Theoretical calculations and some indirect observations show that massive exoplanets on tight orbits must decay due to tidal dissipation within their host stars. This orbital evolution could be ...observationally accessible through precise transit timing over a course of decades. The rate of planetary in-spiraling may not only help us to understand some aspects of evolution of planetary systems, but also can be used as a probe of the stellar internal structure. In this paper we present results of transit timing campaigns organized for a carefully selected sample of the Northern hemisphere hot Jupiter-like planets which were found to be the best candidates for detecting planet-star tidal interactions. Among them, there is the WASP-12 system which is the best candidate for possessing an in-falling giant exoplanet. Our new observations support the scenario of orbital decay of WASP-12 b and allow us to refine its rate. The derived tidal quality parameter of the host star Q'*=(1.82±0.32)×105 is in agreement with theoretical predictions for subgiant stars. For the remaining systems – HAT-P-23, KELT-1, KELT-16, WASP-33, and WASP-103 – our transit timing data reveal no deviations from the constant-period models, hence constraints on the individual rates of orbital decay were placed. The tidal quality parameters of host stars in at least four systems – HAT-P-23, KELT-1, WASP-33, and WASP-103 – were found to be greater than the value reported for WASP-12. This is in line with the finding that those hosts are main sequence stars, for which efficiency of tidal dissipation is predicted to be relatively weak.
Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of ...stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: δ Scuti stars seem to be characterized with seismic indexes such as the large separation (Δν). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (νmax) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of δ Scuti stars seem to be.
ABSTRACT
We have analysed a selected sample of 36 Kepler short-cadence stars in the field of NGC 6811. The results reveal that all the targets are variable: two red giant stars with solar-like ...oscillations, 21 main-sequence pulsators (16 δ Scuti and five γ Doradus stars), and 13 rotating variables. Three new γ Doradus (γ Dor) variables (one is a hot γ Dor star) are detected in this work together with five new rotating variables. An in-depth frequency analysis of the δ Scuti (δ Sct) and γ Dor stars in the sample shows that the frequency spectra are very rich, in particular for the δ Sct-type variables. They present very dense frequency distributions and wide diversity in frequency patterns, even for stars being members of the cluster and with very similar location in the Hertzsprung–Russell (H–R) diagram. Rotational modulation is found for a high percentage of these main-sequence pulsating stars, which is an indication of stellar activity being common on the surfaces of these hot stars. In some cases, activity dominates the luminosity variations. Significant amplitude variability is also detected in at least some of the pulsation modes of highest amplitude in almost all the δ Sct stars. One of the δ Sct pulsators is a member of a binary system with the pulsating component tidally distorted. This system also shows strong stellar activity, including several flares that probably originate in the δ Sct component.
Thanks to high-precision photometric data legacy from space telescopes like CoRoT and
Kepler
, the scientific community could detect and characterize the power spectra of hundreds of thousands of ...stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules:
δ
Scuti stars seem to be characterized with seismic indexes such as the large separation (Δ
ν
). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (
ν
max
) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of
δ
Scuti stars seem to be.
Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M ...SUBsun/SUB are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The δ Sct stars pulsate in low-order g- and p-modes with periods of order 2 hr, driven by the κ mechanism operating in the He II ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where "hybrid" stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known γ Dor and δ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure δ Sct or γ Dor pulsators, i.e., essentially all of the stars show frequencies in both the δ Sct and the γ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency and is applied to categorize 234 stars as δ Sct, γ Dor, δ Sct/γ Dor or γ Dor/δ Sct hybrids.
Abstract The work reported here demonstrates that it is possible to accurately determine surface gravities of δ Scuti (δ Sct) stars using the frequency content from high-precision photometry and a ...measurement of the parallax. Using a sample of 10 eclipsing binary systems with a δ Sct component and the unique δ Sct star discovered with a transiting planet, WASP-33, we were able to refine the Δν–$\bar{\rho }$ relation. Using this relation and parallaxes, we obtained independent values for the masses and radii, allowing us to calculate the surface gravities without any constraints from spectroscopic or binary analysis. A remarkably good agreement was found between our results and those published, extracted from the analysis of the radial velocities and light curves of the systems. This reinforces the potential of Δν as a valuable observable for δ Sct stars and settles the degeneracy problem for the log g determination through spectroscopy.
We present the search for eclipsing binaries with a pulsating component in the first catalogue of optically variable sources observed by Optical Monitoring Camera (OMC)/INTEGRAL, which contains ...photometric data for more than 1000 eclipsing binaries. Five objects were found and a detailed analysis of one of them, DY Aqr, has been performed. Photometric and spectroscopic observations of DY Aqr were obtained to analyse the binary system and the pulsational characteristics of the primary component. By applying the binary modelling software phoebe to the OMC and ground-based photometric light curves, and to the radial velocity curve obtained using echelle high-resolution spectroscopy, the physical parameters of the system have been determined. Frequency analysis of the residual data has been performed using Fourier techniques to identify pulsational frequencies. We have built a grid of theoretical models to classify spectroscopically the primary component as an A7.5V star (plus or minus one spectral subtype). The best orbital fit was obtained for a semidetached system configuration. According to the binary modelling, the primary component has T
eff = 7625 ± 125 K and log g = 4.1 ± 0.1 and the secondary component has T
eff = 3800 ± 200 K and log g = 3.3 ± 0.1, although it is too faint to isolate its spectral features. From the analysis of the residuals, we have found a main pulsation frequency at 23.37 d−1, which is typical of a δ Scuti star. In the O−C diagram, no evidence of orbital period changes over the last 8 yr has been found.
We present the discovery of an Earth-mass planet (
M
b
sin
i
= 1.26 ± 0.21
M
⊕
) on a 15.6 d orbit of a relatively nearby (
d ~
9.6 pc) and low-mass (0.167 ± 0.011
M
⊙
) M5.0 V star, Wolf 1069. ...Sitting at a separation of 0.0672 ± 0.0014 au away from the host star puts Wolf 1069 b in the habitable zone (HZ), receiving an incident flux of
S
= 0.652 ± 0.029
S
⊕
. The planetary signal was detected using telluric-corrected radial-velocity (RV) data from the CARMENES spectrograph, amounting to a total of 262 spectroscopic observations covering almost four years. There are additional long-period signals in the RVs, one of which we attribute to the stellar rotation period. This is possible thanks to our photometric analysis including new, well-sampled monitoring campaigns undergone with the OSN and TJO facilities that supplement archival photometry (i.e., from MEarth and SuperWASP), and this yielded an updated rotational period range of
P
rot
= 150–170 d, with a likely value at 169.3
−3.6
+3.7
. The stellar activity indicators provided by the CARMENES spectra likewise demonstrate evidence for the slow rotation period, though not as accurately due to possible factors such as signal aliasing or spot evolution. Our detectability limits indicate that additional planets more massive than one Earth mass with orbital periods of less than 10 days can be ruled out, suggesting that perhaps Wolf 1069 b had a violent formation history. This planet is also the sixth closest Earth-mass planet situated in the conservative HZ, after Proxima Centauri b, GJ 1061 d, Teegarden’s Star c, and GJ 1002 b and c. Despite not transiting, Wolf 1069 b is nonetheless a very promising target for future three-dimensional climate models to investigate various habitability cases as well as for sub-m s
−1
RV campaigns to search for potential inner sub-Earth-mass planets in order to test planet formation theories.
The cyclic GMP-AMP synthase (cGAS)-STING pathway is central for innate immune sensing of various bacterial, viral and protozoal infections. Recent studies identified the common HAQ and R232H alleles ...of TMEM173/STING, but the functional consequences of these variants for primary infections are unknown. Here we demonstrate that cGAS- and STING-deficient murine macrophages as well as human cells of individuals carrying HAQ TMEM173/STING were severely impaired in producing type I IFNs and pro-inflammatory cytokines in response to Legionella pneumophila, bacterial DNA or cyclic dinucleotides (CDNs). In contrast, R232H attenuated cytokine production only following stimulation with bacterial CDN, but not in response to L. pneumophila or DNA. In a mouse model of Legionnaires' disease, cGAS- and STING-deficient animals exhibited higher bacterial loads as compared to wild-type mice. Moreover, the haplotype frequency of HAQ TMEM173/STING, but not of R232H TMEM173/STING, was increased in two independent cohorts of human Legionnaires' disease patients as compared to healthy controls. Our study reveals that the cGAS-STING cascade contributes to antibacterial defense against L. pneumophila in mice and men, and provides important insight into how the common HAQ TMEM173/STING variant affects antimicrobial immune responses and susceptibility to infection.
ClinicalTrials.gov DRKS00005274, German Clinical Trials Register.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
CARMENES input catalog of M dwarfs Shan, Y.; Revilla, D.; Skrzypinski, S. L. ...
Astronomy and astrophysics (Berlin),
04/2024, Letnik:
684
Journal Article
Recenzirano
Odprti dostop
Aims. Knowledge of rotation periods ( P rot ) is important for understanding the magnetic activity and angular momentum evolution of late-type stars, as well as for evaluating radial velocity signals ...of potential exoplanets and identifying false positives. We measured photometric and spectroscopic P rot for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully characterize the Guaranteed Time Observation programme stars of the CARMENES survey. Methods. We analyse light curves chiefly from the SuperWASP survey and TESS data. We supplemented these with our own follow-up photometric monitoring programme from ground-based facilities, as well as spectroscopic indicator time series derived directly from the CARMENES spectra. Results. From our own analysis, we determined P rot for 129 stars. Combined with the literature, we tabulated P rot for 261 stars, or 75% of our sample. We developed a framework to evaluate the plausibility of all periods available for this sample by comparing them with activity signatures and checking for consistency between multiple measurements. We find that 166 of these stars have independent evidence that confirmed their P rot . There are inconsistencies in 27 periods, which we classify as debated. A further 68 periods are identified as provisional detections that could benefit from independent verification. We provide an empirical relation for the P rot uncertainty as a function of the P rot value, based on the dispersion of the measurements. We show that published formal errors seem to be often underestimated for periods longwards of ∼10 d. We examined rotation–activity relations with emission in X-rays, H α , Ca II H&K, and surface magnetic field strengths for this sample of M dwarfs. We find overall agreement with previous works, as well as tentative differences in the partially versus fully convective subsamples. We show P rot as a function of stellar mass, age, and galactic kinematics. With the notable exception of three transiting planet systems and TZ Ari, all known planet hosts in this sample have P rot ≳ 15 d. Conclusions. Inherent challenges in determining accurate and precise stellar P rot means independent verification is important, especially for inactive M dwarfs. Evidence of potential mass dependence in activity–rotation relations would suggest physical changes in the magnetic dynamo that warrants further investigation using larger samples of M dwarfs on both sides of the fully convective boundary. Important limitations need to be overcome before the radial velocity technique can be routinely used to detect and study planets around young and active stars.
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