Chaos in multiplanetary extrasolar systems Gajdoš, Pavol; Vaňko, Martin
Monthly Notices of the Royal Astronomical Society,
01/2023, Letnik:
518, Številka:
2
Journal Article
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Odprti dostop
ABSTRACT
Here, we present an initial look at the dynamics and stability of 178 multiplanetary systems that are already confirmed and listed in the NASA Exoplanet Archive. To distinguish between the ...chaotic and regular nature of a system, the value of the Mean Exponential Growth factor of Nearby Orbits (MEGNO) indicator for each system was determined. Almost three-quarters of them could be labelled as long-term stable. Only 45 studied systems show chaotic behaviour. We consequently investigated the effects of the number of planets and their parameters on the system stability. A comparison of results obtained using the MEGNO indicator and machine-learning algorithm SPOCK (Stability of Planetary Orbital Configuration Klassifier) suggests that the SPOCK could be used as an effective tool for reviewing the stability of multiplanetary systems. A similar study was already published by Laskar and Petit. We compared their analysis based on the AMD (Angular Momentum Deficit) criterion with our results. The possible discrepancies are discussed.
ABSTRACT
Chemically peculiar stars in eclipsing binary systems are rare objects that allow the derivation of fundamental stellar parameters and important information on evolutionary status and the ...origin of the observed chemical peculiarities. Here we present an investigation of the known eclipsing binary system BD+09 1467 = V680 Mon. Using spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and own observations, we identify the primary component of the system as a mercury–manganese (HgMn/CP3) star (spectral type kB9 hB8 HeB9 V HgMn). Furthermore, photometric time series data from the Transiting Exoplanet Survey Satellite (TESS) indicate that the system is a ‘heartbeat star’, a rare class of eccentric binary stars with short-period orbits that exhibit a characteristic signature near the time of periastron in their light curves due to the tidal distortion of the components. Using all available photometric observations, we present an updated ephemeris and binary system parameters as derived from a modelling of the system with the elisa code, which indicate that the secondary star has an effective temperature of Teff = $8300_{-200}^{+200}$ (spectral type ∼A4). V680 Mon is only the fifth known eclipsing CP3 star, and the first one in a heartbeat binary. Furthermore, our results indicate that the star is located on the zero-age main sequence and a possible member of the open cluster NGC 2264. As such, it lends itself perfectly for detailed studies and may turn out to be a keystone in the understanding of the development of CP3 star peculiarities.
Transit-timing variations in the system Kepler-410Ab Gajdoš, Pavol; Parimucha, Štefan; Hambálek, Ľubomír ...
Monthly Notices of the Royal Astronomical Society,
08/2017, Letnik:
469, Številka:
3
Journal Article
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Abstract
We present a new analysis of the transit timing variations displayed by the extrasolar planet Kepler-410Ab. We obtained and improved the orbital and physical parameters for the planet and ...analysed 70 transit times obtained by the Kepler satellite. In our analysis of the O-C diagram (observed minus calculated), we assumed that the observed changes in the transit times are probably caused by the gravitational influence of another body in the system. To determine the mass of the perturbing body, we considered the light-time effect and an analytical approximation of the perturbation model. The solutions resulting from both methods give comparable results, with an orbital period P
3 ∼ 970 d and a slightly eccentric orbit of the third body. We also showed that this orbit is nearly coplanar with the orbit of the Neptune-like planet Kepler-410Ab (orbital period 17.8 d). We propose two possible models for the perturbing body orbiting a common barycentre with Kepler-410A: (i) a single star with mass at least 0.906 M⊙, (ii) a binary star with the total mass of its components at least 2.15 M⊙. In both cases, the star Kepler-410B is on a long orbit (period more than 2200 yr). Small amplitude variations (∼5–8 min) detected in O-C residuals can be explained by the stellar activity of the host star (spots and pulsations), which affects the shape of the light curve during the transit. The presence of a single or binary companion of the mentioned masses heavily affects the total observed flux from the system. After removing the flux contamination from the Kepler-410A light curve, we found that the radius of the transiting planet Kepler-410Ab should be in the range from about 3.7 to 4.2 R⊕.
Abstract
There is a small group of peculiar early-type stars on the main sequence that show different rotation velocities from different spectral lines. This inconsistency might be due to the binary ...nature of these objects. We aim to verify this hypothesis by a more detailed spectroscopic and photometric investigation of one such object: HD 183986. We obtained 151 high- and medium-resolution spectra that covered an anticipated long orbital period. There is clear evidence of the orbital motion of the primary component. We uncovered a very faint and broad spectrum of the secondary component. The corresponding SB2 orbital parameters, and the component spectra, were obtained by Fourier disentangling using the
KOREL
code. The component spectra were further modeled by
iSpec
code to arrive at the atmospheric quantities and the projected rotational velocities. We have proven that this object is a binary star with a period
P
= 1268.2(11) days, eccentricity
e
= 0.5728(20), and mass ratio
q
= 0.655. The primary component is a slowly rotating star (
v
sin
i
=
27
km s
−1
) while the cooler and less massive secondary rotates much faster (
v
sin
i
∼
120 km s
−1
). Photometric observations obtained by the Transiting Exoplanet Survey Satellite (TESS) satellite were also investigated to shed more light on this object. A multiperiod photometric variability was detected in the TESS data ranging from hours (the
δ
Sct-type variability) to a few days (spots/rotational variability). The physical parameters of the components and the origin of the photometric variability are discussed in more detail.
Abstract
We studied three exoplanetary systems with transiting planets: WASP-92, WASP-93, and WASP-118. Using ground-based photometric observations of WASP-92 and WASP-93 and Kepler-K2 observations ...of WASP-118, we redetermined the orbital and physical parameters of these planets. The precise times of all transits were determined. We constructed O–C diagrams of transits and analysed possible transit timing variations. We did not observe any significant deviation from a linear ephemeris for any of the selected exoplanets. We put upper mass limits for other hypothetical planets in these systems. Using long-term numerical simulation, we looked for stable regions where another planet could exist for a long time. We used the maximum eccentricity method for this purpose. We discuss the influence of values of initial inclination and eccentricity on the shape and size of regions of stability.
Abstract
Transit timing variations (TTVs) of Kepler-410Ab were already reported in a few papers. Their semi-amplitude is about 14.5 min. In our previous paper, we found that the TTVs could be caused ...by the presence of a stellar companion in this system. Our main motivation for this paper was to investigate variation in a radial-velocity (RV) curve generated by this additional star in the system. We performed spectroscopic observation of Kepler-410 using three telescopes in Slovakia and Czech Republic. Using the cross-correlation function, we measured the radial velocities of the star Kepler-410A. We did not observe any periodic variation in an RV curve. Therefore, we rejected our previous hypothesis about additional stellar companion in the Kepler-410 system. We ran different numerical simulations to study mean-motion resonances with Kepler-410Ab. Observed TTVs could be also explained by the presence of a small planet near to mean-motion resonance 2:3 with Kepler-410Ab. This resonance is stable on a long time-scale. We also looked for stable regions in the Kepler-410 system where another planet could exist for a long time.
A revisit to the enigmatic variable star 21 Comae Paunzen, Ernst; Handler, Gerald; Walczak, Przemysław ...
Monthly notices of the Royal Astronomical Society,
05/2019, Letnik:
485, Številka:
3
Journal Article
Recenzirano
Abstract
The magnetic chemically peculiar (Ap/CP2) star 21 Com has been extensively studied in the past, albeit with widely differing and sometimes contradictory results, in particular concerning the ...occurrence of short-term variability between about 5 to 90 min. We have performed a new investigation of 21 Com using Microvariability and Oscillations of Star (MOST) satellite and high-cadence ground-based photometry, time series spectroscopy, and evolutionary and pulsational modelling. Our analysis confirms that 21 Com is a classical CP2 star showing increased abundances of, in particular, Cr and Sr. From spectroscopic analysis, we have derived $T_{\rm eff} = 8\, 900\pm 200$ K, log g = 3.9 ± 0.2, and υsin i = 63 ± 2 km s−1. Our modelling efforts suggest that 21 Com is a main sequence (MS) star seen equator-on with a mass of 2.29 ± 0.10 M⊙ and a radius of R = 2.6 ± 0.2 R⊙. Our extensive photometric data confirm the existence of rotational light variability with a period of 2.052 19(2) d. However, no significant frequencies with a semi-amplitude exceeding 0.2 mmag were found in the frequency range from 5 to 399 d−1. Our RV data also do not indicate short-term variability. We calculated pulsational models assuming different metallicities and ages, which do not predict the occurrence of unstable modes. The star 18 Com, often employed as comparison star for 21 Com in the past, has been identified as a periodic variable (P = 1.416 45 d). While it is impossible to assess whether 21 Com has exhibited short-term variability in the past, the new observational data and several issues/inconsistencies identified in previous studies strongly suggest that 21 Com is neither a δ Scuti nor a roAp pulsator but a 'well-behaved' CP2 star exhibiting its trademark rotational variability.
Cerro Armazones spectroscopic survey of F dwarfs Pribulla, Theodor; Sebastian, Daniel; Ammler-von Eiff, Matthias ...
Monthly Notices of the Royal Astronomical Society,
09/2014, Letnik:
443, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present a spectroscopic survey of a sample of F stars that have not yet been searched for planets. The observations of 187 stars obtained with the Bochum Echelle Spectrographic Observer of the ...Cerro Armazones Observatory were aimed at nearby (closer than 70 pc) main-sequence stars without sufficient archive (fiber-fed extended range optical spectrograph (FEROS)/high accuracy radial velocity planet search (HARPS)) spectroscopy. The primary goal of the survey was to select the best candidates for radial-velocity searches of extrasolar planets. The spectra were analysed using the broadening-function technique, the method of choice for rapid rotators later than about A5. The analysis was focused not only at the determination of projected rotational velocity (defining precision of radial-velocity determination), but also at the detection of previously unknown spectroscopic binaries/multiples or stars showing strong line asymmetries. 12 previously unknown spectroscopic binaries/triples were detected. For all observed targets the spectral type was determined. About 140 stars are rotating faster than the resolution limit of 10 km s−1 sampling the onset of convection and slow rotation at mid-F spectral types in great detail. Radial-velocity precision of the data (about 100 m s−1) is insufficient to detect planets but could indicate most SB1 systems with stellar companions. As there are already 2–3 observations per object for these newly detected binary stars, only a few additional follow-up observations will be needed to obtain constraints on orbital parameters. We identified a sample of 68 bright F-type dwarf stars which are perfect targets for future planet searches. They rotate moderately or slowly and do not show any sign of binarity, pulsations, or surface activity.
Project Dwarf is a new observing campaign focused on the detection of substellar companions to low-mass (composed of late-type, subdwarf (sd) or/and white dwarf (WD) components) detached eclipsing ...binaries using minima timing. The crucial condition for the object selection for this campaign is possibility to determine times of the minima with high precision. This is naturally fullfilled for eclipsing binaries with deep and narrow minima or systems hosting a WD component showing fast ingress or egress. The observing project includes three groups of close eclipsing binaries indicating presence of substellar circum-binary components:
(i)systems with K or/and M dwarf components(ii)systems with hot subdwarf (sd) and M dwarf components(iii)systems with white dwarf (WD) component(s).
The sample of the eclipsing systems have orbital periods in range of 0.1 to almost 3 days and their brightness fits possibilities of small telescopes equipped with a low-end CCD camera and at least VRI filter set. Such kind of telescopes allow us to develop observing network including also amateur astronomers.
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