Georg-August-Universität
CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near infrared channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelvin level, which operates at cryogenic temperatures (140 K), poses significant engineering this http URL CARMENES-PLUS project was initiated to improve the instruments intrinsic RV precision. In this article, we focus on the thermal stability improvements made to the NIR channels cooling system. The NIR cooling system was originally conceived to operate with a discontinuous flow of cryogenic nitrogen gas. As part of CARMENES-PLUS, this was upgraded to a continuous flow configuration. Additional changes included the installation of an automatic vacuum system, a proportional control valve, and a pressure regulation system. These upgrades were designed to reduce thermal fluctuations and enhance long-term stability. The implemented upgrades significantly improved the intrinsic RV precision of the NIR channel. We quantified this improvement using Fabry Perot calibration spectra, obtaining an intrinsic RV precision of 0.67 ms after the interventions, an improvement of nearly 2 ms . We also assessed the stability of the nightly zero points, finding a reduced scatter of 3.9 ms post upgrade, compared to 6.1 ms before. For a sample of slowly rotating stars (vsin i below 2 kms), the median scatter decreased from 8.8 ms to 6.7 ms after the upgrades. These results demonstrate that the thermal control upgrades introduced in CARMENES PLUS have enhanced the NIR channels RV performance, bringing it closer to the VIS channels stability and reinforcing CARMENES capabilities for exoplanet detection around M dwarfs.
We obtain constraints from black hole superradiance in an ensemble of compactifications of type IIB string theory. The constraints require knowing only the axion masses and self-interactions, and are insensitive to the cosmological model. We study more than 21052 \cdot 10^5 Calabi-Yau manifolds with Hodge numbers 1h1,14911\leq h^{1,1}\leq 491 and compute the axion spectrum at two reference points in moduli space for each geometry. Our computation of the classical theory is explicit, while for the instanton-generated axion potential we use a conservative model. The measured properties of astrophysical black holes exclude parts of our dataset. At the point in moduli space corresponding to the tip of the stretched Kähler cone, we exclude 50%\approx 50\% of manifolds in our sample at 95% C.L., while further inside the Kähler cone, at an extremal point for realising the Standard Model, we exclude a maximum of 7%\approx 7\% of manifolds at h1,1=11h^{1,1}=11, falling to nearly zero by h1,1=100h^{1,1}=100.
Characterisation of atmospheres undergoing photo-evaporation is key to understanding the formation, evolution, and diversity of planets. However, only a few upper atmospheres that experience this kind of hydrodynamic escape have been characterised. Our aim is to characterise the upper atmospheres of the hot Jupiters HAT-P-32 b and WASP-69 b, the warm sub-Neptune GJ 1214 b, and the ultra-hot Jupiter WASP-76 b through high-resolution observations of their HeI triplet absorption. In addition, we also reanalyse the warm Neptune GJ 3470 b and the hot Jupiter HD 189733 b. We used a spherically symmetric 1D hydrodynamic model coupled with a non-local thermodynamic equilibrium model. Comparing synthetic absorption spectra with observations, we constrained the main parameters of the upper atmosphere of these planets and classify them according to their hydrodynamic regime. Our results show that HAT-P-32 b photo-evaporates at (130±\pm70)×\times1011^{11} gs1^{-1} with a hot (12 400±\pm2900 K) upper atmosphere; WASP-69 b loses its atmosphere at (0.9±\pm0.5)×\times1011^{11} gs1^{-1} and 5250±\pm750 K; and GJ 1214 b, with a relatively cold outflow of 3750±\pm750 K, photo-evaporates at (1.3±\pm1.1)×\times1011^{11} gs1^{-1}. For WASP-76 b, its weak absorption prevents us from constraining its temperature and mass-loss rate significantly; we obtained ranges of 6000-17 000\,K and 23.5±\pm21.5×\times1011^{11} gs1^{-1}. Our reanalysis of GJ 3470 b yields colder temperatures, 3400±\pm350 K, but practically the same mass-loss rate as in our previous results. Our reanalysis of HD 189733 b yields a slightly higher mass-loss rate, (1.4±\pm0.5)×\times1011^{11} gs1^{-1}, and temperature, 12 700±\pm900 K compared to previous estimates. Our results support that photo-evaporated outflows tend to be very light.
Aims: Previous estimates of planet occurrence rates in the CARMENES survey indicated increased numbers of planets on short orbits for M dwarfs with masses below 0.34\,M_\odot. Here we focused on the lowest-mass stars in the survey, comprising 15 inactive targets with masses under 0.16\,M_\odot. Methods: To correct for detection biases, we determined detection sensitivity maps for individual targets and the entire sample. Using Monte Carlo simulations, we estimated planet occurrence rates for orbital periods of 1\,d to 100\,d and minimum masses from 0.5\,M_\oplus to 10\,M_\oplus. Results: The radial velocity (RV) data from CARMENES reveal four new planets around three stars in our sample, namely G~268--110\,b, G~261--6\,b, and G~192--15\,b and c. All three b planets have minimum masses of 1.03--1.52\,M_\oplus and orbital periods of 1.43--5.45\,d, while G~192--15\,c is a 14.3\,M_\oplus planet on a wide, eccentric orbit with $P \approx 1218dand\,d and e \approx 0.68$. Our occurrence rates suggest considerable dependencies with respect to stellar masses. For planets below 3\,M_\oplus we found rates consistent with one planet per star across all investigated periods, but the rates decrease almost by an order of magnitude for larger planet masses up to 10\,M_\oplus. Compared to previous studies, low-mass stars tend to harbor more planets with P <10\,d. We also demonstrate that synthetic planet populations based on the standard core accretion scenario predict slightly more massive planets on wider orbits than observed. Conclusions: Our findings confirm that planet occurrence rates vary with stellar masses even among M dwarfs, as we found more planets with lower masses and on shorter orbits in our subsample of very low-mass stars compared to more massive M dwarfs. Therefore, we emphasize the need for additional differentiation in future studies.
Deriving metallicities for solar-like stars follows well-established methods, but for cooler stars such as M dwarfs, the determination is much more complicated due to forests of molecular lines that are present. Several methods have been developed in recent years to determine accurate stellar parameters for these cool stars (TeffT_{\rm eff} \lesssim 4000 K). However, significant differences can be found at times when comparing metallicities for the same star derived using different methods. In this work, we determine the effective temperatures, surface gravities, and metallicities of 18 well-studied M dwarfs observed with the CARMENES high-resolution spectrograph following different approaches, including synthetic spectral fitting, analysis of pseudo-equivalent widths, and machine learning. We analyzed the discrepancies in the derived stellar parameters, including metallicity, in several analysis runs. Our goal is to minimize these discrepancies and find stellar parameters that are more consistent with the literature values. We attempted to achieve this consistency by standardizing the most commonly used components, such as wavelength ranges, synthetic model spectra, continuum normalization methods, and stellar parameters. We conclude that although such modifications work quite well for hotter main-sequence stars, they do not improve the consistency in stellar parameters for M dwarfs, leading to mean deviations of around 50-200 K in temperature and 0.1-0.3 dex in metallicity. In particular, M dwarfs are much more complex and a standardization of the aforementioned components cannot be considered as a straightforward recipe for bringing consistency to the derived parameters. Further in-depth investigations of the employed methods would be necessary in order to identify and correct for the discrepancies that remain.
High quality wavelength calibration is crucial for science cases like radial-velocity studies of exoplanets, the search for a possible variation of fundamental constants, and the redshift drift experiment. However, for state-of-the-art spectrographs it has become difficult to verify the wavelength calibration on sky, because no astrophysical source provides spectra with sufficiently stable or accurate wavelength information. We therefore propose to use iodine absorption cells to validate the wavelength calibration. Observing a bright and featureless star through the iodine cell emulates an astrophysical target with exactly known spectral features that can be analyzed like any other science target, allowing to verify the wavelength calibration derived from the internal calibration sources and to identify systematics in the data processing. As demonstration, we temporarily installed an I2_2 absorption cell at ESPRESSO. Employing a full forward modeling approach of the I2_2 spectrum, including the instrumental line-spread function, we demonstrate wavelength calibration accuracy at the level of a few m/s. We also show that wavelength measurements do depend on the geometry of the light-injection into the spectrograph fibers. This highlights the importance of probing exactly the same light path as science targets, something not possible with internal calibration sources alone. We also demonstrate excellent radial-velocity stability at the <20 cm/s level in a full end-to-end fashion, from sky to data product. Our study therefore showcases the great potential of absorption cells for the verification and long-term monitoring of the wavelength calibration as well as the unique insights they can provide.
Ultra-hot Jupiters (UHJs) are highly irradiated giant exoplanets with extremely high day-side temperatures, which lead to thermal dissociation of most of the molecular species. It is expected that the neutral hydrogen atom is one of the main species in the upper atmospheres of ultra-hot Jupiters. Neutral hydrogen has been detected in several UHJs by observing its Balmer line absorption. Here, we report four transit observations of the ultra-hot Jupiter WASP-33b, performed with the CARMENES and HARPS-North spectrographs, and the detection of the Hα{\alpha}, Hβ{\beta}, and Hγ{\gamma} lines in the planetary transmission spectrum. The combined Hα\alpha transmission spectrum of the four transits has an absorption depth of 0.99±\pm0.05 %, which corresponds to an effective radius of 1.31±\pm0.01 Rp . The strong Hα{\alpha} absorption indicates that the line probes the high-altitude thermosphere. We further fitted the three Balmer lines using the PAWN model, assuming that the atmosphere is hydrodynamic and in LTE. We retrieved a thermosphere temperature 122001000+130012200^{+1300}_{-1000} K and a mass-loss rate ${\rm \dot{M}}=10^{11.8^{+0.6}_{-0.5}}$ g/s. The retrieved large mass-loss rate is compatible with the "Balmer-driven" atmospheric escape scenario, in which the stellar Balmer continua radiation in the near-ultraviolet is substantially absorbed by the excited hydrogen atoms in the planetary thermosphere.
Context. The HARPS spectrograph provides state-of-the-art stellar radial velocity (RV) measurements with a precision down to 1 m/s. The spectra are extracted with a dedicated data-reduction software (DRS) and the RVs are computed by CCF with a numerical mask. Aims. The aim of this study is three-fold: (i) Create easy access to the public HARPS RV data set. (ii) Apply the new public SERVAL pipeline to the spectra, and produce a more precise RV data set. (iii) Check whether the precision of the RVs can be further improved by correcting for small nightly systematic effects. Methods. For each star observed with HARPS, we downloaded the publicly available spectra from the ESO archive and recomputed the RVs with SERVAL. We then computed nightly zero points (NZPs) by averaging the RVs of quiet stars. Results. Analysing the RVs of the most RV-quiet stars, whose RV scatter is < 5 m/s, we find that SERVAL RVs are on average more precise than DRS RVs by a few percent. We find three significant systematic effects, whose magnitude is independent of the software used for the RV derivation: (i) stochastic variations with a magnitude of 1 m/s; (ii) long-term variations, with a magnitude of 1 m/s and a typical timescale of a few weeks; and (iii) 20-30 NZPs significantly deviating by a few m/s. In addition, we find small (< 1 m/s) but significant intra-night drifts in DRS RVs before the 2015 intervention, and in SERVAL RVs after it. We confirm that the fibre exchange in 2015 caused a discontinuous RV jump, which strongly depends on the spectral type of the observed star: from 14 m/s for late F-type stars, to -3 m/s for M dwarfs. Conclusions. Our NZP-corrected SERVAL RVs can be retrieved from a user-friendly, public database. It provides more than 212 000 RVs for about 3000 stars along with many auxiliary information, NZP corrections, various activity indices, and DRS-CCF products.
Scallop-shell stars, a recently discovered class of young M dwarfs, show complex optical light curves that are characterized by periodic dips as well as other features that are stable over tens to hundreds of rotation cycles. The origin of these features is not well-understood. 2MASS J05082729-2101444 is a \sim25 Myr old scallop-shell star that was identified using TESS data; it has a photometric period of 6.73h that has been attributed to rotation. Of the \sim50 recently confirmed scallop-shell stars, it is one of the few detected at radio frequencies between 1 and 8 GHz. We observed this rare system with the upgraded Giant Meterwave Radio Telescope at 575--720 MHz, covering 88% of the photometric period in each of the two observations scheduled almost a month apart in 2023. We detected \simmillijansky emission from the target in both epochs, with a significant circular polarization fraction: V/I|V/I|\sim20--50%. The 3.5-min phase-folded light curves reveal unique variability in circular polarization, showing an \simhour-long helicity reversal in both epochs, similar in amplitude, length, and (possibly) phase. These results suggest two emission components: The first is a persistent, moderately polarized component possibly ascribable to gyro-synchrotron emission driven by centrifugal breakout events. The second is a highly polarized, short burst-like component, likely due to an electron cyclotron maser (ECM), indicative of auroral emission and potentially responsible for the helicity reversal. To explain this, we discuss the different origins of the plasma responsible for the radio emission, including the possibility that the occulting material is acting as a plasma source. Future coordinated multifrequency radio and optical observations can further constrain the underlying scenario, as well as the magnetic geometry of the system, if we assume an ECM-like auroral emission.
Atmospheres of transiting exoplanets can be studied spectroscopically using space-based or ground-based observations. Each has its own strengths and weaknesses, so there are benefits to both approaches. This is especially true for challenging targets such as cooler, smaller exoplanets whose atmospheres likely contain many molecular species and cloud decks. We aim to study the atmosphere of the warm Neptune-like exoplanet WASP-107 b (Teq~740 K). Several molecular species have been detected in this exoplanet in recent space-based JWST studies, and we aim to confirm and expand upon these detections using ground-based VLT, evaluating how well our findings agree with previously retrieved atmospheric parameters. We observe two transits of WASP-107 b with VLT/CRIRES+ and create cross-correlation templates of the target atmosphere based on retrieval results from JWST studies. We create different templates to investigate the impact of varying volume mixing ratios of species and inclusion or exclusion of clouds. Considering this target's observational challenges, we create simulated observations prior to evaluating real data to assess expected detection significances. We report detections of two molecular species, CO (~6 S/N) and H2O (~4.5 S/N). This confirms previous space-based detections and demonstrates, for the first time, the capability of VLT/CRIRES+ to detect species in targets cooler than hot Jupiters using transmission spectroscopy. We show our analysis is sensitive to cloud inclusion, but less so to different volume mixing ratios. Interestingly, our detection deviates from its expected location in our Kp-vsys diagrams, and we speculate on possible reasons for this. We demonstrate that the error budget for relatively cooler exoplanets is severely reduced in comparison to hotter exoplanets, and underline need for further work in context of high-resolution spectroscopy.
Context: The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. Aims: We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity Analyser (SERVAL), a publicly available python code. Methods: We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star.We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. Results: Using HARPS data, our SERVAL code achieves a RV precision at the level of 1m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. Conclusions: We find that at the red optical wavelengths (700--900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.
Ultralight axions and other bosons are dark matter candidates present in many high energy physics theories beyond the Standard Model. In particular, the string axiverse postulates the existence of up to O(100)\mathcal{O}(100) light scalar bosons constituting the dark sector. Considering a mixture of axions and cold dark matter, we obtain upper bounds for the axion relic density $\Omega_a h^2 < 0.004foraxionsofmass for axions of mass 10^{-31}\;\mathrm{eV}\leq m_a \leq 10^{-26}\;\mathrm{eV}$ at 95% confidence. We also improve existing constraints by a factor of over 4.5 and 2.1 for axion masses of 102510^{-25} eV and 103210^{-32} eV, respectively. We use the Fourier-space galaxy clustering statistics from the Baryon Oscillation Spectroscopic Survey (BOSS) and demonstrate how galaxy surveys break important degeneracies in the axion parameter space compared to the cosmic microwave background (CMB). We test the validity of the effective field theory of large-scale structure approach to mixed ultralight axion dark matter by making our own mock galaxy catalogs and find an anisotropic ultralight axion signature in the galaxy quadrupole. We also observe an enhancement of the linear galaxy bias from 1.8 to 2.4 when allowing for 5% of the dark matter to be composed of a 102810^{-28} eV axion in our simulations. Finally, we develop an augmented interpolation scheme allowing a fast computation of the axion contribution to the linear matter power spectrum leading to a 70% reduction of the computational cost for the full Monte Carlo Markov chains analysis.
Only 40 exoplanetary systems with five or more planets are currently known. These systems are crucial for our understanding of planet formation and planet-planet interaction. The M dwarf L 98-59 has previously been found to show evidence of five planets, three of which are transiting. Our aim is to confirm the fifth planet in this system and to refine the system characteristics namely minimum masses, radii and the orbital parameters of the planets around L 98-59. We reanalysed RV and activity data from HARPS and ESPRESSO alongside TESS and HST transit data using a joint model. The parameter space was sampled using the dynesty nested sampler. We confirm the previously known fifth planet in the system's habitable zone with an orbital period of 23.07±0.08d23.07\pm0.08\,d, a minimum mass of 3.0±0.5M3.0\pm0.5\,M_{\oplus} and an effective temperature of 289 K. We find an additional planet candidate in the RV data with an orbital period of 1.73610.0008+0.0007d1.7361^{+0.0007}_{-0.0008}\,d and a minimum mass of 0.58±0.12M0.58\pm0.12\,M_{\oplus}. This candidate (L 98-59.06) has a statistical significance between 2.9σ2.9\sigma and 4.2σ4.2\sigma, details depending on the modelling of stellar variability. Moreover, we present evidence for a stellar rotation period of 76±4d76\pm4\,d.
The HIRES spectrograph, mounted on the 1010-m Keck-I telescope, belongs to a small group of radial-velocity (RV) instruments that produce stellar RVs with long-term precision down to 1\sim1 ms1^{-1}. In 20172017, the HIRES team published 64,48064,480 RVs of 1,6991,699 stars, collected between 19961996 and 20142014. In this bank of RVs, we identify a sample of RV-quiet stars, whose RV scatter is &lt;10 ms1^{-1}, and use them to reveal two small but significant nightly zero-point effects: a discontinuous jump, caused by major modifications of the instrument in August 20042004, and a long-term drift. The size of the 20042004 jump is 1.5±0.11.5\pm0.1 ms1^{-1}, and the slow zero-point variations have a typical magnitude of 1\lesssim1 ms1^{-1}. In addition, we find a small but significant correlation between stellar RVs and the time relative to local midnight, indicative of an average intra-night drift of 0.051±0.0040.051\pm0.004 ms1^{-1}hr1^{-1}. We correct the 64,48064,480 HIRES RVs for the systematic effects we find, and make the corrected RVs publicly available. Our findings demonstrate the importance of observing RV-quiet stars, even in the era of simultaneously-calibrated RV spectrographs. We hope that the corrected HIRES RVs will facilitate the search for new planet candidates around the observed stars.
A technique is presented which maps the parameters of a bead spring model, using the Flory Huggins theory, to a specific experimental system. By keeping only necessary details, for the description of these systems, the mapping procedure turns into an estimation of a few characteristic parameters. An asset of this technique is that it is simple to apply and captures the behavior of block copolymer phase separation. In our study this mapping technique is utilized in conjunction with a Monte Carlo (MC) algorithm to perform simulations on block copolymer systems. The microphase separation is investigated in the bulk and under confinement, on unpatterned and patterned surfaces.
Radial velocity (RV) jitter represents an intrinsic limitation on the precision of Doppler searches for exoplanets that can originate from both instrumental and astrophysical sources. We aim to determine the RV jitter floor in M dwarfs and investigate the stellar properties that lead to RV jitter induced by stellar activity. We determined the RV jitter in 239 M dwarfs from the CARMENES survey that are predominantly of mid to late spectral type and solar metallicity. We also investigated the correlation between stellar rotation and magnetic fields with RV jitter. The median jitter in the CARMENES sample is 3.1 m/s, and it is 2.3 m/s for stars with an upper limit of 2 km/s on their projected rotation velocities. We provide a relation between the stellar equatorial rotation velocity and RV jitter in M dwarfs based on a subsample of 129 well-characterized CARMENES stars. RV jitter induced by stellar rotation dominates for stars with equatorial rotation velocities greater than 1 km/s. A jitter floor of 2 m/s dominates in stars with equatorial rotation velocities below 1 km/s. This jitter floor likely contains contributions from stellar jitter, instrumental jitter, and undetected companions. We study the impact of the average magnetic field and the distributions of magnetic filling factors on the RV jitter. We find a series of stars with excess RV jitter and distinctive distributions of magnetic filling factors. These stars are characterized by a dominant magnetic field component between 2-4 kG. An RV jitter floor can be distinguished from RV jitter induced by activity and rotation based on the stellar equatorial rotation velocity. RV jitter induced by activity and rotation primarily depends on the equatorial rotation velocity. This RV jitter is also related to the distribution of magnetic filling factors, and this emphasizes the role of the magnetic field in the generation of RV jitter.
Ultra hot Jupiters orbit very close to their host star and consequently receive strong irradiation that makes their atmospheric chemistry different from the common gas giants. Here, we study the atmosphere of one of these particular hot planets, MASCARA-2b/KELT-20b, using four transit observations with high resolution spectroscopy facilities. Three of these observations were performed with HARPS-N and one with CARMENES. We simultaneously observed one of the transits with MuSCAT2 to monitor possible spots in the stellar surface. At high resolution, the transmission residuals show the effects of Rossiter-McLaughlin and center-to-limb variations from the stellar lines profiles, which we correct to finally extract the transmission spectra of the planet. We clearly observe absorption of CaII, FeII, NaI, Hα\alpha and Hβ\beta in the atmosphere of MASCARA-2b, and indications of Hγ\gamma and MgI at low SNR. The results obtained with CARMENES and HARPS-N are consistent, measuring an Hα\alpha absorption depth of 0.68±0.05%0.68\pm0.05\% and 0.59±0.07%0.59\pm0.07\%, and NaI absorption of 0.11±0.04%0.11\pm0.04\% and 0.09±0.05%0.09\pm0.05\% (0.75A˚0.75\r{A} passband), in both instruments respectively. For Hβ\beta only HARPS-N covers this wavelength range, measuring 0.28±0.06%0.28\pm0.06\% of absorption. The CaII is only covered with CARMENES, measuring an average absorption of 0.32±0.05%0.32\pm0.05\%. Three additional FeII lines are observed in the transmission spectrum by HARPS-N, with mean absorption depth of 0.08±0.04%0.08\pm0.04\%. The results presented here are consistent with theoretical models of ultra hot Jupiters atmospheres, suggesting the emergence of an ionised gas on the day-side of such planets. Ca and Fe, with other elements, are expected to be singly ionised at these temperatures and be more numerous than its neutral state. The CaII triplet lines are detected here for the first time in transmission in an exoplanet atmosphere.
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-{\alpha} 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. [Additional notes by authors: Furthermore, we provide upper limits for helium signals in the atmospheres of the exoplanets HD 209458b, KELT-9b, and GJ 436b. We investigate the host stars of all planets with detected helium signals and those of the three planets we derive upper limits for. In each case we calculate the X-ray and extreme ultraviolet flux received by these planets. We find that helium is detected in the atmospheres of planets (orbiting the more active stars and) receiving the larger amount of irradiation from their host stars.]
Stellar activity can induce signals in the radial velocities of stars, complicating the detection of orbiting low-mass planets. We present a method to determine the number of planetary signals present in radial-velocity datasets of active stars, using only radial-velocity observations. Instead of considering separate fits with different number of planets, we use a birth-death Markov chain Monte Carlo algorithm to infer the posterior distribution for the number of planets in a single run. In a natural way, the marginal distributions for the orbital parameters of all planets are also inferred. This method is applied to HARPS data of CoRoT-7. We confidently recover both CoRoT-7b and CoRoT-7c although the data show evidence for additional signals.
The Information Dynamics Toolkit xl (IDTxl) is a comprehensive software package for efficient inference of networks and their node dynamics from multivariate time series data using information theory. IDTxl provides functionality to estimate the following measures: 1) For network inference: multivariate transfer entropy (TE)/Granger causality (GC), multivariate mutual information (MI), bivariate TE/GC, bivariate MI 2) For analysis of node dynamics: active information storage (AIS), partial information decomposition (PID) IDTxl implements estimators for discrete and continuous data with parallel computing engines for both GPU and CPU platforms. Written for Python3.4.3+.
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