[vsnet-chat 680] T Phe V Sequence

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

Colleagues,
The Mira variable 0025-46 T Phe has been on the VSS, RASNZ program for more than
thirty years (charts 74 & 75, Jan. 1966). Range 8.7-14.6v, using the sequence of
visual magnitudes from Harvard.
Recently, while browsing the NASA ADC "Selected Astronomical Catalogs, Vol. 2"
on CD-ROM, I noticed the listing of UBVRI Photometric Stars by A. Landolt
(1992).
One subset is a sequence of seven stars around T Phe. It turns out to be a good
set of modern magnitudes, for a future revised chart. However, the data for one
of the comp. stars is rather unusual (no variability is implied), and I think
it worthwhile bringing the whole dataset to the attention of observers before
a chart is published. The UBV data below is rounded and condensed from the
original subset.

Letter   GSC #    RA 2000    DEC 2000    V    B-V   U-B   mv/other ids.
========================================================================
A   8024.00394  0:30:09.5 -46:31:28.9  14.65  0.79  0.38  ....
B   8024.00363  0:30:16.3 -46:27:58.8  12.33  0.41  0.16  RW Phe
C   8024.00400  0:30:16.9 -46:32:21.2  14.38 -0.30 -1.22  14.1,LB 1558
D   8024.00677  0:30:18.2 -46:31:20.4  13.12  1.55  1.87  13.6
E   8024.00755  0:30:19.6 -46:24:35.8  11.63  0.44 -0.10  12.2
F   8024.00830  0:30:49.6 -46:33:24.0  12.47  0.86  0.53  13.2, NSV 184
G   8024.00627  0:31:04.2 -46:22:51.7  10.44  1.55  1.92  10.8 

Comments:
---------
In most cases, the mv value currently in use understates the brightness
of the star by 0.5mag.
Star B has long been known as RW Phe (EA, 12.4-14.0v) and should not be
used.  F is NSV 184, but its variablity is considered very doubtful.
Star C and D lie only one arc minute apart; C is extremely blue and D is
rather red.  Because of its blueness C is listed in Luyten's catalogues
of Blue Stars as LB 1558. I am not sure what kind of star it is - it is
not a white dwarf (not listed as such, and anyway white dwarfs rarely, if
ever, have such extremely blue colours). Not a known variable.

In the current mv scale, C and D (which are in close proximity to each
other) have magnitudes of 13.6 and 14.1 respectively - a difference of 0.5.
According to Landolt's measurements, the difference in V is 1.26!!

I wonder if any visual observers have ever noticed (or merely suspected)
that the chart values for C and D do not agree with what they see through
the telescope??
Or, is is that the extreme colours of these stars, especially C, leads to
an exaggerated difference in V? 

I would very much like to receive reports on how visual observers (and other
types of observers too!) see the difference between C and D. Is there a
colour term at work?
The GSC mags. are virtually identical at about 14.0.

VISUAL OBSERVERS SHOULD CONTINUE TO USE THE CURRENT VISUAL SEQUENCE, PENDING
THE FINALIZATION OF A NEW SEQUENCE.











 


















   




 
/Mati

  /=====================================\
  |  MOREL ASTROGRAPHICS                |
  |  Stellar Data & Information Centre  |
  |  c/o M. Morel                       |
  |  6 Blakewell Road,                  |
  |  Thornton  NSW 2322  AUSTRALIA      |
  |  Tel./fax: (02) 4966 2078                                   |
  |  151d38'33" E, 32d46'47"S           |
  |  e-mail: morel@ozemail.com.au       |
  \=====================================/

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp