[vsnet-chat 2213] Sequence for GM Sgr

["Bruce Sumner" <b.sumner@bom.gov.au>]

	To assist observers during the current outburst of GM Sgr 
here is the comparison star sequence I have created for this 
variable. This sequence is based on photometry obtained by Arne 
Henden at Flagstaff Station. 
	Be aware that this GM Sgr is not the same as the GM Sgr 
originally discovered by Luyten in 1927. Some notes on the 
identification of Luyten's red variable follow the sequence.
-------------------------
143  GM SAGITTARII   (NL?)   Range: 12.4-15.3B
     Position:   18 19 21.64  -25 24 25.7 (J2000, from .dat file)
     Magnitude:  V=13.332  B-V=0.355      (from .dat file)

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

1   18 19 05.1  -25 22 20  -224  126  3  10.452  0.102   0.622  0.047 
2   18 19 20.0  -25 22 25   -22  121  3  11.382  0.044   1.641  0.026 
3   18 19 16.5  -25 20 38   -69  228  3  11.582  0.033   0.264  0.007 
4   18 19 19.3  -25 21 31   -31  175  3  11.901  0.026   1.627  0.012 
5   18 19 45.3  -25 20 21   321  246  3  12.344  0.036   0.729  0.022 
6   18 19 24.5  -25 21 28    39  178  3  12.680  0.023   1.799  0.015 
7   18 19 25.2  -25 23 03    49   84  3  13.256  0.029   0.799  0.019 
8   18 19 25.1  -25 24 41    48  -15  3  13.422  0.030   1.186  0.014 
9   18 19 22.6  -25 24 09    14   17  3  13.563  0.025   1.914  0.014 
10  18 19 17.2  -25 24 39   -59  -13  3  13.748  0.020   1.654  0.014 
11  18 19 20.9  -25 23 54   -10   32  3  14.033  0.028   1.644  0.021 
12  18 19 16.7  -25 24 01   -67   25  4  14.536  0.046   0.707  0.036 
13  18 19 23.6  -25 25 19    28  -53  3  14.734  0.022   1.862  0.027 
14  18 19 19.5  -25 25 21   -28  -55  3  15.016  0.018   1.685  0.068 
15  18 19 22.4  -25 25 04    10  -38  3  15.605  0.026   1.117  0.014 
16  18 19 20.9  -25 25 42   -10  -76  3  15.806  0.031   1.342  0.036 
17  18 19 21.2  -25 25 08    -6  -42  3  16.257  0.026   1.669  0.039 
18  18 19 21.2  -25 25 24    -6  -58  2  16.940  0.023   1.356  0.129 

Notes:

Star 1 is saturated, and its magnitude and colour are approximate.

GM Sgr was discovered in 1927 by Luyten who classified it as a 
long-period variable with a range of 15.2-<17p.

In 1978 Goranskij discovered an outbursting star in this same 
region. This outbursting object was identified with GM Sgr. 
However this identification is incorrect, as Luyten's red variable 
can be easily identified on the DSS quick-V image as a brightish 
object at approximate magnitude 14.0V and located some 1.2 arcmin 
south of Goranskij's object. Thus it is Goranskij's object that 
now carries the designation GM Sgr, and not Luyten's discovery.

Using Luyten's range, combined with the magnitude and colour 
obtained by Henden in May 1999, leads to a revised range for 
Luyten's variable of 13.0-<16.3V. It is most likely a long-period 
mira variable.

The J2000 coordinates of Luyten's red variable, taken from Henden's 
.dat file, with X and Y offsets referred to the new GM Sgr, are:

    18 19 21.5  -25 25 38    -1  -72  3  16.240  0.088   2.183  0.081 

Bruce Sumner
Revised 11 August 1999

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