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On the Relations between Carriers of Interstellar Absorptions

100%

Krełowski J. , Strobel A.

Acta Astronomica

2024

tom Vol. 74, No. 1

69--76

The paper demonstrates that intensities of the unidentified diffuse interstellar bands, likely carried by some complex molecules, are not correlated with the amount of reddening (color excess). Apparently the above mentioned molecules and dust grains causing the reddening do not occupy the same places in the interstellar medium extended along the sight-lines to the relatively nearby and young objects of the Eta Car stellar aggregate

Gray Extinction in the Orion Trapezium

80%

Krełowski J. , Galazutdinov G. A. , Strobel A. , Mulas G.

tom Vol. 66, No. 4

469--480

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

Statistical Indicators of Astrophysical Parameters

80%

Wąż P. , Bielińska-Wąż D. , Strobel A. , Pleskacz A.

Acta Astronomica

2010

tom Vol. 60, No. 3

283--293

The aim of this paper is to introduce a new tool for a simple identification of spectral types. We use methods of statistical spectroscopy, in particular the method of intensity-distribution moments. The statistical approach revealed a characteristic behavior of moments of the stellar spectra for different spectral types. The transition from one spectral type to another may be expressed as a regular function of appropriate moments of the intensity distribution of the spectra. Moment-based diagrams localize particular spectral types in different areas of the plots. Since the intensity-distribution moments may be easily derived from the observed spectra, the presented method facilitates a simple auxiliary tool for the classification of stars to specific spectral types. It is also helpful in checking the correctness of the existing classifications. The intensity-distribution moments depend on all kinds of stellar characteristics, including the metallicity and the age. Therefore, using an inverse approach, from the knowledge of moments one may predict these properties.

Open Clusters in 2MASS Photometry. I. Structural and Basic Astrophysical Parameters

80%

Bukowiecki Ł. , Maciejewski G. , Konorski P. , Strobel A.

Acta Astronomica

2011

tom Vol. 61, No. 3

231--246

The main goal of our project is to obtain a complete picture of individual open clusters from homogeneous data and then search for correlations between their astrophysical parameters. The near-infrared JHKS photometric data from the 2-Micron All Sky Survey were used to determine new coordinates of the centers, angular sizes and radial density profiles for 849 open clusters in the Milky Way. Additionally, age, reddening, distance, and linear sizes were also derived for 754 of them. For these open clusters our results are in satisfactory agreement with the literature data. The analyzed sample contains open clusters with ages in the range from 7 Myr to 10 Gyr. The majority of these clusters are located up to 3 kpc from the Sun, less than 0.4 kpc from the Galactic plane and 6-12 kpc from the Galactic center. The majority of clusters have core radii of about 1.5 pc and the limiting radii of the order of 10 pc. We notice that in the near-infrared, open clusters seem to be greater than in optical bands. We notice that a paucity of clusters is observed at galactic longitudes range from 140° to 200° which probably reflects the real spatial distribution of open clusters in the Galaxy. The lack of clusters was also found in earlier studies.

Spectrophotometric Distances - Problem of Interstellar Extinction

80%

Krełowski J. , Galazutdinov G. A. , Strobel A. , Bondar A.

2017

tom Vol. 67, No. 3

281--296

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.