MBCAA Observatory

ASAS1826+12: the eclipsing CepheidObserved: 7, 12, 13, 14, 15, 17, 19 July, 5, 18 Aug, 5, 6, 12, 15, 19, 20 Sept, 2, 4, 13, 14, 15, 16, 18 Oct, 3, 8 Nov 2007Michel Bonnardeau

ID  RA(J2000)  DEC  V  BV  VRc  RcIc  VIc 
comp  18:26:09.44  +12:17:37.2  11.914  0.748  0.444  0.432  0.876 
check  18:26:23.68  +12:15:47.2  10.892  0.665  0.383  0.358  0.738 
The phase coverage of the observations:
Red solid line: the orbital phase;
Blue dot line: the pulsational phase;
Red squares: the orbital phases of the V measurements;
Blue circles: the pulsational phases of the V measurements.
The measured b,v magnitudes may be transformed
for the instrument response. The transformed B,V magnitudes are then:
V = v + TvTbv*[(bv)(BcVc)]
B = b + TbTbv*[(bv)(BcVc)]
Bc,Vc are the magnitudes of the comparison star. The transformation coefficients
were measured HERE; they are:
TbTbv = 0.002 +/ 0.027
TvTbv = 0.025 +/ 0.015
The transformed R magnitudes (Rc filter) are computed from the observed
r magnitudes the same way:
R = r + TrTvr*[(vr)(VcRc)]
with the transformation coefficient:
TrTvr = 0.134 +/ 0.017
(one Rc measurement without a match in V in transformed
using a Ic measurement).
And the transformed I magnitudes (Ic filter) from the observed i magnitudes:
I = i + TiTri*[(ri)(RcIc)]
with the transformation coefficient:
TiTri =0.022 +/ 0.011
The raw magnitudes and the transformed magnitudes of the check star
are:
Blue circles: the raw magnitudes, the error bars are +/ the 1 sigma
statistical uncertainties;
Red squares: the transformed magnitudes, the errors bars are computed
from the +/ 1 sigma statistical uncertainties on the raw magnitudes and
the standard deviations on the transformation coefficients;
11.557 is the magnitude according to the AAVSO.
Assuming that the eclipses have a width of 0.25 phase, the transformed
magnitudes as a function of the pulsational phases are:
Blue: for the orbital phases around the primary eclipse;
Cyan: for the orbital phases around the secondary eclipse;
Red: all the other (they are still modulated by the orbital movement according
to Antipin et al (2007)).
The error bars are computed from the 1 sigma statistical uncertainties
on the raw magnitudes and the standard deviations on the transformation
coefficients.
Another pulsational phase plot:
The magnitudes are for the orbital phases outside
the eclipses:
Blue: B magnitudes;
Green: V magnitudes;
Red: Rc magnitudes;
Brown: Ic magnitudes.
Late by 0.12 pulsational period?
The diameter of a cepheid is at its maximum when the brightness is diminishing (around phase 0.25) and it is at its minimium when the brightness is on its rise (~0.75); see for example TX Mon.
When the cepheid of this binary system is eclipsed, the eclipse width should then be larger when the diameter is at its maximum.
Antipin S.V., Sokolovsky K.V., Ignatieva T.I. (2007) MNRAS arXiv/astroph:0705.0605.
Telescope and camera configuration.
Computer and software configuration.
Transformations for differential photometry.
Transformation coefficients: B, V measurements.
Transformation coefficients: V, Rc measurements.
Transformation coefficients: Rc, Ic measurements.
Pulsating stars and its links.
KU Her, a slow irregular variable in the field of view of ASAS1826+12.









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