  GJ9827 is a bright star hosting a planetary system with three transiting
planets. As a multi-planet system with planets that sprawl within the
boundaries of the radius gap between terrestrial and gaseous planets, GJ9827 is
an optimal target to study the evolution of the atmospheres of close-in planets
with a common evolutionary history and their dependence from stellar
irradiation. Here, we report on the Hubble Space Telescope (HST) and CARMENES
transit observations of GJ9827 planets b and d. We performed a stellar and
interstellar medium characterization from the ultraviolet HST spectra,
obtaining fluxes for Ly-alpha and MgII of F(Ly-alpha) = (5.42+0.96-0.75) X
10^{-13} erg cm^{-2} s^{-1} and F(MgII) = (5.64 +- 0.24) X 10^{-14} erg cm^{-2}
s^{-1}. We also investigated a possible absorption signature in Ly-alpha in the
atmosphere of GJ9827b during a transit event from HST spectra, as well as
H-alpha and HeI signature for the atmosphere of GJ9827b and d from CARMENES
spectra. We found no evidence of an extended atmosphere in either of the
planets. This result is also supported by our analytical estimations of
mass-loss based on the measured radiation fields for all the three planets of
this system, which led to a mass-loss rate of 0.4, 0.3, and 0.1 planetary
masses per Gyr, for GJ9827b, c, and d respectively. These values indicate that
the planets could have lost their volatiles quickly in their evolution and
probably do not retain an atmosphere at the current stage.
