EH Lib: 2007 follow up
Observed: 24 Apr, 7, 12 July 2007
16 Nov 2007
Time-series of this DSCT pulsating star with a period of 2.1h are
presented and compared with 2004-2005 observations.
EH Lib is a pulsating star of the DSCT (delta Scuti) type. Stars of this
type have radial and non radial pulsations. The period of the pulsations
of EH Lib is 2.12 hours.
I already observed this star in 2004-2005;
these new time-series are to assess the pulsational stability.
The observations were carried out with a 203mm f/6.3 SC telescope, a V filter
(a Rc filter in 2004-2005) and a SBIG ST7E camera (KAF401E CCD).
318 images were obtained, each exposure is 60s long.
The comparison star is TYC4987.00657/1 with a V magnitude of 9.796,
computed from the Bt and Vt magnitudes owing to Mamajek et al (2002) & (2006).
There are 3 check stars: K=GSC4987-00415 with a measured magnitude of 11.209
and a standard deviation of 0.013, K1=GSC4987-00180 (12.206+/-0.023), K2=GSC4987-00262
An example of a light curve:
Red: EH Lib; magenta, dark, blue: the K star shifted by -1 mag,
K1 shifted by -1.7, K2 shifted by -1.2, respectively. The error bars are +/- the
1 sigma statistical uncertainties.
All the light curves are HERE.
According to the GCVS the ephemeris for the pulsation is:
t = 2433438.6082 (6 Jun 1950) + 0.0884132445*E
This yields the phase plot:
The pulsation is 0.035 period or 4mn late from the ephemeris.
This can be compared with my 2004 and 2005 observations (Rc filter):
Red: these 2007 observations (V filter);
Green: 2005 (Rc filter) shifted by -0.95 mag;
Blue: 2004 (Rc filter) shifted by -1.1.
There may be some hint that the pulsation is slowing down (or that the
period needs to be refined), but no hard evidence.
I also looked at the ROTSE and ASAS measurements, but I have not enough data
to precisely time the pulsation.
Mamajek E.E., Meyer M.R., Liebert J. (2002) AJ 124 1670 Appendix C;
erratum (2006) AJ 131 2360.
Telescope and camera configuration.
Computer and software configuration.
My 2004-2005 observations.
Pulsating stars and its links.