Constraints on atmospheric water abundance and cloud deck pressure in the warm Neptune GJ 3470 b via CARMENES transmission spectroscopy

Observations of cooler atmospheres of super-Earths and Neptune sized objects often show flat transmission spectra. The most likely cause of this trend is the presence of aerosols (i.e. clouds and hazes) in the atmospheres of such objects. High-resolution spectroscopy provides an opportunity to test this hypothesis by targeting molecular species whose spectral line cores extend above the level of such opaque decks. In this work, we analyse high-resolution infrared observations of the warm Neptune GJ 3470 b taken over two transits using CARMENES (R ∼ 80,000) and look for signatures of H2O (previously detected using HST WFC3+Spitzer observations) in these transits with a custom pipeline fully accounting for the effects of data cleaning on any potential exoplanet signal. We find that our data are potentially able to weakly detect (∼

HD 191939 revisited: New and refined planet mass determinations, and a new planet in the habitable zone

HD 191939 (TOI-1339) is a nearby (d = 54 pc), bright (V = 9 mag), and inactive Sun-like star (G9 V) known to host a multi-planet transiting system. Ground-based spectroscopic observations confirmed the planetary nature of the three transiting sub-Neptunes (HD 191939 b, c, and d) originally detected by TESS and were used to measure the masses for planets b and c with 3\ucf precision. These previous observations also reported the discovery of an additional Saturn-mass planet (HD 191939 e) and evidence for a further, very long-period companion (HD 191939 f). Here, we report the discovery of a new non-transiting planet in the system and a refined mass determination of HD 191939 d. The new planet, HD 191939 g, has a minimum mass of 13.5\ub12.0 M- and a period of about 280 days. This period places the planet within the conservative habitable zone of the host star, and near a 1:3 resonance with HD 191939 e. The compilation of 362 radial velocity measurements with a baseline of 677 days from four different high-resolution spectrographs also allowed us to refine the properties of the previously known planets, including a 4.6\ucf mass determination for planet d, for which only a 2\ucf upper limit had been set until now. We confirm the previously suspected low density of HD 191939 d, which makes it an attractive target for attempting atmospheric characterisation. Overall, the planetary system consists of three sub-Neptunes interior to a Saturn-mass and a Uranus-mass planet plus a high-mass long-period companion. This particular configuration has no counterpart in the literature and makes HD 191939 an exceptional multi-planet transiting system with an unusual planet demographic worthy of future observation

A Transiting, Temperate Mini-Neptune Orbiting the M Dwarf TOI-1759 Unveiled by TESS

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.-- Full list of authors: Espinoza, Néstor; Pallé, Enric; Kemmer, Jonas; Luque, Rafael; Caballero, José A.; Cifuentes, Carlos; Herrero, Enrique; Sánchez Béjar, Víctor J.; Stock, Stephan; Molaverdikhani, Karan; Morello, Giuseppe; Kossakowski, Diana; Schlecker, Martin; Amado, Pedro J.; Bluhm, Paz; Cortés-Contreras, Miriam; Henning, Thomas; Kreidberg, Laura; Kürster, Martin; Lafarga, Marina; Lodieu, Nicolas; Morales, Juan Carlos; Oshagh, Mahmoudreza; Passegger, Vera M.; Pavlov, Alexey; Quirrenbach, Andreas; Reffert, Sabine; Reiners, Ansgar; Ribas, Ignasi; Rodríguez, Eloy; López, Cristina Rodríguez; Schweitzer, Andreas; Trifonov, Trifon; Chaturvedi, Priyanka; Dreizler, Stefan; Jeffers, Sandra V.; Kaminski, Adrian; López-González, María José; Lillo-Box, Jorge; Montes, David; Nowak, Grzegorz; Pedraz, Santos; Vanaverbeke, Siegfried; Zapatero Osorio, Maria R.; Zechmeister, Mathias; Collins, Karen A.; Girardin, Eric; Guerra, Pere; Naves, Ramon; Crossfield, Ian J. M.; Matthews, Elisabeth C.; Howell, Steve B.; Ciardi, David R.; Gonzales, Erica; Matson, Rachel A.; Beichman, Charles A.; Schlieder, Joshua E.; Barclay, Thomas; Vezie, Michael; Villaseñor, Jesus Noel; Daylan, Tansu; Mireies, Ismael; Dragomir, Diana; Twicken, Joseph D.; Jenkins, Jon; Winn, Joshua N.; Latham, David; Ricker, George; Seager, Sara.We report the discovery and characterization of TOI-1759 b, a temperate (400 K) sub-Neptune-sized exoplanet orbiting the M dwarf TOI-1759 (TIC 408636441). TOI-1759 b was observed by TESS to transit in Sectors 16, 17, and 24, with only one transit observed per sector, creating an ambiguity regarding the orbital period of the planet candidate. Ground-based photometric observations, combined with radial-velocity measurements obtained with the CARMENES spectrograph, confirm an actual period of 18.85019 ± 0.00014 days. A joint analysis of all available photometry and radial velocities reveals a radius of 3.17 ± 0.10 R⊕ and a mass of 10.8 ± 1.5 M⊕. Combining this with the stellar properties derived for TOI-1759 (R⋆ = 0.597 ± 0.015 R⊙; M⋆ = 0.606 ± 0.020 M⊙; Teff = 4065 ± 51 K), we compute a transmission spectroscopic metric (TSM) value of over 80 for the planet, making it a good target for transmission spectroscopy studies. TOI-1759 b is among the top five temperate, small exoplanets (Teq 200 days seem to be present in our radial velocities. While our data suggest both could arise from stellar activity, the later signal's source and periodicity are hard to pinpoint given the ∼200 days baseline of our radial-velocity campaign with CARMENES. Longer baseline radial-velocity campaigns should be performed in order to unveil the true nature of this long-period signal. © 2022. The Author(s). Published by the American Astronomical Society.CARMENES is an instrument at the Centro Astronómico Hispano-Alemán (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Junta de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Científicas (CSIC), the Ministerio de Economía y Competitividad (MINECO), and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciëncies de l'Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología, and Centro Astronómico Hispano-Alemán), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft through the Major Research Instrumentation Programme and Research Unit FOR2544 "Blue Planets around Red Stars," the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. This work was based on data from the CARMENES data archive at CAB (CSIC-INTA). We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4], PGC2018-098153-B-C33, AYA2018-84089, PID2019-107061GB-C64, PID2019-110689RB-100, AYA2016-79425-C3-1/2/3-P, and BES-2017-080769, and the Centre of Excellence "Severo Ochoa" and "María de Maeztu" awards to the Instituto de Astrofísica de Canarias (CEX2019-000920-S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737), NASA (NNX17AG24G), and the Generalitat de Catalunya/CERCA program. Data were partly collected with the 90 cm telescope at the Sierra Nevada Observatory (SNO) operated by the Instituto de Astrofí fica de Andalucí a (IAA, CSIC). We acknowledge the telescope operators from the Sierra Nevada Observatory for their support. G.M. has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 895525. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products.Peer reviewe

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme-precision radial-velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The Extreme-precision Spectrograph (EXPRES) Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed radial-velocity (RV) correction, or separated out shape- and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV rms than classic linear decorrelation, but no method is yet consistently reducing the RV rms to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets—such as solar data or data with known injected planetary and/or stellar signals—to better understand method performance and whether planetary signals are preserved

Stellar activity and exoplanets ofMdwarfs from CARMENES visible to near-infrared spectroscopy

Després del descobriment dels primers exoplanetes fa unes tres dècades, la detecció i caracterització de companys planetaris s'ha convertit en un tema de recerca prominent, especialment la cerca de planetes semblants a la Terra, cossos rocosos que orbiten a la zona habitable (HZ) de les seves estrelles hostes. Un dels principals mètodes utilitzats per trobar i caracteritzar exoplanetes és la tècnica de l'espectroscòpia Doppler o velocitat radial (RV), basada en l'ús d'espectres estel·lars per mesurar canvis periòdics en la RV d'una estrella causats per l'atracció gravitatòria d'un exoplaneta en òrbita. Actualment, la variabilitat intrínseca de les estrelles hostes és el principal repte en l'estudi d'exoplanetes. Les estrelles no són cossos invariables i homogenis, sinó que presenten variabilitat en diferents escales de temps. La més rellevant és l'activitat magnètica estel·lar, que inclou fenòmens com ara taques o fàcules que apareixen a la superfície de l'estrella i estan modulades per la seva rotació. Aquests fenòmens distorsionen els espectres estel·lars, introduint biaixos en les RVs prou grans com per amagar o fins i tot imitar el senyal causat per un planeta. Per tant, per continuar detectant i estudiant exoplanetes de baixa massa, és clau aconseguir una millor comprensió d'aquests fenòmens estel·lars i els seus efectes en les nostres observacions. Aquesta tesi se centra en l'estudi dels efectes de l'activitat estel·lar en observacions espectroscòpiques d'estrelles fredes obtingudes amb l'instrument CARMENES. CARMENES és un espectrògraf d'alta resolució capaç d'observar el rang de longitud d'ona visible i infraroig proper. Està realitzant un estudi de més de 300 nanes M, les estrelles amb menor massa de la seqüència principal, amb l'objectiu primordial de detectar exoplanetes petits. En primer lloc, hem desenvolupat un codi que implementa el mètode de la funció de correlació creuada (CCF) per mesurar RVs i indicadors d'activitat estel·lar en observacions d'alta resolució, i l'hem aplicat a les dades de CARMENES. Aquest mètode utilitza màscares binàries ponderades, un template estel·lar simplificat construït mitjançant la selecció de línies espectrals. Hem creat diverses màscares en funció del subtipus espectral i de la velocitat de rotació de l'estrella a analitzar. A continuació, hem utilitzat els indicadors d'activitat derivats de la CCF, juntament amb altres indicadors d'activitat espectroscòpics, per analitzar les seves variacions temporals en una mostra de quasi 100 nanes M de diverses masses i nivells d'activitat. Aproximadament la meitat de les estrelles analitzades mostren RVs amb senyals d'activitat clars. Diferents indicadors són sensibles a l'activitat de manera diferent segons les característiques de l'estrella: indicadors cromosfèrics són més útils per a estrelles de baixa activitat, indicadors relacionats amb el canvi de RV amb longitud d'ona funcionen millor per a les estrelles més actives, i altres indicadors relacionats amb el canvi d'amplada de les línies fotosfèriques proporcionen resultats similars en tot tipus d'estrelles, però són especialment útils per a les més actives i de menor massa. Finalment, hem analitzat els efectes de l'activitat sobre línies d'absorció individuals presents en l'espectre d'estrelles actives. Estudiant les correlacions entre les RVs de línies individuals i els indicadors d'activitat, podem classificar les línies observades segons la seva sensibilitat a l'activitat. Això ens permet seleccionar línies afectades de forma diferent per l'activitat i utilitzar-les per tornar a calcular RVs. Així obtenim RVs per a les quals mitiguem o incrementem el senyal d'activitat en diversos graus. També observem que les mateixes línies en diferents estrelles mostren diferent sensibilitat a l'activitat.Después del descubrimiento de los primeros exoplanetas hace unas tres décadas, la detección y caracterización de compañeros planetarios se ha convertido en un tema de investigación prominente, especialmente la búsqueda de planetas parecidos a la Tierra, cuerpos rocosos que orbitan en la zona habitable (HZ) de sus estrellas huéspedes. Uno de los principales métodos utilizados para encontrar y caracterizar exoplanetas es la técnica de la espectroscopía Doppler o velocidad radial (RV), basada en el uso de espectros estelares para medir cambios periódicos en la RV de una estrella causados por la atracción gravitatoria de un exoplaneta en órbita. Actualmente, la variabilidad intrínseca de las estrellas huéspedes es el principal reto en el estudio de exoplanetas. Las estrellas no son cuerpos invariables ni homogéneos, sino que presentan variabilidad en distintas escalas de tiempo. La más relevante es la actividad magnética estelar, que incluye fenómenos como manchas o fáculas que aparecen en la superficie de la estrella y están moduladas por su rotación. Estos fenómenos distorsionan los espectros estelares, introduciendo sesgos en las RVs suficientemente grandes como para esconder o hasta imitar la señal causada por un planeta. Por lo tanto, para continuar detectando y estudiando exoplanetas de baja masa, una mejor comprensión de estos fenómenos estelares y sus efectos en nuestras observaciones es clave. Esta tesis se centra en el estudio de los efectos de la actividad estelar en observaciones espectroscópicas de estrellas frías obtenidas con el instrumento CARMENES. CARMENES es un espectrógrafo de alta resolución capaz de observar en el rango de longitudes de onda visible e infrarojo cercano. Está realizando un estudio de más de 300 enanas M, las estrellas con menor masa de la secuencia principal, con el objetivo primordial de detectar exoplanetas pequeños. En primer lugar, hemos desarrollado un código que implementa el método de la función de correlación cruzada (CCF) para medir RVs e indicadores de actividad estelar en observaciones de alta resolución, y lo hemos aplicado a los datos de CARMENES. Este método usa máscaras binarias ponderadas, un template estelar simplificado construido seleccionando líneas espectrales. Hemos creado varias máscaras en función del subtipo espectral y de la velocidad de rotación de la estrella a analizar. A continuación, hemos utilizado los indicadores de actividad derivados de la CCF, juntamente con otros indicadores de actividad espectroscópicos, para analizar sus variaciones temporales en una muestra de casi 100 enanas M de varias masas y niveles de actividad. Aproximadamente la mitad de las estrellas analizadas muestran RVs con señales de actividad claros. Distintos indicadores son sensibles a la actividad de forma diferente según las características de la estrella: indicadores cromosféricos son más útiles para estrellas de baja actividad, indicadores relacionados con el cambio de RV con la longitud de onda funcionan mejor para estrellas más activas, y otros indicadores relacionados con el cambio de anchura de las líneas fotosféricas proporcionan resultados similares en todo tipo de estrellas, pero son especialmente útiles para las más activas y de menor masa. Finalmente, hemos analizado los efectos de la actividad sobre líneas de absorción individuales presentes en el espectro de estrellas activas. Estudiando las correlaciones entre las RVs de líneas individuales y los indicadores de actividad, podemos clasificar las líneas observadas según su sensibilidad a la actividad. Esto nos permite seleccionar líneas afectadas de forma distinta por la actividad y usarlas para volver a calcular RVs. De esta forma obtenemos RVs para las cuales mitigamos o incrementamos la señal de actividad en diversos grados. También observamos que las mismas líneas en distintas estrellas muestran diferente sensibilidad a la actividad.After the discovery of the first exoplanets about three decades ago, the detection and characterization of planetary companions has become a prominent research topic, especially the search for Earth-like planets, rocky bodies orbiting in the habitable zone (HZ) of their host stars. One of the main methods used to find and characterise exoplanets is the Doppler spectroscopy or radial velocity (RV) technique, based on using stellar spectra to measure periodic changes in the RV of a star caused by the gravitational pull of an orbiting exoplanet. Currently, the intrinsic variability of the host stars is the major challenge faced in the study of exoplanets. Stars are not quiet, homogeneous bodies, but display variability on different timescales, the most concerning being stellar magnetic activity, phenomena such as spots or faculae appearing on the stellar surface and modulated by the stellar rotation. These features distort the stellar spectra, introducing biases in our RVs that can be large enough to hide or even mimic the signal caused by a planet. Therefore, to continue detecting and studying low-mass exoplanets, a better understanding of these stellar phenomena and their effects on our observations is key. This thesis is focused on the study of stellar activity effects on spectroscopic observations of cool stars obtained with the CARMENES instrument. CARMENES is a high-resolution spectrograph capable of observing on the visible and near-infrared wavelength ranges. It is performing a survey of over 300 M dwarfs, stars at the low-mass end of the main sequence, with the main goal of detecting small exoplanets. Firstly, we developed a pipeline that implements the cross-correlation function (CCF) method to measure RVs and indicators of stellar activity on high-resolution observations, and applied it to the CARMENES survey data. This method uses weighted binary masks, a simplified stellar template built by selecting sharp spectral lines, of which we created different kinds depending on the spectral subtype and the rotational velocity of the target star. We then used the activity indicators derived from the CCF, together with other spectroscopic activity proxies, to analyse their temporal variations in a sample of almost 100 M dwarfs with a range of masses and activity levels. We found that about half of the stars analysed show RVs with clear signals of activity. Different indicators trace activity differently depending on the characteristics of the star: chromospheric indicators are the most useful for low-activity stars, indicators related to the change in RV with wavelength work better for the most active stars, and other indicators related to the change in width of the photospheric lines provide similar results in all types of stars, but are especially useful for the most active and lowest-mass ones. Finally, we analysed the effects of activity on individual absorption features present on the spectra of active stars. By studying the correlations between the individual line RVs and activity indicators, we are able to classify the observed lines according to their sensitivity to activity. This allow us to select differently affected lines and use them to recompute RVs for which we mitigate or enhance the activity signal to varying degrees. We also observe that the same lines on different stars show different sensitivities to activity

Unambiguous localization of titanium and iron cations in doped manganese hollandite nanowires

New insights into the chemical and structural features of iron or titanium-doped KxMnO2 hollandites are reported. Neutron diffraction and atomically resolved transmission electron microscopy elucidate the localization of the dopant cations that could be one of the key factors governing the functional activity of these nanomaterials.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEpu

Exceptional Low-Temperature CO Oxidation over Noble-Metal-Free Iron-Doped Hollandites: An In-Depth Analysis of the Influence of the Defect Structure on Catalytic Performance

A family of iron-doped manganese-related hollandites, KxMn1−yFeyO2−δ (0 ≤ y ≤ 0.15), with high performance in CO oxidation have been prepared. Among them, the most active catalyst, K0.11Mn0.876Fe0.123O1.80(OH)0.09, is able to oxidize more than 50% of CO at room temperature. Detailed compositional and structural characterization studies, using a wide battery of thermogravimetric, spectroscopic, and diffractometric techniques, both at macroscopic and microscopic levels, have provided essential information about this never-reported behavior, which relates to the oxidation state of manganese. Neutron diffraction studies evidence that the above compound stabilizes hydroxyl groups at the midpoints of the tunnel edges as in isostructural β- FeOOH. The presence of oxygen and hydroxyl species at the anion sublattice and Mn3+, confirmed by electron energy loss spectroscopy, appears to play a key role in the catalytic activity of this doped hollandite oxide. The analysis of these detailed structural features has allowed us to point out the key role of both OH groups and Mn3+ content in these materials, which are able to effectively transform CO without involving any critical, noble metal in the catalyst formulation.This work was supported by FEDER/Spanish Ministry of Science and Innovation through Research Projects MAT2017- 87579-R, MAT2017-82252-R, RTI2018-101604-B-I00, MCIN/AEI/10.13039/501100011033, Project PID2020- 113006-RB-I00, and ENE2017-82451-C3-2-R. The authors acknowledge the National Centre for Electron Microscopy (ELECMI National Singular Scientific Facility) for provision of corrected aberration microscopy

The HADES RV Programme with HARPS-N@TNG GJ 3998: An early M-dwarf hosting a system of Super-Earths

Many efforts to detect Earth-like planets around low-mass stars are presently devoted in almost every extra-solar planet search. M dwarfs are considered ideal targets for Doppler radial velocity searches because their low masses and luminosities make low-mass planets orbiting in their habitable zones more easily detectable than those around higher mass stars. Nonetheless, the statistics of frequency of low-mass planets hosted by low mass stars remains poorly constrained. Our M-dwarf radial velocity monitoring with HARPS-N within the GAPS (Global architectures of Planetary Systems) – ICE (Institut de Ciències de l’Espai/CSIC-IEEC) – IAC (Instituto de Astrofísica de Canarias) project can provide a major contribution to the widening of the current statistics through the in-depth analysis of accurate radial velocity observations in a narrow range of spectral sub-types (79 stars, between dM0 to dM3). Spectral accuracy will enable us to reach the precision needed to detect small planets with a few earth masses. Our survey will bring a contribute to the surveys devoted to the search for planets around M-dwarfs, mainly focused on the M-dwarf population of the northern emisphere, for which we will provide an estimate of the planet occurrence. We present here a long duration radial velocity monitoring of theM1 dwarf star GJ 3998 with HARPS-N to identify periodic signals in the data. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programs to characterize the stellar activity and to distinguish from the periodic signals those due to activity and to the presence of planetary companions. We run an MCMC simulation and use Bayesian model selection to determine the number of planets in this system, to estimate their orbital parameters and minimum masses and for a proper treatment of the activity noise. The radial velocities have a dispersion in excess of their internal errors due to at least four superimposed signals, with periods of 30.7, 13.7, 42.5 and 2.65 days. Our data are well described by a 2-planet Keplerian (13.7 d and 2.65 d) and 2 sinusoidal functions (stellar activity, 30.7 d and 42.5 d) fit. The analysis of spectral indices based on Ca II H & K and Hα lines demonstrates that the periods of 30.7 and 42.5 days are due to chromospheric inhomogeneities modulated by stellar rotation and differential rotation. This result is supported by photometry and is consistent with the results on differential rotation of M stars obtained with Kepler. The shorter periods of 13.74 ± 0.02 d and 2.6498 ± 0.0008 d are well explained with the presence of two planets, with minimum masses of 6.26 ± 0.79 M⊕ and 2.47 ± 0.27 M⊕ and distances of 0.089 AU and 0.029 AU from the host, respectively