STARK BROADENING IN ASTROPHYSICS Milan S. Dimitrijević1,2 and Zoran Simić1 1. Astronomical Observatory, 11060 Belgrade, Volgina 7, Serbia 2. Observatoire de Paris, 92195 Meudon Cedex, France

1. INTRODUCTION

Spectral type and effective temperature of a star can be determined by comparing its spectrum with a standard spectrum for a spectral type and effective temperature. In Fig. left are spectral types and right effective temperatures.

NEEDS FOR LARGE STARK BROADENING DATA SET - DEVELOPMENT OF COMPUTERS FOR EXAMPLE: PHOENIX CODE FOR MODELLING OF STELLAR ATMOSPHERES INCLUDES A PERMANENTLY GROWING DATABASA WITH ATOMIC DATA FOR MORE THAN 500 MILLIONS TRANSITIONS - SATELLITE BORNE SPECTROSCOPY

Example of advance of satellite born spectroscopy Part of Chi Lupi spectrum obtained with International Ultraviolet explorer (IUE) and with Godhard High Resolution Spectrograph on Hubble telescope (GHRS). One can see how lines of trace elements become more and more important.

STARK BROADENING IS IMPORTANT FOR: - PLASMAS IN ASTRONOMY - LABORATORY PLASMAS - PLASMA TECHNOLOGIES

PLASMAS IN ASTRONOMY Stark broadening may be important for plasma conditions from NEUTRON STARS T=10+6-10+7K Ne=10+22-10+24cm-3, white dwarfs, hot stars, up to other extreme conditions : FOR RADIO RECOMBINATION LINES FROM H I (T=50K) AND H II (T=10000K) REGIONS Ne = 1-1000 cm-3

F. Paerels, 1997, ApJ, 476, L47 A possibility to obtain M and R of a neutron star from a spectral line profile W = 163Zˉ¹(M⁄R²)²⁄³T²⁄³ eV Gravitational shift ~ M/R

Radio recombination lines are emitted from interstellar clouds H I (T=30K) and H II (T=10000K) Ne = 1-1000 cm-3

INTERSTELLAR MOLECULAR CLOUDS In interstellar molecular clouds, typical electron temperatures are around 30 K or smaller, and typical electron densities are 2-15 cmˉ³. In such conditions, free electrons may be captured (recombination) by an ion in very distant orbit with principal quantum number (n) values of several hundreds and deexcite in cascade to energy levels n-1, n-2,... radiating in radio domain. Such distant electrons are weakly bounded with the core and may be influenced by very weak electric microfield. Consequently, Stark broadening may be significant.

Since the influence of Stark broadening in a spectral series increases with the increase of the principal quantum number of the upper level, the contribution of Stark broadening may be important even in Solar spectrum.

WHITE DWARFS The first - 40 Еridani Herschel 31.01.1783 The second, Sirius B, 1862 Alvan Graham Clarck The third 1917 Van Maanen 1950 a hundred 1999 around 2000 Sloan Digital Sky Survay more than 9000

WHITE DWARFS This will be the destiny of 97% of stars in our Galaxy Small masses – helium core, Average masses (majority of observed) – core of C and O Big masses – core of O, Ne and Mg

White dwarfs TRADITIONAL DIVISION DA – HYDROGEN RICH DB – HELIUM RICH

1979 was discovered prototype of a new class of hot hydrogen defficient degenerate stars PG1159-035 McGraw J. T., Starrfield S., Liebert J., Green R. F. 1979, Proc. IAU Coll. 53: White dwarfs and variable degenerate stars, H. M. van Horn, V. Weidemann eds., Univ. of Rochester, 377

K. Werner, U. Heber, K. Hunger, 1991, A&A, 244, 437

PG 1159 100 000 K < Teff< 150 000 K The hotest PG 1159 star H 1504+65 Teff = 175 000 K DO 40 000 K < Teff < 100 000 K DB 12 000 K < Teff < 40 000 K He I DQ 4 000 K < Teff < 12 000 K C2 Swan band DZ lines of metals, accretion DC continuum

STARK BROADENING DATA ARE NEEDED IN ASTRONOMY FOR EXAMPLE FOR: ` STELLAR PLASMA DIAGNOSTIC - ABUNDANCE DETERMINATIONS - STELLAR SPECTRA MODELLING, ANALYSIS AND SYNTHESIS - CHEMICAL STRATIFICATION - SPECTRAL CLASSIFICATION - NUCLEAR PROCESSES IN STELLAR INTERIORS - RADIATIVE TRANSFER - STELLAR OPACITIES

Line shapes enter in the models of radiative envelopes by the determination of the Rosseland optical depth .

Maximal (upper line) and minimal (lower line) of the ratio of equivalent widths for different stellar types. Maximal and minimal value of EWSt/EW0 are given for 38 considered Nd II lines. THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 135:109-114, 2001 STARK BROADENING EFFECT IN STELLAR ATMOSPHERES: Nd II LINES L. C. POPOVIC , S. SIMIC, N. MILOVANOVIC, M. S.DIMITRIJEVIC

R. Hamdi, N. Ben Nessib, N. Milovanović, L. Č. Popović, M. S R. Hamdi, N. Ben Nessib, N. Milovanović, L. Č. Popović, M. S. Dimitrijević and S. Sahal-Brécho, MNRAS, 387, 871 (2008). Si VI 2p4(3P)3s 2P- 2p4(3P)3p 2 Do (λ = 1226, 7Å) DО WHITE DWARFS Teff = 50 000–100 000 K and log g = 8.

M. S. Dimitrijević, T. Ryabchikova, Z. Simić, L. Č. Popović and M M. S. Dimitrijević, T. Ryabchikova, Z. Simić, L. Č. Popović and M. Dačić, Astron. Astrophys., 469, 681 (2007). We investigated Stark broadening of Cr II lines in Ap star HD 133792 for which careful abundance and stratification analysis was performed by Kochukov et al. 2006, A&A, 460, 831. For this star Teff=9400 K, log g = 3.7. Code SYNTH3

SCP CALCULATIONS OF ELECTRON AND ION IMPACT WIDTHS AND SHIFTS OF SPECTRAL LINES

STARK-B http://stark-b.obspm.fr 42

43

Group for Astrophysical spectroscopy

LSST 8.4 m 30Тb/night petabits of data

THANK YOU FOR ATTENTION