Index of /~bessell/FTP/Andreas

Icon  Name                    Last modified      Size  Description
[DIR] Parent Directory                             -   
[   ] 300bred23.fits          02-Feb-2009 08:44   17K  
[   ] 600bred23.fits          02-Feb-2009 08:44   17K  
[   ] he1327_600b_300b_618..> 02-Feb-2009 09:25  1.4M  
[   ] temp6180g35m500.fits    02-Feb-2009 08:44   37K  
[   ] temp6180g40m500.fits    02-Feb-2009 08:44   37K  
[   ] temp6180g375m500.fits   02-Feb-2009 08:44   37K  

Andreas

Three spectra were obtained with the 2.3m Double Beam Spectrograph (DBS).
In June 2006 a 600B spectrum from 3200 A to 5200A was obtained.

In January 2009 a 300B spectrum from 3200A - 6200A and a
316R spectrum from 6000A - 9900A were obtained. 

The spectra were taken with the atmospheric dispersion along the 
slit to ensure that the relative absolute fluxes were accurately measured.

The spectra had wavelengths fitted from a NeAr arc and corrected for
continuous atmospheric distinction. The red spectrum had the telluric
absorption lines removed by division by a smooth spectrum star taken at 
similar airmass. The blue spectra were also divided by a continous 
white dwarf spectrum to remove the spectrograph and dochroic response as
described by Bessell (1999: PASP 111, 1421; 2007: PASP, 119, 605). 

The spectra were then scrunched and flux corrected using more than five 
spectrophotometric standards selected each night from the Next Generation 
Stellar Library STIS observations of Michael Gregg 
http://www.stsci.edu/hst/HST_overview/documents/calworkshop/workshop2005/papers/gregg.pdf
as rereduced by Heap and Lindler.  
http://archive.stsci.edu/prepds/stisngsl/index.html 
The relative absolute fluxes of the NGSL stars are precise to within 2 percent.

The 300B and 600B spectra show excellent agreement. The 316R and 300B spectra
have an overlap of only 100A insufficient to unequivocally combine the spectra,
especially as the ends of the spectra are the least well calibrated.    

300bobs.fits, 316robs.fits and 600bobs.fits are the flux corrected 
and normalised spectra uncorrected for reddening. 

I found that a reddening correction of about Av=0.23 (E(B-V)=0.075) produced
a reasonable fit to a temperature of  6180K and a gravity between logg=3.5 
and 3.75. (The model spectra were interpolated from the grid spectra).

300bred23.fits, and 600bred23.fits are the reddening corrected 
spectra.

temp6180g375m500.fits and temp6180g35m500.fits are the normalised MARCS 
[M/H]=-5.0 spectra (g40 is the log 4 spectrum).

The figure shows the 600b spectrum and the 300b spectrum
overplotted with the MARCS model spectra for logg 3.5 and 3.75 for 6180K.


Mike  
2 Feb 2009