  M-dwarfs have proven to be ideal targets for planetary radial velocity (RV)
searches due to their higher planet-star mass contrast. The HADES and CARMENES
programs aim to carry out extensive searches of exoplanetary systems around
this type of stars in the northern hemisphere, allowing us to address
statistically the properties of the planets orbiting these objects. In this
work, we perform a spectroscopic and photometric study of one of the program
stars (GJ 740), which exhibits a short-period RV signal compatible with a
planetary companion. We carried out a spectroscopic analysis based on 129
HARPS-N spectra taken over a time-span of 6 yr combined with 57 HARPS spectra
taken over 4 yr, as well as 32 CARMENES spectra taken during more than 1 yr,
resulting in a dataset with a time coverage of 10 yr. We also relied on 459
measurements from the public ASAS survey with a time-coverage of 8 yr along
with 5 yr of photometric magnitudes from the EXORAP project taken in the $V$,
$B$, $R$, and $I$ filters to carry out a photometric study. Both analyses were
made using Markov Chain Monte Carlo (MCMC) simulations and Gaussian Process
regression to model the activity of the star. We present the discovery of a
short-period super-Earth with an orbital period of
2.37756$^{+0.00013}_{-0.00011}$ d and a minimum mass of 2.96$^{+0.50}_{-0.48}$
M$_{\oplus}$. We offer an update to the previously reported characterization of
the magnetic cycle and rotation period of the star, obtaining values of $P_{\rm
rot}$=35.563$\pm$0.071 d and $P_{\rm cycle}$=2800$\pm$150 d. Furthermore, the
RV time-series exhibits a possibly periodic long-term signal which might be
related to a Saturn-mass planet of $\sim$ 100 M$_{\oplus}$.
