[vsnet-chat 4482] Re: Apogee AP-7p

[Seiichi Yoshida <comet@aerith.net>]

Dear Dr. Skiff, Dr. Henden, and colleagues,

I am Seiichi Yoshida working on the MISAO Project.

While I was trying to estimate the coefficient of (B-V) for our
systems, I found one interesting example.

Two bright stars in the following image are recorded both in Tycho-1
and Tycho-2 Catalogue.

  http://vsnet.aerith.net/tmp/ohkura.20000914.2035+5500none.014.gif
  http://vsnet.aerith.net/tmp/ohkura.20000914.2035+5500none.014.fts

The catalog data of them are as follows.

  Tycho-1:
  Star                     V     B-V     BT      VT
  ---------------------------------------------------
  Left   TYC 3957-310-1  10.59  0.585  11.300  10.656
  Right  TYC 3957-12-1    9.89  0.463  10.432   9.941

  Tycho-2:
  Star                     V     B-V     BT      VT
  ---------------------------------------------------
  Left   TYC 3957-310-1  10.697 0.361  11.160  10.735
  Right  TYC 3957-12-1    9.860 0.431  10.431   9.906

I measured the magnitude of them by hand on the FITS image. The pixel
count of the left is 69576, the right is 102960. So the right star is
0.426 brighter than the left.

The difference of V magnitude in Tycho-1 and Tycho-2 catalogs are
larger than the difference of the measured magnitude. It implies that
the left star is more reddish, and became brighter on the unfiltered
CCD image, then the difference became smaller.

However, the B-V value in the Tycho-2 catalog does not coincide
this. On the other hand, the B-V value in the Tycho-1 catalog does.

The magnitude error of VT and BT are smaller than 0.2 mag in the
Tycho-2 Catalogue. The difference of V, VT and BT magnitude of the two
stars between the Tycho-1 and Tycho-2 Catalogue are smaller than 0.2
mag. But estimating the coefficient 'k' based on the B-V value, the
accuracy is not enough...

Best regards,

--
Seiichi Yoshida
comet@aerith.net
http://vsnet.aerith.net/

VSNET Home Page

Return to Daisaku Nogami

---

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