scholarly journals Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

2020 ◽  
Vol 642 ◽  
pp. A72 ◽  
Author(s):  
C. Moutou ◽  
S. Dalal ◽  
J.-F. Donati ◽  
E. Martioli ◽  
C. P. Folsom ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Radial Velocity ◽  
Large Scale ◽  
Near Infrared ◽  
Field Studies ◽  
High Spectral Resolution ◽  
Planetary Orbit ◽  
Dominant Factor ◽  
Stellar Activity ◽  
Orbital Parameters

SPIRou is the newest spectropolarimeter and high-precision velocimeter that has recently been installed at the Canada-France-Hawaii Telescope on Maunakea, Hawaii. It operates in the near-infrared and simultaneously covers the 0.98–2.35 μm domain at high spectral resolution. SPIRou is optimized for exoplanet search and characterization with the radial-velocity technique, and for polarization measurements in stellar lines and subsequent magnetic field studies. The host of the transiting hot Jupiter HD 189733 b has been observed during early science runs. We present the first near-infrared spectropolarimetric observations of the planet-hosting star as well as the stellar radial velocities as measured by SPIRou throughout the planetary orbit and two transit sequences. The planetary orbit and Rossiter-McLaughlin anomaly are both investigated and modeled. The orbital parameters and obliquity are all compatible with the values found in the optical. The obtained radial-velocity precision is compatible with about twice the photon-noise estimates for a K2 star under these conditions. The additional scatter around the orbit, of about 8 m s−1, agrees with previous results that showed that the activity-induced scatter is the dominant factor. We analyzed the polarimetric signal, Zeeman broadening, and chromospheric activity tracers such as the 1083nm HeI and the 1282nm Paβ lines to investigate stellar activity. First estimates of the average unsigned magnetic flux from the Zeeman broadening of the FeI lines give a magnetic flux of 290 ± 58 G, and the large-scale longitudinal field shows typical values of a few Gauss. These observations illustrate the potential of SPIRou for exoplanet characterization and magnetic and stellar activity studies.

scholarly journals The GAPS Programme at TNG

2020 ◽  
Vol 638 ◽  
pp. A5 ◽  
Author(s):  
I. Carleo ◽  
L. Malavolta ◽  
A. F. Lanza ◽  
M. Damasso ◽  
S. Desidera ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Semimajor Axis ◽  
Young Stars ◽  
Homogeneous Sample ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Hot Jupiters ◽  
Multi Band ◽  
Hot Jupiter

Context. The existence of hot Jupiters is still not well understood. Two main channels are thought to be responsible for their current location: a smooth planet migration through the protoplanetary disk or the circularization of an initial highly eccentric orbit by tidal dissipation leading to a strong decrease in the semimajor axis. Different formation scenarios result in different observable effects, such as orbital parameters (obliquity and eccentricity) or frequency of planets at different stellar ages. Aims. In the context of the GAPS Young Objects project, we are carrying out a radial velocity survey with the aim of searching and characterizing young hot-Jupiter planets. Our purpose is to put constraints on evolutionary models and establish statistical properties, such as the frequency of these planets from a homogeneous sample. Methods. Since young stars are in general magnetically very active, we performed multi-band (visible and near-infrared) spectroscopy with simultaneous GIANO-B + HARPS-N (GIARPS) observing mode at TNG. This helps in dealing with stellar activity and distinguishing the nature of radial velocity variations: stellar activity will introduce a wavelength-dependent radial velocity amplitude, whereas a Keplerian signal is achromatic. As a pilot study, we present here the cases of two known hot Jupiters orbiting young stars: HD 285507 b and AD Leo b. Results. Our analysis of simultaneous high-precision GIARPS spectroscopic data confirms the Keplerian nature of the variation in the HD 285507 radial velocities and refines the orbital parameters of the hot Jupiter, obtaining an eccentricity consistent with a circular orbit. Instead, our analysis does not confirm the signal previously attributed to a planet orbiting AD Leo. This demonstrates the power of the multi-band spectroscopic technique when observing active stars.

scholarly journals Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b

2018 ◽  
Vol 613 ◽  
pp. A50 ◽  
Author(s):  
I. Carleo ◽  
S. Benatti ◽  
A. F. Lanza ◽  
R. Gratton ◽  
R. Claudi ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Hot Spots ◽  
Near Infrared ◽  
High Resolution Spectroscopy ◽  
Velocity Measurements ◽  
Stellar Activity ◽  
Multi Wavelength ◽  
First Time ◽  
Multi Band

Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique. Aims. We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion. Methods. We compare VIS data with high precision RVs in the near-infrared (NIR) range by using the GIANO–B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO–B and HARPS–N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS. Results. The NIR radial velocity measurements from GIANO–B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region. Conclusions. In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi-wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.

scholarly journals Deploying four optical UAV-based sensors over grassland: challenges and limitations

2015 ◽  
Vol 12 (1) ◽  
pp. 163-175 ◽  
Author(s):  
S. K. von Bueren ◽  
A. Burkart ◽  
A. Hueni ◽  
U. Rascher ◽  
M. P. Tuohy ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Infrared Camera ◽  
Ground Level ◽  
Analysis Data ◽  
High Spectral Resolution ◽  
Spectral Measurements ◽  
Pasture Management ◽  
Vegetation Monitoring ◽  
Multispectral Camera

Abstract. Unmanned aerial vehicles (UAVs) equipped with lightweight spectral sensors facilitate non-destructive, near-real-time vegetation analysis. In order to guarantee robust scientific analysis, data acquisition protocols and processing methodologies need to be developed and new sensors must be compared with state-of-the-art instruments. Four different types of optical UAV-based sensors (RGB camera, converted near-infrared camera, six-band multispectral camera and high spectral resolution spectrometer) were deployed and compared in order to evaluate their applicability for vegetation monitoring with a focus on precision agricultural applications. Data were collected in New Zealand over ryegrass pastures of various conditions and compared to ground spectral measurements. The UAV STS spectrometer and the multispectral camera MCA6 (Multiple Camera Array) were found to deliver spectral data that can match the spectral measurements of an ASD at ground level when compared over all waypoints (UAV STS: R2=0.98; MCA6: R2=0.92). Variability was highest in the near-infrared bands for both sensors while the band multispectral camera also overestimated the green peak reflectance. Reflectance factors derived from the RGB (R2=0.63) and converted near-infrared (R2=0.65) cameras resulted in lower accordance with reference measurements. The UAV spectrometer system is capable of providing narrow-band information for crop and pasture management. The six-band multispectral camera has the potential to be deployed to target specific broad wavebands if shortcomings in radiometric limitations can be addressed. Large-scale imaging of pasture variability can be achieved by either using a true colour or a modified near-infrared camera. Data quality from UAV-based sensors can only be assured, if field protocols are followed and environmental conditions allow for stable platform behaviour and illumination.

scholarly journals Stellar activity of planetary host star HD 189733

2008 ◽  
Vol 4 (S253) ◽  
pp. 462-465
Author(s):  
I. Boisse ◽  
C. Moutou ◽  
A. Vidal-Madjar ◽  
F. Bouchy ◽  
F. Pont ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
High Precision ◽  
Velocity Gradient ◽  
Orbital Motion ◽  
Spectral Lines ◽  
Stellar Surface ◽  
Stellar Activity ◽  
Orbital Parameters

AbstractExoplanet search programs need to study how to disentangle radial-velocity (RV) variations due to Doppler motion and the noise induced by stellar activity. We monitored the active K2V HD 189733 with the high-resolution SOPHIE spectrograph (OHP, France). We refined the orbital parameters of HD 189733b and put limitations on the eccentricity and on a long-term velocity gradient. We subtracted the orbital motion of the planet and compared the variability of activity spectroscopic indices (HeI, Hα, Ca II H&K lines) to the evolution of the RV residuals and the shape of spectral lines. All are in agreement with an active stellar surface in rotation. We used such correlations to correct for the RV jitter due to stellar activity. This results in achieving a high precision on the orbital parameters, with a semi-amplitude: K=200.56±0.88m⋅s−1 and a derived planet mass of MP=1.13±0.03 MJup.

scholarly journals Detection of Exomoons Inside the Habitable Zone

2012 ◽  
Vol 8 (S293) ◽  
pp. 168-170
Author(s):  
Luis Ricardo M. Tusnski ◽  
Adriana Valio
Keyword(s):  
The Other ◽  
Planetary Orbit ◽  
Habitable Zone ◽  
The Moon ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Hot Jupiters ◽  
Habitable Zones ◽  
Observational Bias ◽  
Host Stars

AbstractSince the discovery of the first exoplanets, those most adequate for life to begin and evolve have been sought. Due to observational bias, however, most of the discovered planets so far are gas giants, precluding their habitability. However, if these hot Jupiters are located in the habitable zones of their host stars, and if rocky moons orbit them, then these moons may be habitable. In this work, we present a model for planetary transit simulation considering the presence of moons around a planet. The moon orbit is considered to be circular and coplanar with the planetary orbit. The other physical and orbital parameters of the star, planet, and moon, can be adjusted in each simulation. It is possible to simulate as many successive transits as desired. Since the presence of spots on the surface of the star may produce a signal similar to that of the presence of a moon, our model also allows for the inclusion of starspots. The goal is to determine the criteria for detectability of moons using photometry with the CoRoT and Kepler telescopes taking into account the stellar activity.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 627 ◽  
pp. A116 ◽  
Author(s):  
S. Lalitha ◽  
D. Baroch ◽  
J. C. Morales ◽  
V. M. Passegger ◽  
F. F. Bauer ◽  
...  
Keyword(s):  
Near Infrared ◽  
Correlated Noise ◽  
Stellar Rotation ◽  
M Dwarfs ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Rotation Periods ◽  
Planetary Mass ◽  
Low Mass ◽  
Orbital Periods

Although M dwarfs are known for high levels of stellar activity, they are ideal targets for the search of low-mass exoplanets with the radial velocity (RV) method. We report the discovery of a planetary-mass companion around LSPM J2116+0234 (M3.0 V) and confirm the existence of a planet orbiting GJ 686 (BD+18 3421; M1.0 V). The discovery of the planet around LSPM J2116+0234 is based on CARMENES RV observations in the visual and near-infrared channels. We confirm the planet orbiting around GJ 686 by analyzing the RV data spanning over two decades of observationsfrom CARMENES VIS, HARPS-N, HARPS, and HIRES. We find planetary signals at 14.44 and 15.53 d in the RV data for LSPM J2116+0234 and GJ 686, respectively. Additionally, the RV, photometric time series, and various spectroscopic indicators show hints of variations of 42 d for LSPM J2116+0234 and 37 d for GJ 686, which we attribute to the stellar rotation periods. The orbital parameters of the planets are modeled with Keplerian fits together with correlated noise from the stellar activity. A mini-Neptune with a minimum mass of 11.8 M⊕ orbits LSPM J2116+0234 producing a RV semi-amplitude of 6.19 m s−1, while a super-Earth of mass 6.6 M⊕ orbits GJ 686 and produces a RV semi-amplitude of 3.0 m s−1. Both LSPM J2116+0234 and GJ 686 have planetary companions populating the regime of exoplanets with masses lower than 15 M⊕ and orbital periods <20 d.

FIESTA – disentangling stellar variability from exoplanets in the Fourier domain

2019 ◽  
Vol 491 (3) ◽  
pp. 4131-4146 ◽  
Author(s):  
J Zhao ◽  
C G Tinney
Keyword(s):  
Radial Velocity ◽  
Line Profile ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Velocity Shift ◽  
Analysis Methodology ◽  
Spectral Line Profile ◽  
Periodogram Analysis

ABSTRACT We propose a new analysis methodology – FourIEr phase SpecTrum Analysis (FIESTA, or $\mathit {\Phi }$ESTA) – for the study of spectral line profile variability in Fourier space. The philosophy of $\mathit {\Phi }$ESTA is highlighted in its interpretation of a line deformation as various shifts of the composing Fourier modes. With this ability, $\mathit {\Phi }$ESTA excels in distinguishing the effects of a bulk shift in a line profile, from changes in a line profile shape. In other words, it can distinguish a radial velocity shift due to orbiting companions like planets, from an apparent radial velocity shift due to stellar variability (often referred to as ‘jitter’). Most importantly, it can quantify the radial velocity impact of stellar jitter on each epoch. Our simulations show that (compared to a model that does not account for stellar activity), $\mathit {\Phi }$ESTA can almost triple the fraction of planets recovered with orbital parameters measured to within 10 per cent of their input parameters, when extracting a 2 m s−1 amplitude planetary signal in the midst of ∼2 m s−1 amplitude starspot jitter for high signal-to-noise ratio (&gt;200 pixel−1) data. $\mathit {\Phi }$ESTA can also be used to identify stellar activity related periods in a periodogram analysis and classify relative amplitudes of stellar jitter and planetary signals, with examples for the analysis of HARPS data of the active star HD 224789 and the active planet-host star HD 103720. In the end, we demonstrate that $\mathit {\Phi }$ESTA’s framework is working as well as other activity indicators in correlating with stellar jitter.

scholarly journals U Geminorum: a Test Case for Orbital Parameters Determination

2006 ◽  
Vol 2 (S240) ◽  
pp. 309-312
Author(s):  
Juan Echevarría ◽  
Eduardo de la Fuente ◽  
Rafael Costero
Keyword(s):  
Radial Velocity ◽  
Accretion Disk ◽  
Near Infrared ◽  
Hot Spot ◽  
High Resolution Spectroscopy ◽  
Test Case ◽  
Late Type ◽  
Radial Velocity Curve ◽  
Disk Radius ◽  
Orbital Parameters

AbstractHigh-resolution spectroscopy of U Gem was obtained during quiescence. We did not find a hot spot or gas stream around the outer boundaries of the accretion disk. Instead, we detected a strong narrow emission near the location of the secondary star. We measured the radial velocity curve from the wings of the double-peaked Hα emission line, and obtained a semi-amplitude value in excellent agreement with the ultraviolet results by Long & Gilliland (1999). We present also a new method to obtain K2, which enhances the detection of absorption or emission features arising in the late-type companion. Our results are compared with published values derived from the near-infrared NaI line doublet. From a comparison of the TiO band with those of late type M stars, we find that a best fit is obtained for a M6 V star, contributing 5% of the total light at that spectral region. Assuming that the radial velocity semi-amplitudes reflect accurately the motion of the binary components, then from our results: Kem = 108 ± 2 km s−1; Kabs = 310 ± 5 km s−1, and using the inclination angle by Zhang & Robinson (1987); i = 69°.7 ± 0.7, the system parameters become: MWD = 1.20 ± 0.05 M⊙; MRD = 0.42 ± 0.04 M⊙; and a = 1.55 ± 0.02 R⊙. Based on the separation of the double emission peaks, we calculate an outer disk radius of Rout/a ∼ 0.63, close to the distance of the inner Lagrangian point L1/a ∼ 0.63. Therefore we suggest that, at the time of observations, the accretion disk was filling the Roche-Lobe of the primary, and that the matter leaving the L1 point was colliding with the disc directly, producing the hot spot at this location. Specific details not included in the printed version can be found in the Electronic Poster (EP).

scholarly journals The CARMENES search for exoplanets around M dwarfs

2020 ◽  
Vol 636 ◽  
pp. A119 ◽  
Author(s):  
S. Stock ◽  
J. Kemmer ◽  
S. Reffert ◽  
T. Trifonov ◽  
A. Kaminski ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Radial Velocity ◽  
Model Comparison ◽  
Gaussian Process Regression ◽  
System Stability ◽  
M Dwarfs ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Orbital Periods

Context. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is imin = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of imax = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters.

scholarly journals The impact of unresolved magnetic spots on high-precision radial velocity measurements

2020 ◽  
Vol 497 (3) ◽  
pp. 4009-4021
Author(s):  
M Lisogorskyi ◽  
S Boro Saikia ◽  
S V Jeffers ◽  
H R A Jones ◽  
J Morin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radial Velocity ◽  
High Precision ◽  
Large Scale ◽  
Magnetic Activity ◽  
Velocity Measurements ◽  
Stellar Activity ◽  
Solar Type ◽  
Rotating Star ◽  
The Impact

ABSTRACT The Doppler method of exoplanet detection has been extremely successful, but suffers from contaminating noise from stellar activity. In this work, a model of a rotating star with a magnetic field based on the geometry of the K2 star ϵ Eridani is presented and used to estimate its effect on simulated radial velocity (RV) measurements. A number of different distributions of unresolved magnetic spots were simulated on top of the observed large-scale magnetic maps obtained from 8 yr of spectropolarimetric observations. The RV signals due to the magnetic spots have amplitudes of up to 10 m s−1, high enough to prevent the detection of planets under 20 Earth masses in temperate zones of solar-type stars. We show that the RV depends heavily on spot distribution. Our results emphasize that understanding stellar magnetic activity and spot distribution is crucial for the detection of Earth analogues.

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