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1.
The hump in the ultraviolet part of the interstellar extinction curve is interpreted as a broad diffuse absorption band. Its equivalent width is estimated for 36 stars by means of OAO-2 data. The equivalent widths are correlated with the following parameters: colour excessE(B-V), colour excessE(B – V), depth of the band m max, equivalent widths of the diffuse bands at 5780 and 6284 Å, and the column density of neutral hydrogenN HI. The physical parameters half-width and oscillator strength of the band at 2175 Å are estimated.  相似文献   

2.
Data on interstellar extinction are interpreted to imply an identification of interstellar grains with naturally freeze-dried bacteria and algae. The total mass of such bacterial and algal cells in the galaxy is enormous, 1040 g. The identification is based on Mie scattering calculations for an experimentally determined size distribution of bacteria. Agreement between our model calculations and astronomical data is remarkably precise over the wavelength intervals µ–1 < ;–2 < 1.94µ–1 and 2.5µ–1 < ;–1 < 3.0 ;–1. Over the more restricted waveband 4000–5000 Å an excess interstellar absorption is found which is in uncannily close agreement with the absorption properties of phytoplankton pigments. The strongest of the diffuse interstellar bands are provisionally assingned to carotenoid-chlorophyll pigment complexes such as exist in algae and pigmented bacteria. The 2200 Å interstellar absorption feature could be due to degraded cellulose strands which form spherical graphitic particles, but could equally well be due to protein-lipid-nucleic acid complexes in bacteria and viruses. Interstellar extinction at wavelengths <1800 Å could be due to scattering by virus particles.  相似文献   

3.
Medium-resolution (1.5-2.5 Å) spectrum has been obtained for SC star GP Ori in a wide range of wavelengths from 3730 to 6250 Å. It is characterised mainly by strong atomic lines, as well as moderately strong bands of the CN violet system and CH (0,0) and (0,1) bands at 4315 and 4890 Å. Weak bands of C2, C3, and ZrO molecules are observed, however, no evidence is found for the presence of either SiC2 (Merrill-Sanford bands) or YO. The most prominent atomic lines along with the NaID12 are those of CaII (K,H), CaI at 4227 Å, SrI at 4607 Å, SrII at 4077 and 4215 Å, and BaII at 4554 Å. H seems to be in emission.  相似文献   

4.
Twenty-eight of the thirty-nine diffuse interstellar bands identified by Herbig (1975) are shown to constitute three vibronic systems with origins at 14 321, 15 153, and 15 343 cm–1 (vac). Structure within these three systems arises from the excitation of vibrational modes withv 1=275 cm–1,v 2=445.5 cm–1, andv 3=793 cm–1. The electronic origins at 14 321 and 15 343 cm–1 correspond to narrow lines observed in the spectrum of Cr3+ ions at cubic sites in MgO solids while the 15 153 cm–1 origin arises in Mn4+ : MgO. Hence, many of the diffuse bands in the visible likely are due to small MgO particles containing these ions. This observation is compatible with recent experimental data showing broad bands at 160 nm and 220 nm from finely divided MgO solids that match features in the interstellar extinction curve.  相似文献   

5.
Surface excitons in very small (10–20 Å) particles of MgO and CaO and other oxides are shown to absorb at the wavelength of the 2175 Å extinction bump. Required column densities of these oxides are compatible with cosmic elemental abundances if it is assumed that the Mie scattering theory is invalid for these quantum particles.  相似文献   

6.
It is suggested that certain sharp lines in the visible and near ultraviolet spectra of nebule may be due to fluorescence from grains. Evidence is presented that some of these lines could arise from MgO or CaO grains. Some sharp diffuse interstellar bands may also appear in the spectra of nebulae.  相似文献   

7.
The possiblity of the excitation of a new class of spectral lines, so calledpseudo-resonance absorption lines in the conditions of planetary nebulae, is predicted. These lines are formed by permitted atomic transitions from the metastable levels to the upper subordinate, but not metastable, levels. To observe pseudo-resonance lines of nebular origin is possible only on the spectra of the nuclei of planetary and diffuse nebulae in the form of absorption lines.The preliminary list of pseudo-resonance lines is given in Table I; all of them are located in the region of vacuum ultra-violet (1000–3000 Å), therefore, their observation is possible only under space conditions.In stellar photospheres as well as in the interstellar medium the formation of pseudo-resonance lines is impossible.  相似文献   

8.
We show that the recently observed 3.3 m emission feature in the diffuse radiation from the galactic disk might be due to an ensemble of aromatic molecules distributed within very small interstellar grains. The same particles also provide an explanation of the 2200 Å interstellar absorption feature.  相似文献   

9.
Moderate dispersion (25–35 Å mm–1) spectra were obtained from two carbon stars, LW Cyg and Y Tau, in a wide range of wavelengths ( 3400–6800 Å) with the 6 m echellespectrometer ZEBRA and two dimensional photon-counting system. Spectral feature identification was carried out from 3800 to 6300 Å. Most of the bands are due to C2, CN, and SiC2, however, atomic lines of the iron peak and s-process element also are represented. LW Cyg have intense isotopic carbon bands. The wavelengths and band-intensity were estimated.  相似文献   

10.
After general remarks on the diffuse interstellar lines (DIL) the necessity to select the objects under investigation upon astrophysical criteria is stressed. The dependence on galactic longitude of the relative strength of the DIL at =4430 Å is given. A possible connection between the strength of DIL originating in stellar aggregates and radiation density is shown and discussed.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.  相似文献   

11.
The diffuse interstellar absorption bands at 4890 and 6180 are believed to belong to electric quadrupole transitions enforced by the presence of the interstellar magnetic field. Their intensities relative to the bands at 4430 and 4760 and their state of polarisation might be used for an investigation of the field.  相似文献   

12.
The paper presents a survey of profiles of reasonably strong diffuse interstellar bands (DIBs) based on the extensive set of high-resolution spectra acquired with the aid of echelle spectrographs installed at the 2-m Terskol, 2-m Pic du Midi and 1-m SAO telescopes. The surveyed diffuse interstellar bands cover the spectral ranges of blue and near-infrared, i.e the DIBs not surveyed by Krełowski & Schmidt . The possible modifications caused by stellar and telluric lines are discussed. The very broad features such as 4430 are not discussed because the shapes of their profiles, extracted from echelle spectra, are very uncertain. The signal-to-noise (S/N) ratios of the spectra are not high enough to enable discussion of the profiles of numerous weak interstellar features discovered recently.  相似文献   

13.
The 3.28 m feature observed in the diffuse galactic emission and the 2200 Å interstellar extinction feature must have a common source. This requirement rules out graphitic-type PAH molecules such as coronone and tends to favour naturally occurring bi-cyclic ring structures typified by quinoline and its derivatives.  相似文献   

14.
The consequences on the chemistry in diffuse clouds of the injection of small hydrocarbon molecules is explored. It is assumed that the injection arises from the erosion of carbonaceous grains at cloud boundaries, and that the injected species take part in conventional interstellar chemistry. The models indicate that for plausible injection rates the daughter species of the injected parent molecules should appear in significant amounts, at least during the injection period, and that daughter species can appear in gas that is otherwise almost entirely atomic. Therefore, injection of hydrocarbons is a mechanism that is capable of providing polyatomic molecules in detectable amounts in diffuse atomic regions of the interstellar medium. The implications of this result for the carriers of the unidentified diffuse interstellar bands are briefly described.  相似文献   

15.
The coefficients of correlation between spectroscopic data published by Yamashita (1967) and others for carbon stars and the statistical population indices calculated for these stars at the Toru Observatory are calculated (Table II). The intensity estimates of Cai 4227 Å, Nai D lines, the C13/C12 ratio, then=n(Li/Ca) index, as well as CN and probably C2 bands are higher in population I carbon stars. The CH(G) band and probably hydrogen (H, H, H) lines as well as Baii 4554 and 4934 Å lines are stronger in population II carbon stars. The photoelectric colour indices, corrected for interstellar reddening do not show significant population effects. They can be used as spectral type equivalents. For a population criterion the CH/CN intensity ratio is proposed.  相似文献   

16.
Moderate dispersion (25-35 Å mm–1) spectra were obtained from two carbon stars, V Cyg and WZ Cas, in a wide range of wavelengths (3400-6800 Å) with the echelle-spectrometer, ZEBRA, of the 6 m telescope and two-dimensional photon-counting system. Spectral feature identification was carried out from 3850 to 6200 Å. Most of the bands are due to C2, SiC2, and CN, however, particularly in WZ Cas, moderate atomic lines of the iron peak and s-process elements are also found. WZ Cas is a so-called lithium star, however, we have found no evidence for a strong line of Li. The spectra of V Cyg contain an emission line of H.  相似文献   

17.
Moderate dispersion (46 Å mm–1 at H) image-tube spectrum (5800–7300 Å) of the S star 1 Gru is found to exhibit several unidentified molecular features, in addition to the well-known bands of the oxides ofs-process elements. A list is presented of 28 measured unidentified red-degraded bands, of which six, at 5998, 6128, 6143, 6223, 6257, and 6557 Å, are prominent. Of the reported 28 bands, 22 are observed for the first time. A discussion is included on the expected molecular sources of the unidentified features. The possible presence of two new molecules, Pr O and Nd O, in 1 Gru is suggested.This paper is dedicated to the memory of Dr. M. K. V. Bappu.  相似文献   

18.
The four diffuse interstellar absorption bands at 4430, 4760, 4890, and 6180 and the two diffuse lines at 5780 and 5797 are interpreted as belonging to pre-ionization transitions in H– and O–, respectively. In both cases the identifications are supported by extrapolations of wave numbers of resonance lines along isoelectronic sequences.In the H– case the hypothesis as to the origin of the bands is supported by quantum-mechanical results byHerzenberg andMandl (1963) as to the positions of resonances in collisions between neutral hydrogen atoms and free electrons. The relatively large intensities of the forbidden transitions indicate that the extent of the ion in its excited states may be very large as compared to ordinary atomic dimensions. In the O– case the relative doublet separation, as extrapolated along the isoelectronic sequence, is used for the identification of the doublet.  相似文献   

19.
After 2 years of operation onboard the Spanish satellite MINISAT, EURDhas achieved an unprecedented success in the observation of the terrestrialnightglow in the EUV, covering a range of 350-1100 Å EURD hasprovided a total of more than 543 hours ofintegration in the long wavelength spectrometer and more than898 hours in the short wavelength one, allowing the achievement of the most detailed atlas of the terrestrial EUV nightglow ever obtained. We present here the spectra obtained, together with the identification of the lines, some of themdetected for the first time in the nightglow. These spectrarepresent an improvement in sensitivity of several orders of magnitude with respect to previous observations. It has beenpossible, for the first time, to identify the complete Lymanseries of atomic hydrogen, resolving up to Lyman-. It hasalso been possible to identify the helium Lyman- line at 537 Å andto detect other lines of the blended Lyman series of helium, at 515 and522 Å. The spectra clearly show the presenceof the OII lines at 617, 644, 673, and 718 Å, previouslyobserved in the dayglow but seen here for the first time in thenightglow. In addition to the recombination continuum of the atomicoxygen at 911 Å, two features of OI have been detected in thenightglow: the 3s 3Do transition at 989 Å, previouslyobserved by Chakrabarti (1984) and the 2p34s3So transition at 1040 Å, partially overlapped with Lyman , but clearly distinguishable from it. This feature has been seen for the first timein the terrestrial nightglow. The radiative recombination continuum of atomic oxygen at 911 Å, that wasabsent in the observations of the first year of operation of EURD,is now clearly visible. The reasons of the absence of the OIfeature during the first year of operation are still unknown.Anderson et al. (1976) also noticed a strong variation with time of this 911 Å emission.  相似文献   

20.
The data deduced from the UV-spectroscope on theCopernicus satellite strongly suggest that the most important ionization source in interstellar space near the solar system is a UV radiation field originating from B-stars. Adopting this hypothesis, we have used the ionization state of several elements in the interstellar medium observed byCopernicus to determine the required radiation field. From this, the degree of ionization of elements that could not be observed byCopernicus is estimated.It is shown that this interpretation of thecopernicus data can be made consistent with neutral interstellar hydrogen densities inferred from extraterrestrial L observations and with electron densities deduced from pulsar dispersion measures. Furthermore, it is shown that the ratio of neutral interstellar helium to neutral interstellar hydrogen is likely to be 2 to 3 times as large as the cosmic abundance ratio of these elements. The possibility that this ratio is about 10 times as large, meaning equal interstellar neutral hydrogen and helium densities near the solar system, cannot be ruled out. It would, however, require an interstellar radiation temperature near 9000 K. A comparison of the intensity of the interplanetary back scattered He 584 Å and the H 1216 Å radiation would lead to a direct determination of this ratio provided the solar radiation at these lines is known.  相似文献   

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