[vsnet-chat 1831] Re: Luyten's variable (not GSC 6848.03786)

[Mati Morel <morel@ozemail.com.au>]

Date: Tue, 27 Apr 1999 21:58:46
To: vsnet-chat@kusatro.kyoto-u.ac.jp
From: Mati Morel <morel@ozemail.com.au>
Subject: Re: Luyten's variable (not GSC 6848.03786)

There has been much interest in GM Sgr, with the assumption that Luyten's
declination
is in error by more than 1'. A simple adjustment of Luyten's declination
places it
near GSC 6848.03786, which is now awarded the designation of GM Sgr. How
likely is
it that Luyten's position can be out by 1' (or more)?  Most of the variables
reported
by him in HB 852 are rather faint, and in the absence of finder charts or
accurate
positions would be hard to identify.  From scanning the GCVS (I have not
seen HB 852)
Luyten reported variables in two galactic centre regions - Scorpius and
Sagittarius.
Most of his variables appear to be Mira variables, and it there seemed to be
a good 
chance of finding them in the IRAS Point Source Cat.  I decided to look for
these
variables in the IRAS PSC, and by get a "feel" for the general accuracy of the
Luyten/GCVS positions.
I looked for the following Scorpius variables:
BW,BZ,CC,CD,CE,CH,CI,CM,CN,CO,CP.
I looked for the following Sagittarius variables:
GM,GN,GT,HI,HY,II.

Most of the Sco variables were found in IRAS PSC. The positions are given below,
with the difference, in the sense  Diff_RA (IRAS-GCVS) and Diff_Dec (IRAS-GCVS).

BW Sco   (1950)  16h14m12.8s -24 56'56"   +1.8s  -20"
BZ  "            16 26 51.1  -36 08 35    -0.9   - 5
CD  "            16 29  7.0  -36 13 46    +2.0   -10
CE  "            16 29 38.9  -37 44 01    -0.1   - 1
CI  "            16 38 52.8  -29 39 32    +1.8   -26
CO  "            16 59 25.2  -31 08 51    +0.2   - 9

                                 Average  +0.8   -11.8

II Sgr           18 28 16.1  -33 31 01    -0.9   -1"
Only one Sgr variable found, out of 6.

Now, this suggests to me that if GM Sgr (Luyten's faint variable) follows the
pattern of his other discoveries in HB 852, then a declination error of 1'
or more
is out of character (not impossible, but somewhat unlikely) considering the
above
comparison of IRAS and GCVS positions. 

I tend to think that Luyten's original GM Sgr is still  awaiting recovery.

Cheers,
Mati
/Mati

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