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1
Content available remote Relation between NH and other Simple Molecules
Weselak T.
Acta Astronomica
|
2023
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Vol. 73, No. 3
233--242
EN
Relations between abundances of interstellar NH molecule and other diatomic species as OH, CH, CH+ and molecular/atomic hydrogen are presented based on 16 available sight-lines. Spacial correlations between column densities of diatomic molecules suggest that the NH molecule is rather related to interstellar CN (correlation coefficient equal to 0.82±0.09). A good relation with molecular hydrogen with correlation coefficient equal to 0.79±0.12 is also presented.
2
Content available remote Profiles of Interstellar Spectral Features Caused by Physical Parameters of Clouds
Krełowski J., Bondar A.
Acta Astronomica
|
2022
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Vol. 72, No. 1
69--76
EN
The disk of our Galaxy is filled with clouds of diffuse matter, modifying spectra of distant stars. These clouds are sources of extinction, polarization and of spectral features such as atomic and molecular lines as well as the diffuse interstellar bands (DIBs), still of unknown origin, though likely molecular. Apparently physical parameters of individual translucent clouds are various. We try to provide some constraints on theoretical models of translucent interstellar clouds. It is demonstrated that intensities and profile details of DIBs can be determined using the ESPRESSO spectrograph fed by VLT. This possibility follows its very high resolution and signal-to-noise ratio, necessary to analyze atomic and molecular features, detectable in spectra of OB-stars, and originated in single (thus - likely optically thin) interstellar clouds. Our set of five high resolution (λ/δλ =140 000) ESPRESSO spectra of hot, reddened stars allows us to analyze profiles of some DIBs. It is argued that more high quality spectra from ESPRESSO are necessary to identify the DIB cariers.
3
Content available remote On the Relation between OH and CH Radicals, Molecular/Neutral Hydrogen and Major 5780/5797 Diffuse Interstellar Bands
Weselak T.
Acta Astronomica
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2022
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Vol. 72, No. 3
233--243
EN
A precise relation between column densities of OH and CH molecule in the ISM has been found based on spectra of 24 stars (four of them new) and new published oscillator strengths of lines near 3078 Å and 30828 Å of OH molecule (0.001007 and 0.0006226, respectively). Observed column density ratio of OH and CH molecules in the ISM is equal to 3.20±0.17. A very good relation (with correlation coefficient equal to 0.85) between abundances of OH molecule and molecular hydrogen is also presented.
4
Content available remote On the Relation between OH+, OH and CH+ Molecules, Neutral/Molecular Hydrogen and Major 5780/5797 DIBs
Weselak T.
Acta Astronomica
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2020
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Vol. 70, No. 4
301--312
EN
Relations between column densities of OH+, OH+ and CH+ molecules and between atomic and molecular hydrogen and intensities of major 5780 Å and 5797 Å diffuse interstellar bands are examined based on spectra of 46 stars. Data on OH+, OH, CH+ and atomic/molecular hydrogen were taken from the literature. Data on 5780 Å and 5797 Å DIBs are based mostly on our own measurements. Column densities of the OH+ are very well correlated with abundances of OH molecule and not correlated with CH+ and hydrogen in any form. Column densities of OH+ are better correlated with narrow 5797 Å than 5780 Å major DIB. The value of abundance ratio in the case of OH and OH+ molecules in the ISM is equal to 5.73±0.45.
5
Content available remote On the Relation between Interstellar Spectral Features and Reddening
Krełowski J., Galazutdinov G., Godunova V., Bondar A.
Acta Astronomica
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2019
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Vol. 69, No. 2
159--175
EN
It is well known that interstellar spectral features correlate with color excess E(B-V). This suggests that measuring intensities of these features allows one to estimate reddening of stars. The aim of this paper is to check how tight intensities of interstellar diffuse bands (DIBs) are related to the amount of extinction, measured using E(B-V). We have measured equivalent widths of the strongest DIBs (centered at λλ 5780.6 Å, 5797.0 Å, 6196.0 Å, 6379.3 Å, 6613.5 Å, and 8620 Å), as well as of CH (near 4300.3 Å) and CH+ (near 4232.5 Å) in high resolution, high S/N ratio échelle spectra from several spectrographs. The equivalent widths of the 8620 DIB in noisy spectra were measured using a template which was constructed using the high quality spectrum of BD+40 4220. DIB relations with the color excess in the range 0.1-2.0 mag were examined. Our analysis demonstrates that all the above mentioned interstellar spectral features (except for, perhaps, 6379 DIB) do correlate with E(B-V) relatively tightly (with the Pearson's correlation coefficient of 0.8+). Moreover, the observed scatter is apparently not caused by measurement errors but of physical origin. We present several examples where the strength ratios of a DIB/molecule to E(B-V) are different than the average.
6
Content available remote On the Distance Measurements in the Thin Milky Way Disk
Krełowski J., Strobel A., Galazutdinov G. A., Musaev F., Bondar A.
Acta Astronomica
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2018
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Vol. 68, No. 3
285--300
EN
We present a test how far the direct, trigonometric parallax measurements and those, based on interstellar CaII H and K lines lead to distances to OB stars similar to those, based on spectrophotometrically determined ones. For this we use relatively nearby objects where the extinction effects are negligible. A test is based on observations of interstellar CaII H and K lines, that determine distances, in spectra of bright, nearby objects, free of extinction effects. For these objects one can find also trigonometric parallaxes. CaII H and K lines are weak in spectra of nearby stars and thus measurable only in high S/N ratio spectra. Such spectra being at our disposal also allow us to check the spectral classification of our targets and thus to comment the observed differences between distances acquired using different methods. Using four methods, we determined distances to nearly fifty B0-5 type stars, practically free of any extinction effects. We demonstrate that direct, astrometric, CaII H and K and spectrophotometric distances agree reasonably well in the absence of substantial interstellar extinction and when spectral classification is reliable. Apparently the absolute magnitude calibration, provided by Schmidt-Kaler, appears to be correct.
7
Content available remote Spectrophotometric Distances - Problem of Interstellar Extinction
Krełowski J., Galazutdinov G. A., Strobel A., Bondar A.
Acta Astronomica
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2017
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Vol. 67, No. 3
281--296
EN
Distances to 112 hot reddened stars in the thin Galactic disk have been estimated with different methods and, their accuracies have been compared. Also, we have applied the CaII-method to test its relation to trigonometric parallax and the spectrophotometric one. Some interstellar clouds apparently contain especially large size dust grains which cause interstellar gray (neutral) extinction. The latter does not correlate with the typical color extinction and may falsify spectrophotometric distance estimates. We conclude that CaII and TiII based method provides in many cases the most correct and reliable distance estimates to hot, bright, distant stars in the thin disk of the Milky Way - more accurate than obtained with the spectrophotometric method.
8
Content available remote Constant Intensities of Diffuse Interstellar Bands in the Spectrum of AE Aur
Krełowski J., Galazutdinov G. A., Bondar A., Byeong-Cheol L.
Acta Astronomica
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2017
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Vol. 67, No. 1
71--80
EN
Using spectra of the star AE Aur (HD 34078), covering the period 1997-2016, we prove that all strong diffuse interstellar bands are of the same intensity during the whole period of observations (inside 3-5% of the intensity). This is in sharp contrast to the behavior of both CH and CH+ features which, during the last six years, declined sharply by 13% and 28% respectively. Diffuse bands seem to behave more or less as interstellar atomic lines. We checked also the behavior of CaII lines which should be of constant intensities as the carrier fills the space evenly. Our observations confirm this and allow us to re-estimate the distance to HD 34078.
9
Content available remote Gray Extinction in the Orion Trapezium
Krełowski J., Galazutdinov G. A., Strobel A., Mulas G.
Acta Astronomica
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2016
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Vol. 66, No. 4
469--480
EN
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
10
Content available remote Interstellar Medium in the M43 Nebula
Gnaciński P.
Acta Astronomica
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2009
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Vol. 59, No. 3
325--334
EN
We present a list of interstellar absorption lines in the direction of HD 37061 in the M43 nebula. Some of the absorption lines arise from atomic excited levels that are uncommon in interstellar clouds. The excited levels of FeII are populated by fluorescence. We found a large number of H2 molecular absorption lines arising from vibrationally excited levels. The ortho/para H2 ratio is equal to 2.7. The H2 rotational temperature of vibrational levels 1-5 exceeds 2000 K.
11
Content available remote Interstellar C2 Toward X Persei (HD 24534)
Kaczmarczyk G.
Acta Astronomica
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2000
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Vol. 50, No. 1
151--162
EN
Interstellar C2 bands D-X (2313 Å) and F-X (1342 Å) in the spectrum of X Per were detected in the archive echelle spectra acquired by the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The population of C2 rotational levels was determined from the rotational lines in the D-X band to obtain kinetic temperature Tk=45±15 K. The total C2 column density N(C2)=(3.4±0.5)×1013 cm-2 was calculated using the D-X band with f-value of 0.0545. The analysis of F-X band with an adopted f-value of 0.1 gave different population of rotational levels of C2. Possible reasons of this discrepancy are discussed. The FWHM of the C2 line profile was estimated to be ΔV=2.7±1.0 km/s.
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