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941.
Part five of optically identified point sources from the IRAS Point Source Catalog (PSC) contains data on 19 late-type stars.
The identifications were based on the Digitized Sky Survey (DSS), the First Byurakan Survey (FBS), blue and red maps of the
Palomar survey (POSS), and infrared fluxes at 12, 25, 60, and 100 mm in the region of +61° ≤ δ ≤ +65° and 05
h
30
m
≤ α ≤ 18
h
35
m
with an area of 357 sq. deg. Of the 76 objects given in the IRAS PSC as unidentified sources of infrared radiation, 51 are
associated with known stars in existing catalogs, 6 are objects from the FBS of late-type stars, and 19 sources remained unknown
in the optical range. For the identified stars we determined the optical coordinates, their departures from the IR coordinates,
the Vstellar magnitudes, the color indices CI,and the preliminary spectral subtypes. The objects have optical magnitudes in the range of 8
m
−16
m
.Gas-dust shells are assumed to exist around four of the sources. Finder charts from the DSS are given for 19 of the objects.
Translated from Astrofizika, Vol. 42, No. 1, pp. 53–59, January–March, 1999. 相似文献
942.
943.
ZHAO Xiaoxia Michael G FOX David C. LASENBY Alexis C. ARMIT Dolly N. KOTHAWALA 《中国海洋湖沼学报》2007,25(2):215-220
The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas. 相似文献
944.
Pavlenko E. P. Sosnovskii A. A. Antonyuk K. A. Antonyuk O. I. Pit’ N. V. Kokhirova G. I. Rakhmatullaeva F. J. Baklanov A. V. 《Astrophysics》2021,64(3):293-305
Astrophysics - Photometric studies of the type SU UMa dwarf nova NY Her were made during 2017 and 2020 at the Crimean Astrophysical Observatory and at the Sanglokh Observatory over a total of 77... 相似文献
945.
946.
947.
A few methods of estimating Fried's parameter (r
0) from specklegrams of solar features are described. Some of these methods were used to estimate r
0 for the speckle data obtained from Kodaikanal Observatory (KO), Uttar Pradesh State Observatory (UPSO) and Udaipur Solar Observatory (USO). The average value of r
0 was found to be 3 cm at USO and UPSO during our observations. At KO, values of r
0 ranging from 6 to 10 cm were estimated. 相似文献
948.
The pseudo-luminosity effect in the metallic line A-type stars found by Abt & Morgan (1976) is confirmed in a random sample of 27 Am stars. From a morphological study of their spectra in the wavelength interval 3850-4400 Å at a reciprocal dispersion of 66 Å/mm, revised spectral types are given on the MK system for their K-line and metallic-line spectra. This shows that: (a) our segregation of weak Am from the Am stars largely agrees with that by Cowleyet al. (1969); (b) all the stars in the sample are dwarfs according to their K-line classification; (c) more than 80 per cent exhibit the pseudo-luminosity effect significantly, with their metallic-line spectra resembling a giant or even a supergiant in the violet (3850-4100 Å), and a giant rather than a dwarf in the blue region (4260-4400 Å); (d) in two-thirds of the stars under (c), the Sr n 4077 Å line is found to have a markedly brighter luminosity class compared to any region, and in more than one-third of the sample it is comparable to that in Ap stars; (e) at least five stars exhibit characteristics which might suggest a spectrum variability: among these, the most striking example is 41 Sex A which was found to show a phase-modulated spectrum variation hitherto unknown in Am stars; (f) the metallic-line spectra of another five stars appear to be similar to A-shell type in differing degrees; (g) less than 20 per cent of the sample comprises stars which do not show any significant differential luminosity effect; these stars might have been misclassified or perhaps they are in a quiescent state. We also confirm the conclusion arrived at by Böhm-Vitense & Johnson (1978) that all Am stars may vary and our observations suggest that groups may exist among them. 相似文献
949.
950.
V. Chavushyan R. Mujica A. G. Gorshkov V. K. Konnikova M. G. Mingaliev 《Astronomy Letters》2000,26(6):339-343
We obtained optical spectra of four objects identified with variable radio sources. Three objects (0029+0554, 0400+0550, 2245+0500) were found to be quasars with redshifts of 1.314, 0.761, and 1.091. One object (2349+0534) has a continuum spectrum characteristic of BL Lac objects. We analyze spectra of the radio sources in the range 0.97–21.7 GHz for the epoch 1997 and in the range 3.9–11.1 GHz for the epoch 1990, as well as the pattern of variability of their flux densities on time scales of 1.5 and 7 years. 相似文献