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25 papers found.
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Optical polarimetry, high–resolution spectroscopy and IR analysis of the Chamaeleon I dark cloud

We present optical polarimetry and high resolution spectroscopy of a sample of stars toward the Chamaeleon I dark cloud. We use our polarimetry which includes 33 stars to study the wavelength dependence of the degree and position angle of polarization.
From fits to the normalized wavelength dependence of interstellar polarization, we derive estimates of ranging from 4500 Å to...

Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-type M dwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at...

On the accretion properties of young stellar objects in the L1615/L1616 cometary cloud

. , Randich , S. , et al. 2011b, A &A, 526 , A6 Rigliaco , E. , Natta , A. , Testi , L. , et al. 2012 , A &A, 548 , A56 Schisano , E. , Covino , E. , Alcalá , et al. 2009 , A &A, 501 , 1013 Sergison, D. J

The eclipsing binary TY CrA revisited: what near-IR light curves tell us★

New photometric observations of the hierarchical eclipsing TY CrA system were taken in the optical with Variable Young Stellar Object Survey 6 (VYSOS6) and in the near-infrared (IR) with Son of ISAAC (SOFI) and Rapid Eye Mount Infra Red (REMIR). They are the first observations showing the deep eclipse minimum of the pre-main-sequence secondary in the near-IR. For the first time...

X-shooter spectroscopy of young stellar objects - I. Mass accretion rates of low-mass T Tauri stars in σ Orionis

We present high-quality, medium-resolution X-shooter/VLT spectra in the range 300−2500 nm for a sample of 12 very low mass stars in the σ Orionis cluster. The sample includes eight stars with evidence of disks from Spitzer and four without disks, with masses ranging from 0.08 to 0.3 M⊙. The aim of this first paper is to investigate the reliability of the many accretion tracers...

The Chamaeleon II low-mass star-forming region: radial velocities, elemental abundances, and accretion properties

. , & Hartmann , L. E. 2010 , ApJ, 710 , 597 Schisano , E. , Covino , E. , Alcalá , J. M. , et al. 2009 , A &A, 501 , 1013 Soderblom , D. R. , Jones , B. F. , & Balachandran , S. , et al. 1993 , AJ, 106 , 1059

The chemical composition of nearby young associations: s-process element abundances in AB Doradus, Carina-Near and Ursa Major

Recently, several studies have shown that young, open clusters are characterized by a considerable overabundance in their barium content. In particular, D’Orazi et al. reported that in some younger clusters [Ba/Fe] can reach values as high as ∼0.6 dex. The work also identified the presence of an anticorrelation between [Ba/Fe] and cluster age. For clusters in the age range ∼4.5...

IRAS 12556–7731: a “chamaeleonic” lithium-rich M-giant

Aims. In this letter we characterise IRAS 12556–7731 as the first lithium-rich M-type giant. Based on its late spectral type and high lithium content, and because of its proximity in angular distance to the Chamaeleon II star-forming region, the star was misclassified as a young low-mass star in a previous work.Methods. Based on HARPS data, synthetic spectral modelling, and...

Crossing the Gould Belt in the Orion vicinity

Context. The recent star formation history in the solar vicinity is not yet well constrained, and the real nature of the so-called Gould Belt is still unclear.Aims. We present a study of the large-scale spatial distribution of 6482 ROSAT All-Sky Survey (RASS) X-ray sources in approximately 5000 deg2 in the general direction of Orion. We examine the astrophysical properties of a...

X-shooter spectroscopy of young stellar objects - II. Impact of chromospheric emission on accretion rate estimates

Context. The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) young stellar objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is...

K-band transit and secondary eclipse photometry of exoplanet OGLE-TR-113b

I. A. G. Snellen 1 E. Covino 0 0 INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy 1 Leiden Observatory, Leiden University , Postbus 9513, 2300 RA, Leiden, the

The GAPS programme with HARPS-N at TNG - VII. Putting exoplanets in the stellar context: magnetic activity and asteroseismology of τ Bootis A

12 M. Esposito 16 17 R. Gratton 13 L. Affer 15 M. Barbieri 11 C. Boccato 13 R. U. Claudi 13 R. Cosentino 6 9 E. Covino 7 S. Desidera 13 A. F. M. Fiorenzano 6 D. Gandolfi 4 9 A. Harutyunyan 6 J

The GAPS programme with HARPS-N at TNG - IX. The multi-planet system KELT-6: Detection of the planet KELT-6 c and measurement of the Rossiter-McLaughlin effect for KELT-6 b

Aims. For more than 1.5 years we spectroscopically monitored the star KELT-6 (BD+31 2447), which is known to host the transiting hot-Saturn KELT-6 b, because a previously observed long-term trend in radial velocity time series suggested that there is an outer companion.Methods. We collected a total of 93 new spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit...

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits - I. Sample definition and characterization

Context. Young, close stars are ideal targets for searching planets using the direct imaging technique. The determination of stellar parameters is crucial for the interpretation of imaging survey results, particularly since the luminosity of substellar objects has a strong dependence on system age.Aims. We have conducted a large program with NaCo at the VLT to search for planets...

Pre-main-sequence stars in the star-forming complex Sh 2-284

Located at the Galactic anticentre, Sh 2-284 is an H ii region that harbours several young open clusters. Dolidze 25, a rare metal-poor (Z∼ 0.004) young cluster, is one of these. Given its association with Sh 2-284, it is reasonable to assume a low metallicity for the whole H ii region. Sh 2-284 is expected to host a significant population of pre-main-sequence (PMS) stars of both...

BS Indi: An enigmatic object in the Tucana association

BS Ind (=HD 202947) is a young K0V star in the Tucana association. Photometric observations with the Hipparcos satellite show an eclipse-like light-curve with primary and secondary eclipse. The eclipsing binary has a period of 0.435338 days and a circular orbit. Our spectroscopic observations however show that the K0V primary is a single-line spectroscopic binary with a period of...

A WFI survey in the Chamaeleon II dark cloud

Aims.We present the results of an optical multi-band survey for low-mass pre-main sequence (PMS) stars and young brown dwarfs (BDs) in the Chamaeleon II (Cha II) dark cloud. This survey constitutes the complementary optical data to the c2d Spitzer Legacy survey in Cha II.Methods.Using the wide-field imager (WFI) at the ESO 2.2 m telescope, we surveyed a sky area of about 1.75...

Pre-main sequence spectroscopic binaries suitable for VLTI observations

Context.A severe problem for research in star-formation is that the masses of young stars are almost always estimated from evolutionary tracks alone. Since the tracks published by different groups differ, it is often only possible to give a rough estimate of the masses of young stars. It is thus crucial to test and calibrate the tracks. Up to now, only a few tests of the tracks...

MO Lup: a hierarchical triple T Tauri system*

M. Esposito E. Covino J. M. Alcal a E. W. Guenther E. Schisano Universita` di Salerno Via S. Allende I- Baronissi Italy INAF - Osservatorio Astronomico di Capodimonte Via Moiariello I- Napoli Italy

The first brown dwarf with a disk in Chamaeleon II

In this letter we characterize the candidates for young stars and brown dwarfs detected in a survey with ISOCAM in the Chamaeleon II dark cloud. Photometric data coming from a wide-field optical imaging survey, combined with IR measurements from the 2MASS catalogue and from the Spitzer satellite, allow us to study the nature of the candidates. Using intermediate-band filters we...