SY Andromedae / SY And
Light curve and phase diagram of the EA type eclipsing binary SY Andromedae / SY And. These were constructed from photometry of 249 V filtered images taken with the Open University COAST telescope between 2017 July 6 and 2022 March 1.
The 'picket fence' effect is due to aliasing between the period of the star and the observing regime of the telescopes.
The catalogued period for the star is 34.90847d (AAVSO VSX and GCVS). (Accessed 2022 March 13).
The catalogued period for the star is 34.90847d (AAVSO VSX and GCVS). (Accessed 2022 March 13).
SY And model
The following is a model binary system which fits the above observations, using Binary Maker 3 (BM3). It uses no other observations and does not include any radial velocity data (which I could not find) so it is not a 'definitive' model by any means.
In this model the primary has a mass of 2 solar masses and a surface temperature of 10 200 K while the secondary has a mass of 0.9 solar masses and a surface temperature of 4300 K. Note that the temperatures used here are not quite consistent with the catalogued spectral classes of A0 and K1 respectively (ref AAVSO VSX). The inclination of the perpendicular to the plane of the orbits to our line of sight is 89 degrees.
This results in the following light curve, in blue, compared to my observations.
This results in the following light curve, in blue, compared to my observations.
The following are some details of the model from BM3, showing the model from our viewpoint and the critical potentials together with the centres of mass of the two stars and the barycentre of the system.
Below is a more detailed schematic of the gravitational potentials from my Python program. The Lagrangian points are labelled L1 to L5. The barycentre is marked by a black 'X'.
Finally, another plot of the gravitational potentials, this time showing the gradient of the field. (The stars are replaced by point masses at their centres of mass.)
Output from Binary Maker
mass ratio input = 0.454500 mass ratio < 1 = 0.454500
Omega 1 = 7.619425 Omega 2 = 4.243283
Omega inner = 2.787317 Omega outer = 2.513301
C 1 = 10.574680 C 2 = 5.932339
C inner = 3.930323 C outer = 3.553540
Fillout 1 = -0.628327 Fillout 2 = -0.337475
Lagrangian L1 = 0.580292 Lagrangian L2 = 1.566467
AG = r1(back) = 0.140000 AS = r2(back) = 0.155000
BG = r1(side) = 0.139761 BS = r2(side) = 0.153289
CG = r1(pole) = 0.139484 CS = r2(pole) = 0.152417
DG = r1(point) = 0.140050 DS = r2(point) = 0.155418
Surface area 1 = 0.245688 Surface area 2 = 0.296824
Volume 1 = 0.011360 Volume 2 = 0.015084
Mean radius 1 = 0.139748 Mean radius 2 = 0.153569
Mean radius 1 (vol) = 0.139452 Mean radius 2 (vol) = 0.153275
Eccentricity = 0.00000 Longitude of Periastron = 0.0000
Phase of periastron = 0.00000 Phase of conjunction = 0.00000
Angular Rotation F1 = 1.0000 Angular Rotation F2 = 1.0000
Normalization Phase = 0.25000 Normalization Factor = 0.96000
inclination = 89.000 wavelength = 5500.00
temperature 1 = 10200.00 temperature 2 = 4300.00
luminosity 1 = 0.9679 luminosity 2 = 0.0321
gravity coefficient 1 = 1.000 gravity coefficient 2 = 0.320
limb darkening 1 = 0.430 limb darkening 2 = 0.620
reflection 1 = 1.000 reflection 2 = 0.500
Third light = 0.0000 Period = 34.91000000
[Page updated 2022 May 31]