[vsnet-campaign-v838mon 367] Re: V838 Mon observations (S. Kiyota)

[aah@nofs.navy.mil]

Kiyota-san questioned whether his latest 020502 V-band measure
might be affected by the nebula.  At V-band, the nebula surface
brightness is brighter than the star and is definitely a difficulty.
Automatic detection software has problems finding a peak at
the star's position, and for photometry you have to set the
sky annulus outside the light-echo shell.  At Rc-band, the
star is roughly the same brightness as the shell; at Ic-band,
the star is 60x brighter than the shell.  Photometry at Ic and
redder bandpasses (such as near-IR) is still definitely dominated
by the star and is quite easy.
  Since late April when the star starting fading quickly,
you need to be very careful how you measure the brightness
of the star.  the last measure I have fully reduced showed
V838 Mon on 020505 to be V=13.9; it is much fainter now.
Arne

VSNET Home Page

Return to Daisaku Nogami

---

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