majda smole and sanja tomić menthor:michaela kraus
TRANSCRIPT
![Page 1: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/1.jpg)
Majda Smole and Sanja TomićMenthor:Michaela Kraus
![Page 2: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/2.jpg)
B1 star HD2905 (kap Cas) B9 star HD202850 (sig Cyg)
We were given raw spectra obtained via observations starting from 15.8.2009. to 19.3.2011.
Our task was to reduce spectra and then to analyse it.
![Page 3: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/3.jpg)
B1 HD2905 (kap Cas) B9 HD202850 (sig Cyg)
![Page 4: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/4.jpg)
1. subtracting the over-scan, bias and flat-fielding
2. wavelengths calibration
3. telluric and heliocentric correction
![Page 5: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/5.jpg)
The over-scan is region of the CCD chip that is not exposed to the light.
The over-scan need to be subtracting from all images (bias, flat-fields, lamps and raw spectra).
IRAF task fit1d
![Page 6: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/6.jpg)
Example of bias in IRAF
Bias frame is dark frame with almost
zero second exposure. Bias images are
combined into one masterbias (imcombine task).
Imarith task for subtracting the bias from all images.
![Page 7: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/7.jpg)
Example of flat-field in IRAF
A CCD chip exposed to an uniform light
does not produce equally uniform image.
Several flat-fields are combined into one master-flat (imcombine task).
Images need to be devided by master-flat (imarith task).
![Page 8: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/8.jpg)
Example of lamp in IRAF
In order to use wavelenghts instead of pixels we had to identify lines in arc spectra (Thorium-Argon lamp).
Identify task in IRAF The calibrated arc
spectrum can be used to wavelenght calibrate the object spectra.
Refspec and dispcor tasks in IRAF.
![Page 9: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/9.jpg)
Telluric correction is used for removing absorption and emission of the Earth's atmosphere.
To do so it is necessary to use fast rotating comparison star with well known spectra.
We used Regulus and HR7880.
![Page 10: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/10.jpg)
To make heliocentric correction we
needed to obtain list of heliocentric speeds
for our spectra.
λcor=λobs*(1+Vhelio/c)
Exemple of spectra after heliocentriccorrection
![Page 11: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/11.jpg)
1. Identication of lines
2. Calculating radial velocities
3. Determination of period of pulsation
![Page 12: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/12.jpg)
NIST Atomic Spectra Database
a) encyclopedias of lines expected for our stars
b) ionisation energies
c) solar abundances
![Page 13: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/13.jpg)
Once we knew both theoretical and measured line proles we were able to calculate radial velocities.
λm=λth*(1+V/c)
![Page 14: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/14.jpg)
Hα He I
![Page 15: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/15.jpg)
Hα He I
![Page 16: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/16.jpg)
Si II 6347Å Si II 6371Å
![Page 17: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/17.jpg)
After plotting we saw that there is some periodical change in radial velocities for some lines, so the next step was to determine their period and to fit the sine curve trough the data.
To determine period of pulsation for HD202850 we used silicone lines.
![Page 18: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/18.jpg)
Si II 6347Å Si II 6371Å
![Page 19: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/19.jpg)
For HD202850 (sig Cyg) we got the periodicity of 1.59h.
For kap Cas we did not have enough data to conclude anything.
Our results support the hypothesis that HD202850 has pulsating atmosphere.
![Page 20: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/20.jpg)
P.North and S.Paltani, HD37151: A new "slowly pulsating B star". A&A,1994.
C. Aerts, M. De Pauw and C. Waelkens, Mode identication of pulsating stars from line profile variations with the moment method.
A&A, 1992. Charlotte E. Moore, Ionization potentials and Ionization Limits Derived
from the analyses of Optical spectra. 1970. M. Asplund, N. Grevesse and A. J. Sauval, The solar chemical
composition. D. J. Lennon, P. L. Dufton and A. Fitzsimmons, Galactic B-supergiants.
A&A,1992. N.R. Walborn and E.L. Fitzpatrick, Contemporary optical spectral
classication of the OB stars. A digital atlas. PASP, 1990. N. Markova and J. Puls, Bright OB stars in the galaxy. A&A, 2008. P.A. Crowther, D.J. Lennon and N.R. Walborn, Physical parameters and
wind properties of galactic early B supergiants. A&A, 2006.
![Page 21: Majda Smole and Sanja Tomić Menthor:Michaela Kraus](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649e8b5503460f94b909f5/html5/thumbnails/21.jpg)