High-resolution echelle spectra of five reddened OB stars are used to analyse details of the profiles of diffuse interstellar bands (DIBs) at 4726, 4735, 5418, 5850, 6196, 6376, 6379 Å together with ...the well studied 5797, 5780 and 6614 ones. All targets do not show Doppler splitting in the interstellar CH 4300 band with the applied resolving power R= 115 000. The profiles of DIBs differ from object to object except 5418 which looks invariant in our sample: the DIB is a good candidate for further study of possible isotopic effect. We also found that the width of bands at 5797 and 6614 Å probably is more sensitive to the temperature (and density) effects than that of other DIBs in the sample, though almost all diffuse bands are narrowest in most ζ-type object (HD 179406) of the sample. On the other hand, it can be just peculiar effect as in a case of unusual line of sight HD 147889 which demonstrates very broad 5780 and 6614 Å diffuse bands what hardly can be explained by temperature effects.
High-resolution echelle spectra (acquired with the ESO/HARPS spectrograph) of a few OB reddened stars, where no Doppler splitting is observed in interstellar atomic lines, are analyzed. The observed ...profile shapes allow us to divide the diffuse interstellar bands (DIBs) into several sets, characterized by very similar shapes and widths and thus likely carried by similar molecular species. However, not all DIBs behave in the same way; profiles of broader features remain unchanged (are difficult to divide into sets of similar shapes), while evident differences are seen in the narrow ones. Profiles of DIBs may change slightly from object to object, apparently due to different physical parameters in the intervening clouds; this supports the idea of their molecular origin. We also introduce a new parameter, which is a result of dividing the equivalent width of a diffuse band (in mAa) by the depth of the feature (in percent). This parameter facilitates grouping of similar DIBs, as well as providing some quantitative information that allows us to estimate the broadness of a feature even for very complex profiles, vastly differing from Gaussian.
We report on the detection of a metastable He i* absorption line at 3889 Å in a spectrum of ζ Ophiuchi from the Ultraviolet and Visual Echelle Spectrograph with an extremely high signal-to-noise ...ratio (∼3500), which was collected using the 8-m telescope UT2 at Paranal. We cannot conclusively determine whether the He i* absorption arises within the H ii region or within the foreground H i clouds, which are responsible for interstellar CH, CH+, Na i, Ca ii, K i, etc., absorption, because the radial velocities of the main mass of gas are nearly identical in both regions. The measured equivalent width (1.0 ± 0.07 mÅ) of the line gives a column density of 1.158(± 0.081) × 1011 cm−2, when we assume the absence of saturation effects, and an oscillator strength of f= 0.0645. We estimate the ionization rate of helium to be 1.491 × 10−13, if the helium relative abundance in the H i cloud (with respect to hydrogen) is solar, and 7.475 × 10−14 cm−2, if the helium abundance is enhanced by the nearby star.
We report on the detection of a metastable Hei* absorption line at 3889 Å in a spectrum of zeta Ophiuchi from the Ultraviolet and Visual Echelle Spectrograph with an extremely high signal-to-noise ...ratio (3500), which was collected using the 8-m telescope UT2 at Paranal. We cannot conclusively determine whether the Hei* absorption arises within the Hii region or within the foreground Hi clouds, which are responsible for interstellar CH, CH+, Nai, Caii, Ki, etc., absorption, because the radial velocities of the main mass of gas are nearly identical in both regions. The measured equivalent width (1.0 ± 0.07 mÅ) of the line gives a column density of 1.158(± 0.081) × 1011 cm-2, when we assume the absence of saturation effects, and an oscillator strength of f= 0.0645. We estimate the ionization rate of helium to be 1.491 × 10-13, if the helium relative abundance in the Hi cloud (with respect to hydrogen) is solar, and 7.475 × 10-14 cm-2, if the helium abundance is enhanced by the nearby star. PUBLICATION ABSTRACT
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We report the detection of eight vibronic bands of C3, seven of which have been hitherto unobserved in astrophysical objects, in the translucent cloud towards HD 169454. Four of these bands are also ...found towards two additional objects: HD 73882 and HD 154368. Very high signal-to-noise ratio (∼1000 and higher) and high resolving power (R = 80 000) UVES-VLT spectra (Paranal, Chile) allow for detecting novel spectral features of C3, even revealing weak perturbed features in the strongest bands. The work presented here provides the most complete spectroscopic survey of the so far largest carbon chain detected in translucent interstellar clouds. High-quality laboratory spectra of C3 are measured using cavity ring-down absorption spectroscopy in a supersonically expanding hydrocarbon plasma, to support the analysis of the identified bands towards HD 169454. A column density of N(C3) = (6.6 ± 0.2) × 1012 cm−2 is inferred and the excitation of the molecule exhibits two temperature components; T
exc = 22 ± 1 K for the low-J states and T
exc = 187 ± 25 K for the high-J tail. The rotational excitation of C3 is reasonably well explained by models involving a mechanism including inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. These models yield gas kinetic temperatures comparable to those found for T
exc. The assignment of spectral features in the UV-blue range 3793–4054 Å may be of relevance for future studies aiming at unravelling spectra to identify interstellar molecules associated with the diffuse interstellar bands (DIBs).
Abundance relationships between the interstellar NH molecule and other diatomic species are presented based on 10 currently available sightlines (two of them taken from the literature). Spacial ...correlations between column densities of diatomic molecules suggest that the NH molecule is more closely related to neutral species than it is to CH+.
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We estimated distances to several Orion Trapezium stars using our CaII-method and confirm the distance recommended by Menten et al. However, we found that in the case of HD 37020 both individual ...distances (based on the trigonometric VLBI parallax and/or CaII-method) differ from the spectrophotometric distance by a factor of 2.5. We interpret this fact as a result of presence of gray (neutral) extinction of about 1.8 mag in front of this star. The correctness of the applied spectral type/ luminosity class, Sp/L, (based on new original spectra from HARPS-N) and measurements of color indices is discussed.
We present a study of the influence of magnetically induced control of external convection in stars of different types, in particular white dwarfs, on their thermal evolution. In the work preceding ...this study, we argued that for the cooling down white dwarf stars that have exhausted the sources of thermonuclear combustion, cessation of convection by a magnetic field significantly slows down their cooling. To test this asertion, we performed an observational program to search for new highly magnetized white dwarfs. The program is described in detail in the same issue of the journal. Our observations, together with the observations of other researchers, allowed us to construct the observed luminosity function of strongly magnetized white dwarfs with stopped convection and compare it with the well-known similar luminosity function of white dwarfs with weak fields that allow effective convective heat removal from their insides. As a result of the model analysis of these functions, the hypothesis that strongly magnetized white dwarfs cool down slower than weakly magnetic ones is confirmed. The article also qualitatively examines the effect of magnetic braking of convection in solar-type stars and cool M-dwarf stars of the Main Sequence on the periodicity of their radiation activity. The geophysical aspect of the problem and the practical application of magnetic field control of the heat removal in electrically conductive media are discussed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We present the results of observations within the program for the search for new highly magnetized white dwarfs among evolutionary old stars of this class. The program was carried out for two years ...at the 1-m telescope of the SAO RAS. As a result, new white dwarf candidates of different ages with super-strong (several megagauss, tens, hundreds of megagauss) magnetic fields were discovered. These observations, along with the observations of other authors made it possible to make a new estimate of the frequency of occurrence of magnetic white dwarfs among old stars. Our results confirm our earlier assumptions that the frequency of occurrence of far-evolved magnetic white dwarfs with magnetic fields of several megagauss or higher and with the temperatures of less than 10 000 K is at the level of 15% or higher, while the frequency of occurrence of such stars among young white dwarfs does not exceed 4–6%. This fact means that the thermal evolution of the physical properties of magnetic white dwarfs differs from the thermal evolution of their weakly magnetic counterparts.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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