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Central Wavelengths and Profile Shapes of Diffuse Interstellar Bands versus Physical Parameters of Intervening Clouds

Krełowski J., Marić T., Karipis A., Strobel A., Galazutdinov G. A.

Acta Astronomica

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2019

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Vol. 69, No. 4

369--380

EN

We investigate whether there are variations of the central wavelengths or the profile shapes of diffuse interstellar bands and whether these variations are caused by different physical parameters of translucent clouds. For this purpose we used spectra of two stars seen through two different single clouds: HD 34078 (AE Aur) and HD 73882. The wavelength displacements of the diffuse interstellar bands at 6196 Å, 6203 Å, 6376 Å, 6379 Å and 6614 Å with respect to the well known interstellar atomic and molecular lines (KI and CH) were measured. The shift is seemingly absent in the diffuse interstellar bands at 4726 Å, 4964 Å, 4763 Å, and 4780 Å. In addition the considered profiles may show (in HD 34078) extended red wings. The observed phenomena are likely related to physical parameters of intervening clouds (rotational temperatures of molecular species) and may help in the identification of the diffuse interstellar band carriers.

2

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.

3

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.

4

Looking for the Weak Members of the C60+ Family in the Interstellar Medium

Galazutdinov G. A., Krełowski J.

Acta Astronomica

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2017

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Vol. 67, No. 2

159--169

EN

We demonstrate, using the high resolution spectra from the ESPADONS spectrograph, fed with the 3.6 m CFH telescope, that the strength ratios of the strong-to-weak spectral features, attributed to C60+, are variable. We found that in the range of expected 9366 Å C60+ feature there are two diffuse bands centered at 9362.0±0.1 Å and 9365.3±0.1 Å with variable intensity ratio. We confidently confirm the lack of 9428 Å feature which, in the laboratory spectra of C60+, is stronger than 9366 Å. The weakest laboratory feature, near 9348.4 Å, remains below the level of detection in all spectra. The intensity ratio 9577/9365 is variable. These facts contradict the possibility of their common origin and so - the identification of some interstellar spectral features as being carried by the cation of the "soccer ball". We also refined the rest wavelength position of the strongest diffuse band in this range: it is 9576.8±0.1 Å.

5

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.

6

Variable Intensities of Molecular Features in the Spectrum of AE Aur

Krełowski J., Galazutdinov G. A., Mulas G., Bondar A., Musaev F. A., Shapovalova A., Cecchi-Pestellini C., Beletsky Y., Lee B. C.

Acta Astronomica

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2016

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Vol. 66, No. 3

391--403

EN

Using spectra of the star AE Aur (HD 34078), covering the period 1997-2015, we suggest that two strong molecular features of CH and CH+ underwent detectable changes of intensity. In the last five years both CH and CH+ declined sharply and systematically, with the CH/CH+ ratio steadily growing. No variations in the radial velocities of the observed interstellar features was detected during the covered period.

7

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

8

Consistent System of Oscillator Strengths of A2Δ-X2Π (0,0) and B2Σ--X2Π (0,0) Bands of CH Molecule

Weselak T., Galazutdinov G. A., Gnaciński P., Krełowski J.

Acta Astronomica

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2014

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Vol. 64, No. 3

277--292

EN

Detailed analysis of intensity ratios of unsaturated methylidyne (CH) A-X and B-X bands suggests consistency of the recently published oscillator strengths of A2Δ-X2Π (0,0) - 4300 Å and B2Σ- - X2Π (0,0) - (3878 Å, 3886 Å and 3890 Å) bands (i.e. 506, 107, 320 and 213×10-5 respectively). This result is based on extremely high S/N ratio spectra of 45 stars, acquired with three high-resolution spectrographs, situated in Chile: ESO La Silla (HARPS), ESO Paranal (UVES) and Las Campanas (MIKE) and MAESTRO instrument situated in Northern Caucasus (Russia). The calculated methylidyne column densities, obtained using the consistent system of the oscillator strengths toward the observed targets, are given as well. We verify oscillator strengths of the CH+ A-X (0,0) and (0,1) bands at 4232 Å and 3957 Å equal to 545 and 342×10-5 respectively. We also confirm the lack of correlation between abundances of neutral CH and CH+ which demonstrates that they are originated in different environments.

9

Carriers of 4964 and 6196 Diffuse Interstellar Bands and Environments Dominated by either CH or CH+ Molecules

Weselak T., Galazutdinov G. A., Sergeev O., Godunova V., Kołos R., Krełowski J.

Acta Astronomica

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2014

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Vol. 64, No. 4

371--382

EN

The analysis of radial velocities of interstellar spectral features: CH, CH+ as well as 4964 and 6196 diffuse interstellar bands, seen in spectra of HD 151932 and HD 152233, suggests that carrier of the former is spatially correlated with CH while that of the latter - with CH+. A further analysis, done in this paper and based on the sample of 106 reddened OB stars, partly confirms this suggestion, showing that the CH column density correlates indeed much better with the equivalent width of the 4964 DIB than with that of the 6196 DIB. However, the strengths of the 6196 DIB correlate only marginally better with CH+ than with CH.