Very Low Mass Stars, Brown Dwarfs and Planets

    General
    Description

    Our goal is to study the processes that lead to the formation of low mass stars, brown dwarfs and planets and to characterize the physical properties of these objects in various evolutionary stages. Low mass stars and brown dwarfs are likely the most numerous type of objects in our Galaxy but due to their low intrinsic luminosity they are not so well known. We aim to study the frequency, multiplicity and spatial distribution of these objects in the solar neighbourhood and in nearby star forming regions and stellar clusters in order to better understand the mechanism of formation, characterise their optical and infrared properties and establish the relation between spectral properties, mass and luminosity.. Most of our effort will be dedicated to push toward lower mass limits the detection of these astros either bounded to stars and brown dwarfs and/or free-floating in interstellar space. The lowest mass objects display a lower intrinsic luminosity and cooler effective temperatures thus they are remarkably difficult to detect using direct imaging techniques. However, these techniques allow a full photometric and spectroscopic characterization and a best determination of their physical and chemical properties. We also aim to investigate the presence of planets around low mass stars using radial velocity measurements and techniques for high spatial resolution imaging. We will develop ultrastable spectrographs for large telescopes and systems for ultrafast imaging. With the spectrographs it would be possible to detect planets of similar mass to the Earth around G, K and M-type stars. The goal is to establish the frequency of these planets in stars of the solar neighbourhood and characterise the properties of the associated planetary systems.

    1. The optical and near-infrared sequence of 10 Myr-old L dwarfs in the nearest OB association to the Sun, Upper Scorpius
    2. The lithium depletion boundary of the Hyades cluster.

    Related publications

    • Photometric follow-up of the 20 Myr old multi-planet host star V1298 Tau with CHEOPS and ground-based telescopes

      Context. The 20 Myr old star V1298 Tau hosts at least four planets. Since its discovery, this system has been a target of intensive photometric and spectroscopic monitoring. To date, the characterisation of its architecture and planets' fundamental properties has been very challenging. Aims: The determination of the orbital ephemeris of the

      Damasso, M. et al.

      Advertised on:

      12
      2023
      Citations
      1
    • The GAPS programme at TNG. XLVIII. The unusual formation history of V1298 Tau

      Context. Observational data from space- and ground-based campaigns have revealed that the 10-30 Ma old V1298Tau star hosts a compact and massive system of four planets. Mass estimates are available for the two outer giant planets and point to unexpectedly high densities for their young ages. Aims: We investigate the formation of these two outermost

      Turrini, D. et al.

      Advertised on:

      11
      2023
      Citations
      2
    • A compact multi-planet system transiting HIP 29442 (TOI-469) discovered by TESS and ESPRESSO. Radial velocities lead to the detection of transits with low signal-to-noise ratio

      Context. One of the goals of the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) Guaranteed Time Observations (GTO) consortium is the precise characterisation of a selected sample of planetary systems discovered by TESS. One such target is the K0V star HIP 29442 (TOI-469), already known to host a validated

      Damasso, M. et al.

      Advertised on:

      11
      2023
      Citations
      0
    • An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)

      Context. Small planets located at the lower mode of the bimodal radius distribution are generally assumed to be composed of iron and silicates in a proportion similar to that of the Earth. However, recent discoveries are revealing a new group of low-density planets that are inconsistent with that description. Aims: We intend to confirm and

      Castro-González, A. et al.

      Advertised on:

      7
      2023
      Citations
      4
    • Planetary system around LTT 1445A unveiled by ESPRESSO: Multiple planets in a triple M-dwarf system

      We present radial velocity follow-up obtained with ESPRESSO of the M-type star LTT 1445A (TOI-455), for which a transiting planet b with an orbital period of 5.4 days was detected by TESS. We report the discovery of a second transiting planet (LTT 1445A c) and a third non-transiting candidate planet (LTT 1445A d) with orbital periods of 3.12 and 24

      Lavie, B. et al.

      Advertised on:

      5
      2023
      Citations
      6
    • Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433

      Context. Although the number of exoplanets reported in the literature exceeds 5000 so far, only a few dozen of them are young planets (≤900 Myr). However, a complete characterization of these young planets is key to understanding the current properties of the entire population. Hence, it is necessary to constrain the planetary formation processes

      Zechmeister, M. et al.

      Advertised on:

      3
      2023
      Citations
      2
    • The CARMENES search for exoplanets around M dwarfs. Guaranteed time observations Data Release 1 (2016-2020)

      Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to

      Ribas, I. et al.

      Advertised on:

      2
      2023
      Citations
      17
    • Two temperate Earth-mass planets orbiting the nearby star GJ 1002

      We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ 1002 based on the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs. The host star is the quiet M5.5 V star GJ 1002 (relatively faint in the optical, V ~ 13.8 mag, but brighter in

      Suárez Mascareño, A. et al.

      Advertised on:

      2
      2023
      Citations
      14
    • Lower-than-expected flare temperatures for TRAPPIST-1

      Aims: Stellar flares emit thermal and nonthermal radiation in the X-ray and ultraviolet (UV) regime. Although high energetic radiation from flares is a potential threat to exoplanet atmospheres and may lead to surface sterilization, it might also provide the extra energy for low-mass stars needed to trigger and sustain prebiotic chemistry. Despite

      Maas, A. J. et al.

      Advertised on:

      12
      2022
      Citations
      1
    • A quarter century of spectroscopic monitoring of the nearby M dwarf Gl 514. A super-Earth on an eccentric orbit moving in and out of the habitable zone

      Context. Statistical analyses based on Kepler data show that most of the early-type M dwarfs host multi-planet systems consisting of Earth- to sub-Neptune-sized planets with orbital periods of up to ~250 days, and that at least one such planet is likely located within the habitable zone. M dwarfs are therefore primary targets to search for

      Damasso, M. et al.

      Advertised on:

      10
      2022
      Citations
      12
    • TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley

      We report the discovery and characterization of two small transiting planets orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose transit signals were detected in the photometric time series in three sectors of the TESS mission. We confirm the planetary nature of both of them using precise radial velocity measurements from the CARMENES

      Chaturvedi, P. et al.

      Advertised on:

      10
      2022
      Citations
      7
    • The CARMENES search for exoplanets around M dwarfs. Stable radial-velocity variations at the rotation period of AD Leonis: A test case study of current limitations to treating stellar activity

      Context. A challenge with radial-velocity (RV) data is disentangling the origin of signals either due to a planetary companion or to stellar activity. In fact, the existence of a planetary companion has been proposed, as well as contested, around the relatively bright, nearby M3.0 V star AD Leo at the same period as the stellar rotation of 2.23

      Kossakowski, D. et al.

      Advertised on:

      10
      2022
      Citations
      13
    • SPECULOOS Northern Observatory: Searching for Red Worlds in the Northern Skies

      SPECULOOS is a ground-based transit survey consisting of six identical 1 m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report

      Burdanov, Artem Y. et al.

      Advertised on:

      10
      2022
      Citations
      8
    • A detailed analysis of the Gl 486 planetary system

      Context. The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R⊕ and 3.0 M⊕. It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. Aims: To prepare for future studies, we aim to thoroughly

      Caballero, J. A. et al.

      Advertised on:

      9
      2022
      Citations
      17
    • The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc

      We report the discovery of a multiplanetary system transiting the M0 V dwarf HD 260655 (GJ 239, TOI-4599). The system consists of at least two transiting planets, namely HD 260655 b, with a period of 2.77 d, a radius of Rb = 1.240 ± 0.023 R⊕, a mass of Mb = 2.14 ± 0.34 M⊕, and a bulk density of ρb = 6.2 ± 1.0 g cm−3, and HD 260655 c, with a period

      Luque, R. et al.

      Advertised on:

      8
      2022
      Citations
      12
    • The CARMENES search for exoplanets around M dwarfs. Rotational variation in activity indicators of Ross 318, YZ CMi, TYC 3529-1437-1, and EV Lac

      Context. The Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Échelle Spectrographs (CARMENES) instrument is searching for periodic radial-velocity (RV) variations of M dwarfs, which are induced by orbiting planets. However, there are other potential sources of such variations, including rotational

      Schöfer, P. et al.

      Advertised on:

      7
      2022
      Citations
      9
    • The CARMENES search for exoplanets around M dwarfs. Benchmarking the impact of activity in high-precision radial velocity measurements

      Context. Current exoplanet surveys using the radial velocity (RV) technique are targeting M dwarfs because any habitable zone terrestrial-mass planets will induce a high RV and orbit on shorter periods than for more massive stars. One of the main caveats is that M dwarfs show a wide range of activity levels from inactive to very active, which can

      Jeffers, S. V. et al.

      Advertised on:

      7
      2022
      Citations
      16
    • The CARMENES search for exoplanets around M dwarfs. Two Saturn-mass planets orbiting active stars

      The CARMENES radial-velocity survey is currently searching for planets in a sample of 387 M dwarfs. Here we report on two Saturn-mass planets orbiting TYC 2187-512-1 (M* = 0.50 M⊙) and TZ Ari (M* = 0.15 M⊙), respectively. We obtained supplementary photometric time series, which we use along with spectroscopic information to determine the rotation

      Quirrenbach, A. et al.

      Advertised on:

      7
      2022
      Citations
      13
    • Magnetism, rotation, and nonthermal emission in cool stars. Average magnetic field measurements in 292 M dwarfs

      Stellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of Sun-like and low-mass stars, and for the development of their planetary systems. As a key to understanding stellar dynamos, empirical relations between stellar parameters and magnetic fields are required for comparison to ab initio

      Reiners, A. et al.

      Advertised on:

      6
      2022
      Citations
      65
    • A study of flares in the ultra-cool regime from SPECULOOS-South

      We present a study of photometric flares on 154 low-mass (≤0.2 M⊙) objects observed by the SPECULOOS-South Observatory from 2018 June 1 to 2020 March 23. In this sample, we identify 85 flaring objects, ranging in spectral type from M4 to L0. We detect 234 flares in this sample, with energies between 1029.2 and 1032.7 erg, using both automated and

      Murray, C. A. et al.

      Advertised on:

      6
      2022
      Citations
      11

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