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1.
A comparison between theGeneral Catalogue of Cool Carbon Stars (CCS) and theAFGL Catalogue has been performed.Eighty-five stars have been found in common between the two lists. Eighty-four stars which were present in Baumert's comparison between CCS and the 2 Sky Survey have no counterpart in the AFGL. Four new tentative identifications are given. The analysis of the two colours diagrams K-[4.2 ] vs. I-K and I-[4.2 ] vs. [4.2 ]-[11 ] led to the conclusion that all the infrared emission from the sources seems to come from a single circumstellar shell.  相似文献   

2.
The spectra of galactic infrared sources over the waveband 2.5–4 m provide clear evidence for an organic composition of interstellar grains.  相似文献   

3.
Optical identification of infrared sources from the IRAS Point Source Catalogue (PSC) is made by means of low-dispersion spectra of the First Byurakan Survey (FBS) and Palomar Observatory Sky Survey (POSS) red and blue images. The purpose of this work is to examine the composition of the PSC sample of fainter sources at high galactic latitudes and to reveal QSOs, infrared galaxies, red stars (C and M), planetary nebulae, for their further investigation at the optical range. 100 of 108 unknown IRAS sources in the region with 3h50m 7h40m and + 69° + 73° are optically identified. Optical coordinates, V magnitudes, color indices, and preliminary classes are determined. According to preliminary classification 3 objects turned out to be QSOs, 36 are galaxies with very interesting morphology, 5 are faint planetary nebulae, 9 are carbon stars, and 47 are late M-type stars.Published in Astrofizika, Vol. 38, No. 4, pp. 625–629, October–December, 1995.  相似文献   

4.
The IR emission of 640 Markarian galaxies (MrkG), included in the IRAS Survey, is considered as an evidence for enhanced star formation rate (SFR) in these objects. About 73% of the MrkG have high far-infrared luminosities (ca. 10E + 44 erg s–1) in 1–500 mcm IR spectral band. The distribution of log(f 60/f 100), peaked at about 45 K, shows that IRAS MrkGs have a tendency to extend the relationf 60/f 100 vsL ir/L bifor normal S glaxies. They emit up to hundred times more IR energy in 40–120 mcm band than in optics. The mean ratio log L ir/L b for 621 IRAS MrkG with known redshifts is 2.2.It is suggested that there are two IR emitting components in the IRAS MrkG - a warm one connected with the UV-fluxes of the newborn massive stars, re-radiated by dust, and a cool one, originated from the dust in galactic disks and heated by the general interstellar radiation field. The warm IR luminosities and warm IR fractions are determined on the basis of IR colour-colour diagrams(25/12),(60/25), and(100/60). The mean warm IR fraction for all Mrk IRAS detected galaxies with well-defined IR fluxes is 0.83 when the grain mass absorption coefficient model withn = 0.0 is used. The dust mass responsible for the IR flux at 60 mcm is derived to be about 10E + 5M , assuming the dust clouds are optically thin, and using the dust temperatureT d 46 K (deduced from thef(60)/f(100) ratio). There is a relation betweenL irandL blwhich points out that the most IRAS MrkG have rather enhanced SFR.  相似文献   

5.
The main constituents of the dust, produced around late-type carbon stars, are thought to be carbon and silicon carbide (SiC), although their exact nature is not yet well established. This subject has been addressed by several authors and good fits of a large number of IRAS sources (chosen among the carbon stars exhibiting the SiC feature at about 11.3 m) were obtained. In this work we use the same procedure on a limited number of objects, of the same type, taking into account the variability of such sources and the changes induced in their IR spectra. For this purpose, the chosen stars have been observed with a spectral resolution higher than that available for the IRAS data (/ 50), using the CGS3 instrument of the UKIRT telescope, both in the low ( / 160) and in the high ( / 500) resolution configuration. The results are discussed and some preliminary conclusions are drawn.  相似文献   

6.
We have detected 1.1 mm continuum emission from 24 of 53 Herbig Ae/Be stars surveyed with the JCMT. Survival analysis shows that 1.1 mm luminosity is correlated with bolometric luminosity and with IRAS 25µm luminosity. For those stars that were also detected at 0.45 or 0.8 mm we find a typical flux dependence of the form S #x03BD; 3, which is steeper than that of most classical T Tauri stars.  相似文献   

7.
The observed energy spectra in synchrotron sources are power laws,N (E)=KE –, with the distribution in peaked around 2.5. These are consistent with initially injected spectra with between 1 and 2, subsequently steepened by synchrotron losses. Contrary to the results of Kardashev (1962), it is shown that statistical acceleration when coupled with synchrotron losses lead naturally to the formation of flat stationary spectra with 1. These stationary spectra have bends near the energy at which synchrotron losses balance the energy gains by acceleration. Above this bend the spectrum tends to =2. The time evolution of an initial spectrum towards the stationary spectrum is investigated. It is suggested that the initially flat spectra with 1 to 1.5 observed in some variable sources result from an incomplete approach to the stationary spectrum, and that in sources with constant acceleration spectra with 2 are to be expected.  相似文献   

8.
A sample of 14708 extragalactic IRAS sources selected from the Point Source Catalog via statistical classification has been cross-correlated with the ROSAT All Sky Survey (Bolleret al., 1992). 244 galaxies emerge as being detected both by ROSAT and IRAS.The most interesting point is the discovery of a dozen of normal spirals whose X-ray luminosities reach nearly 1043 erg s–1 (0.1–2.4 keV), higher than previous detection limits of a few 1041 erg s–1 (Stockeet al. 1991; Green, Anderson and Ward, 1992). We obtained optical spectra for nine of them, showing Seyfert spectra for three of the objects (thus previous mis-classifications), spectra close to LINERs for two further objects and normal IRAS galaxy spectra for the last four.In the case of normal galaxies, the source of energy is not clear yet and could be related to the high rate of star formation likely to occur in the central regions or also to a low level active nucleus. The study of these objects is of interest to the nature of LINERs and, more generally, to possible relations between AGN and starbursts (Sanderset al., 1988).  相似文献   

9.
The eighth list of blue stellar objects in the second part of the First Byurakan Spectral Sky Survey (FBS) is presented. The objects are located in the zone +65° +69° and 5 h 15m 18 h 05m.The list contains data on 98 blue stellar objects detected, of which 73 are previously unknown. A preliminary classification of the objects is given. The exact coordinates of the centers and the limiting magnitudes of the plates for this zone have been determined using the charts of the Palomar Sky Survey.Translated from Astrofizika, Vol. 37, No. 2, pp. 197–206, April–June, 1994.This work has been performed with financial support of the ESO C&EE fund (A-02-043).  相似文献   

10.
We study near-Lagrange collinear configurations in the three-dimensional three-body problem, with arbitrary gravitating masses. A general method, previously developed for Coulombian systems, which provides a unique formalism for treating few-body systems close to the breakup threshold, has been employed to study the motion of three bodies both for bounded and unbounded configurations. The dependence of the triple-escape function on the small total energy E has been evaluated, as well as rovibronic configurations for bounded motion. An approximate characteristic constant is found for symmetrical systems, /, where and are the vertical libration mode and rotational mode angular frequencies, respectively, and is the threshold exponent. For equal-mass systems this constant acquires the value 1.05288.  相似文献   

11.
A fifth list of point sources from the IRAS Point Source Catalog (PSC) that are optically identified with stars of late spectral types is given. The list contains data on 75 objects. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps of the Palomar Observatory Sky Survey, and infrared fluxes at the wavelengths 12, 25, 60, and 100 m in the regions of +73° +80° and 03h30m 18h30m and of +80° +90° and 00h00m 20h00m. Of the 99 objects, which are given in the IRAS PSC as unidentified sources of infrared emission, 24 are associated with known stars in existing catalogs while 75 sources proved to be unknown in the optical range. The optical coordinates, their departures from the IR coordinates, the V stellar magnitudes, the color indices CI, and the preliminary spectral subtypes have been determined. The objects have optical magnitudes in the range of 6 m .5-17 m .2. Finder charts from the DSS are given for the 69 new objects.  相似文献   

12.
We have searched for CO outflows in eight embedded IRAS sources located in the Taurus molecular cloud using the 45m telescope of Nobeyama Radio Observatory. We have detected CO wing emission in four of these sources. CO outflow associated with TMC1A (04365+2535) is strong and spatially compact (radius 0.04 pc). The dynamical timescale of 2.5 × 103 yr suggests this outflow is the youngest one in Taurus.We have combined our data with previously published survey data and have analyzed the physical properties of the outflow sources. We found that 12 out of 16 embedded sources ( 75 %) have CO outflows associated with them; this indicates that almost all stars experience a phase of molecular outflow in their embedded stage. The IRAS color of the outflow sources suggests that the outflows appear in considerably early phase of the evolution of YSOs, that is, as early as YSOs became observable with IRAS and that visible outflow sources are in a transient phase of evolution between embedded sources and visible T Tauri stars without outflow. Visible outflow sources are systematically more luminous than visible no-outflow sources, while embedded outflow sources have comparable luminosities with visible no-outflow sources. Such luminosity function suggests that the YSOs with outflow undergo mass accretion and increase their stellar mass as they progress from embedded sources to visible outflow sources. Typical mass accretion rate derived from the bolometric luminosity is 2 ×10–6 M yr –1. The timescale for mass accretion to acquire typical stellar mass, 0.5 – 0.8M , is 2.5 – 4 × 105 yr.  相似文献   

13.
A sixth list of objects from the BIG (Byurakan—IRAS galaxies) sample is given: 87 galaxies identified with 60 point sources from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps from the Palomar Observatory Sky Survey, and infrared fluxes at 12, 25, 60, and 100 µm in the region of +65° +69° and 9h15m 14h00m with an area of 111 deg2. We determined the optical coordinates of the identified galaxies, their departures from the IR coordinates, and their V magnitudes, morphological types, angular sizes, and position angles. The objects have optical magnitudes in the range of 12 m .5-21 m .5 and angular sizes in the range of 2-29. Finder charts from the DSS are given for these objects.  相似文献   

14.
I compute the maximum number of observable brown dwarfs for various infrared surveys by combining the maximum possible Oort limit (0.1 missing Mpc–3 with all possible brown dwarf mass and age distributions. This approach shows what limits will be placed on the contribution of brown dwarfs to any possible missing mass if no brown dwarfs are observed. I consider brown dwarfs with masses of 0.01—0.08 M and ages of 109—1010 years.The full range of predicted numbers of brown dwarfs above 6 times the noise of each of the below surveys is: IRAS Point Source Catalog 0.02—6 IRAS Faint Source Catalog |b| > 10° 0.05—16 ISO (2 week 12µm survey) 0.15—80 SIRTF (2 week 12µm survey) 2.50—1600 WIRE (4 month 12µm survey) 21.80—6000 DENIS (half sky) |b| > 10° 0.00—2000 2MASS (full sky) |b| > 10° 0.00—8000A failure to find brown dwarfs in the IRAS FSC would just barely rule out about half of the mass—age range for Oort limit total masses. A failure to find brown dwarfs in 2MASS/DENIS would rule out roughly the same mass—age range, but would set a limit of 0.1—0.01 times the Oort mass in that mass—age region. No limits would be set for the other half of the mass—age range since both IRAS and 2MASS/DENIS have insufficient sensitivity for brown dwarfs with T < 750 K.A failure to find brown dwarfs with ISO would rule out almost all of the mass—age range for Oort limit total masses, but would not set a significantly lower limit to the brown dwarf mass limit. A failure to find brown dwarfs with SIRTF or WIRE would rule out the entire mass—age range for Oort limit total masses and set an upper limit of 0.1—0.001 times the Oort mass.To date, about 18% of the IRAS FSC has been searched down to 6, and no brown dwarfs have been found. This sets a 95% upper limit of 3 in 18% of the sky, or 13 in the entire FSC for |b| > 10°. To begin to set useful limits from 2MASS or DENIS, approximately 400 square degrees needs to be analyzed. To date, only a few square degrees of results from the 2MASS prototype camera have been examined, with no brown dwarfs found so far.  相似文献   

15.
Further exploration of the -field theory as first proposed by Yu (1989) is here presented to cover the equation of motion of a test particle which induces gravitational radiation. The same theory is shown to contain an exact gravitational radiation equation derived as a logical consequence of field equations without extra postulates. In this general dynamic context the theory is renamed The (,A µ )-field Theory.  相似文献   

16.
Wan, Wilson and Sen (1986) have examined the scope of Modified Spherical Harmonic Method in a plane medium scattering anisotropically. They have used the phase functionp(µ, µ) = 1 +aµµ. In this paper, the Transfer Equation has been solved by the Modified Spherical Harmonic Method using the phase functionp(µ, µ) = 1 + 1 P 1(µ)P 1(µ) + 2)P 2(µ)P 2(µ) and a few sets of numerical solution have been predicted for three different cases.  相似文献   

17.
Following the discovery, by IRAS, of the dust disc around Vega and three other main sequence stars, searches have been made for other candidates. The-Pic-like candidates have 12µm excesses and 100µm fluxes (unlike the Vega-like candidates), so they can be further investigated using ground-based techniques. Data are presented here, comprising 10µm spectroscopy and sub-mm observations, for several candidates from the Walker & Wolstencroft list, showing that the stars have silicate dust, and optically thick dust discs even at 1300µm.  相似文献   

18.
A crossed Yagi antenna array at 35 MHz was employed in conjunction with a polarization switch so as to enable spectral observations of solar noise storm activity in R and L polarizations. Intense decametric solar noise storms were recorded during the third week of November 1975 and fourth week of March 1976 with the help of a high resolution spectroscope operating near 35 MHz.The paper describes some of the new microscopic spectral features observed during these two noise storms. Three sets of high resolution dynamic spectra of decametric solar bursts, two of which are explained in terms of induced scattering of Langmuir waves by thermal ions and the third in terms of additional propagation effects through dense coronal irregularities, are presented. The microscopic bursts, classified as inverted U U and dots, represent small-scale (104 km) phenomena with durations of less than a second.Some burst spectra appear as chain of dots with individual bandwidths 40 kHz and durations 0.3 sec. It is suggested that the bandwidth of such dot emissions (40 kHz) provides an evidence that they might indeed be generated by the process of induced scattering of plasma waves which predicts emission bandwidth f × 10–3, where f is the center frequency.Some bursts are observed as a chain of striations showing curvature along the frequency axis which is attributed to dispersion in propagation delays through the dense coronal irregularities.  相似文献   

19.
To explain the scattering of sunlight observed from theF-corona and from the zodiac, the scattering particles must have radii of order 15 m, and must have an imaginary component of the refractive index that requires the presence of from 5 to 10% of free carbon. The particles, therefore, have a composition very like the material of C 1 carbonaceous chondrites and like extraterrestrial particles which have been recovered from the high atmosphere.Such particles absorb sunlight, the absorbed solar energy being reradiated in the infrared with a close approximation to black-body emission, even as far into the infrared as 100 m, a deduction in good agreement with recently published observations from the IRAS satellite.The IRAS observations at high ecliptic latitudes require similar particles to be present in large quantity in the interstellar medium, 106 solar masses or more of them. The presence of such a quantity of material with properties very like the material of the C 1 carbonaceous chondrites is a remarkable outcome of the IRAS observations and is likely to have profound implications in many directions.  相似文献   

20.
We show that a 3 extinction feature in galactic infrared sources cannot be due to water-ice grains. Infrared spectra with a resolution of /=0.015 are in remarkably close agreement with the 2.5–4 extinction properties calculated for bacterial grains.  相似文献   

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