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In this work we investigate the stellar content of three circumnuclear giant H II regions in the starburst galaxy NGC 7714. We model the stellar population that best reproduces the observational constraints given by the Ha image and the optical spectroscopy from 3710 to 9700 Ó. In this paper we address a robust method for analyzing the stellar content of giant extragalactic H II regions (GEHRs) as a Ðrst step in a strategy that should allow us to understand better how star formation proceeds. To test the power of the method, we have chosen three very well-studied regions in which many observational constraints are known. The models reproduce simultaneously the observed sizes derived from the Ha image, the emission-line spectrum from the gaseous component, and the optical features from the massive stars such as Wolf-Rayet bumps in emission, and the near-infrared calcium triplet, CaT, in absorption when detected. We Ðt the stellar populations through evolutionary synthesis models plus the photoionization code CLOUDY, under the assumption of a shell geometry for the regions. This approach allows us to derive the physical properties of the star clusters, such as mass, age, and metallicity, inside these GEHRs. The method is based on previous work of a complete grid of photoionization models for giant H II regions ionized by evolving star clusters of di †erent metallicities (from 0.05 to 2.5 times solar) and ages between 1 and 5.4 Myr. For the present work, we have followed the cluster evolution further, even after the ionization phase has come to an end, in order to reproduce the observed values of the continuum luminosity at 9000 and the equivalent widths of Hb in emission and CaT in absorption. Ó From the results, we Ðnd in two of the three studied regions that a single ionizing stellar burst is sufficient to explain all the observational constraints if no reddening is a †ecting the cluster continuum. Otherwise, the observed values of the Hb equivalent widths imply the existence of an older component. In this latter case, we Ðnd that a model in which two bursts of star formation are considered, a young ionizing one, with ages 3È5 Myr and an older one of 7È9 Myr, that can reproduce the observations. In the third region, the presence of CaT in the near-IR indicates the presence of a non-ionizing population, whose origin is thoroughly discussed.

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We present long‐slit observations in the optical and near‐infrared of eight H ii regions in the spiral galaxy NGC 4258. Six of the observed regions are located in the south‐east inner spiral arms, and the other two are isolated in the northern outer arms. A detailed analysis of the physical conditions of the gas has been performed. For two of the regions, an electron temperature has been derived from the [S iii] λ6312 line. For the rest, an empirical calibration based on the red and near‐infrared sulphur lines has been used. The oxygen abundances derived by both methods are found to be significantly lower (by a factor of 2) than previously derived by using empirical calibrations based on the optical oxygen lines. In the brightest region, 74C, the observation of a prominent feature caused by Wolf–Rayet (WR) stars provides an excellent constraint over some properties of the ionizing clusters. In the light of the current evolutionary synthesis models, no consistent solution is found to explain at the same time both the WR feature characteristics and the emission‐line spectrum of this region. In principle, the presence of WR stars could lead to large temperature fluctuations and also to a hardening of the ionizing radiation. None of these effects is found in region 74C, for which the electron temperatures found from the [S iii] λ6312 line and the Paschen discontinuity at 8200 Å are equal within the errors, and the effective temperature of the ionizing radiation is estimated at around 35 300 K. Both more observations of confirmed high‐metallicity regions and a finer metallicity grid for the evolutionary synthesis models are needed in order to understand the ionizing populations of H ii regions.

We have studied the physical conditions in the central 300 pc of the prototypical starburst galaxy NGC 7714. Our analysis is based on ultraviolet spectroscopy with the HST /GHRS and ground-based optical observations, and it also covers X-ray and radio data taken from the literature. The data are interpreted using evolutionary models optimized for young starburst regions. The massive stellar population is derived in a self-consistent way using the continuum and stellar absorption lines in the ultraviolet and the nebular emission-line optical spectrum. The central starburst has an age of about 4.5 Myr, with little evidence for an age spread. Wolf-Rayet features at the ultraviolet indicate a stellar population of D2000 Wolf-Rayet stars. The overall properties of the newly formed stars are quite similar to those derived, e.g., in 30 Doradus. A standard Salpeter initial mass function is consistent with all observational constraints. The nucleus of NGC 7714 has a bolometric luminosity of (0.5È1)]1010 and a mass of(if low-mass stars have formed). We Ðnd evidence for spatial structure within the M _ central 300 pc sampled. Therefore it is unlikely that the nucleus of NGC 7714 hosts a single star cluster exceeding the properties of other known clusters. Contrary to previous suggestions, we Ðnd no evidence for a nuclear supernova rate that would signiÐcantly exceed the total disk-integrated rate. About one supernova event per century is predicted. Most of these events are associated with the core collapse of a hydrogen-free or -poor progenitor. An older stellar generation, with ages of tens of Myr and older, is suggested as well. This population is less concentrated toward the nucleus and extends over kiloparsec scales.

The CARMENES instrument has been operational at the 3.5 m telescope of Calar Alto Observatory since January 2016. It consists of two cross-dispersedéchelle spectrographs covering the wavelength range from 0.52 to 1.71 µm. CARMENES is currently conducting a radial-velocity survey of more than 300 M dwarfs, with a sensitivity sufficient to detect terrestrial planets in their habitable zones. This survey has already yielded a comprehensive spectral atlas of 324 M dwarfs, and it is providing a wealth of diagnostic information on activity in cool stars. The CARMENES Survey data have confirmed a number of known M star planets, and revealed previously unknown planets of GJ 15 A, GJ 1148, and GJ 617 A. CARMENES data have also been used to determine the mass of the transiting planet K2-18 b, and to measure atomic and molecular absorption in planetary atmospheres through transit spectroscopy.

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