luminosities
at the minimum and the second maximum are used to constrain the properties of the progenitor star. The total mass of the hydrogen
envelope MH, in the star is found to be ≲ 0.2 M⊙ at the time of explosion, and the explosion ejected about 0.05 M⊙ of Ni56. Thin hydrogen envelope combined with a sufficient presupernova luminosity suggest that the exploding star was in a binary
with a probable period range of 5yr ≤P
orb
≤ 11yr. 相似文献
20.
We study variations of the lifetimes of high-ℓ solar p modes in the quiet and active Sun with the solar activity cycle. The lifetimes in the degree range ℓ=300 – 600 and ν=2.5 – 4.5 mHz were computed from SOHO/MDI data in an area including active regions and quiet Sun using the time – distance
technique. We applied our analysis to the data in four different phases of solar activity: 1996 (at minimum), 1998 (rising
phase), 2000 (at maximum), and 2003 (declining phase). The results from the area with active regions show that the lifetime
decreases as activity increases. The maximal lifetime variations are between solar minimum in 1996 and maximum in 2000; the
relative variation averaged over all ℓ values and frequencies is a decrease of about 13%. The lifetime reductions relative to 1996 are about 7% in 1998 and about
10% in 2003. The lifetime computed in the quiet region still decreases with solar activity, although the decrease is smaller.
On average, relative to 1996, the lifetime decrease is about 4% in 1998, 10% in 2000, and 8% in 2003. Thus, measured lifetime
increases when regions of high magnetic activity are avoided. Moreover, the lifetime computed in quiet regions also shows
variations with the activity cycle. 相似文献