Scheduling strategies for the ESPRESSO follow-up of TESS targets

2021 ◽  
Vol 503 (4) ◽  
pp. 5504-5521
Author(s):  
L Cabona ◽  
P T P Viana ◽  
M Landoni ◽  
J P Faria
Keyword(s):  
Radial Velocity ◽  
Planetary Systems ◽  
Data Set ◽  
Noise Component ◽  
Orbital Parameters ◽  
Transiting Planets ◽  
Accuracy And Precision ◽  
Scheduling Strategies ◽  
The Masses

ABSTRACT Radial-velocity follow-up of stars harbouring transiting planets detected by TESS is expected to require very large amounts of expensive telescope time in the next few years. Therefore, scheduling strategies should be implemented to maximize the amount of information gathered about the target planetary systems. We consider myopic and non-myopic versions of a novel uniform-in-phase scheduler, as well as a random scheduler, and compare these scheduling strategies with respect to the bias, accuracy and precision achieved in recovering the mass and orbital parameters of transiting and non-transiting planets. This comparison is carried out based on realistic simulations of radial-velocity follow-up with ESPRESSO of a sample of 50 TESS target stars, with simulated planetary systems containing at least one transiting planet with a radius below 4R⊕. Radial-velocity data sets were generated under reasonable assumptions about their noise component, including that resulting from stellar activity, and analysed using a fully Bayesian methodology. We find the random scheduler leads to a more biased, less accurate, and less precise, estimation of the mass of the transiting exoplanets. No significant differences are found between the results of the myopic and non-myopic implementations of the uniform-in-phase scheduler. With only about 22 radial velocity measurements per data set, our novel uniform-in-phase scheduler enables an unbiased (at the level of 1 per cent) measurement of the masses of the transiting planets, while keeping the average relative accuracy and precision around 16 per cent and 23 per cent, respectively. The number of non-transiting planets detected is similar for all the scheduling strategies considered, as well as the bias, accuracy and precision with which their masses and orbital parameters are recovered.

scholarly journals Simulating radial velocity observations of trappist-1 with SPIRou

2019 ◽  
Vol 488 (4) ◽  
pp. 5114-5126 ◽  
Author(s):  
Baptiste Klein ◽  
J-F Donati
Keyword(s):  
White Noise ◽  
Radial Velocity ◽  
Gaussian Process Regression ◽  
Data Set ◽  
Stellar Activity ◽  
Sampling Schemes ◽  
Activity Curve ◽  
To Come ◽  
The Masses

ABSTRACT We simulate a radial velocity (RV) follow-up of the TRAPPIST-1 system, a faithful representative of M dwarfs hosting transiting Earth-sized exoplanets to be observed with SPIRou in the months to come. We generate an RV curve containing the signature of the seven transiting TRAPPIST-1 planets and a realistic stellar activity curve statistically compatible with the light curve obtained with the K2 mission. We find a ±5 m s−1 stellar activity signal comparable in amplitude with the planet signal. Using various sampling schemes and white noise levels, we create time-series from which we estimate the masses of the seven planets. We find that the precision on the mass estimates is dominated by (i) the white noise level for planets c, f, and e and (ii) the stellar activity signal for planets b, d, and h. In particular, the activity signal completely outshines the RV signatures of planets d and h that remain undetected regardless of the RV curve sampling and level of white noise in the data set. We find that an RV follow-up of TRAPPIST-1 using SPIRou alone would likely result in an insufficient coverage of the rapidly evolving activity signal of the star, especially with bright-time observations only, making statistical methods such as Gaussian Process Regression hardly capable of firmly detecting planet f and accurately recovering the mass of planet g. In contrast, we show that using bi-site observations with good longitudinal complementary would allow for a more accurate filtering of the stellar activity RV signal.

scholarly journals The TROY project: Searching for co-orbital bodies to known planets

2018 ◽  
Vol 609 ◽  
pp. A96 ◽  
Author(s):  
J. Lillo-Box ◽  
D. Barrado ◽  
P. Figueira ◽  
A. Leleu ◽  
N. C. Santos ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Planetary Systems ◽  
Occurrence Rate ◽  
Velocity Data ◽  
Transiting Planets ◽  
Extrasolar Systems ◽  
Upper Limits ◽  
And Migration ◽  
The Masses ◽  
Radial Velocity Data

Context. The detection of Earth-like planets, exocomets or Kuiper belts show that the different components found in the solar system should also be present in other planetary systems. Trojans are one of these components and can be considered fossils of the first stages in the life of planetary systems. Their detection in extrasolar systems would open a new scientific window to investigate formation and migration processes. Aims. In this context, the main goal of the TROY project is to detect exotrojans for the first time and to measure their occurrence rate (η-Trojan). In this first paper, we describe the goals and methodology of the project. Additionally, we used archival radial velocity data of 46 planetary systems to place upper limits on the mass of possible trojans and investigate the presence of co-orbital planets down to several tens of Earth masses. Methods. We used archival radial velocity data of 46 close-in (P < 5 days) transiting planets (without detected companions) with information from high-precision radial velocity instruments. We took advantage of the time of mid-transit and secondary eclipses (when available) to constrain the possible presence of additional objects co-orbiting the star along with the planet. This, together with a good phase coverage, breaks the degeneracy between a trojan planet signature and signals coming from additional planets or underestimated eccentricity. Results. We identify nine systems for which the archival data provide >1σ evidence for a mass imbalance between L4 and L5. Two of these systems provide >2σ detection, but no significant detection is found among our sample. We also report upper limits to the masses at L4/L5 in all studied systems and discuss the results in the context of previous findings.

scholarly journals Distribution of RV- and transiting exoplanets by masses and orbital periods taking into account observational selection

2021 ◽  
Author(s):  
Vladislava Ananyeva ◽  
Alexander Tavrov ◽  
Oleg Korablev ◽  
Jean-Loup Bertaux
Keyword(s):  
Radial Velocity ◽  
Mass Distribution ◽  
Power Law ◽  
Planetary Systems ◽  
Similar Distribution ◽  
Statistical Distributions ◽  
Population Synthesis ◽  
Transiting Planets ◽  
Orbital Periods

&lt;p&gt;More than 95% of the known exoplanets were discovered by the transit- and radial velocity techniques. However, the observed distributions of planets by their masses and by their orbital periods are significantly distorted by numerous observational selections, different for these techniques and different surveys.&lt;/p&gt; &lt;p&gt;We found and studied the de-biased statistical distributions of exoplanets by masses and by orbital periods for three groups of exoplanets: I. transiting planets discovered by Kepler ST, whose masses were measured by the follow-up radial velocity technique, II. transiting planets discovered by ground-based surveys (SuperWASP, HATNet, NGTS, XO, KELT, etc.), III. planets discovered by the radial velocity technique. The synthetic projective-mass distribution of RV planets obeys the piecewise power law with the breakpoints at ~0.14MJ and ~1.7MJ. The distribution of RV-planets with m = (0.011-0.087)MJ (or (3.5-28)ME) accurately obeys the power law with an exponent of -2, dN/dm &amp;#8733; m^-2. The distribution of RV planets with m = (0.21-1.7)MJ follows the power law with an exponent ranging from -0.7 to -0.8, dN/dm &amp;#8733; m^(-0.7&amp;#8230;-0.8). The distribution of RV planets with m = (1.7-13)MJ is fitted by a power law with an exponent ranging from -1.7 to -2.0, dN/dm &amp;#8733; m^(-1.7&amp;#8230;-2.0). In general, the synthetic projective-mass distribution of RV planets well agrees with the predictions of the population synthesis theory (Mordasini, 2018) and includes more detailed features to be discussed.&lt;/p&gt; &lt;p&gt;The exoplanets distribution by periods generally follows a power law with an exponent of -0.75 and indicates a predominant (averaged) structuring of the planetary systems.&lt;/p&gt; &lt;p&gt;De-biased mass distribution of RV-planets with orbital periods of 2-58 days is well consistent with a similar distribution of the Kepler planets. The mass distribution of the transit exoplanets detected by ground-based surveys is consistent with the similar distribution of RV planets with periods of 1-20 days.&lt;/p&gt;

scholarly journals DEMONEX: The DEdicated MONitor of EXotransits

2008 ◽  
Vol 4 (S253) ◽  
pp. 408-411 ◽  
Author(s):  
J. D. Eastman ◽  
B. S. Gaudi ◽  
D. L. DePoy
Keyword(s):  
Radial Velocity ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Signal To Noise ◽  
Data Set ◽  
Transiting Planets ◽  
Readout Time ◽  
Robotic Telescope ◽  
Homogeneous Data

AbstractDEMONEX is a low-cost, 0.5 meter, robotic telescope assembled mostly from commercially available parts dedicated to obtaining precise photometry of bright stars with transiting planets. This photometry will provide a homogeneous data set for all transits visible from its location at Winer Observatory in Sonoita, Arizona. We will also search for additional planets via transit timing variations, measure or place limits on the albedos from secondary eclipses, systematically search known radial velocity planets for those that transit, and follow up promising KELT candidates. Despite its modest size, the signal-to-noise ratio per transit is comparable to that obtained with larger, 1m-class telescopes because of its short readout time and high z-band quantum efficiency. However, its main strength is that it will be used every night for transit follow-up and gather an unprecedented data set on transiting planets. With the 24 known transiting planets and 112 radial velocity planets visible from Winer Observatory, over 90% of all nights have at least one full event to observe.

scholarly journals Detection and Doppler monitoring of K2-285 (EPIC 246471491), a system of four transiting planets smaller than Neptune

2019 ◽  
Vol 623 ◽  
pp. A41 ◽  
Author(s):  
E. Palle ◽  
G. Nowak ◽  
R. Luque ◽  
D. Hidalgo ◽  
O. Barragán ◽  
...  
Keyword(s):  
Bulk Composition ◽  
Velocity Measurements ◽  
Good Test ◽  
Transiting Planets ◽  
Atmospheric Escape ◽  
Outer Planets ◽  
Upper Limits ◽  
The Masses ◽  
Better Than

Context. The Kepler extended mission, also known as K2, has provided the community with a wealth of planetary candidates that orbit stars typically much brighter than the targets of the original mission. These planet candidates are suitable for further spectroscopic follow-up and precise mass determinations, leading ultimately to the construction of empirical mass-radius diagrams. Particularly interesting is to constrain the properties of planets that are between Earth and Neptune in size, the most abundant type of planet orbiting Sun-like stars with periods of less than a few years. Aims. Among many other K2 candidates, we discovered a multi-planetary system around EPIC 246471491, referred to henceforth as K2-285, which contains four planets, ranging in size from twice the size of Earth to nearly the size of Neptune. We aim here at confirming their planetary nature and characterizing the properties of this system. Methods. We measure the mass of the planets of the K2-285 system by means of precise radial-velocity measurements using the CARMENES spectrograph and the HARPS-N spectrograph. Results. With our data we are able to determine the mass of the two inner planets of the system with a precision better than 15%, and place upper limits on the masses of the two outer planets. Conclusions. We find that K2-285b has a mass of Mb = 9.68−1.37+1.21 M⊕ and a radius of Rb = 2.59−0.06+0.06 R⊕, yielding a mean density of ρb = 3.07−0.45+0.45 g cm−3, while K2-285c has a mass of Mc = 15.68−2.13+2.28 M⊕, radius of Rc = 3.53−0.08+0.08 R⊕, and a mean density of ρc = 1.95−0.28+0.32 g cm−3. For K2-285d (Rd = 2.48−0.06+0.06 R⊕) and K2-285e (Re = 1.95−0.05+0.05 R⊕), the upper limits for the masses are 6.5 M⊕ and 10.7 M⊕, respectively. The system is thus composed of an (almost) Neptune-twin planet (in mass and radius), two sub-Neptunes with very different densities and presumably bulk composition, and a fourth planet in the outermost orbit that resides right in the middle of the super-Earth/sub-Neptune radius gap. Future comparative planetology studies of this system would provide useful insights into planetary formation, and also a good test of atmospheric escape and evolution theories.

scholarly journals An improved test of the strong equivalence principle with the pulsar in a triple star system

2020 ◽  
Vol 638 ◽  
pp. A24 ◽  
Author(s):  
G. Voisin ◽  
I. Cognard ◽  
P. C. C. Freire ◽  
N. Wex ◽  
L. Guillemot ◽  
...  
Keyword(s):  
Equivalence Principle ◽  
Strong Field ◽  
Stellar System ◽  
Sampled Data ◽  
Theory Of Relativity ◽  
Data Set ◽  
Orbital Parameters ◽  
Timing Model ◽  
The Masses ◽  
Strong Equivalence Principle

Context. The gravitational strong equivalence principle (SEP) is a cornerstone of the general theory of relativity (GR). Hence, testing the validity of SEP is of great importance when confronting GR, or its alternatives, with experimental data. Pulsars that are orbited by white dwarf companions provide an excellent laboratory, where the extreme difference in binding energy between neutron stars and white dwarfs allows for precision tests of the SEP via the technique of radio pulsar timing. Aims. To date, the best limit on the validity of SEP under strong-field conditions was obtained with a unique pulsar in a triple stellar system, PSR J0337+1715. We report here on an improvement of this test using an independent data set acquired over a period of 6 years with the Nançay radio telescope. The improvements arise from a uniformly sampled data set, a theoretical analysis, and a treatment that fixes some short-comings in the previously published results, leading to better precision and reliability of the test. Methods. In contrast to the previously published test, we use a different long-term timing data set, developed a new timing model and an independent numerical integration of the motion of the system, and determined the masses and orbital parameters with a different methodology that treats the parameter Δ, describing a possible strong-field SEP violation, identically to all other parameters. Results. We obtain a violation parameter Δ = ( + 0.5 ± 1.8) × 10−6 at 95% confidence level, which is compatible with and improves upon the previous study by 30%. This result is statistics-limited and avoids limitation by systematics as previously encountered. We find evidence for red noise in the pulsar spin frequency, which is responsible for up to 10% of the reported uncertainty. We use the improved limit on SEP violation to place constraints on a class of well-studied scalar-tensor theories, in particular we find ωBD >  140 000 for the Brans-Dicke parameter. The conservative limits presented here fully take into account current uncertainties in the equation for state of neutron-star matter.

scholarly journals Periodic transit timing variations and refined system parameters of the exoplanet XO-6b

2019 ◽  
Author(s):  
Zoltán Garai ◽  
Theodor Pribulla ◽  
Richard Komžík ◽  
Emil Kundra ◽  
Ľubomír Hambálek ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Rotating Stars ◽  
Velocity Measurements ◽  
Orbital Parameters ◽  
Orbit Inclination ◽  
Consistent Solution ◽  
Low Mass ◽  
Academy Of Sciences ◽  
Fast Rotating

Abstract Only a few exoplanets are known to orbit around fast rotating stars. One of them is XO-6b, which orbits an F5V-type star. Shortly after the discovery, we started multicolor photometric and radial-velocity follow-up observations of XO-6b, using the telescopes of Astronomical Institute of the Slovak Academy of Sciences. Our main scientific goals were to better characterize the planetary system and to search for transit timing variations. We refined several planetary and orbital parameters. Based on our measurements, the planet XO-6b seems to be about 10% larger, which is, however, only about 2σ difference, but its orbit inclination angle, with respect to the plane of the sky, seems to be significantly smaller, than it was determined originally by the discoverers. In this case we found about 9.5σ difference. Moreover, we observed periodic transit timing variations of XO-6b with a semi-amplitude of about 14 min and with a period of about 450 days. There are two plausible explanations of such transit timing variations: (1) a third object in the system XO-6 causing light-time effect, or (2) resonant perturbations between the transiting planet XO-6b and another unknown low-mass planet in this system. From the O-C diagram we derived that the assumed third object in the system should have a stellar mass, therefore significant variations are expected in the radial-velocity measurements of XO-6. Since this is not the case, and since all attempts to fit radial velocities and O-C data simultaneously failed to provide a consistent solution, more realistic is the second explanation.

scholarly journals Revisiting theKeplerfield withTESS: Improved ephemerides usingTESS2 min data

2021 ◽  
Vol 503 (3) ◽  
pp. 4092-4104
Author(s):  
Matthew P Battley ◽  
Michelle Kunimoto ◽  
David J Armstrong ◽  
Don Pollacco
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Photometric Method ◽  
Velocity Data ◽  
Signal To Noise ◽  
Data Set ◽  
The Future ◽  
Radial Velocity Data ◽  
Very High

ABSTRACTUp to date planet ephemerides are becoming increasingly important as exoplanet science moves from detecting exoplanets to characterizing their architectures and atmospheres in depth. In this work, ephemerides are updated for 22 Kepler planets and 4 Kepler planet candidates, constituting all Kepler planets and candidates with sufficient signal to noise in the TESS 2 min data set. A purely photometric method is utilized here to allow ephemeris updates for planets even when they do not posses significant radial velocity data. The obtained ephemerides are of very high precision and at least seven years ‘fresher’ than archival ephemerides. In particular, significantly reduced period uncertainties for Kepler-411d, Kepler-538b, and the candidates K00075.01/K00076.01 are reported. O–C diagrams were generated for all objects, with the most interesting ones discussed here. Updated TTV fits of five known multiplanet systems with significant TTVs were also attempted (Kepler-18, Kepler-25, Kepler-51, Kepler-89, and Kepler-396), however these suffered from the comparative scarcity and dimness of these systems in TESS. Despite these difficulties, TESS has once again shown itself to be an incredibly powerful follow-up instrument as well as a planet-finder in its own right. Extension of the methods used in this paper to the 30 min-cadence TESS data and TESS extended mission has the potential to yield updated ephemerides of hundreds more systems in the future.

scholarly journals Getting More For Your Money: Identifying and Confirming Long-Period Planets with Kepler

2008 ◽  
Vol 4 (S253) ◽  
pp. 560-563
Author(s):  
Jennifer C. Yee ◽  
B. Scott Gaudi
Keyword(s):  
Radial Velocity ◽  
Circular Orbits ◽  
Transiting Planets ◽  
Long Period ◽  
The Masses ◽  
Better Than

AbstractKepler will monitor enough stars that it is likely to detect single transits of planets with periods longer than the mission lifetime. We show that by combining the Kepler photometry of such transits with precise radial velocity (RV) observations taken over ~3 months, and assuming circular orbits, it is possible to estimate the periods of these transiting planets to better than 20% (for planets with radii greater than that of Neptune) and the masses to within a factor of 2 (for planet masses mp ≥ MJup). We also explore the effects of eccentricity on these quantities.

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