Spectroscopic Variability of IRAS 22272+5435

A time series of high-resolution spectra was observed in the optical wavelength region for the bright proto-planetary nebula IRAS 22272+5435 (HD 235858), along with a simultaneous monitoring of its radial velocity and BV R C magnitudes. The object is known to vary in light, color, and velocity owing to pulsation with a period of 132 days. The light and color variations are accompanied by significant changes in spectral features, most of which are identified as lines of carbon-bearing molecules. According to the observations, the C 2 Swan system and CN Red system lines are stronger near the light minimum. A photospheric spectrum of the central star was calculated using new self-consistent atmospheric models. The observed intensity variations in the C 2 Swan system and CN Red system lines were found to be much larger than expected if due solely to the temperature variation in the atmosphere of the pulsating star. In addition, the molecular lines are blueshifted relative to the photospheric velocity. The site of formation of the strong molecular features appears to be a cool outflow triggered by the pulsation. The variability in atomic lines seems to be mostly due variations of the effective temperature during the pulsation cycle. The profiles of strong atomic lines are split, and some of them are variable in a timescale of a week or so, probably because of shock waves in the outer atmosphere

Determination of gravity in stellar atmospheres

Darbā apskatīta brīvās krišanas paātrinājuma (g) ietekme uz zvaigznes spektru, kā arī aprakstītas darbā izmantotās metodes tā noteikšanai. Praktiskajā daļā, vienlaicīgi izmantojot dzelzs un titāna neitrālo un jonu absorbcijas līniju koncentrācijas salīdzināšanas metodi, tiek noteikts log g (cgs) Saulei un zvaigznei HD 27277. Tiek veikta kvalitatīva log g noteikšana, izmantojot CaI λ6162 līnijas spārnu platumu salīdzināšanu Saulei un HD 27277, kā arī izmantoti sintētisko spektru modeļi, lai iegūtu precīzāku log g vērtību. Log g Saulei tiek noteikts, lai novērtētu izmantotās metodes precizitāti. Iegūtie rezultāti tiek salīdzināti ar vērtībām, kas iegūtas no neatkarīgām metodēm. Pēc iegūtajiem HD 27277 log g rezultātiem, iespējams secināt, ka tā pieder vaļējai zvaigžņu kopai NGC 1545. Šajā darbā HD 27277 augstas izšķirtspējas spektroskopiskie pētījumi veikti pirmo reizi pasaulē.Gravity affects to stellar spectrum and methods about measurement of it are examined in this research. Gravity of Sun and HD 27277 is established by comparing simultaneously concentration of element in neutral and ionized iron and titanium absorption lines in practical part. Qualitative measurement of gravity is made by comparing width of wings of CaI λ6162 spectral line of Sun and HD 27277. There is used also synthetic spectrum, to get more precise result. In case of HD 27277 we can not use wings of CaI λ6162 spectral line, because they are not enough sensitive to gravity changes in models of synthetic spectrum. Gravity of Sun is determined to get preciseness of method which is used to measure gravity of HD 27277. Findings are compared with results from independent methods. Basing on results of log g for HD 27277, it is possible to say that this star belongs to cluster NGC 1545. High accuracy spectroscopic measurements have not been made for HD 27277 before that is why this is the first research of this kind for this star

Spectroscopy of stars in the clusters NGC1545 and Tr2

Šī darba mērķis ir Galaktikas zvaigžņu kopu NGC1545 un Tr2 ķīmiskā sastāva noteikšana un fundamentālo parametru precizēšana un zvaigžņu evolūcijas un konvekcijas teoriju pārbaude. Šis ir oriģināls pētījums, kur izvēlētajām kopas NGC1545 un Tr2 zvaigznēm tika veikta augstas izšķirtspējas spektroskopija. Pētījuma daļā izvērtēta izvēlēto zvaigžņu – potenciālo kopas locekļu piederība kopām NGC1545 un Tr2. Darba gaitā tika iegūts zvaigžņu radiālais ātrums, izmantojot Doplera metodi, efektīvā temperatūra, mikroturbulences ātrums, brīvās krišanas paātrinājuma un ķīmiskā sastāva koncentrāciju vērtības, izmantojot atmosfēras modeļu metodi, kā arī precizēts kopas NGC1545 vecums, zvaigžņu masa un noteikta zvaigzņu evolūcijas stadija, izmantojot zvaigžņu evolūcijas teorijas modeļaprēķinus.The aim of this Master’s paper is to determinate chemical composition of open star clusters NGC1545 and Tr2 in Galaxy, to update fundamental parameters, and to verify stellar evolution and convection theory. This is original research, where high resolution spectroscopy for elected stars in clusters NGC1545 and Tr2 is made. Evaluation of the membership of elected stars – suspected members in clusters in the research part, is made. Radial velocity of stars by using Doppler method, effective temperature, microturbulence velocity, gravity and abundances of chemical elements, by using model photospheres method is determinated. Age of cluster NGC1545, stellar mass and evolution stage by using theoretical model calculations of stellar evolution was updated