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1.
A. P. Mahtessian 《Astrophysics》2011,54(2):162-176
The Schmidt method for constructing the luminosity function of galaxies is generalized to include the dependence of the density
of galaxies on distance in the near universe. The logarithmic luminosity function (LLF) of the field galaxies as a function
of morphological type is constructed. It is found that the LLF for all the galaxies, as well as separately for elliptical
and lenticular galaxies, can be represented as a Schechter function within a narrow range of absolute magnitudes. The LLF
for spiral galaxies is a Schechter function over a rather wide range of absolute magnitudes, −21.0 ≤ M ≤ −14 . The parameter
M* varies little over the spiral galaxies. The parameter α in the Schechter function decreases on going from early to later
spirals. On going from elliptical to lenticular galaxies, from early spiral galaxies and onward to later spiral galaxies,
a decrease in the average luminosity of the galaxies is observed in the bright end, −23 ≤ M ≤ −17.8 . The completeness and
average density of the samples are estimated for galaxies of different morphological types. The average number density of
all the galaxies within the range −23 ≤ M ≤ −13 is 0.126 Mpc-3. 相似文献
2.
Optical spectroscopic data are presented on nova LW Serpentis 1978, obtained during its decline fromV 9.0 to ≃10.2 (compared to a value of ∼ 8.0 at recorded maximum). The spectrum and its evolution compare well with a typical
nova, though the principal absorption (∼ −750 km s−l) was very weak in comparison with the diffuse-enhanced absorption (∼ −1300 km s−1). The principal absorption could be identified only in the lines of O I λλ7774, 8446, and in moderate-resolution observations
of Hα. The salient features of spectral evolution follow: The near-infrared triplet of Ca n continuously weakened. O I λ8446
was always brighter than O I λ 7774, indicating continued importance of Lyman Β fluorescence. The lines due to [O I], [N II]
and N n brightened considerably near the end of our observations (37 days from maximum). The Hα emission line was asymmetric
all through with more emission towards the red. Its emission profile showed considerable structure. Based on the individual
peaks in the Hα line profile, a kinematical model is proposed for the shell of LW Ser. The model consists of an equatorial
ring, and a polar cone on the side away from the earth. The nearer polar cone did not show significant emission of Hα during
our observations. The polar axis of the shell is inclined at a small angle (∼ 15‡) to the line of sight. 相似文献
3.
Davis John K. Geballe Thomas R. Hanner Marthe S. Weaver H. A. Crovisier Jacques Bockelée-Morvan Dominique 《Earth, Moon, and Planets》1997,78(1-3):293-298
We present 10 and 20 μm spectra of comet Hale-Bopp taken at UKIRT on 1996 June 20 and 1996 September 29.The 10 μm spectra
clearly show a strong silicate feature with peaks at 10.0 and 11.2 μm. The 20 μm spectrum on September 29 has strong excess
flux relative to a blackbody and a peak near 19μm, in good agreement with the ISO SWS spectra obtained a week later. However,
the 20 μm spectrum on June 20 has significantly lower flux than would be expected based on a blackbody extrapolation from
the flux at 12.5 μm.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The properties of powerful (flux >10−19 W m−2 Hz−1) type III bursts observed in July – August 2002 by the radio telescope UTR-2 at frequencies 10 – 30 MHz are analyzed. Most
bursts have been registered when the active regions associated to these bursts were located near the central meridian or at
40° – 60° to the East or West from it. All powerful type III bursts drift from high to low frequencies with frequency drift
rates 1 – 2.5 MHz s−1. It is important to emphasize that according to our observations the drift rate is linearly increasing with frequency. The
duration of the bursts changes mainly from 6 s at frequency 30 MHz up to 12 s at 10 MHz. The instantaneous frequency bandwidth
does not depend on the day of observations, i.e. on the disk location of the source active region, and is increasing with frequency. 相似文献
5.
C. E. DeForest J. T. Hoeksema J. B. Gurman B. J. Thompson S. P. Plunkett R. Howard R. C. Harrison D. M. Hasslerz 《Solar physics》1997,175(2):393-410
On 7 and 8 March 1996, the SOHO spacecraft and several other space- and ground-based observatories cooperated in the most
comprehensive observation to date of solar polar plumes. Based on simultaneous data from five instruments, we describe the
morphology of the plumes observed over the south pole of the Sun during the SOHO observing campaign. Individual plumes have
been characterized from the photosphere to approximately 15 R⊙ yielding a coherent portrait of the features for more quantitative
future studies. The observed plumes arise from small (∼ 2-5 arc sec diameter) quiescent, unipolar magnetic flux concentrations,
on chromospheric network cell boundaries. They are denser and cooler than the surrounding coronal hole through which they
extend, and are seen clearly in both Feix and Fexii emission lines, indicating an ionization temperature between 1.0–1.5 x
106 K. The plumes initially expand rapidly with altitude, to a diameter of 20–30 Mm about 30 Mm off the surface. Above 1.2 R⊙
plumes are observed in white light (as ‘coronal rays’) and extend to above 12 R⊙. They grow superradially throughout their
observed height, increasing their subtended solid angle (relative to disk center) by a factor of ∼10 between 1.05 R⊙ and 4–5
R⊙ and by a total factor of 20–40 between 1.05 R⊙ and 12 R⊙. On spatial scales larger than 10 arc sec, plume structure in
the lower corona (R < 1.3 R⊙) is observed to be steady-state for periods of at least 24 hours; however, on spatial scales
smaller than 10 arc sec, plume XUV intensities vary by 10–20% (after background subtraction) on a time scale of a few minutes.
(Dr. Hassler is now employed by Southwest Research Institute, Boulder, CO) 相似文献
6.
A. Takeda 《Solar physics》2011,273(1):295-306
The temperature response functions of the Yohkoh/SXT are re-calculated based on the most recent elemental abundances and ionization balance available in the CHIANTI atomic
database version 6.0.1. The new standard responses are calculated for three types of abundance; i.e., ‘coronal’, ‘hybrid’, and ‘photospheric’ abundances included in the CHIANTI database, and are available in SolarSoft since
2010. Comparison plots of the new and old response functions and filter ratios are available at the Yohkoh Legacy data Archive
(). The three new responses generally peak at higher temperatures (at ≈ 10 MK) than the former standard response (at ≈ 5.6 MK)
based on Mewe’s spectral model. The new responses with coronal and hybrid abundances have higher peak counts by a factor of
3 and 2, respectively, than those with the photospheric abundances and the former response based on Mewe’s model. The correction
of the filter ratios depends on the type of filter and the range of the ratios to be used. In the significant cases, the new
filter ratio produces 20 to 30% higher temperatures than the previous calibration. The choice of elemental abundance has a
strong influence on the derived temperatures and emission measures, and often produces a variation significantly larger than
the statistical and systematic errors considered so far. 相似文献
7.
“Elementary bursts” refer to fine time structures on scales of tens of milli-second to a few seconds in flare radiations.
In this paper, we investigate temporal and spatial properties of elementary bursts by exploiting high-cadence Hα (100 ms)
and hard X-ray (125 – 500 ms) observations of an impulsive flare on March 16, 2000. We find that the time scale of 2 – 3 s
is likely an upper limit of the elementary bursts in this event, at which hard X-ray emissions observed by different instruments
correlate, low energy (≤30 keV) hard X-rays and Hα flux correlate, and Hα emissions at conjugate flare kernels correlate.
From our methods, and also largely limited by instrument resolutions, there is a weak indication of existence of sub-second
structures. With the high-resolution Hα data, we also attempt to explore the spatial structure of “elementary bursts” by determining
the average spatial displacement of Hα peak emission between successive “elementary bursts” defined from hard X-ray light
curves. We find that, at the time scale of 3 s, the smallest spatial scale, as limited by the imaging resolution, is about
0.4″. We discuss these results with respect to mechanisms of fragmented magnetic energy release. 相似文献
8.
R. Vasundhara 《Journal of Astrophysics and Astronomy》1991,12(1):69-87
Results of the observations of mutual eclipses of Galilean satellites observed from the Vainu Bappu Observatory during 1985
are presented. Theoretical models assuming a uniform disc, Lambert’s law and Lommel-Seeliger’s law describing the scattering
characteristics of the surface of the eclipsed satellite were used to fit the observations. Light curves of the 1E2 event
on 1985 September 24 and the 3E1 event on 1985 October 24 observed from VBO and published light curves of the 1E2 event on
1985 September 14, the 3E1 event on 1985 September 26 and the 2E1 event on 1985 October 28 (Arlotet al 1989) were fitted with theoretical light curves using Marquardt’s algorithm. The best fitting was obtained using Lommel-Seeliger’s
law to describe the scattering over the surface of Io and Europa. During the fitting, a parameterδxshift which shifts the theoretical light curve along the direction of relative motion of the eclipsed satellite with respect
to the shadow centre, on the sky plane (as seen from the Sun) was determined along with the impact parameter. In absence of
other sources like prominent surface features or non perfect sky conditions which could lead to asymmetric light curves,δxshift would be a measure of the phase correction (Aksnes, Franklin & Magnusson 1986) with an accuracy as that of the midtime.
Heliocentric Δα cos (δ) and gDδ at mid times derived from fitted impact parameters are reported 相似文献
9.
In addition to the detection of an asteroid moon or a binary asteroid, the knowledge of the satellite’s true orbit is of high importance to derive fundamental physical parameters of the binary system such as its mass and to shed light on its possible formation history and dynamical evolution (prograde/retrograde orbit, large/small eccentricity or inclination, etc.). A new methodology for preliminary orbit determination of binary asteroids – and visual binaries in general – is proposed. It is based on Thiele–Innes method combined with a ‘trial and error’ Monte-Carlo technique. This method provides the full set of solutions (bundle of orbits, with the 7 orbital elements) even for a reduced number of observations. The mass is a direct by-product of this orbit determination, from which one can next infer the bulk-density and porosity. In addition to the bundle of orbits, the method provides the marginal probability densities of the foreseen parameters. Such error analysis – since it avoids linear approximation – can be of importance for the prediction of the satellite’s position in the plane-of-sky during future stellar occultations or subsequent observations, but also for the analysis of the orbit’s secular evolution. After briefly describing the method, we present the algorithm and its application to some practical cases, with particular emphasis on asteroids binaries and applications on orbital evolution. 相似文献
10.
V. N. Melnik A. A. Konovalenko H. O. Rucker V. V. Dorovskyy E. P. Abranin A. Lecacheux A. S. Lonskaya 《Solar physics》2010,264(1):103-117
Solar S-bursts observed by the radio telescope UTR-2 in the period 2001 – 2002 are studied. The bursts chosen for a detailed
analysis occurred in the periods 23 – 26 May 2001, 13 – 16 and 27 – 39 July 2002 during three solar radio storms. More than
800 S-bursts were registered in these days. Properties of S-bursts are studied in the frequency band 10 – 30 MHz. All bursts
were always observed against a background of other solar radio activity such as type III and IIIb bursts, type III-like bursts,
drift pairs and spikes. Moreover, S-bursts were observed during days when the active region was situated near the central
meridian. Characteristic durations of S-bursts were about 0.35 and 0.4 – 0.6 s for the May and July storms, respectively.
For the first time, we found that the instantaneous frequency width of S-bursts increased with frequency linearly. The dependence
of drift rates on frequency followed the McConnell dependence derived for higher frequencies. We propose a model of S-bursts
based on the assumption that these bursts are generated due to the confluence of Langmuir waves with fast magnetosonic waves,
whose phase and group velocities are equal. 相似文献
11.
Graça Rocha 《Astrophysics and Space Science》2003,283(4):589-594
We update the bounds on a time-varying fine structure constant α at the time of BBN (z∼1010) and CMB (z∼103) and present the current CMB constraints on α, through a combined analysis of the BOOMERanG, MAXIMA and DASI datasets. We
also present a discussion of the constraints on α coming from large-scale structure observations, focusing in particular on
the power spectrum from the 2dF survey. Finally we provide a analysis of the degeneracies between α and the other cosmological
parameters and discuss ways to break these with both existing and/or forthcoming data. Our results are consistent with no
variation in α from the epoch of recombination to the present day, and restrict any such variation to be less than about 4%.We
show that the forthcoming MAP and Planck experiments will be able to break most of the currently existing degeneracies between
α and other parameters, and measure α to better than percent accuracy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
J. Javaraiah 《Solar physics》2011,270(2):463-483
Using the combined Greenwich (1874 – 1976) and Solar Optical Observatories Network (1977 – 2009) data on sunspot groups, we
study the long-term variations in the mean daily rates of growth and decay of sunspot groups. We find that the minimum and
the maximum values of the annually averaged daily mean growth rates are ≈ 52% day−1 and ≈ 183% day−1, respectively, whereas the corresponding values of the annually averaged daily mean decay rates are ≈ 21% day−1 and ≈ 44% day−1, respectively. The average value (over the period 1874 – 2009) of the growth rate is about 70% more than that of the decay
rate. The growth and the decay rates vary by about 35% and 13%, respectively, on a 60-year time scale. From the beginning
of Cycle 23 the growth rate is substantially decreased and near the end (2007 – 2008) the growth rate is lowest in the past
about 100 years. In the extended part of the declining phase of this cycle, the decay rate steeply increased and it is largest
in the beginning of the current Cycle 24. These unusual properties of the growth and the decay rates during Cycle 23 may be
related to cause of the very long declining phase of this cycle with the unusually deep and prolonged current minimum. A ≈ 11-year
periodicity in the growth and the decay rates is found to be highly latitude and time dependent and seems to exist mainly
in the 0° – 10° latitude interval of the southern hemisphere. The strength of the known approximate 33 – 44-year modulation
in the solar activity seems to be related to the north-south asymmetry in the growth rate. Decreasing and increasing trends
in the growth and the decay rates indicate that the next 2 – 3 solar cycles will be relatively weak. 相似文献
13.
We present an analysis of the behaviour of the ‘coarse-grained’ (‘mesoscopic’) rank partitioning of the mean energy of collections
of particles composing virialized dark matter halos in a Λ-CDM cosmological simulation. We find evidence that rank preservation
depends on halo mass, in the sense that more massive halos show more rank preservation than less massive ones. We find that
the most massive halos obey Arnold’s theorem (on the ordering of the characteristic frequencies of the system) more frequently
than less massive halos. This method may be useful to evaluate the coarse-graining level (minimum number of particles per
energy cell) necessary to reasonably measure signatures of ‘mesoscopic’ rank orderings in a gravitational system. 相似文献
14.
V. A. Sheminova 《Solar physics》2009,254(1):29-50
The properties of solar magnetic fields on scales less than the spatial resolution of solar telescopes are studied. A synthetic
infrared spectropolarimetric diagnostic based on a 2D MHD simulation of magnetoconvection is used for this. Analyzed are two
time sequences of snapshots that likely represent two regions of the network fields with their immediate surroundings on the
solar surface with unsigned magnetic flux densities of 300 and 140 G. In the first region from the probability density functions
of the magnetic field strength it is found that the most probable field strength at log τ
5=0 is equal to 250 G. Weak fields (B<500 G) occupy about 70% of the surface, whereas stronger fields (B>1000 G) occupy only 9.7% of the surface. The magnetic flux is −28 G and its imbalance is −0.04. In the second region, these
parameters are correspondingly equal to 150 G, 93.3%, 0.3%, −40 G, and −0.10. The distribution of line-of-sight velocities
on the surface of log τ
5=−1 is estimated. The mean velocity is equal to 0.4 km s−1 in the first simulated region. The average velocity in the granules is −1.2 km s−1 and in the intergranules it is 2.5 km s−1. In the second region, the corresponding values of the mean velocities are equal to 0, −1.8, and 1.5 km s−1. In addition the asymmetry of synthetic Stokes V profiles of the Fe i 1564.8 nm line is analyzed. The mean values of the amplitude and area asymmetry do not exceed 1%. The spatially smoothed
amplitude asymmetry is increased to 10% whereas the area asymmetry is only slightly varied. 相似文献
15.
The problem of lithium in chemically peculiar Ap-CP stars has been the subject of debate for many years. The main reason for
this is a lack of spectral observations of Ap stars in the neighborhood of the lithium resonance doublet Li I 6708 Å. An international
cooperation project on “Lithium in cool CP stars with magnetic fields” was started in 1996. Systematic observations of CP
stars in spectral regions of the 6708 Å and 6103 Å lines at the ZTSh (CrAO), CAT (ESO), Feros (ESO), and the 74″ telescope
of the Mount Stromlo Observatory (Australia) have been used to analyze spectra of several CP stars studied by the way the
6708 Å lithium line varies with the stars’ rotational phase. Monitoring of the spectra of the oscillating CP stars (group
I) HD 83368, HD 60435, and HD 3980, for which significant Doppler shifts of the Li I 6708 Å line are observed led to the discovery
of “lithium spots” on the surface of these stars whose positions are related to the magnetic field structure. Models of the
surfaces of these stars with the special program “ROTATE” based on the profiles of the Li I 6708 Å line are used to estimate
the size of the spots, their positions on the stars’ surface, and the lithium abundances in these spots. A detailed analysis
and modelling of the spectra of slowly rotating oscillating CP stars with strong, invariant lithium 6708 Å emission, including
blending with lines of the rare earth elements, reveals an enhanced lithium abundance, with the abundance determined from
the lithium 6103 Å line being higher than that determined from the 6708 Å line for all the stars. This may indicate vertical
stratification of lithium in the atmospheres of CP stars with an anomalous isotopic composition (6Li/7Li = 0.2–0.5). HD 101065, an ultraslow rotator (vsini ≈ 1.5) visible from the poles and with powerful oscillations which cause pulsating line broadening in its spectrum, is unique
among these stars. The amount of lithium in the atmosphere of HD 101065 logN(Li) = 3.1 on a scale of logN(H) = 12.0 and the isotope ratio 6Li/7Li ≈ 0.3. The high estimates of 6Li/7Li may be explained by the production of lithium in spallation reactions and the preservation of surface 6Li and 7Li by strong magnetic fields in the upper layers of the atmosphere near the magnetic poles.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 463–492 (August 2007). 相似文献
16.
V. N. Melnik A. A. Konovalenko V. V. Dorovskyy H. O. Rucker E. P. Abranin V. N. Lisachenko A. Lecacheux 《Solar physics》2005,231(1-2):143-155
The results of observations of solar decametric drift pair bursts are presented. These observations were carried out during
a Type III burst storm on July 11–21, 2002, with the decameter radio telescope UTR-2, equipped with new back-end facilities.
High time and frequency resolution of the back-end allowed us to obtain new information about the structure and properties
of these bursts. The statistical analysis of more than 700 bursts observed on 13–15 July was performed separately for “forward”
and “reverse” drift pair bursts. Such an extensive amount of these kind of bursts has never been processed before. It should
be pointed out that “forward” and “reverse” drift pair bursts have a set of similar parameters, such as time delay between
the burst elements, duration of an element, and instant bandwidth of an element. Nevertheless some of their parameters are
different. So, the absolute average value of frequency drift rate for “forward” bursts is 0.8 MHz s−1, while for “reverse” ones it is 2 MHz s−1. The obtained functional dependencies “drift rate vs. frequency” and “flux density vs. frequency” were found to be different
from the current knowledge. We also report about the observation of unusual variants of drift pairs, in particular, of “hook”
bursts and bursts with fine time and frequency structure. A possible mechanism of drift pairs generation is proposed, according
to which this emission may originate from the interaction of Langmuir waves with the magnetosonic waves having equal phase
and group velocities. 相似文献
17.
The spatial and spectral behaviors of two solar flares observed by the Nobeyama Radioheliograph (NoRH) on 24 August 2002 and
22 August 2005 are explored. They were observed with a single loop-top source and double footpoint sources at the beginning,
then with looplike structures for the rest of the event. NoRH has high spatial and temporal resolution at the two frequencies
of 17 and 34 GHz where a nonthermal radio source is often optically thin. Such capabilities give us an opportunity to study
the spatial and spectral behaviors of different microwave sources. The 24 August 2002 flare displayed a soft – hard – soft
(SHS) spectral pattern in the rising – peak – decay phases at 34 GHz, which was also observed for the spectral behavior of
both loop-top and footpoint sources. In contrast, the 22 August 2005 flare showed a soft – hard – harder (SHH) spectral pattern
for its both loop-top and footpoint sources. It is interesting that this event showed a harder spectrum in the early rising
phase. We found a positive correlation between the spectral index and microwave flux in both the loop-top source and the footpoint
sources in both events. The conclusions drawn from the flux index could apply to the electron index as well, because of their
simple linear relationship under the assumption of nonthermal gyrosynchrotron mechanism. Such a property of spatial and spectral
behaviors of microwave sources gives an observational constraint on the electron acceleration mechanism and electron propagation. 相似文献
18.
Liu Rui-yuan Hu Hong-qiao Liu Yong-hua Xu Zhong-hua Sato N. Fraser B.J. 《Solar physics》2001,204(1-2):305-313
Simultaneous observations at Zhongshan Station, Antarctica, are presented for the interval of 13–17 July 2000 to show responses
of the polar ionosphere to the Bastille Day (14 July 2000) solar event. The polar ionosphere was highly disturbed, as shown
by frequently large deviations of the geomagnetic H-component, large riometer absorption events and strong ULF waves. Associated
with the huge solar proton event produced by the X5/3B flare, a polar cap absorption (PCA) was observed. It began at ∼ 10:40 UT
on 14 July and ended at ∼ 19:40 UT on 17 July. Superposed on it, there was a large absorption event with a peak of 26 dB,
starting at ∼ 03:00 UT and ending at ∼ 11:10 UT on 15 July. This kind of absorption was probably produced by an intense `cloud
of energetic electrons' during an auroral substorm. The ULF waves were very intense during the main phase and the recovery
phase of the severe magnetic storm on 15 and 16 July. The ionospheric absorption was so strong that the digisonde signal was
blacked out most of the time. The ionosphere returned to normal in the afternoon on 17 July. 相似文献
19.
Roberto F. Viotti Rosario González-Riestra Takashi Iijima Stefano Bernabei Riccardo Claudi Jochen Greiner Michael Friedjung Vito Francesco Polcaro Corinne Rossi 《Astrophysics and Space Science》2005,296(1-4):435-439
We review the main characteristics of the symbiotic system AG Draconis, with special emphasis on its optical and X-ray variations.
We also discuss the X-ray to visual energy distribution during quiescence and outburst and describe our spectroscopic and
X-ray observations during the 2003 outburst.
Based on X-ray observations collected with the XMM–Newton Observatory, on INES data from the IUE satellite, and on optical
spectra collected with the Asiago–Cima Ekar, Bologna–Loiano and La Palma–Galileo Italian telescopes. 相似文献
20.
The north – south (N – S) asymmetry of solar activity is investigated by using the data on coronal green-line brightness and
total number and total area of sunspots over the period of 1939 – 2001. Typical time variations of the N – S asymmetry are
found to be consonant in these indices. Quasi-biennial oscillations (QBO) of solar activity are well recognizable in the N – S
asymmetry of the examined indices. Moreover, the QBO are much better manifested in the N – S asymmetry of the individual indices
than in the original (N plus S) indices. The time variations of relative QBO power are synchronous for the N – S asymmetry
of various solar activity indices whereas such a synchronization is weaker for the indices themselves. It is revealed that
the relative QBO power found in the N – S asymmetry of the studied indices has a negative correlation with the value of the
N – S asymmetry itself. The findings indicate that the N – S asymmetry should be regarded as a fundamental phenomenon of solar
activity similarly manifested in different activity indices. These findings should be taken into account when any dynamo theory
of solar activity is constructed. 相似文献