31 research outputs found
New evidence about HW Vir's circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling
The post common-envelope eclipsing binary HW Virginis has had many
circumbinary companions proposed based on eclipse timing variations. Each
proposed solution has lacked in predictability and orbital stability, leaving
the origin of the eclipse timing variations an active area of research.
Leveraging the catalogue of \textit{Hipparcos} and \textit{Gaia} proper motion
anomalies, we show there is slight evidence for a circumbinary companion
orbiting HW Vir. We place an upper limit in mass for such a companion which
excludes some previously claimed companions. We also apply this method to V471
Tauri and confirm the non-detection of a previously claimed brown dwarf. We
adapt the {\tt kima} nested sampling code to analyse eclipse timing variations
and re-analyse archival data on HW Vir, varying the order of the ephemeris that
we fit for and the amount of the data that we use. Although signals are clearly
present, we find two signals around 2500 and 4000 day periods that are not
coherent between different \textit{chunks} of the data, so are likely to not be
of planetary origin. We analyse the whole dataset and find the best solution to
contain four signals. Of these four we argue the outermost is the most
compatible with astrometry and thus the most likely to be of planetary nature.
We posit the other three pseudo-periodic signals are caused by physical
processes on the white dwarf. The eventual release of the full \textit{Gaia}
epoch astrometry is a promising way to confirm whether circumbinary planets
exist around HW Vir (and other similar systems), and explore white dwarf
physics.Comment: 10 pages, 5 figures, 5 tables, published in Monthly Notices of the
Royal Astronomical Societ
GJ 9404 b:A Confirmed Eccentric Planet, and not a Candidate
Eccentric orbits can be decomposed into a series of sine curves which affects
how the false alarm probability is computed when using traditional periodograms
on radial-velocity data. Here we show that a candidate exoplanet orbiting the M
dwarf GJ 9404, identified by the HADES survey using data from the HARPS-N
spectrograph, is in fact a bona-fide planet on a highly eccentric orbit. Far
from a candidate, GJ 9404 b is detected with a high confidence. We reach our
conclusion using two methods that assume Keplerian functions rather than sines
to compute a detection probability, a Bayes Factor, and the FIP periodogram. We
compute these using nested sampling with {\tt kima}.Comment: 3 pages, 1 figur
Improving circumbinary planet detections by fitting their binary's apsidal precession
Apsidal precession in stellar binaries is the main non-Keplerian dynamical
effect impacting the radial-velocities of a binary star system. Its presence
can notably hide the presence of orbiting circumbinary planets because many
fitting algorithms assume perfectly Keplerian motion. To first order, apsidal
precession () can be accounted for by adding a linear term to the
usual Keplerian model. We include apsidal precession in the kima package, an
orbital fitter designed to detect and characterise planets from radial velocity
data. In this paper, we detail this and other additions to kima that improve
fitting for stellar binaries and circumbinary planets including corrections
from general relativity. We then demonstrate that fitting for
can improve the detection sensitivity to circumbinary exoplanets by up to an
order of magnitude in some circumstances, particularly in the case of
multi-planetary systems. In addition, we apply the algorithm to several real
systems, producing a new measurement of aspidal precession in KOI-126 (a tight
triple system), and a detection of in the Kepler-16 circumbinary
system. Although apsidal precession is detected for Kepler-16, it does not have
a large effect on the detection limit or the planetary parameters. We also
derive an expression for the precession an outer planet would induce on the
inner binary and compare the value this predicts with the one we detect.Comment: 10 pages, 5 figures Re-submitted to MNRAS after reviewer comment
ESPRESSO Observations of Gaia BH1:High-precision Orbital Constraints and no Evidence for an Inner Binary
We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary. A BH + BH binary is expected in some models where Gaia BH1 formed as a hierarchical triple, which is attractive because they avoid many of the difficulties associated with forming the system through isolated binary evolution. Our observations test the inner binary scenario. We have measured 115 precise RVs of the G star, including 40 from ESPRESSO with a precision of 3–5 m s−1, and 75 from other instruments with a typical precision of 30–100 m s−1. Our observations span 2.33 orbits of the G star and are concentrated near a periastron passage, when perturbations due to an inner binary would be largest. The RVs are well-fit by a Keplerian two-body orbit and show no convincing evidence of an inner binary. Using REBOUND simulations of hierarchical triples with a range of inner periods, mass ratios, eccentricities, and orientations, we show that plausible inner binaries with periods Pinner ≳ 1.5 days would have produced larger deviations from a Keplerian orbit than observed. Binaries with Pinner ≲ 1.5 days are consistent with the data, but these would merge within a Hubble time and would thus imply fine-tuning. We present updated parameters of Gaia BH1's orbit. The RVs yield a spectroscopic mass function f(MBH)=3.9358±0.0002M⊙—about 7000σ above the ∼2.5 M⊙ maximum neutron star mass. Including the inclination constraint from Gaia astrometry, this implies a BH mass of MBH = 9.27 ± 0.10 M⊙
New methods for radial-velocity measurements of double-lined binaries, and detection of a circumbinary planet orbiting TIC 172900988
Ongoing ground-based radial-velocity observations seeking to detect circumbinary planets focus on single-lined binaries even though over 9 in every 10 binary systems in the solar neighbourhood are double lined. Double-lined binaries are on average brighter, and should in principle yield more precise radial velocities. However, as the two stars orbit one another, they produce a time-varying blending of their weak spectral lines. This makes an accurate measure of radial velocities difficult, producing a typical scatter of . This extra noise prevents the detection of most orbiting circumbinary planets. We develop two new data-driven approaches to disentangle the two stellar components of a double-lined binary, and extract accurate and precise radial velocities. Both approaches use a Gaussian process regression, with the first one working in the spectral domain, whereas the second works on cross-correlated spectra. We apply our new methods to TIC 172900988, a proposed circumbinary system with a double-lined binary, and detect a circumbinary planet with an orbital period of , different than previously proposed. We also measure a significant residual scatter, which we speculate is caused by stellar activity. We show that our two data-driven methods outperform the traditionally used TODCOR and TODMOR, for that particular binary system
BEBOP V. Homogeneous stellar analysis of potential circumbinary planet hosts
Planets orbiting binary systems are relatively unexplored compared to those around single stars. Detections of circumbinary planets and planetary systems offer a first detailed view into our understanding of circumbinary planet formation and dynamical evolution. The BEBOP (binaries escorted by orbiting planets) radial velocity survey plays a special role in this adventure as it focuses on eclipsing single-lined binaries with an FGK dwarf primary and M dwarf secondary allowing for the highest radial velocity precision using the HARPS and SOPHIE spectrographs. We obtained 4512 high-resolution spectra for the 179 targets in the BEBOP survey which we used to derive the stellar atmospheric parameters using both equivalent widths and spectral synthesis. We furthermore derive stellar masses, radii, and ages for all targets. With this work, we present the first homogeneous catalogue of precise stellar parameters for these eclipsing single-lined binaries
BEBOP V. Homogeneous stellar analysis of potential circumbinary planet hosts
Planets orbiting binary systems are relatively unexplored compared to those around single stars. Detections of circumbinary planets and planetary systems offer a first detailed view into our understanding of circumbinary planet formation and dynamical evolution. The BEBOP (binaries escorted by orbiting planets) radial velocity survey plays a special role in this adventure as it focuses on eclipsing single-lined binaries with an FGK dwarf primary and M dwarf secondary allowing for the highest radial velocity precision using the HARPS and SOPHIE spectrographs. We obtained 4512 high-resolution spectra for the 179 targets in the BEBOP survey which we used to derive the stellar atmospheric parameters using both equivalent widths and spectral synthesis. We furthermore derive stellar masses, radii, and ages for all targets. With this work, we present the first homogeneous catalogue of precise stellar parameters for these eclipsing single-lined binaries
BEBOP V. Homogeneous stellar analysis of potential circumbinary planet hosts
Funding: This research is supported from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 803193/BEBOP), and by a Leverhulme Trust Research Project Grant (no. RPG-2018-418). ACC acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1. PM and NM were supported by STFC grant number ST/S001301/1. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project SPICE DUNE, grant agreement no. 947634). DJA is supported by UKRI through the STFC (ST/R00384X/1) and EPSRC (EP/X027562/1). AC acknowledge funding from the French ANR under contract number ANR18CE310019 (SPlaSH). This work is supported by the French National Research Agency in the framework of the Investissements d’Avenir program (ANR-15-IDEX-02), through the funding of the ‘Origin of Life’ project of the Grenoble-Alpes University. EW acknowledges support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, grant agreement no. 772293 http://www.asterochronometry.eu). MRS acknowledges support from the UK Science and Technology Facilities Council (ST/T000295/1).Planets orbiting binary systems are relatively unexplored compared to those around single stars. Detections of circumbinary planets and planetary systems offer a first detailed view into our understanding of circumbinary planet formation and dynamical evolution. The BEBOP (Binaries Escorted by Orbiting Planets) radial velocity survey plays a special role in this adventure as it focuses on eclipsing single-lined binaries with an FGK dwarf primary and M dwarf secondary allowing for the highest-radial velocity precision using the HARPS and SOPHIE spectrographs. We obtained 4512 high-resolution spectra for the 179 targets in the BEBOP survey which we used to derive the stellar atmospheric parameters using both equivalent widths and spectral synthesis. We furthermore derive stellar masses, radii, and ages for all targets. With this work, we present the first homogeneous catalogue of precise stellar parameters for these eclipsing single-lined binaries.Peer reviewe
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant, in the transition between the super-Jupiters and brown-dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480+0.0004−0.0005 d, Mp = 12.74+1.01−1.01 MJ, Rp =1.026+0.065−0.067 RJ and e = 0.018+0.004−0.004 . In addition, the RV time series revealed a significant trend at the ∼ 350 m s−1 yr−1level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949+0.0003−0.0003 d, Mp =2.340+0.197−0.195 MJ, Rp = 1.030+0.050−0.050 RJ and e = 0.021+0.024−0.015 , making this object a new example of a growing population of transiting warm giant planets