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1.
Xin-Fa Deng 《Astronomy Letters》2019,45(11):740-749
In this work, I construct a LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 from the Sloan Digital Sky Survey Data Release 15 (SDSS DR15), which contains 184172 CMASS LRGs and 27158 eBOSS LRGs and examine the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors in this galaxy sample. I divide this LRG sample into subsamples with a redshift binning size of Δz = 0.01, and analyze the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors for these subsamples in each redshift bin. Overall, the u–r, u–g, g–r, and r–i colors of galaxies in LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 are very weakly correlated with the local environment, which shows that minimal environmental dependence of galaxy parameters can continue to higher redshifts. It is noteworthy that i–z color of this CMASS + eBOSS LRG sample shows substantial correlation with the local environment in the redshift region 0.70 ≤ z ≤ 0.75. 相似文献
2.
R. P. Kane 《Solar physics》2007,246(2):487-493
Three series (1876 – 1986, 1886 – 1996, and 1896 – 2006) of 111 annual values of sunspot number R
z in each were subjected to spectral analysis to detect periodicities by the maximum entropy method (MEM), and the periodicities
so obtained were used in a multiple regression analysis (MRA) to estimate the amplitudes and phases. All series showed roughly
similar spectra with many periodicities (24 or more), but most of these were insignificant. The significant periodicities
(far exceeding 2σ) were near 5, 8 – 12, 18, and 37 years. Using the amplitudes and phases of these, we obtained reconstructed series, which
showed good correlations (+ 0.7 and more) with the original series. When extrapolated further in time, the reconstructed series
indicated R
z(max) in the ranges 80 – 101 (mean 92) for cycle 24 during years 2011 – 2014, 112 – 127 (mean 119) for cycle 25 during years
2022 – 2023, 115 – 120 (mean 118) for cycle 26 during years 2032 – 2034, and 100 – 113 (mean 109) for cycle 27 during 2043 – 2045. 相似文献
3.
Small ballistic ranges were used to perform controlled laboratory shock experiments on 12 selected silicates [quartz (30–310
kb), oligoclase (30–340 kb), andesine (40–100 kb), olivine (80–500 kb), forsterite (50–150 kb), enstatite (60–150 kb), biotite
(10–90 kb), hornblende (50–150 kb, garnet (40–160 kb), kunzite (60–150 kb), beryl (60–140 kb), topaz (60–150 kb)]. At least
4 pressure points per mineral are available.
Debye-Scherrer investigations of shocked materials revealed a gradual lattice breakdown of crystalline matter under shock.
Individual mineral species behave selectively. Sheet silicates break down very easily, followed by tecto-silicates. Chain-,
ino- and ortho-silicates are of considerably higher shock resistance. Depending on the mineral species, the first sign of
shock damage is evidenced in the long range order at 20–70 kb. At intermediate pressures (100–200 kb) the long range order
is essentially destroyed with the short range order heavily disturbed. At pressures exceeding 300 kb tecto-silicates are completely
collapsed. The degree of internal fragmentation is strongly related to shock pressure, thus providing a sensitive tool for
absolute pressure calibration of shocked materials.
The internal fragmentation is structurally controlled, leading to polycrystalline aggregates of strongly preferred orientation.
The grain size distribution of the fragmentation products is highly heterogeneous. The mechanisms leading to fragmentation
as evidenced by the X-ray patterns are highly complex. The formation of high pressure polymorphs is discussed.
Though application of the new results to naturally shocked rocks may have some limitations, the usefulness of Debye-Scherrer
investigations in the study of shocked materials is demonstrated.
Lunar Science Institute Contribution, No 2. 相似文献
4.
In the present work we study (i) the charged black hole in Einstein–Gauss–Bonnet (EGB) theory, known as the Einstein–Maxwell–Gauss–Bonnet
(EMGB) black hole and (ii) the black hole in EGB gravity with a Yang–Mills field. The thermodynamic geometry of these two
black hole solutions has been investigated, using the modified entropy in Gauss–Bonnet theory. 相似文献
5.
We have analysed the observations of Solar Ca+K daily plage area for the period 1951-1977 to find evidence for the existence of short period (around 12–13 days) variation
in the data. We divided the data in three groups—two corresponding to 10–20‡N and 10–20‡S latitude belts, and one corresponding
to the total plage area—and used the power spectrum and autocorrelation techniques for the analysis. Both the techniques clearly
show the 27-day periodicity due to solar rotation modulation in all the sets. A 12–13 day periodicity is seen in only 3, out
of a total of 57 data sets when autocorrelation technique is used. A generally weak peak around 12–13 days is, however, seen
in the power spectrum of all the data sets. The relative power in the 12–13 day peak is found to be significantly higher in
those three data sets where the autocorrelation also shows this periodicity. On these two epochs the sunspot area distribution
showed the existence of two distinct active longitudes separated by about 140–170 degrees. This seems to be the cause for
the existence of a periodicity around 12–13 days in the autocorrelation and enhancement in the relative power of the 12–13
days peak in the power spectrum of these two epochs 相似文献
6.
Variations of solar differential rotation have been studied using observations of solar quiescent Hα filaments obtained during
1965–1993 at the Abastumani Astrophysical Observatory.
In both hemispheres of the Sun, propagation of a quasi-biennial pulse of residual rotation velocities of filaments was found.
There is a pulse drift from high latitudes to the equator in the northern hemisphere in 1968–1970, 1979–1981, 1988–1990 and
in the southern one in 1969–1971, 1979–1981, 1989–1991.
Propagation of a pulse starts near the time of the polarity reversal of the circumpolar regions of the Sun. High-latitude
double peaks of rapid motion were found in the northern hemisphere for cycle 20 and in the southern hemisphere for cycle 22.
The relation of the appearance of suggested double pulse peaks of residual velocities with the threefold polarity changing
of the circumpolar areas is suggested. 相似文献
7.
L. N. Katkar 《Astrophysics and Space Science》2010,326(1):19-26
By adopting the Newman–Penrose–Jogia–Griffith formalism, the field equations in Einstein–Cartan theory for matter with spin
creating torsion in space–time are solved in a spherically symmetric space–time by assuming only one non-vanishing component
of spin. The exact solution might be the prototype for more realistic models. 相似文献
8.
The IRAS and 2MASS associations for 193 T Tauri stars are identified in this paper. From the color–color diagrams and spectral index, it is found that the IR excesses for most samples are due to thermal emission from the circumstellar material, as suggested previously. It is also found that the IR excesses at IRAS region for few T Tauri stars and the near-IR excesses for some T Tauri stars are likely attributed to free-free emission or free-bound emission from the circumstellar ionized gas. Moreover, It is found in deredened J–H versus H–K color–color diagram that there is a slight separation in different spectral groups. The T Tauri stars locus equation in J–H versus H–K color–color diagram for our sample is also presented. 相似文献
9.
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
10.
11.
Kotaro Kohno Koichiro Nakanishi Tomoka Tosaki Kazuyuki Muraoka Rie Miura Hajime Ezawa Ryohei Kawabe 《Astrophysics and Space Science》2008,313(1-3):279-285
Dense molecular medium plays essential roles in galaxies. As demonstrated by the tight and linear correlation between HCN(1–0)
and FIR luminosities among star-forming galaxies, from very nearby to high-z ones, the observation of a dense molecular component
is indispensable to understand the star formation laws in galaxies. In order to obtain a general picture of the global distributions
of dense molecular medium in normal star-forming galaxies, we have conducted an extragalactic CO(3–2) imaging survey of nearby
spiral galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). From the survey (ADIoS; ASTE Dense gas Imaging
of Star-forming galaxies), CO(3–2) images of M 83 and NGC 986 are presented. Emphasis is placed on the correlation between
the CO(3–2)/CO(1–0) ratio and the star formation efficiency in galaxies. In the central regions of some active galaxies, on
the other hand, we often find enhanced or overluminous HCN(1–0) emission. The HCN(1–0)/CO(1–0) and HCN(1–0)/HCO+(1–0) intensities are often enhanced up to ∼0.2–0.3 and ∼2–3, respectively. Such elevated ratios have never been observed
in the nuclear starburst regions. One possible explanation for these high HCN(1–0)/CO(1–0) and HCN(1–0)/HCO+(1–0) ratios is X-ray induced chemistry in X-ray dominated regions (XDRs), i.e., the overabundance of the HCN molecule in
the X-ray irradiated dense molecular tori. If this view is true, the known tight correlation between HCN(1–0) and the star-formation
rate breaks in the vicinity of active nuclei. Although the interpretation of these ratios is still an open question, these
ratios have a great potential for a new diagnostic tool for the energy sources of dusty galaxies in the ALMA era because these
molecular lines are free from dust extinction. 相似文献
12.
It is shown that an analog of Birkhoff’s theorem of general relativity exists in the Einstein–Cartan–Kalb–Ramond (ECKR) theory
of gravity when Kalb–Ramond (KR) field strength, which occurs in the theory is independent of time. 相似文献
13.
Evaluation of the intermediate-term periodicities in solar and cosmic ray activities during cycle 23
In this paper we investigate the presence and temporal evolution of galactic cosmic rays (GCRs) time-series and three solar
parameters, namely the daily sunspot number, the coronal green line and the 10.7 cm solar radio flux over the period 1996–2003
by the wavelet technique. A number of short- and intermediate-term quasi-periodicities were also detected in both GCR and
solar parameters. For the short-term range, we have identified quasi-periods of 16–30 days, 40–55 days, 60–70 days, 80–90 days
and 80–100 days. In the case of intermediate range, the significant periods were 120–140 days, 150–170 days, 190–210 days,
240–260 days, ≈1.09 yr. and ≈1.23 yr. The wavelet power spectra show that all the above-mentioned periods are intermittent
in nature and occurred in different time-series in different intervals. The result exhibits that the well-known “Rieger period”
of (150–160 days) was prominent in both GCR and solar data sets during the ascending phase of cycle 23. Possible reasons behind
the observed periods were discussed with the help of previous results and existing numerical models. 相似文献
14.
In the present study, the short-term periodicities in the daily data of the sunspot numbers and areas are investigated separately
for the full disk, northern, and southern hemispheres during Solar Cycle 23 for a time interval from 1 January 2003 to 30
November 2007 corresponding to the descending and minimum phase of the cycle. The wavelet power spectrum technique exhibited
a number of quasi-periodic oscillations in all the datasets. In the high frequency range, we find a prominent period of 22 – 35
days in both sunspot indicators. Other quasi-periods in the range of 40 – 60, 70 – 90, 110 – 130, 140 – 160, and 220 – 240
days are detected in the sunspot number time series in different hemispheres at different time intervals. In the sunspot area
data, quasi-periods in the range of 50 – 80, 90 – 110, 115 – 130, 140 – 155, 160 – 190, and about 230 days were noted in different
hemispheres within the time period of analysis. The present investigation shows that the well-known “Rieger periodicity” of
150 – 160 days reappears during the descending phase of Solar Cycle 23, but this is prominent mainly in the southern part
of the Sun. Possible explanations of these observed periodicities are delivered on the basis of earlier results detected in
photospheric magnetic field time series (Knaack, Stenflo, and Berdyugina in Astron. Astrophys.
438, 1067, 2005) and solar r-mode oscillations. 相似文献
15.
The cosmic-ray (CR) time series were compared with the green 530.3 nm coronal emission line intensity over the period 1951–2003.
There is a clear asymmetry in the cross-correlation between the cosmic rays and green emission corona for the even- and odd-numbered
solar cycles, where a time lag is ranging between 0 and 380 days. While over the period 1954–1964 and 1978–1985 the time lag
is above 200 days, over the period 1965–1976 and 1986–1995 the time lag is below 130 days. A possible reason for the lag asymmetry
is discussed. The cross-correlations between the cosmic rays and Wolf sunspot number over the period 1951–2003 is also presented. 相似文献
16.
Yves Grandati Alain Bérard Hervé Mohrbach 《Celestial Mechanics and Dynamical Astronomy》2009,103(2):133-141
In the category of motions preserving the angular momentum direction, Gorringe and Leach exhibited two classes of differential
equations having elliptical orbits. After enlarging slightly these classes, we show that they are related by a duality correspondence
of the Arnold–Vassiliev type. The specific associated conserved quantities (Laplace–Runge–Lenz vector and Fradkin–Jauch–Hill
tensor) are then dual reflections of each other. 相似文献
17.
Navin Chandra Joshi Neeraj Singh Bankoti Seema Pande Bimal Pande Kavita Pandey 《Solar physics》2009,260(2):451-463
In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP)
for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and
asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution
shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West
(E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice
in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar
cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in
the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical
study shows that the N – S asymmetry is more significant then the E – W asymmetry. 相似文献
18.
Morgenthaler Jeffrey P. Harris Walter M. Scherb Frank Doane Nathaniel E. Oliversen Ronald J. 《Earth, Moon, and Planets》2002,90(1-4):89-97
We present hydrogen Balmer-α spectra of comet C/1995 O1(Hale–Bopp) recorded on 5 nights from 1997 February 1 to April 19 by
ahigh-resolution (Δ v = 5 km s-1) Fabry–Pérot spectrometer for a4'.1 (∼2.7 × 105 km) FOV centered 5' sunwardof the nucleus. The Hα line profile is an important diagnostic ofphotolytic heating in cometary
atmospheres. Extraction of the spectrafrom the Fabry–Pérot ring images was complicated by obscuration of the telescope FOV
due to Hale–Bopp's low elevation, but the measuredH-α line widths of 11–13 km s-1 (FWHM) are insensitive to the spectral extraction technique. The line widths are consistent withestimates derived from a
successful model of Hale–Bopp's hydrogenLyman-α coma assuming the inner coma is opaque to Hα. Wediscuss methods for improving
the spectral extraction technique andderiving a precise instrument profile which will allow the detailedshape of the line
profile to constrain coma models. 相似文献
19.
L. N. Dzhimbeeva 《Solar System Research》2011,45(1):84-91
The use of integral characteristics of radio spots showed that in addition to the known 3–5-min oscillations, the above-spot
regions of sunspots exhibit quasiperiodic oscillations of intensity, perimeter, sectional area, and area of the surface of
the above-spot source radio image with periods in the ranges of 25–80, 90–110, 120–140, and 160–210 min. These periods are
observed for all spots studied using the different characteristics of a radio source, which does not contradict the interpretation
of these low-frequency oscillations as natural oscillations of spots near a certain position of stable equilibrium. 相似文献
20.
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