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36 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...

X-shooter spectroscopy of young stellar objects in Lupus - Accretion properties of class II and transitional objects

The mass accretion rate, Ṁacc, is a key quantity for the understanding of the physical processes governing the evolution of accretion discs around young low-mass (M⋆ ≲ 2.0 M⊙) stars and substellar objects (YSOs). We present here the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III...

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

X-shooter spectroscopy of young stellar objects - V. Slow winds in T Tauri stars

Disks around T Tauri stars are known to lose mass, as best shown by the profiles of the forbidden emission lines of low-ionization species. At least two separate kinematic components have been identified, one characterized by velocity shifts of tens to hundreds of km s-1 (HVC) and one with a much lower velocity of a few km s-1 (LVC). The HVC are convincingly associated to the...

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...

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 FU Tauri A

We have analyzed a broad-band optical and near-infrared spectrum of FU Tau A, which is a presumed young brown dwarf in the Taurus star forming region that has intrigued both theorists and observers by its overluminosity in the Hertzsprung-Russell (HR) diagram with respect to standard pre-main sequence evolutionary models. FU Tau A is brighter than any other Taurus member of the...

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

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 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...

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...

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

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...

REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion - Rotation periods and starspot parameters

Aims. We aim at determining the rotational periods and the starspot properties in very young low-mass stars belonging to the Ori OB1c star forming region, contributing to the study of the angular momentum and magnetic activity evolution in these objects. Methods. We performed an intensive photometric monitoring of the PMS stars falling in a field of about 10 in the vicinity 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...

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 young active star SAO 51891 (V383 Lacertae)

Aims. The aim of this work is to investigate the surface inhomogeneities of a young, late-type star, SAO 51891, at different atmospheric levels, from the photosphere to the upper chromosphere, analyzing contemporaneous optical high-resolution spectra and broad-band photometry.Methods. The full spectral range of FOCES@CAHA (R 40 000) is used to perform the spectral classification...

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...