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Orbital motion and dynamical mass of the complex periodic variable binary system 2MASS J05082729-2101444
S. Curiel, G. N. Ortiz-León, V. J. S. Béjar +22
We used very long baseline interferometry to constrain the orbit of the binary system 2MASS J05082729-2101444. We observed the system with the VLBA in three epochs at a frequency o…
The CARMENES search for exoplanets around M dwarfs. A homogeneous catalogue of projected rotational velocities accounting for limb-darkening
R. Varas, G. Morello, M. Zechmeister +18
Stellar rotation is closely linked to both age and magnetic activity. Through gyrochronology, it provides a means to estimate stellar ages and trace the evolution of planetary syst…
Unveiling the nature of HE 0107-5240
E. Caffau, M. Steffen, P. Molaro +27
The vast majority of the most iron-poor stars in the Galaxy exhibit a strong carbon enhancement, with C/H ratios only about two orders of magnitude below solar. This unusual chemic…
Detection of -band photometric periodicity in the T8 dwarfs 2MASS J09393548-2448279 and EQ J1959-3338
P. A. Miles-Páez, S. Metchev, M. R. Zapatero Osorio +1
Aims: We aim to study the near-infrared variability of the T8 dwarfs 2MASS J09393548-2448279 and EQ J1959-3338 by analyzing their -band photometric signal, which can provide new…
Detection of Methane in the Closest Extreme Metal-poor T Dwarf WISEA J181006.18-101000.5
Jerry Jun-Yan Zhang, Nicolas Lodieu, Eduardo L. Martín +7
WISEA J181006.18-101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as extreme early-T subdwarf. H…
The CARMENES search for exoplanets around M dwarfs: Magnesium and silicon abundances of K7-M5.5 stars
H. M. Tabernero, Y. Shan, J. A. Caballero +13
We present the abundances of magnesium (Mg) and silicon (Si) for 314 dwarf stars with spectral types in the interval K7.0-M5.5 (Teff range ~4200-3050 K) observed with the CARMENES…
On the 12C/13C isotopic ratio at the dawn of chemical evolution
P. Molaro, D. S. Aguado, E. Caffau +21
The known Mega and Hyper Metal-Poor (MMP-HMP) stars with [Fe/H]<-6.0 and <-5.0, respectively, likely belong to the CEMP-no class, i.e. carbon-enhanced stars with low or absent seco…
The CARMENES search for exoplanets around M dwarfs. Line-by-line sensitivity to activity in M dwarfs
M. Lafarga, I. Ribas, M. Zechmeister +17
Radial velocities (RVs) measured from high-resolution stellar spectra are routinely used to detect and characterise orbiting exoplanet companions. The different lines present in st…
The pristine nature of SMSS 16051443 revealed by ESPRESSO
D. S. Aguado, E. Caffau, P. Molaro +20
SMSS J160540.18144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H]=-6.2, which was first reported with the SkyMapper tele…
The CARMENES search for exoplanets around M dwarfs. Variability on long timescales as seen in chromospheric indicators
B. Fuhrmeister, S. Czesla, V. Perdelwitz +19
It is clearly established that the Sun has an 11-year cycle that is caused by its internal magnetic field. This cycle is also observed in a sample of M dwarfs. In the framework of…
Espresso observations of HE 01075240 and other CEMP-no stars with
D. Aguado, P. Molaro, E. Caffau +22
HE 01075240 is a hyper metal-poor star with . We performed high-res observations with the ESPRESSO spectrograph at the VLT to constrain the kinematical propert…
Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5101002.3
N. Lodieu, M. R. Zapatero Osorio, E. L. Martin +2
Our goal is to characterise the physical properties of the metal-poor brown dwarf population. In particular, we focus on the recently discovered peculiar dwarf WISE J18100551010…
The CARMENES search for exoplanets around M dwarfs. Diagnostic capabilities of strong K I lines for photosphere and chromosphere
B. Fuhrmeister, S. Czesla, E. Nagel +20
There are several strong K I lines found in the spectra of M dwarfs, among them the doublet near 7700 AA and another doublet near 12 500 AA. We study these optical and near-infrare…
GTC/CanariCam deep mid-infrared imaging survey of northern stars within 5 pc
Bartosz Gauza, Víctor J. S. Béjar, Rafael Rebolo +7
In this work we present the results of a direct imaging survey for brown dwarf companions around the nearest stars at the mid-infrared 10 micron range (=8.7m, =1.1…
Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs
Z. H. Zhang, D. J. Pinfield, M. C. Galvez-Ortiz +11
We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0, and a usdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfs by optical spectra obt…
Confirming the least massive members of the Pleiades star cluster
M. R. Zapatero Osorio, V. J. S. Béjar, N. Lodieu +1
We present optical photometry (i- and Z-band) and low-resolution spectroscopy (640-1015 nm) of very faint candidate members (J = 20.2-21.2 mag) of the Pleiades star cluster (120 My…
Radio emission in ultracool dwarfs: the nearby substellar triple system VHS 12561257
J. C. Guirado, R. Azulay, B. Gauza +4
With the purpose to investigate the radio emission of new ultracool objects, we carried out a targeted search in the recently discovered system VHS J125601.92125723.9 (hereafter…
The CARMENES search for exoplanets around M dwarfs: High-resolution optical and near-infrared spectroscopy of 324 survey stars
A. Reiners, M. Zechmeister, J. A. Caballero +170
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectr…
Testing the existence of optical linear polarization in young brown dwarfs
E. Manjavacas, P. A. Miles-Páez, M. R. Zapatero-Osorio +5
Linear polarization can be used as a probe of the existence of atmospheric condensates in ultracool dwarfs. Models predict that the observed linear polarization increases withthe d…
Optical and near-infrared linear polarization of low and intermediate-gravity ultra-cool dwarfs
P. A. Miles-Páez, M. R. Zapatero Osorio, E. Pallé +1
We aim to study the optical and near-infrared linear polarimetric properties of a sample of young M7-L7 dwarfs (1-500 Myr) with spectroscopic signatures of low- and interm…
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS
N. Lodieu, M. Espinoza Contreras, M. R. Zapatero Osorio +4
We aim at developing an efficient method to search for late-type subdwarfs (metal-depleted dwarfs with spectral types >M5) to improve the current statistics. Our objectives are: im…
A new free-floating planet in the Upper Scorpius association
K. Peña Ramírez, V. J. S. Béjar, M. R. Zapatero Osorio
We report on a deep photometric survey covering an area of 1.17 deg in the young Upper Scorpius stellar association using VIMOS and UKIDSS data taking several years…
Parallax of the L4.5 dwarf 2M182114 from high-precision astrometry with OSIRIS at GTC
J. Sahlmann, P. F. Lazorenko, H. Bouy +4
We used the OSIRIS camera at the 10.4 m Gran Telescopio Canarias (GTC) to monitor the astrometric motion of the L4.5 dwarf 2M182114 over 17 months. The astrometric residuals of…
Hunting for brown dwarf binaries and testing atmospheric models with X-Shooter
E. Manjavacas, B. Goldman, J. M. Alcalá +7
The determination of the brown dwarf binary fraction may contribute to the understanding of the substellar formation mechanisms. Unresolved brown dwarf binaries may be revealed thr…