Doublestar analysis of lunar occultation of SAO77494 on Apr.1 2009
Observed by Masayuki Ishida
Analized by Kazuhisa Miyashita
Fig.1 Brightness of main star only.
M. Ishida observed lunar occultation of SAO77494(=XZ7500=WDS A496) and he confirmed a step change on the light curve.
Catalogue details (Washington Doublestar Catalog)
WDS Discovr Comp EPOCH # THETA RHO Magnitudes Spectral Prop Mot 2nd PM DM Desig Note Precise |
Identifier Frst Last Fst Lst First Last Pri Sec Type RA" DEC" RA" DEC" Coordinate
05449+2621A 496 1903 2004 22 11 7 0.2 0.3 7.91 8.35 B9 -001-007 +26 937 054455.56+262032.7
Place name Moriyama, Shiga, Japan
Observer Masayuki Ishida
Fig.2 Limovie analysis
A step is visible clearly at 80% of full brightness.
Diffraction fitting and photometry
Fig.3 Fitting observation to diffraction simulation.
(1) Timming data and component's magnitude
It is assuming combined magnitude is 7.34 mag.
|Object ||Phenomenon ||Time||magnitude||Component B ||Appearance ||11h40m00.51s +/- 0.017sec ||9.01
||Component A ||Appearance ||11h40m00.61s +/- 0.017sec||7.60
||Time difference ||0.101 sec
(2) Compare with catalogues
| This observation || 1.41 mag |
| Wasington Doublestar Catalog || 0.44 mag |
| XZ Doublestar File || 0.5 mag |
Elements of separation to the radial direction of lunar is ..
Radial Velocity * Time Difference = 0.472 * 0.101 = 0.048 (arcsec)
Expected time difference from catalogue and prediction is ..
Dp: Position angle around lunar limb - Position angle of component = 94-7= 87 degree
Expected time difference = separation(catalogue) * cos(DP) = 0.3*cos(87) = 0.016 arcsec
Assuming, the lunar has a complete spherical surface, and the position angle on catalogue is correct, it
is expected that the primary star disappears first.
However, at this observed event, the secondary star disappeared first.
An accurate lunar limb chart become to necessary to solve this issue.
As an other solution of this issue, it is possible to think that a discovery of a new (tertiary) component was done.
Because the observed magnitude drop is much smaller than expected by disappearance of secondary star.
It is difficult to think that previous photometrical observations have large error on component's magnitude.
And also, the possibility of which the CCD camera indicates such a large error on luminous intensity is very small.
If these are correct, it is presumed that the situation was below.
The line passed primary star with secondary star is parallel to the lunar limb,
and a new tertiary component is distant from the line passed other two stars by 48 milliarcsecond.