The Interstellar Ti II Distance Scale Galazutdinov, G. A.; Santander, T. A.; Babina, E. ...
Astrophysical bulletin,
12/2023, Volume:
78, Issue:
4
Journal Article
Peer reviewed
We measured the equivalent widths (
s) of interstellar Ti II absorption lines at
3383.759 for about 250 reddened objects and found a good correlation of the
s with distances to the background stars, ...estimated using Gaia DR3 parallaxes. Hipparcos trigonometric parallaxes were used for very bright objects which were not observed by Gaia. The Ti II based distance estimation procedure is similar to the well known Ca II-method (Megier et al., 2005, 2009). However, there are at least 3 advantages of the Ti II method: in contrast to interstellar Ca II H and K lines, blending of Ti II with stellar lines is not an issue even for late B stars; Ti II is to a much less extent influenced by the saturation effect; only a single line must be measured, i.e. there is only a single measurement error to be taken into account. The relation of between Ti II
and distance is given by simple equation
, where
is the distance in pc and
is the equivalent width of the Ti II
3383.759 line in mÅ.
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
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+.
The light curves for almost 50 thousand stars with magnitudes
have been obtained over 2.5 years at SAO RAS in the process of conducting an exoplanet survey in roughly
-sized fields around the white ...dwarfs WD 0009
501 and GRW
708247. In this paper we present a catalog of variable stars that have been found in the considered regions. Periodogram analysis was used as the main variation search method. The catalog includes 150 periodic variable stars: 113 of them have been known previously, and for the remaining 37 variations have been discovered for the first time. These stars were classified according to the nature of the variations into four eclipsing variable and three pulsating types, as well as rotating stars. We present the periods and variation amplitudes in the range of
and
, determined from the investigated data.
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.
PDF
