Context. The recently completed re-reduction of the Hipparcos data by van Leeuwen (2007a, Astrophysics and Space Science Library, 350) makes it possible to search for the astrometric signatures of ...planets and brown dwarfs known from radial velocity surveys in the improved Hipparcos intermediate astrometric data. Aims. Our aim is to put more significant constraints on the orbital parameters which cannot be derived from radial velocities alone, i.e. the inclination and the longitude of the ascending node, than was possible before. The determination of the inclination in particular allows to calculate an unambiguous companion mass, rather than the lower mass limit which can be obtained from radial velocity measurements. Methods. We fitted the astrometric orbits of 310 substellar companions around 258 stars, which were all discovered via the radial velocity method, to the Hipparcos intermediate astrometric data provided by van Leeuwen. Results. Even though the astrometric signatures of the companions cannot be detected in most cases, the Hipparcos data still provide lower limits on the inclination for all but 67 of the investigated companions, which translates into upper limits on the masses of the unseen companions. For nine companions the derived upper mass limit lies in the planetary and for 75 companions in the brown dwarf mass regime, proving the substellar nature of those objects. Two of those objects have minimum masses also in the brown dwarf regime and are thus proven to be brown dwarfs. The confirmed planets are the ones around Pollux (β Gem b), ϵ Eri b, ϵ Ret b, μ Ara b, υ And c and d, 47 UMa b, HD 10647 b and HD 147513 b. The confirmed brown dwarfs are HD 137510 b and HD 168443 c. In 20 cases, the astrometric signature of the substellar companion was detected in the Hipparcos data, resulting in reasonable constraints on inclination and ascending node. Of these 20 companions, three are confirmed as planets or lightweight brown dwarfs (HD 87833 b, ι Dra b, and γ Cep b), two as brown dwarfs (HD 106252 b and HD 168443 b), and four are low-mass stars (BD –04 782 b, HD 112758 b, ρ CrB b, and HD169822 b). Of the others, many are either brown dwarfs or very low mass stars. For ϵ Eri, we derive a solution which is very similar to the one obtained using Hubble Space Telescope data.
Context.
Planet formation is sensitive to the conditions in protoplanetary disks, for which scaling laws as a function of stellar mass are known.
Aims.
We aim to test whether the observed population ...of planets around low-mass stars can be explained by these trends, or if separate formation channels are needed.
Methods.
We address this question by confronting a state-of-the-art planet population synthesis model with a sample of planets around M dwarfs observed by the HARPS and CARMENES radial velocity (RV) surveys. To account for detection biases, we performed injection and retrieval experiments on the actual RV data to produce synthetic observations of planets that we simulated following the core accretion paradigm.
Results.
These simulations robustly yield the previously reported high occurrence of rocky planets around M dwarfs and generally agree with their planetary mass function. In contrast, our simulations cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses. This potentially indicates an alternative formation channel for giant planets around the least massive stars that cannot be explained with current core accretion theories. We further find a stellar mass dependency in the detection rate of short-period planets. A lack of close-in planets around the earlier-type stars (
M
*
> 0.4
M
⊙
) in our sample remains unexplained by our model and indicates dissimilar planet migration barriers in disks of different spectral subtypes.
Conclusions.
Both discrepancies can be attributed to gaps in our understanding of planet migration in nascent M dwarf systems. They underline the different conditions around young stars of different spectral subtypes, and the importance of taking these differences into account when studying planet formation.
Context. Accurate parallax measurements allow us to determine physical properties of brown dwarfs and help us constrain evolutionary and atmospheric models, break age-mass degeneracy, and reveal ...unresolved binaries. Aims. We measured absolute trigonometric parallaxes and proper motions of six cool brown dwarfs using background galaxies to establish an absolute reference frame. We derive the absolute J-band magnitude. The six T brown dwarfs in our sample have spectral types between T2.5 and T8 and magnitudes between 13.9 and 18.0 in the Two Micron All Sky Survey (2MASS) with photometric distances below 25 pc. Methods. The observations were taken in the J-band with the Omega-2000 camera on the 3.5 m telescope at Calar Alto during a time period of 27 months between March 2011 and June 2013. The number of epochs varied between 11 and 12 depending on the object. The reduction of the astrometric measurements was carried out with respect to the field stars. The relative parallax and proper motions were transformed into absolute measurements using the background galaxies in our fields. Results. We obtained absolute parallaxes for our six brown dwarfs with a precision between 3 and 6 mas. We compared our results in a color–magnitude diagram with other brown dwarfs with determined parallax and with the BT-Settl 2012 atmospheric models. For four of the six targets, we found a good agreement in luminosity with objects of similar spectral types. We obtained an improved accuracy in the parallaxes and proper motions in comparison to previous works. The object 2MASS J11061197+2754225 is more than 1 mag overluminous in all bands, which point to binarity or high order multiplicity.
Dynamical histories of planetary systems, as well as the atmospheric evolution of highly irradiated planets, can be studied by characterizing the ultra-short-period planet population, which the TESS ...mission is particularly well suited to discover. Here, we report on the follow-up of a transit signal detected in the TESS sector 19 photometric time series of the M3.0 V star TOI-1685 (2MASS J04342248+4302148). We confirm the planetary nature of the transit signal, which has a period of
P
b
= 0.6691403
−0.0000021
+0.0000023
d, using precise radial velocity measurements taken with the CARMENES spectrograph. From the joint photometry and radial velocity analysis, we estimate the following parameters for TOI-1685 b: a mass of
M
b
= 3.78
−0.63
+0.63
M
⊕
, a radius of
R
b
= 1.70
−0.07
+0.07
R
⊕
, which together result in a bulk density of
ρ
b
= 4.21
−0.82
+0.95
g cm
−3
, and an equilibrium temperature of
T
eq
= 1069
−16
+16
K. TOI-1685 b is the least dense ultra-short-period planet around an M dwarf known to date. TOI-1685 b is also one of the hottest transiting super-Earth planets with accurate dynamical mass measurements, which makes it a particularly attractive target for thermal emission spectroscopy. Additionally, we report with moderate evidence an additional non-transiting planet candidate in the system, TOI-1685 c, which has an orbital period of
P
c
= 9.02
−0.12
+0.10
d.
HIP 65426 b is a recently discovered exoplanet imaged during the course of the SPHERE-SHINE survey. Here we present new L′ and M′ observations of the planet from the NACO instrument at the VLT from ...the NACO-ISPY survey, as well as a new Y –H spectrum and K-band photometry from SPHERE-SHINE. Using these data, we confirm the nature of the companion as a warm, dusty planet with a mid-L spectral type. From comparison of its SED with the BT-Settl atmospheric models, we derive a best-fit effective temperature of Teff = 1618 ± 7 K, surface gravity log g = 3.78−0.03+0.04 $\log g\,{=}\,3.78^{+0.04}_{-0.03}$logg = 3.78−0.03+0.04 and radius R = 1.17 ± 0.04RJ (statistical uncertainties only). Using the DUSTY and COND isochrones we estimate a mass of 8 ± 1MJ. Combining the astrometric measurements from our new datasets and from the literature, we show the first indications of orbital motion of the companion (2.6σ significance)and derive preliminary orbital constraints. We find a highly inclined orbit ( i = 1.07−10+13 $i\,{=}\,107^{+13}_{-10}$i = 107−10+13 deg) with an orbital period of 800−400+1200 $800^{+1200}_{-400}$800−400+1200 yr. We also report SPHERE sparse aperture masking observations that investigate the possibility that HIP 65426 b was scattered onto its current orbit by an additional companion at a smaller orbital separation. From this data we rule out the presence of brown dwarf companions with masses greater than 16 MJ at separations larger than 3 AU, significantly narrowing the parameter space for such a companion.
ABSTRACT
The single-lined spectroscopic binary ν Octantis provided evidence of the first conjectured circumstellar planet demanding an orbit retrograde to the stellar orbits. The planet-like ...behaviour is now based on 1437 radial velocities (RVs) acquired from 2001 to 2013. ν Oct’s semimajor axis is only 2.6 au with the candidate planet orbiting $\nu ~{\rm Oct\, A}$ about mid-way between. These details seriously challenge our understanding of planet formation and our decisive modelling of orbit reconfiguration and stability scenarios. However, all non-planetary explanations are also inconsistent with numerous qualitative and quantitative tests including previous spectroscopic studies of bisectors and line-depth ratios, photometry from Hipparcos and the more recent space missions TESS and Gaia (whose increased parallax classifies $\nu ~{\rm Oct\, A}$ closer still to a subgiant, ∼K1 IV). We conducted the first large survey of $\nu ~{\rm Oct\, A}$’s chromosphere: 198 $\rm Ca\,{\small II}$ H-line and 1160 $\rm {H}\, \alpha$ indices using spectra from a previous RV campaign (2009–2013). We also acquired 135 spectra (2018–2020) primarily used for additional line-depth ratios, which are extremely sensitive to the photosphere’s temperature. We found no significant RV-correlated variability. Our line-depth ratios indicate temperature variations of only ±4 K, as achieved previously. Our atypical $\rm Ca\,{\small II}$ analysis models the indices in terms of S/N and includes covariance significantly in their errors. The $\rm {H}\, \alpha$ indices have a quasi-periodic variability that we demonstrate is due to telluric lines. Our new evidence provides further multiple arguments realistically only in favour of the planet.
Consideration of both low- and high-resolution transmission spectroscopy is key for obtaining a comprehensive picture of exoplanet atmospheres. In studies of transmission spectra, the continuum ...information is well established with low-resolution spectra, while the shapes of individual lines are best constrained with high-resolution observations. In this work, we aim to merge high- with low-resolution transmission spectroscopy to place tighter constraints on physical parameters of the atmospheres. We present the analysis of three primary transits of WASP-69 b in the visible (VIS) channel of the CARMENES instrument and perform a combined low- and high-resolution analysis using additional data from HARPS-N, OSIRIS/GTC, and WFC3/HST already available in the literature. We investigate the Na
I
D
1
and D
2
doublet, H
α
, the Ca
II
infra-red triplet (IRT), and K
I
λ
7699 Å lines, and we monitor the stellar photometric variability by performing long-term photometric observations with the STELLA telescope. During the first CARMENES observing night, we detected the planet Na
I
D
2
and D
1
lines at ~7 and ~3
σ
significance levels, respectively. We measured a D
2
/D
1
intensity ratio of 2.5 ± 0.7, which is in agreement with previous HARPS-N observations. Our modelling of WFC3 and OSIRIS data suggests strong Rayleigh scattering, solar to super-solar water abundance, and a highly muted Na feature in the atmosphere of this planet, in agreement with previous investigations of this target. We use the continuum information retrieved from the low-resolution spectroscopy as a prior to break the degeneracy between the Na abundance, reference pressure, and thermosphere temperature for the high-resolution spectroscopic analysis. We fit the Na
I
D
1
and D
2
lines individually and find that the posterior distributions of the model parameters agree with each other within 1
σ
. Our results suggest that local thermodynamic equilibrium processes can explain the observed D
2
/D
1
ratio because the presence of haze opacity mutes the absorption features.
We discuss supersymmetry breaking via 3-form fluxes in chiral supersymmetric type IIB orientifold vacua with D3- and D7-branes. After a general discussion of possible choices of fluxes allowing for ...stabilizing of a part of the moduli, we determine the resulting effective action including all soft supersymmetry breaking terms. We also extend the computation of our previous work
hep-th/0404134 concerning the matter field metrics arising from various open string sectors, in particular focusing on the
1
/
2
BPS D3/D7-brane configuration. Afterwards, the F-theory lift of our constructions is investigated.
Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. ...Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.
Context. The Rossiter-McLaughlin (RM) effect, a rotational effect in eclipsing systems, provides unique insight into the relative orientation of stellar spin axes and orbital axes of eclipsing binary ...systems. Aims. Our aim is to develop a robust method to analyze the RM effect in an eclipsing system with two nearly equally bright components. This gives access to the orientation of the stellar rotation axes and may shed light on questions of binary formation and evolution. For example, a misalignment between the spin axes and the angular momentum of the system could bring the observed and theoretical apsidal motion into better agreement for some systems, including V1143 Cyg. Methods. High-resolution spectra have been obtained both out of eclipse and during the primary and secondary eclipses in the V1143 Cyg system, using the 0.6 m Coude Auxiliary Telescope (CAT) and the high- resolution Hamilton Echelle Spectrograph at the Lick Observatory. The Rossiter-McLaughlin effect is analyzed in two ways: (1) by measuring the shift of the line center of gravity during different phases of the eclipses and (2) by analysis of the line shape change of the rotational broadening function during eclipses. Results. We measured the projection of the stellar rotation axes using the rotation effect for both main-sequence stars in an eclipsing binary system. The projected axes of both stars are aligned with the orbital spin within the observational uncertainties, with the angle of the primary rotation axis \beta_{\rm p}=0.3\pm 1.5\circ}, and the angle of the secondary rotation axis \beta_{\rm s}=-1.2\pm 1.6\circ}, thereby showing that the remaining difference between the theoretical and observed apsidal motion for this system is not due to a misalignment of the stellar rotation axes. Both methods utilized in this paper work very well, even at times when the broadening profiles of the two stars overlap.
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