[vsnet-obs 42506] Variable star V11 in M13

["Francisco A. Violat Bordonau" <fviolat@yahoo.es>]

Dear Colleagues:

Using telescopes of 30.5 and 20.3 cm, installed in
Palma de Mallorca and Cáceres (Spain), we have studied
the behavior of the red variable star V11 (SRD),
located in M13, during a period of 521 days (of DJ
2,452,076 to DJ 2,452,596, both inclusively), and in
measured him during 129 nights in 2001 and 189 nights
in 2002 (318 nights altogether), its magnitude V
Johnson.
Of the analysis of these measurements we verified that
V11 presents (at least) two different cycles of
pulsation: one length, of 128 days, in which it clears
11,8ª magnitude and another short (around 101 days) in
which his brightness maximum round 12ª magnitude.
Our instruments are of 3 to 7 times smaller than the
used ones by the professionals who have preceded to us
(Demers, Osborn, Welty, Russev, 60 to 150 cm
aperture), so that the dispersion of our measurements
arrives, in some cases, to 0.1 magnitudes; whatsoever
we have not been able to confirm the cycle of 92 days
that appears in the official data of V11, but that we
found it quite greater.
We can send the light curves to that us request them.
A greeting from Spain.


Francisco A. Violat Bordonau

Observatorio Astronomico de Cáceres
Asociación de Variabilistas de España
Asesores Astronómicos Cacereños

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