Search

Large surveys with new-generation high-contrast imaging instruments are needed to derive the frequency and properties of exoplanet populations with separations from $\sim$5 to 300 AU. A careful assessment of the stellar properties is crucial for a proper understanding of when, where, and how frequently planets form, and how they evolve. The sensitivity of detection limits to stellar age makes this a key parameter for direct imaging surveys. We describe the SpHere INfrared survey for Exoplanets (SHINE), the largest direct imaging planet-search campaign initiated at the VLT in 2015 in the context of the SPHERE Guaranteed Time Observations of the SPHERE consortium. In this first paper we present the selection and the properties of the complete sample of stars surveyed with SHINE, focusing on the targets observed during the first phase of the survey (from February 2015 to February 2017). This early sample composed of 150 stars is used to perform a preliminary statistical analysis of the SHINE data, deferred to two companion papers presenting the survey performance, main discoveries, and the preliminary statistical constraints set by SHINE. Based on a large database collecting the stellar properties of all young nearby stars in the solar vicinity (including kinematics, membership to moving groups, isochrones, lithium abundance, rotation, and activity), we selected the original sample of 800 stars that were ranked in order of priority according to their sensitivity for planet detection in direct imaging with SPHERE. The properties of the stars that are part of the early statistical sample were revisited, including for instance measurements from the GAIA Data Release 2.

We detect the accreting low-mass companion HD142527B at a separation of 73 mas (11.4 au) from the star. No other companions with mass greater than 10 MJ are visible in the field of view of IFS (\sim 100 au centered on the star) or in the IRDIS field of view (\sim 400 au centered on the star). Measurements from IFS, SAM IFS, and IRDIS suggest an M6 spectral type for HD142527B, with an uncertainty of one spectral subtype, compatible with an object of M=0.11 \pm 0.06 MSun and R=0.15 \pm 0.07 RSun. The determination of the mass remains a challenge using contemporary evolutionary models, as they do not account for the energy input due to accretion from infalling material. We consider that the spectral type of the secondary may also be earlier than the type we derived from IFS spectra. From dynamical considerations, we further constrain the mass to 0.26^{+0.16}_{-0.14} MSun , which is consistent with both our spectroscopic analysis and the values reported in the literature. Following previous methods, the lower and upper dynamical mass values correspond to a spectral type between M2.5 and M5.5 for the companion. By fitting the astrometric points, we find the following orbital parameters: a period of P=35-137 yr; an inclination of i=121-130 deg.; , a value of Omega=124-135 deg for the longitude of node, and an 68% confidence interval of \sim 18 - 57 au for the separation at periapsis. Eccentricity and time at periapsis passage exhibit two groups of values: \sim0.2-0.45 and \sim0.45-0.7 for e, and \sim 2015-2020 and \sim2020-2022 for T_0. While these orbital parameters might at first suggest that HD142527B is not the companion responsible for the outer disk truncation, a previous hydrodynamical analysis of this system showed that they are compatible with a companion that is able to produce the large cavity and other observed features., Comment: 15, pages, 11 figures, Accepted for publication on Astronomy and Astrophysics

Low-mass members of young stellar associations exhibit a wide spread of rotation periods. Such a spread originates from distributions of masses and initial rotation periods. However, multiplicity can also play a significant role. We investigate the role played by physical companions in shortening the primordial disc lifetime. We have compiled the most extensive list of low-mass members of the young 25-Myr beta Pictoris association. We have measured the rotation periods of about all members and used updated UVWXYZ components to assess their membership. We built the rotation period distribution distinguishing between bona fide members and candidate members and according to their multiplicity status. We found that single stars and components of multiple systems in wide orbits (>80 AU) have rotation periods that exhibit a well defined sequence arising from mass distribution. All components of multiple systems in close orbits (<80 AU) have rotation periods significantly shorter than their equal-mass single counterparts. A comparison with the younger 13 Myr h Per cluster and with the older 40-Myr open clusters/stellar associations NGC2547, IC2391, Argus, and IC2602 and the 130-Myr Pleiades shows that whereas the evolution of F-G stars is well reproduced by angular momentum evolution models, this is not the case for the slow K and early-M stars. Finally, we found that the amplitude of their light curves is correlated neither with rotation nor with mass. Once single stars and wide components of multiple systems are separated from close components of multiple systems, the rotation period distributions exhibit a well defined dependence on mass that allows to make a meaningful comparison with similar distributions of either younger or older associations/clusters. Such cleaned distributions allow to use the stellar rotation period as age indicator, meaningfully for F and G type stars., Comment: 20 pages, 9 figures, 4 tables; accepted by Astronomy and Astrophysics

Context. The SAO 206462 (HD 135344B) disk is one of the few known transitional disks showing asymmetric features in scattered light and thermal emission. Near-infrared scattered-light images revealed two bright outer spiral arms and an inner cavity depleted in dust. Giant protoplanets have been proposed to account for the disk morphology. Aims. We aim to search for giant planets responsible for the disk features and, in the case of non-detection, to constrain recent planet predictions using the data detection limits. Methods. We obtained new high-contrast and high-resolution total intensity images of the target spanning the Y to the K bands (0.95-2.3 mic) using the VLT/SPHERE near-infrared camera and integral field spectrometer. Results. The spiral arms and the outer cavity edge are revealed at high resolutions and sensitivities without the need for image post-processing techniques, which introduce photometric biases. We do not detect any close-in companions. For the derivation of the detection limits on putative giant planets embedded in the disk, we show that the knowledge of the disk aspect ratio and viscosity is critical for the estimation of the attenuation of a planet signal by the protoplanetary dust because of the gaps that these putative planets may open. Given assumptions on these parameters, the mass limits can vary from ~2-5 to ~4-7 Jupiter masses at separations beyond the disk spiral arms. The SPHERE detection limits are more stringent than those derived from archival NaCo/L' data and provide new constraints on a few recent predictions of massive planets (4-15 MJ) based on the spiral density wave theory. The SPHERE and ALMA data do not favor the hypotheses on massive giant planets in the outer disk (beyond 0.6). There could still be low-mass planets in the outer disk and/or planets inside the cavity., Comment: A&A, in press. 16 pages, 17 figures. Updated to match proofs

We intended to compile the most complete catalog of bona fide members and candidate members of the beta Pictoris association, and to measure their rotation periods and basic properties from our own observations, public archives, and exploring the literature. We carried out a multi-observatories campaign to get our own photometric time series and collected all archived public photometric data time series for the stars in our catalog. Each time series was analyzed with the Lomb-Scargle and CLEAN periodograms to search for the stellar rotation periods. We complemented the measured rotational properties with detailed information on multiplicity, membership, and projected rotational velocity available in the literature and discussed star by star. We measured the rotation periods of 112 out of 117 among bona fide members and candidate members of the beta Pictoris association and, whenever possible, we also measured the luminosity, radius, and inclination of the stellar rotation axis. This represents to date the largest catalog of rotation periods of any young loose stellar association. We provided an extensive catalog of rotation periods together with other relevant basic properties useful to explore a number of open issues, such as the causes of spread of rotation periods among coeval stars, evolution of angular momentum, and lithium-rotation connection., Comment: Forthcoming article, Received: 20 June 2016 / Accepted: 09 September 2016; 40 pages, 2 figures. The online figures A1-A73 are available at CDS

There is evidence in the 125-Myr Pleiades cluster, and more recently in the 5-Myr NGC 2264 cluster, that rotation plays a key role in the Lithium (Li) depletion processes among low-mass stars. Fast rotators appear to be less Li-depleted than equal-mass slow rotators. We intend to explore the existence of a Li depletion - rotation connection among the beta Pictoris members at an age of about 24 Myr, and to use such correlation either to confirm or to improve the age estimate based on the Lithium Depletion Boundary (LDB) modeling. We have photometrically monitored all the known members of the beta Pictoris association with at least one Lithium equivalent width (Li EW) measurement from the literature. We measured the rotation periods of 30 members for the first time and retrieved from the literature the rotation periods for other 36 members, building a catalogue of 66 members with measured rotation period and Li EW. We find that in the 0.3 < M < 0.8 Msun range, there is a strong correlation between rotation and Li EW. For higher mass stars, no significant correlation is found. For very low mass stars in the Li depletion onset, at about 0.1 Msun, data are too few to infer a significant correlation. The observed Li EWs are compared with those predicted by the Dartmouth stellar evolutionary models that incorporate the effects of magnetic fields. After decorrelating the Li EW from the rotation period, we find that the hot side of the LDB is fitted well by Li EW values corresponding to an age of 25$\pm$3 Myr in good agreement with independent estimates from the literature., Comment: 8 pages, 6 figures, 1 table, accepted by A&A

Aims. In this work, we characterize the low mass companion of the A0 field star HR3549. Methods. We observed HR3549AB in imaging mode with the the NIR branch (IFS and IRDIS) of SPHERE@VLT, with IFS in YJ mode and IRDIS in the H band. We also acquired a medium resolution spectrum with the IRDIS long slit spectroscopy mode. The data were reduced using the dedicated SPHERE GTO pipeline, purposely designed for this instrument. We employed algorithms such as PCA and TLOCI to reduce the speckle noise. Results. The companion was clearly visible both with IRDIS and IFS.We obtained photometry in four different bands as well as the astrometric position for the companion. Based on our astrometry, we confirm that it is a bound object and put constraints on its orbit. Although several uncertainties are still present, we estimate an age of ~100-150 Myr for this system, yielding a most probable mass for the companion of 40-50MJup and T_eff ~300-2400 K. Comparing with template spectra points to a spectral type between M9 and L0 for the companion, commensurate with its position on the color-magnitude diagram., Comment: Accepted by A&A, 13 pages, 10 Figures (Figures 9 and 10 degraded to reduce the dimension)

[Abridged] Context. The young systems PZ Tel and HD 1160, hosting known low-mass companions, were observed during the commissioning of the new planet finder SPHERE with several imaging and spectroscopic modes. Aims. We aim to refine the physical properties and architecture of both systems. Methods. We use SPHERE commissioning data and REM observations, as well as literature and unpublished data from VLT/SINFONI, VLT/NaCo, Gemini/NICI, and Keck/NIRC2. Results. We derive new photometry and confirm the nearly daily photometric variability of PZ Tel A. Using literature data spanning 38 yr, we show that the star also exhibits a long-term variability trend. The 0.63-3.8 mic SED of PZ Tel B allows us to revise its properties: spectral type M7+/-1, Teff=2700+/-100 K, log(g)<4.5 dex, log(L/L_Sun)=-2.51+/-0.10 dex, and mass 38-72 MJ. The 1-3.8 mic SED of HD 1160 B suggests a massive brown dwarf or a low-mass star with spectral type M5.5-7.0, Teff=3000+/-100 K, [M/H]=-0.5-0.0 dex, log(L/L_Sun)=-2.81+/-0.10 dex, and mass 39-168 MJ. We confirm the deceleration and high eccentricity (e>0.66) of PZ Tel B. For e<0.9, the inclination, longitude of the ascending node, and time of periastron passage are well constrained. The system is seen close to an edge-on geometry. We reject other brown dwarf candidates outside 0.25" for both systems, and massive giant planets (>4 MJ) outside 0.5" for the PZ Tel system. We also show that K1-K2 color can be used with YJH low-resolution spectra to identify young L-type companions, provided high photometric accuracy (<0.05 mag) is achieved. Conclusions. SPHERE opens new horizons in the study of young brown dwarfs and giant exoplanets thanks to high-contrast imaging capabilities at optical and near-infrared wavelengths, as well as high signal-to-noise spectroscopy in the near-infrared from low (R~30-50) to medium resolutions (R~350)., Comment: 25 pages, 23 figures, accepted for publication in A&A on Oct. 13th, 2015; version including language editing. Typo on co-author name on astroph page corrected, manuscript unchanged