[vsnet-campaign-v838mon 64] Photometric Sequence for the field of V838 Mon

[DWest61506@aol.com]

FROM: Doug West
DATE: 04 January 2002

This report provides V and V-Rc magnitudes for brighter stars in the field 
of V838 Mon.  This is to extent Arne Henden’s photometry of the field.  
As this unusual object brightens, CCD and PEP photometrists will need 
stars of approximately the same magnitude for comparison and check.  

The observations were taken on 11 January 2002 and 04 February 2002 
UT with a 0.2 m SCT and a SBIG ST-8  CCD camera.  Research grade V 
and Rc filters were used. Fluxes were extracted from the CCD images 
with MIRA software and the photometric reductions were accomplished 
with the Kaitchuck and Henden Astronomical Photometry Software.  The 
color transformation terms were determined using primarily the M67 
magnitudes provided by Arne Henden. No correction was made for 
differences in airmass extinction since all the stars were on the same CCD 
image.

Table 1 gives the color corrected average V and V-Rc magnitudes of field 
stars near the position of V838 Mon. The estimated errors err(V) and 
err(V-Rc) are the differences between the magnitude estimates for the two 
nights. Table 2 gives the positions of the all the stars referenced in this 
report. Table 3 gives the magnitudes of the photometric reference stars 
(Henden, 2002).  For comparison, Table 4 gives the Tycho catalog V and B-V 
magnitudes 
for each of these stars.  The median standard error for stars in the 9-10 
magnitude range is 0.027 for the Tycho catalog.

Table 1 - Measured magnitudes 
--------------------------------------------------------------------
  Star                        V     err(V)     V-Rc  err(V-Rc)
--------------------------------------------------------------------
GSC 4822_2895       9.28   0.02      1.21   0.03
GSC 4822_3613       9.18   0.03      0.01   0.00
GSC 4818_21           9.67   0.01      0.59   0.02 
--------------------------------------------------------------------


Table 2 - GSC 1.1 Positions (J2000) of stars referenced in this report. 
--------------------------------------------------------
                             RA          DEC
Star                    h  m  s      d   m   s
--------------------------------------------------------
GSC 4822_3559  7  4   9.5  -3  53   0
GSC 4822_2895  7  3 58.2  -4   3  47
GSC 4822_3613  7  4 47.8  -3  53   2
GSC 4818_21      7  4 46.3  -3  41  42
GSC 4822_3661  7  3 25.8  -3  51  40
---------------------------------------------------------

Table 3 – Henden Magnitudes of the Reference stars
-----------------------------------------------------------------------------
Star                         V       V-Rc       
-----------------------------------------------------------------------------
GSC 4822_3559    10.707   0.031     
GSC 4822_3661     10.085  0.223    
-----------------------------------------------------------------------------   


Table 4 – Tycho Catalog Magnitudes for Field Stars
-----------------------------------------------------------------------------   

Star                                    V             B-V (sigma)
-----------------------------------------------------------------------------   

GSC 4822_2895                 9.26        1.468 (0.120)
GSC 4822_3613                 9.12         -.010 (0.025)
GSC 4818_21                     9.62        1.161 (0.065)
-----------------------------------------------------------------------------   



Reference:

Henden, A.A., 2002, URL: 
http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/v838mon.dat

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