NU ORI: the brightness estimates are weaker than the minimum brightness of the variable ???

Liga Iberoamericana de Astronomia (South America) (LIADA)
Sun, 03/14/2021 - 01:46

Dear: the visual observation chart of this star has a minimum of 6.93, but I find myself searching the database for visual brightness less than 7.1?


American Association of Variable Star Observers (AAVSO)

Hi Daniel,

I don't know exactly what you mean but this object is difficult to measure due to the surrounding nebula.
E.g. different surveys have different resolution power and the amount of nebula contribution will be different. And the emission lines in nebulae cause different response if the same filters are not used.

E.g. one can get get V= 6.74 or so after transforming from Hp magnitudes.
Tycho gives V= 6.87 (from Bt and Vt)
ASAS-3 gets V= 6.66 or so.
GCPD (standard V data) gives V= 6.83 or so.
ASAS should be standard too but their photometric aperture is larger so more nebula light is included.

These differences do not necessarily mean variability, actually each of these sources separately only show scatter below 0.05 mag.

What you see in the light curve it's likely just observational error. Visual sensitivity to the nebula light, magnification used to observe, etc.

Best wishes,