Aims. We look for common proper motion companions to stars of the nearby young beta Pictoris moving group. Methods. First, we compiled a list of 185 beta Pictoris members and candidate members from ...35 representative works. Next, we used the Aladin and STILTS virtual observatory tools and the PPMXL proper motion and Washington Double Star catalogues to look for companion candidates. The resulting potential companions were subjects of a dedicated astro-photometric follow-up using public data from all-sky surveys. After discarding 67 sources by proper motion and 31 by colour-magnitude diagrams, we obtained a final list of 36 common proper motion systems. The binding energy of two of them is perhaps too small to be considered physically bound. Results. Of the 36 pairs and multiple systems, eight are new, 16 have only one stellar component previously classified as a beta Pictoris member, and three have secondaries at or below the hydrogen-burning limit. Sixteen stars are reported here for the first time as moving group members. The unexpected large number of high-order multiple systems, 12 triples and two quadruples among 36 systems, may suggest a biased list of members towards close binaries or an increment of the high-order-multiple fraction for very wide systems.
CARMENES input catalogue of M dwarfs Jeffers, S. V.; Schöfer, P.; Lamert, A. ...
Astronomy and astrophysics (Berlin),
06/2018, Letnik:
614
Journal Article
Recenzirano
Odprti dostop
CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the ...CARMENES guaranteed time observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 M dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present new high-resolution spectroscopic observations with FEROS, CAFE, and HRS of approximately 500 M dwarfs. For each new observation, we determined its radial velocity and measured its H
α
activity index and its rotation velocity. Additionally, we have multiple observations of many stars to investigate if there are any radial velocity variations due to multiplicity. The results of our survey confirm that early-M dwarfs are H
α
inactive with low rotational velocities and that late-M dwarfs are H
α
active with very high rotational velocities. The results of this high-resolution analysis comprise the most extensive catalogue of rotation and activity in M dwarfs currently available.
Context.
It has been suggested that the helium absorption line at 10 830 Å that originates from the metastable triplet state 2
3
S is an excellent probe for the extended atmospheres of hot Jupiters ...and their hydrodynamic escape processes. It has recently been detected in the transmission spectra of a handful of planets. The isotropic reemission will lead to helium airglow that may be observable at other orbital phases.
Aims.
We investigate the detectability of He
I
emission at 10 830 Å in the atmospheres of exoplanets using high-resolution spectroscopy. This would provide insights into the properties of the upper atmospheres of close-in gas giants.
Methods.
We estimated the expected strength of He
I
emission in hot Jupiters based on their transmission signal. We searched for the He
I
10 830 Å emission feature in
τ
Boo b in three nights of high-resolution spectra taken by CARMENES at the 3.5m Calar Alto telescope. The spectra from each night were corrected for telluric absorption, sky emission lines, and stellar features, and were shifted to the planetary rest frame to search for the emission.
Results.
The He
I
emission is not detected in
τ
Boo b at a 5
σ
contrast limit of 4 × 10
−4
for emission line widths of >20 km s
−1
. This is about a factor 8 above the expected emission level (assuming a typical He
I
transit absorption of 1% for hot Jupiters). This suggests that targeting the He
I
emission with well-designed observations using upcoming instruments such as VLT/CRIRES+ and E-ELT/HIRES is possible.
Context. Only a few open clusters are as important for the study of stellar and substellar objects, and their formation and evolution, as the young σ Orionis cluster. However, a complete ...spectroscopic characterisation of its whole stellar population is still missing. Aims. We filled most of that gap with a large spectroscopic and astrometric survey of targets towards σ Orionis. Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion of confirmed cluster members with known uncontrovertible youth features. Methods. We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the 2.5 m Isaac Newton Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li I, Hα, and other key lines from these spectra, and determined spectral types. We complemented this information with Gaia DR2 astrometric data and other features of youth (mid-infrared excess, X-ray emission) compiled with Virtual Observatory tools and from the literature. Results. Of the 168 observed targets, we determined for the first time spectral types of 39 stars and equivalent widths of Li I and Hα of 34 and 12 stars, respectively. We identified 11 close (ρ ≲ 3 arcsec) binaries resolved by Gaia, of which three are new, 14 strong accretors, of which four are new and another four have Hα emission shifted by over 120 km s−1, two juvenile star candidates in the sparse population of the Ori OB1b association, and one spectroscopic binary candidate. Remarkably, we found 51 non-cluster-members, 35 of which were previously considered as σ Orionis members and taken into account in high-impact works on, for example, disc frequency and initial mass function.
CARMENES input catalogue of M dwarfs Jeffers, S. V.; Schöfer, P.; Lamert, A. ...
Astronomy and astrophysics (Berlin),
06/2018, Letnik:
614
Journal Article
Recenzirano
Odprti dostop
CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the ...CARMENES guaranteed time observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 M dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present new high-resolution spectroscopic observations with FEROS, CAFE, and HRS of approximately 500 M dwarfs. For each new observation, we determined its radial velocity and measured its Hα activity index and its rotation velocity. Additionally, we have multiple observations of many stars to investigate if there are any radial velocity variations due to multiplicity. The results of our survey confirm that early-M dwarfs are Hα inactive with low rotational velocities and that late-M dwarfs are Hα active with very high rotational velocities. The results of this high-resolution analysis comprise the most extensive catalogue of rotation and activity in M dwarfs currently available.
Context. Recently, the He I triplet at 10 830 Å was rediscovered as an excellent probe of the extended and possibly evaporating atmospheres of close-in transiting planets. This has already resulted ...in detections of this triplet in the atmospheres of a handful of planets, both from space and from the ground. However, while a strong signal is expected for the hot Jupiter HD 209458 b, only upper limits have been obtained so far. Aims. Our goal is to measure the helium excess absorption from HD 209458 b and assess the extended atmosphere of the planet and possible evaporation. Methods. We obtained new high-resolution spectral transit time-series of HD 209458 b using CARMENES at the 3.5 m Calar Alto telescope, targeting the He I triplet at 10 830 Å at a spectral resolving power of 80 400. The observed spectra were corrected for stellar absorption lines using out-of-transit data, for telluric absorption using the MOLECFIT software, and for the sky emission lines using simultaneous sky measurements through a second fibre. Results. We detect He I absorption at a level of 0.91 ± 0.10% (9 σ) at mid-transit. The absorption follows the radial velocity change of the planet during transit, unambiguously identifying the planet as the source of the absorption. The core of the absorption exhibits a net blueshift of 1.8 ± 1.3 km s−1. Possible low-level excess absorption is seen further blueward from the main absorption near the centre of the transit, which could be caused by an extended tail. However, this needs to be confirmed. Conclusions. Our results further support a close relation between the strength of planetary absorption in the helium triplet lines and the level of ionising, stellar X-ray, and extreme-UV irradiation.
Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, affecting their physical and chemical evolution. Studies of atmospheric escape from exoplanets have ...mostly relied on space-based observations of the hydrogen Lyman-α line in the far ultraviolet which is strongly affected by interstellar absorption. Using ground-based high-resolution spectroscopy we detect excess absorption in the helium triplet at 1083 nm during the transit of the Saturn-mass exoplanet WASP-69b, at a signal-to-noise ratio of 18. We measure line blue shifts of several km s
and post transit absorption, which we interpret as the escape of part of the atmosphere trailing behind the planet in comet-like form.
HD 209458b was the first transiting planet discovered, and the first for which an atmosphere, in particular Na
I
, was detected. With time, it has become one of the most frequently studied planets, ...with a large diversity of atmospheric studies using low- and high-resolution spectroscopy. Here, we present transit spectroscopy observations of HD 209458b using the HARPS-N and CARMENES spectrographs. We fit the Rossiter-McLaughlin effect by combining radial velocity data from both instruments (nine transits in total), measuring a projected spin-orbit angle of − 1.6 ± 0.3 deg. We also present the analysis of high-resolution transmission spectroscopy around the Na
I
region at 590 nm, using a total of five transit observations. In contrast to previous studies where atmospheric Na
I
absorption is detected, we find that for all of the nights, whether individually or combined, the transmission spectra can be explained by the combination of the centre-to-limb variation and the Rossiter-McLaughlin effect. This is also observed in the time-evolution maps and transmission light curves, but at lower signal-to-noise ratio. Other strong lines such as H
α
, Ca
II
IRT, the Mg
I
triplet region, and K
I
D1 are analysed, and are also consistent with the modelled effects, without considering any contribution from the exoplanet atmosphere. Thus, the transmission spectrum reveals no detectable Na
I
absorption in HD 209458b. We discuss how previous pioneering studies of this benchmark object may have overlooked these effects. While for some star–planet systems these effects are small, for other planetary atmospheres the results reported in the literature may require revision.
Context.
Only a few open clusters are as important for the study of stellar and substellar objects, and their formation and evolution, as the young
σ
Orionis cluster. However, a complete ...spectroscopic characterisation of its whole stellar population is still missing.
Aims.
We filled most of that gap with a large spectroscopic and astrometric survey of targets towards
σ
Orionis. Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion of confirmed cluster members with known uncontrovertible youth features.
Methods.
We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the 2.5 m
Isaac Newton
Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li
I
, H
α
, and other key lines from these spectra, and determined spectral types. We complemented this information with
Gaia
DR2 astrometric data and other features of youth (mid-infrared excess, X-ray emission) compiled with Virtual Observatory tools and from the literature.
Results.
Of the 168 observed targets, we determined for the first time spectral types of 39 stars and equivalent widths of Li
I
and H
α
of 34 and 12 stars, respectively. We identified 11 close (
ρ
≲ 3 arcsec) binaries resolved by
Gaia
, of which three are new, 14 strong accretors, of which four are new and another four have H
α
emission shifted by over 120 km s
−1
, two juvenile star candidates in the sparse population of the Ori OB1b association, and one spectroscopic binary candidate. Remarkably, we found 51 non-cluster-members, 35 of which were previously considered as
σ
Orionis members and taken into account in high-impact works on, for example, disc frequency and initial mass function.
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