Extinction study towards hd264111 using IUE data'

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Extinction study towards hd264111 using IUE data.
By Eswaraiah Chakali (ARIES)
David Boyce, Prof. Jayanth Murthy Prof. Ana
Inez Gomez de Castro.
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Objectives

• To study wavelength dependent extinction curve.
• Variation of 2175 Å bump feature so that to
  constrain the size-distribution, composition.
• Why to select only B0-5 III-V stars for
  extinction??
• Followed with-out standards method-SEDs
  instead of standards.

Galactic Distribution of B type stars.
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Data sets used

• IUE Low resolution (low dispersion) larger
  aperture spectra LWRLong wavelength
  Redundant(1850-3350Å) SWP Short Wavelength
  Prime (1150-1980Å) LOW Low resolution
  spectrograph 6Å Large Larger Aperture
  1020 arcsec oval.
• B,V photometric data and 2MASS data sets from
  NstEd.
• TD1 and ANS data sets.

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Model the reddened spectra of HD 264111
http//tauvex.iiap.res.in/htmls/tools/fluxcalc
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How to get the intrinsic spectra

• ? ? K(5500Å) ??e(-???????????????(??????????????
  ?V) - Calibration w.r.to star Vega.
• K(5500Å) Kurucz flux at V filter.
• ??scaling factor (r/d)2
• K Kurucz spectra on surface of the star.
• ??optical depth Av/1.086
• -gt Rv ??E(B-V)/1.086
• -gt Rv -0.261.19 (E(V-K)/E(B-V))
  (Fitzpatrick., 2005)
• V apparent magnitude of the star (Program
  star)
• Scaling factor ???????????????(???????????????V
  ) / K(5500Å) ??e(-???
• ? ? K(?) Intrinsic spectra (flux on earth)

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Construction of extinction curve

• ff010(-0.4Av)
• ff010(-0.4E(B-V)K(?-V)Rv)
• K(?-V) E(??V)/E(B-V)
• A(?)/A(V)-2.5log(f/f0)
• E(??V)/E(B-V) (Fitzpatrick'07)
  c1c2xc3D(x,x0,? ) for x ltc5
  c1c2xc3D(x,x0,? )c4(x-c5)2
  for x gt c5

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Conclusions and Future Plans

• Present ext curve is similar to ave galactic ext
  curve with Rv 2.974 (Ave 3.1), shows ave size
  distribution and composition
• To run the Kurucz model with four parameters as
  input Teff, g, (M/H) and Vturb instead of Zero
  (M/H)
• To model the ext curve with three component dust
  model (Silicates, PAHs and Graphites).(using the
  modified size distr'n by Weingartner'95)
• So that to constrain the size-distr'n and
  composition at different locations of the ext
  curve.
• By studying the variation of bump width and
  strength we can understand abt the distr'n of
  carbonaceous materials in the galaxy.
• Would like to do spectroscopy in optical region??