We report on the discovery and validation of TOI 813b (TIC 55525572 b), a transiting exoplanet identified by citizen scientists in data from NASA's Transiting Exoplanet Survey Satellite (TESS) and ...the first planet discovered by the Planet Hunters TESS project. The host star is a bright (V = 10.3 mag) subgiant (\(R_\star=1.94\,R_\odot\), \(M_\star=1.32\,M_\odot\)). It was observed almost continuously by TESS during its first year of operations, during which time four individual transit events were detected. The candidate passed all the standard light curve-based vetting checks, and ground-based follow-up spectroscopy and speckle imaging enabled us to place an upper limit of \(2 M_{Jup}\) (99 % confidence) on the mass of the companion, and to statistically validate its planetary nature. Detailed modelling of the transits yields a period of \(83.8911_{ - 0.0031 } ^ { + 0.0027 }\) days, a planet radius of \(6.71 \pm 0.38\) \(R_{\oplus}\), and a semi major axis of \(0.423_{ - 0.037 } ^ { + 0.031 }\) AU. The planet's orbital period combined with the evolved nature of the host star places this object in a relatively under-explored region of parameter space. We estimate that TOI-813b induces a reflex motion in its host star with a semi-amplitude of \(\sim6\) ms\(^{-1}\), making this system a promising target to measure the mass of a relatively long-period transiting planet.
Transcranial alternating current stimulation (TACS) is commonly used to synchronize a cortical area and its outputs to the stimulus waveform, but gathering evidence for this based on brain recordings ...in humans is challenging. The corticospinal tract transmits beta oscillations (∼21 Hz) from the motor cortex to tonically contracted limb muscles linearly. Therefore, muscle activity may be used to measure the level of beta entrainment in the corticospinal tract due to TACS over the motor cortex. Here, we assessed whether TACS is able to modulate the neural inputs to muscles, which would provide indirect evidence for TACS‐driven neural entrainment. In the first part of the study, we ran simulations of motor neuron (MN) pools receiving inputs from corticospinal neurons with different levels of beta entrainment. Results suggest that MNs are highly sensitive to changes in corticospinal beta activity. Then, we ran experiments on healthy human subjects (N = 10) in which TACS (at 1 mA) was delivered over the motor cortex at 21 Hz (beta stimulation), or at 7 Hz or 40 Hz (control conditions) while the abductor digiti minimi or the tibialis anterior muscle were tonically contracted. Muscle activity was measured using high‐density electromyography, which allowed us to decompose the activity of pools of motor units innervating the muscles. By analysing motor unit pool activity, we observed that none of the TACS conditions could consistently alter the spectral contents of the common neural inputs received by the muscles. These results suggest that 1 mA TACS over the motor cortex given at beta frequencies does not entrain corticospinal activity.
Key points
Transcranial alternating current stimulation (TACS) is commonly used to entrain the communication between brain regions.
It is challenging to find direct evidence supporting TACS‐driven neural entrainment due to the technical difficulties in recording brain activity during stimulation.
Computational simulations of motor neuron pools receiving common inputs in the beta (∼21 Hz) band indicate that motor neurons are highly sensitive to corticospinal beta entrainment.
Motor unit activity from human muscles does not support TACS‐driven corticospinal entrainment.
figure legend TACS over the primary motor cortex may entrain the neural activity in the descending pathways connecting the brain with the spinal cord and muscles. If this is the case, then motor neurons innervating active muscles may reflect such entrainment given their tight connections with corticospinal neurons. We tested this by looking at how the common neural activity in pools of motor neurons projecting to tonically active muscles changed in the presence of TACS at different frequencies. Results from experiments run on humans were combined with simulations using computational models aimed to determine the expected level of sensitivity of motor neuron pools to changes in common inputs. Results indicate that TACS cannot not alter MN activity, which suggests that TACS‐driven cortical and corticospinal entrainment may not be easy to achieve at standard intensities used in humans.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We present the results from the first two years of the Planet Hunters TESS citizen science project, which identifies planet candidates in the TESS data by engaging members of the general public. Over ...22,000 citizen scientists from around the world visually inspected the first 26 Sectors of TESS data in order to help identify transit-like signals. We use a clustering algorithm to combine these classifications into a ranked list of events for each sector, the top 500 of which are then visually vetted by the science team. We assess the detection efficiency of this methodology by comparing our results to the list of TESS Objects of Interest (TOIs) and show that we recover 85 % of the TOIs with radii greater than 4 Earth radii and 51 % of those with radii between 3 and 4 Earth radii. Additionally, we present our 90 most promising planet candidates that had not previously been identified by other teams, 73 of which exhibit only a single transit event in the TESS light curve, and outline our efforts to follow these candidates up using ground-based observatories. Finally, we present noteworthy stellar systems that were identified through the Planet Hunters TESS project.
We report on the discovery and validation of a two-planet system around a bright (V = 8.85 mag) early G dwarf (1.43 \(R_{\odot}\), 1.15 \(M_{\odot}\), TOI 2319) using data from NASA's Transiting ...Exoplanet Survey Satellite (TESS). Three transit events from two planets were detected by citizen scientists in the month-long TESS light curve (sector 25), as part of the Planet Hunters TESS project. Modelling of the transits yields an orbital period of \Pb\ and radius of \(3.41 _{ - 0.12 } ^ { + 0.14 }\) \(R_{\oplus}\) for the inner planet, and a period in the range 19.26-35 days and a radius of \(5.83 _{ - 0.14 } ^ { + 0.14 }\) \(R_{\oplus}\) for the outer planet, which was only seen to transit once. Each signal was independently statistically validated, taking into consideration the TESS light curve as well as the ground-based spectroscopic follow-up observations. Radial velocities from HARPS-N and EXPRES yield a tentative detection of planet b, whose mass we estimate to be \(11.56 _{ - 6.14 } ^ { + 6.58 }\) \(M_{\oplus}\), and allow us to place an upper limit of \(27.5\) \(M_{\oplus}\) (99 per cent confidence) on the mass of planet c. Due to the brightness of the host star and the strong likelihood of an extended H/He atmosphere on both planets, this system offers excellent prospects for atmospheric characterisation and comparative planetology.
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