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1

Profiles of Interstellar Spectral Features Caused by Physical Parameters of Clouds

Krełowski J., Bondar A.

Acta Astronomica

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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.

2

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.

3

Diffuse Interstellar Bands and Temperatures in the Interstellar Clouds

Gnaciński P., Weselak T., Krełowski J.

Acta Astronomica

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2016

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Vol. 66, No. 1

121--130

EN

The diffuse interstellar bands (DIBs) observed in the optical and infrared spectrum of interstellar clouds remain the oldest unsolved problem in spectroscopy. We have analyzed correlations between normalized DIBs equivalent widths (EW's) and temperatures of interstellar H₂ and CN molecules. The λ6284 Å DIB is well correlated with T temperature of H₂. The correlation may be caused by DIB profile broadening or more effective production of DIB carrier at higher temperatures. The DIBs: λ4964 Å, λ5797 Å and λ6614 Å are anti-correlated with T temperature of H₂. The anti-correlation may be attributed to destruction of DIBs carriers in high-UV radiation fields.

4

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.