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[vsnet-chat 4815] Re: [vsnet-sequence 102] AS270 sequence
- Date: Thu, 06 Sep 2001 10:02:59 +0200
- To: <b.sumner@bom.gov.au>, <vsnet-chat@kusastro.kyoto-u.ac.jp>, <vsnet-sequence@kusastro.kyoto-u.ac.jp>
- From: "Berto Monard" <lagmonar@csir.co.za>
- Subject: [vsnet-chat 4815] Re: [vsnet-sequence 102] AS270 sequence
- Cc: <aah@nofs.navy.mil>
- Disclaimer: The CSIR exercises no editorial control over E-mail messages originating in the organisation and the views in this message are therefore not necessarily those of the CSIR and/or its employees.
- Sender: owner-vsnet-chat@kusastro.kyoto-u.ac.jp
Dear Bruce,
You are quite alert and prompt with distributing this new sequence, for which I like to give you a compliment. This also goes for the master of stellar photometric measurements...
Regarding your note 2, I would agree that during this AS270 brightening, reference stars ought to preferably match the colour of the variable which is now around 1.1. Possibly AS 270 might get bluer if it rises further, we don't know that yet. Perhaps the experts like ao U. Munari might comment.
But then when this symbiotic systems fades again, it will become redder if I am not mistaken. Therefore I would suggest that when you eventually update this sequence (after more field measurements), you might consider to select or add more reddish stars for the magnitude range 13 and higher: applicable B-V values around 1.5 and possibly larger due to expected nebulosity. They are present in Arnes data file....
Kind regards,
Berto
PS I am a bit grumpy and like to complain ... ;-)
>>> "Bruce Sumner" <b.sumner@bom.gov.au> 09/06/01 02:11AM >>>
I have made a single night sequence for this symbiotic
variable from Arne's recent field photometry. As Arne
mentioned the zeropoint error will be in the 0.02mag
range.
Bruce
-------------------------
231 AS270 (SAGITTARII) (ZAND) Range: 11.5-
Position: 18 05 22.73 -20 20 38.1 (J2000, from .dat file)
Magnitude: V=11.544 B-V=1.103 (from .dat file)
ID RA (2000) DEC X Y N V ERR B-V ERR
a) Comparison star sequence
1 18 05 57.3 -20 16 27 333 251 1 11.419 1.435
2 18 05 39.9 -20 24 45 87 -247 1 12.264 1.511
3 18 05 15.4 -20 23 03 -257 -145 1 12.549 0.778
4 18 05 28.9 -20 21 39 -68 -61 1 13.147 1.402
5 18 05 46.0 -20 25 57 172 -319 1 13.413 0.770
6 18 05 44.2 -20 24 02 147 -204 1 13.915 0.790
7 18 05 39.8 -20 17 30 86 188 1 14.237 0.752
8 18 05 36.4 -20 21 02 37 -24 1 14.393 0.779
9 18 05 44.6 -20 21 25 154 -47 1 14.639 0.680
10 18 05 18.1 -20 24 17 -220 -219 1 14.963 1.085
11 18 05 35.3 -20 19 30 22 69 1 15.308 1.053
12 18 05 26.2 -20 19 50 -106 48 1 15.926 1.145
b) Wide-colour extension for CCD calibration
18 05 13.0 -20 19 00 -292 98 1 13.191 0.455
18 05 24.2 -20 24 22 -134 -224 1 13.424 2.019
18 05 54.8 -20 16 27 297 251 1 12.187 2.715
Notes:
1. This single night sequence is expected to have errors of about
+/-0.02 mag.
2. Most of the bright stars in this field are quite red, which explains
why the brighter sequence stars are redder than I would normally choose.
Bruce Sumner
6 September 2001
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