Observation and analysis of R557 (=SAO76216) in Sep. 10, 2009 (UTC)

Oct. 17, 2009
Kazuhisa Miyashita

Doublestar Report to IOTA coordinator

2009 Sep 10 at 16h 24m
Star = R557
Observer        Telescope 
  K. Kenmotsu    20.0cm at  133 44 xx.x  34 41 xx.x
  M. Ishida      16.0cm at  136 28 xx.x  34 35 xx.x

Double star details from the XZ catalogue
Star is the primary of the following pair
HL   26       1885 1885: 217.0 217.0:  71.600  71.600:  6.96 15.00: R   557  ------
OCc 750       1988 1988: 228.0      :   0.100        :  7.40  7.40: R   557  ------

Observation details
           K. Kenmotsu     M. Ishida

Star Mag = 6.96            6.96
   Event = R D             R D
      PA = 325.231         312.046
      AA = 338.426         325.226
       l = -4.500          -4.539
       b = -5.285          -5.313
      RV = 0.1110          0.2025
     CCT = 104.04          117.24
      T1 = 22.60           31.26
   T2-T1 = -0.11           -0.30

Occultation timing report
Place name     Matuzaka, Mie, Japan
Representative Masayuki Ishida
Place name     Soja Okayama, Japan
Representative Kunio Kenmotsu

TA  NED   16   100  +13628xx.x  +3435xx.x  84   xx.xM
TB  CED   20   180  +1334452.6  +3441xx.x  84   xx.xM

OA  M. Ishida
OB  K. Kenmotsu

20090910162430.96 R   557 RD     EG G0.04 1   W      11    AA
20090910162431.30 R   557 RD     EG G0.04 1   E      11    AA
20090910161422.49 R   557 RD     EG G0.04 2   W     F112 16BB
20090910161422.60 R   557 RD     EG G0.04 1   E     T112 16BB

Light curve

Observed by K. Kenmotsu


Observed by M. Ishida

Photometry

Observed by K. Kenmotsu
- Estimation of Magnitude of Doublestar Components -
Assuming magnitude of Pair is  6.94 Mag.
Estimated Magnitude
  First Event  :  8.47 +/- 0.15  Mag.
  Second Event :  7.24 +/- 0.06  Mag.

- Measurement ---------------------------------------
Luminous Intensity derived from Limovie analysis
               Average   Stdv      n
  Combined  :   782.0     98.4     40 
  Step      :   190.0     66.9      8 
  Background:    -1.7     44.7     40
Noise Level (N/S)
               Upper    Lower
  First event: 0.3489   0.2333
     Second event:0.1662   0.1130
Observed by M. Ishida
- Estimation of Magnitude of Doublestar Components -
Assuming magnitude of Pair is  6.96 Mag.
Estimated Magnitude
  First Event  :  8.42 +/- 0.09  Mag.
  Second Event :  7.29 +/- 0.04  Mag.

- Measurement ---------------------------------------
Luminous Intensity derived from Limovie analysis
               Average   Stdv      n
  Combined  :   506.5     53.0     60 
  Step      :   140.3     38.8     16 
  Background:    11.1     23.6     60
Noise Level (N/S)
               Upper    Lower
  First event: 0.2999   0.1830
  Second event:0.1447   0.1058

Catalogue details

 XZ 4940 = SAO 76216 = ZC 557
 RA =   3 48 30.0952   PM = 0.00130s
Dec =  24 20 43.886    PM = -0.0432"
 Mv = 6.96, Mb = 7.09, Mr = 6.89    Spectrum A1    Approx dia. .0002"

Star is the primary of the following pair
Name    Cmpt   Yr1  Yr2: PA1   PA2  :   Sep1   Sep2  :  Mag1  Mag2:     #1      #2  mean
HL   26       1885 1885: 217.0 217.0:  71.600  71.600:  6.96 15.00: R   557  ------
OCc 750       1988 1988: 228.0      :   0.100        :  7.40  7.40: R   557  ------
OCc 750 observed by J Bourgeois on 1988 Aug  6

WDS Discoverer codes
HL   Hall, A.    
                         OCc  Possible occultation discovery

Comment and explanation

Kenmotsu-san found a small step on the light curve of R557 event and he sent a .csv file to me. I had analyzed using diffraction function of Limovie. It is thought that this light curve obviously indicates double star (it is not an influence of noise or a diffraction tail).
Ishida-san also found a step on his R557 video and he sent an .avi file. The light curve of this eventhas a step similar to Kenmotsu-san's observation before the main increasing of this event.

Astrometry

Brian Loader who is the coordinator for double star observation analyzed the astrometry from above two observation. Below is his reply for our reports.
Dear All.

Thank you for the report on the observation by Ishida-san of the occultation of R557.
This appears to confirm that OCc 750 is real and enables a calculation of the separation and position angle of the two stars.
Separation 0.20" PA 240o
I attach the text and graphic* from David Herald's Double Calculator.
The position angles on the Moon's limb of the at 325.23 and 312.05 are rather close, so the accuracy of the solution may be low.

I have re-looked at the two diffraction curves and estimate the magnitudes as being:
  K. Kenmotsu  7.21 + 8.67
  M. Ishida    7.29 + 8.43

Best regards,
Brian

R557 2009  9 10
  T1      T2     T2-T1   P.A.    RV       CCT    slope  *  Year  M  D  Observer
 22.60   22.49   -0.11  325.23  0.1110  104.04    1.27  1  2009  9 10  K. Kenmotsu
    31.26   30.96   -0.30  312.05  0.2025  117.24   -0.84  1  2009  9 10  M. Ishida

Sep = 0.196 +/-0.000"  PA = 239.75 +/-0.00o  RMS fit: 0.00 +/-0.00"

Diffraction fitting

Observed by K. Kenmotsu


Observed by M. Ishida