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[vsolj-alert 315] V4444 Sgr comparison stars

V4444 Sgr comparison stars

　V4444 Sgr = Nova Sgr 1999 の比較星の暗い方への延長が行われました。GSCや
　USNO光度でなく、この等級を用いてご報告ください。

From: "Bruce Sumner" <b.sumner@bom.gov.au>
Subject: [vsnet-chat 1867] Sequence for V4444 Sgr

Hi all observers of V4444 Sgr=Nova Sagittarii 1999. As promised here 
is a preliminary sequence for this nova, based on field photometry 
taken by Arne Henden last Thursday night. As Arne has said, this 
is a very crowded field, and finding 'good' comparison stars has 
proven to be extremely difficult. However the following sequence 
should help observers follow this nova on its current rapid decline.

------------------------------------------------------------------ 

137  V4444 SAGITTARII   (N Sgr 1999)   Range: 7.8-?
     Position:   18 07 36.20  -27 20 13.2 (J2000, from .dat file)
     Magnitude:  V=10.512  B-V=0.740      (from .dat file)

ID     RA (2000)    DEC       X    Y   N    V      ERR     B-V    ERR     

1    18 07 46.3  -27 18 29   135  104  2  11.066  0.004   0.484  0.005   
2    18 07 33.8  -27 16 32   -31  221  2  11.286  0.004   1.229  0.006   
3    18 07 26.3  -27 20 26  -132  -13  2  11.604  0.006   0.765  0.008   
4    18 07 32.7  -27 17 37   -47  156  3  12.149  0.008   0.494  0.015   
5    18 07 22.4  -27 20 35  -184  -22  2  12.405  0.000   1.841  0.007   
6    18 07 46.3  -27 19 25   135   48  2  12.822  0.000   0.780  0.028   
7    18 07 14.6  -27 19 07  -288   66  2  12.912  0.006   1.354  0.018   
8    18 07 40.8  -27 23 09    61 -176  2  13.028  0.006   0.571  0.013   
9    18 07 42.5  -27 23 21    84 -188  2  13.227  0.015   0.694  0.001   
10   18 07 34.5  -27 19 41   -23   32  2  13.646  0.000   1.025  0.036   
11   18 07 35.8  -27 18 38    -5   95  2  13.898  0.000   0.535  0.001   
12   18 07 30.3  -27 19 55   -78   18  2  14.138  0.011   0.676  0.019   
13   18 07 32.3  -27 19 28   -52   45  2  14.299  0.006   1.933  0.018   
14   18 07 38.6  -27 19 15    32   58  2  14.531  0.000   0.724  0.021   
15   18 07 38.0  -27 19 48    24   25  2  14.904  0.026   0.963  0.030   
16   18 07 39.7  -27 20 50    47  -37  2  15.135  0.030   0.903  0.001   
17   18 07 39.2  -27 20 08    40    5  2  15.540  0.044   0.998  0.037   
18   18 07 33.6  -27 19 55   -34   18  2  15.854  0.057   1.879  0.006   
19   18 07 35.5  -27 19 58    -9   15  1  16.165  9.999   2.568  9.999   
20   18 07 35.2  -27 19 47   -14   26  2  16.486  0.000   1.477  0.304   
21   18 07 37.6  -27 19 54    19   19  1  17.187  9.999   1.265  9.999   

X and Y arcsec offsets are positive east and positive north respectively

Star 16 is very red, and is only included because of its proximity to 
V4444 Sgr. It should not be used as a comparison star.

This is an extremely crowded field, and it is important to be very careful
in identifying the comparison stars correctly. Every effort has been made 
to find comparison stars that are isolated and do not have close neighbours 
that confuse identification. However stars 20 and 21 do have close, 
brighter neighbours within 5 to 10 arcsec, so these two comparison stars
may prove difficult to use.

This sequence may be modified if Arne takes additional photometry during 
his next normal observing run, possibly later this month.

For those with access to a preliminary chart from Mati Morel, the lettered
comparison stars on his chart correspond to the following star numbers: 
a=1, b=2, c=3, d=5, e=4, f=7, g=6, h=8, k=10. 


Bruce Sumner
9 May 1999

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