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Joint HEP & PER Seminar
Wednesday, February 13, 2008 at 2:30 p.m.
Amateur Stellar Spectroscopy
A Study of Emission Stars
Tracy Tuttle
Assistant Professor of Physics & Astronomy
Bethel College, North Newton, Kansas
Abstract
Acquisition and analysis of spectra
from approximately 3650Å to 7800Å for 4 stars (Vega, Beta Lyrae, P Cygni and
WR 135) and two standard emission lamps (He and Hg) are used to determine
the dispersion, resolution and integrity of a commercial spectrograph.
The dispersion is 5.3Å/px, the resolution is determined to be 19.6Å
and the data acquired by the spectrograph is determined to be of good and
useful quality.
Amateur
- A person who engages in a pursuit on an unpaid basis.
From the French
amore, from Italian
amatore, from Latin
amator ‘lover’ , from
amare ‘to love’.
Angstrom
(Å) - Unit of length, 1x10-10 meters.
Dispersion
- A measure of how broadly spread are the wavelengths or frequencies of a
spectrum.
Resolution
- How fine of detail can be discerned from one’s data.
Alternatively, how close can two elements of data be to one another
and be distinguishable.
B e Emission *
- A rapidly rotating hot star (surface temperature of perhaps 12,000 K) that
exhibits brilliant emission lines thought to originate from a flattened disk
or envelope in fast rotation (perhaps in excess of 300 km/s) about the star.
Beta Lyrae
- An eclipsing contact binary star system made up of a blue giant (B7V) star
and a massive main sequence (A8V) star. The two stars are close enough that
material from the photosphere of each is pulled towards the other, drawing
the stars into an ellipsoid shape. Beta Lyrae is the prototype for this
class of eclipsing binaries.
P Cygni
- A giant luminous blue
variable (LBV) star of spectral type B2 Ia.
It is one of the most luminous stars in the galaxy and is located
about 5000 to 6000 light years from Earth.
P Cygni gives its name to a type of spectroscopic feature called a P
Cygni profile, where the presence of blue shifted absorption and red shifted
emission in the spectral line profile indicate the existence of a tenuous,
gaseous envelope, or stellar wind, expanding away from the star at high
velocity.
Wolf-Rayet * -
Evolved, massive stars (perhaps over
20 solar masses), losing mass rapidly by means of a very strong stellar wind
(speeds up to 2000 km/s). Typical surface temperatures are in the range of
25,000 K to 50,000 K. Their
spectra is characterized by intense emission lines that are extremely
doppler broadened.
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