Team supervisor: David Boyce

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UV absorption line analysis using FUSE data
Team supervisor David Boyce Team members
M.Y.Anand Ananta
Charan Pradhan
Nguyen Duc Phuong
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Why to Study OVI lines ?
Ultraviolet observation of interstellar OVI
absorption lines with Copernicus first
established the existence of coronal gas in the
galactic disk.
The OVI ion appears with significant fractional
abundance only at Tgt2x105 K for a gas in
collisional equilibrium and there are no known
sources of ionizing radiation that could explain
widespread OVI gas by means of photo ionization
McKee and Ostriker considering the supernova
explosions as the source for ionizing the OVI
gave three component model of ISM
Weaver et al(1975) studied the interaction of a
strong stellar wind with the interstellar medium
resulting in a bubble formation presented a
detailed structure of these bubbles which tried
to explain the formation of OVI ions and also
predicted the abundance of OVI ion.
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Objective
Weaver et al Model
Ambient interstellar medium
Shocked stellar wind
stellar wind free expansion region
Interface region/ thermal conduction region
Swept up H II region
Our objective was to test whether any OVI lines
are present inside the bubble and if possible
Match the theoretical prediction of the Column
density of OVI with that from observation.
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Data and method to reduce the data
We downloaded the data from Multi mission Archive
at Space Telescope institute (MAST). Data
consisted of many exposures observed through
eight different segments 1alif4,2alif4,1blif4,2bli
f4,1asic4,2asic4,1bsic4,2bsic4
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Analysis of the calibrated data
We co-added the spectra from different exposure
using the Photo2.pro and fuseoffi.pro in IDL (
given by David Boyce)
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We used gaussfit in IDL to fit the lines but
later we found it is difficult to analyse the
lines with gaussfit because of blending of lines.
Later we used IRAF to extract radial velocity
and equivalent width.
We used Morton's (1991ApJS..77..119) atomic line
lists to identify the lines
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Results
Component1 Component2
Radial Eqwdth Radial
Eqwdth velocity
velocity
125 0.10 75
0.03
Radial velocity in km/s Eqwdth in Å
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We also found many absorption lines, we could
identify few of them
? is the observed wavelength ?. is the lab
wavelength
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Conclusion
We have observed two components of OVI lines one
of stellar origin having a velocity 122 km/s and
other forming inside the bubble having velocity
75km/s also we have observed the other singly
ionized ions/neutral atoms having velocity 17-23
km/s.
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Acknowledgments
We thank all 9th COSPAR people for there help in
doing this project. We also thank our project
supervisor David Boyce for his guidance.