The near-core rotation of HD 112429

The study of pulsating stars in eclipsing binaries holds the promise of combining two different ways of measuring the physical properties of a star to obtain improved constraints on stellar theory. Gravity (g) mode pulsations such as those found in γ Doradus stars can be used to probe rotational profiles, mixing, and magnetic fields. Until recently few γ Doradus stars in eclipsing binaries were known. We have discovered g-mode pulsations in four detached eclipsing binary systems from light curves obtained by the Transiting Exoplanet Survey Satellite (TESS) and present an analysis of their eclipses and pulsational characteristics. We find unresolved g-mode pulsations at frequencies 1–1.5 d−1 in CM Lac, and measure the masses and radii of the component stars from the TESS data and published radial velocities. MZ Lac shows a much richer frequency spectrum, including pressure modes and tidally excited g-modes. RX Dra is in the northern continuous viewing zone of TESS so has a light-curve covering a full year, but shows relatively few pulsation frequencies. For V2077 Cyg we formally measure four pulsation frequencies, but the available data are inadequate to properly resolve the g-mode pulsations. V2077 Cyg also shows total eclipses, with which we obtain the first measurement of the surface gravity of the faint secondary star. All four systems are bright and good candidates for detailed study. Further TESS observations are scheduled for all four systems, with much improved temporal baselines in the cases of RX Dra and V2077 Cyg.

The NASA Transiting Exoplanet Survey Satellite (TESS) is observing tens of millions of stars with time spans ranging from ∼27 days to about 1 yr of continuous observations. This vast amount of data contains a wealth of information for variability, exoplanet, and stellar astrophysics studies but requires a number of processing steps before it can be fully utilized. In order to efficiently process all the TESS data and make it available to the wider scientific community, the TESS Data for Asteroseismology working group, as part of the TESS Asteroseismic Science Consortium, has created an automated open-source processing pipeline to produce light curves corrected for systematics from the short- and long-cadence raw photometry data and to classify these according to stellar variability type. We will process all stars down to a TESS magnitude of 15. This paper is the next in a series detailing how the pipeline works. Here, we present our methodology for the automatic variability classification of TESS photometry using an ensemble of supervised learners that are combined into a metaclassifier. We successfully validate our method using a carefully constructed labeled sample of Kepler Q9 light curves with a 27.4 days time span mimicking single-sector TESS observations, on which we obtain an overall accuracy of 94.9%. We demonstrate that our methodology can successfully classify stars outside of our labeled sample by applying it to all ∼167,000 stars observed in Q9 of the Kepler space mission.

The flaring M4 dwarf GJ 1243 has become a benchmark for studying stellar flare and starspot activity thanks to the exceptional photometric monitoring archive from the Kepler mission. New light curves from the Transiting Exoplanet Survey Satellite (TESS) mission for this star allow precise stellar activity characterization over more than a decade timescale. We have carried out the first flare and starspot analysis of GJ 1243 from over 50 days of data from TESS Sectors 14 and 15. Using 133 flare events detected in the 2 minute cadence TESS data, we compare the cumulative flare frequency distributions, and find the flare activity for GJ 1243 is unchanged between the Kepler and TESS epochs. Two distinct starspot groups are found in the TESS data, with the primary spot having the same rotational period and phase as seen in Kepler. The phase of the secondary spot feature is consistent with the predicted location of the secondary starspot and measurement of weak differential rotation, suggesting this secondary spot may be long-lived and stable in both latitude and longitude. As expected for this highly active star, the constant spot and flare activity reveal no sign of solar-like activity cycles over 10 yr. However, we highlight the unique ability for Kepler and TESS to use flare rates to detect activity cycles.

In order to gain more information on the 236 M dwarfs identified in the First Byurakan Survey (FBS) low-resolution (lr) spectroscopic database, Gaia EDR3 high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterise these M dwarfs and their possible multiplicity. Among the sample of 236 relatively bright$(7.3 < K_S < 14.4)$M dwarfs, 176 are new discoveries. TheGaiaEDR3 G broadband magnitudes are in the range$11.3 < G < 17.1$. New distance information based on the EDR3 parallaxes are used to estimate theG-band absolute magnitudes. Nine FBS M dwarfs out of 176 newly discovered lie within 25 pc of the Sun. The FBS 0909-082 is the most distant$(r=780$pc) M dwarf of the analysed sample, with aG-band absolute magnitude$M(G) = 9.18$,$M = 0.59$M$_{\odot}$,$L = 0.13597$L$_{\odot}$, and$T_{eff}$= 3844 K; it can be classified as M1 - M2 subtype dwarf. The nearest is FBS 0250+167, a M7 subtype dwarf located at 3.83 pc from the Sun with a very high proper motion (5.13 arcsec yr$^{-1}$). The TESS estimated masses lie in the range 0.095 ($\pm$0.02) M$_{\odot}\leq$$M\leq$0.7 ($\pm$0.1) M$_{\odot}$and$T_{eff}$in the range 4000 K <$T_{eff}$< 2790 K. We analyse colour-colour and colour-absolute magnitude diagram (CaMD) diagrams for the M dwarfs. Results suggest that 27 FBS M dwarfs are double or multiple systems. The observed spectral energy distribution (SED) for some of the M dwarfs can be used to classify potential infrared excess. Using TESS light curves, flares are detected for some FBS M dwarfs. Finally, for early and late sub-classes of the M dwarfs, the detection range for survey is estimated for the first time.

We report the discovery of a close-in (P orb = 3.349 days) warm Neptune with clear transit timing variations (TTVs) orbiting the nearby (d = 47.3 pc) active M4 star, TOI-2015. We characterize the planet's properties using Transiting Exoplanet Survey Satellite (TESS) photometry, precise near-infrared radial velocities (RVs) with the Habitable-zone Planet Finder Spectrograph, ground-based photometry, and high-contrast imaging. A joint photometry and RV fit yields a radius Rp=3.37−0.20+0.15R⊕ , mass mp=16.4−4.1+4.1M⊕ , and density ρp=2.32−0.37+0.38gcm−3 for TOI-2015 b, suggesting a likely volatile-rich planet. The young, active host star has a rotation period of P rot = 8.7 ± 0.9 days and associated rotation-based age estimate of 1.1 ± 0.1 Gyr. Though no other transiting planets are seen in the TESS data, the system shows clear TTVs of super-period Psup≈430days and amplitude ∼100 minutes. After considering multiple likely period-ratio models, we show an outer planet candidate near a 2:1 resonance can explain the observed TTVs while offering a dynamically stable solution. However, other possible two-planet solutions—including 3:2 and 4:3 resonances—cannot be conclusively excluded without further observations. Assuming a 2:1 resonance in the joint TTV-RV modeling suggests a mass of mb=13.3−4.5+4.7M⊕ for TOI-2015 b and mc=6.8−2.3+3.5M⊕ for the outer candidate. Additional transit and RV observations will be beneficial to explicitly identify the resonance and further characterize the properties of the system.

We studied the flaring activities of M4.5 dwarf AD Leo to understand its stellar atmospheres and magnetic activities. We present new observational results on this highly active star, using nonsimultaneous measurement of Transiting Exoplanet Survey Satellite (TESS) data, time-series optical spectra, and Giant Meter Radio Telescope 325 MHz radio data. We revisited the rotation period of 2.23 ± 0.04 days from TESS, which matches well with previously measured literature values. We estimated an extremely rare high-energy superflare of 4.9 × 1035 erg and ∼400 minute duration with a high magnetic field strength of 1.2 kG. Interestingly, we correlated the duration of a flare event with its energy, τ ∝ E bol 0.60 ± 0.02 , and noticed a discrepancy between stellar and solar flares suggesting a difference in coronal magnetic field strength. From time-series spectra, we observed Hα spectral flares in the range of 1030–1031 erg. A 12 minute delay in a spectral flare event was observed between the emission of the Hα and Ca ii H and K lines, possibly due to their origination at different spatial locations in the chromosphere. We noticed the deviation in flare rate distribution and orbital phases indicates the presence of highly active regions. Furthermore, an occasional radio detection with a flux density of 9.46 ± 1.63 mJy at a frequency of 325 MHz might be coherent emission in the presence of the magnetic field, giving a hint of star–planet interaction.

We present the results of our study of the long-period eclipsing binary star V454 Aur. The results are based on spectroscopic data obtained with the UFES échelle spectrograph and photometric observations from Transiting Exoplanet Survey Satellite (TESS). The derived radial velocity curve is based on 17 spectra obtained between 2021 and 2023, covering all orbital phases of this binary system. The orbital period determined from TESS data, P = 27.019803 ± 0.000003 days, agrees within uncertainties with the period established in previous studies. The model constructed for the TESS photometric light curve achieves a precision of 0.01%. The effective temperatures of both components, as well as the system metallicity, were directly derived from the spectra and are T eff,A = 6250 ± 50 K, T eff,B = 5855 ± 50 K, and [Fe/H] = −0.10 ± 0.08, respectively. Our analysis of the photometric and spectroscopic data allowed us to directly compute the luminosities of the components, L A = 1.82 L ⊙ and L B = 1.07 L ⊙, their radii, R A = 1.15 R ⊙ and R B = 1.00 R ⊙, and their masses, M A = 1.137 M ⊙ and M B = 1.023 M ⊙, with uncertainties below 1%. Comparison with evolutionary tracks indicates that the system’s age is 1.18 ± 0.10 Gyr, and both components are still on the main sequence. The V454 Aur system is particularly interesting due to the partial eclipse of the primary component, which results in the “inversion” of the primary and secondary minima in the photometric light curve.

We present I-band time-series photometric variability studies of three known nearby (∼140 pc) and young (∼1 Myr) brown dwarfs (BD) in the Taurus star-forming region in the Perseus molecular cloud. From 10 nights of observations over a time span of 10 yr, with a typical run of 3–6 hr each night, we estimated that the BDs show unstable short-scale periodicity from 1.5 to 4.8 hr. Using the long-term photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability analysis of CFHT-BD-Tau 3 and CFHT-BD-Tau 4, revealing orbital periods of ∼0.96 days and ∼3 days respectively, consistent with earlier studies. We also found two superflares in TESS sector 43 data for CFHT-BD-Tau 4 and estimated the flare energies as 7.09 × 1035 erg and 3.75 × 1036 erg. A magnetic field of ∼3.39 kG is required to generate such flare energies on this BD. We performed spot modeling analysis on CFHT-BD-Tau 3 and CFHT-BD-Tau 4 to address the variability detected in the data using the package BASSMAN. Spectral energy distribution and infrared colors of the sources suggest that they have a sufficient amount of circumstellar material around them.

We present an estimate of the occurrence rate of hot Jupiters (7 R ⊕ ≤ R p ≤ 2 R J, 0.8 ≤ P b ≤ 10 days) around early-type M dwarfs based on stars observed by the Transiting Exoplanet Survey Satellite (TESS) during its primary mission. We adopt stellar parameters from the TESS Input Catalog and construct a sample of 60,819 M dwarfs with 10.5 ≤ T mag ≤ 13.5, effective temperatures 2900 ≤ T eff ≤ 4000 K, and stellar masses 0.45 ≤ M * ≤ 0.65 M ⊙. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic, and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of 0.27% ± 0.09% for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1σ–2σ. There is a trend that the occurrence rate of hot Jupiters has a peak at G dwarfs and falls toward both hotter and cooler stars. Combining results from transit, radial velocity, and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in the occurrence rate per logarithmic semimajor axis bin () when compared with FGK stars.

The Kepler spacecraft provided the first long-baseline, high-precision photometry for large numbers of stars. This enabled the discovery of thousands of new exoplanets, and the characterization of myriad astrophysical phenomena. However, one of the challenges with interpreting Kepler data has been that no instrument has provided a comparison dataset. Therefore, the replication of Kepler time-series data has remained elusive. The Transiting Exoplanet Survey Satellite (TESS) launched in April 2018 and began science operations in July 2018. During the TESS primary mission, it will survey 85% of the sky. NASA's first two observatories dedicated to discovering exoplanets, Kepler and TESS, were simultaneously operating during 2018. While the Kepler's K2 mission surveyed the ecliptic plane, TESS targets fields outside the ecliptic. However, during September 2018, a small region of the sky was observed simultaneously by both TESS and Kepler as part of TESS's Sector 2 (Aug 22 - Sep 20, 2018) and K2 Campaign 19 (Sep 7 - Sep 26, 2018). The overlap region was 0.5 sq. deg. We identified 171 K2 targets that fell inside TESS Sector 2 field of view, all of which are observed at 30-minute cadence by both missions. The targets range in brightness in the TESS bandpass (Tmag) from 6.7-18.4, with 93 targets brighter than Tmag=15, and 17 brighter than Tmag=12. This dataset provides the first simultaneous, long-duration, high-precision observations of the same targets from different space-based observatories and presents an excellent opportunity to explore instrumental systematics present in the two telescopes.

We present the results of a multiwavelength Professional–Amateur campaign to study the behaviour of flares from the active M1.5V star binary CR Draconis. CR Dra was observed with Transiting Exoplanet Survey Satellite (TESS) 20-s photometry, Swift near-ultraviolet (NUV) grism spectroscopy and with ground-based optical photometry and spectroscopy from a global collaboration of amateur astronomers. We detected 14 flares with TESS and Swift simultaneously, one of which also had simultaneous ground-based photometry and spectroscopy. We used the simultaneous two-colour optical and NUV observations to characterize the temperature evolution of the flare and test the accuracy of using optical data to predict NUV emission. We measured a peak temperature of $7100^{+150}_{-130}$ K for this flare, cooler than the typically assumed 9000 K blackbody model used by flare studies. We also found that the 9000 K blackbody overestimated the NUV flux for other flares in our sample, which we attributed to our Swift observations occurring during flare decays, highlighting the phase-dependence for the accuracy of flare models.

Beyond orbital periods of 10 d, there is a dearth of known transiting gas giants. On longer orbits, planets are less affected by their host star, and become ideal probes of planet formation, migration, and evolution. We report the discovery of a long-period Neptune and two Saturns, each initially identified as single transits in the TESS (Transiting Exoplanet Survey Satellite) photometry, and solved through additional transits from ground-based follow-up photometric observations by NGTS (Next Generation Transit Survey) and ASTEP (Antarctic Search for Transiting ExoPlanets). High-resolution radial velocity mass measurements using CORALIE and HARPS (High Accuracy Radial Velocity Planet Searcher) confirm their planetary nature. From joint modelling of the photometric and spectroscopic data, we determine an orbital period of $43.12655_{-0.00017}^{+0.00012}~$ d, radius of $3.65\pm 0.22~\mathrm{R_{\hbox{$\oplus $}}}$, and mass of $19.1_{-4.5}^{+4.9}~\mathrm{M_{\hbox{$\oplus $}}}$ for NGTS-34 b, making it one of the longest period well-characterized transiting Neptunes. Orbiting a late F-type star, bright in the K band (Kmag$~\simeq 7.9$), it is amenable for cool atmosphere studies using James Webb Space Telescope or Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large). TOI-4940 b is a small Saturn on a $25.867811_{-0.000056}^{+0.000058}~$ d orbit with a radius of $6.61\pm 0.37~\mathrm{R_{\hbox{$\oplus $}}}$ and an upper mass limit $< 89~\mathrm{M_{\hbox{$\oplus $}}}$. NGTS-35 b(=TOI-6669 b) is a larger Saturn on a $25.241192\pm 0.000022~$ d, moderately eccentric orbit ($e = 0.192_{-0.033}^{+0.037}$), with a radius of $10.90\pm 0.65~\mathrm{R_{\hbox{$\oplus $}}}$ and a mass of $152_{-19}^{+22}~\mathrm{M_{\hbox{$\oplus $}}}$. With an assumed albedo $A=0.3$, each of these planets has an equilibrium temperature below 700 K, with NGTS-35 b especially cold at $450~$ K. These three giants add to the small but growing population of long-period planets that can further our understanding of planet formation mechanisms.

We study the statistics and properties of microlensing events that can be detected by the Transiting Exoplanet Survey Satellite (TESS) based on Monte Carlo simulations. We simulate potential microlensing events from a sample of TESS Candidate Target List (CTL) stars by assuming different observational time spans (or different numbers of sectors for each star) and a wide range of lens masses, i.e., M l ∈ [0.1 M ⊕, 2 M ⊙]. On average, the microlensing optical depth and the event rate for CTL stars are ≃0.2 × 10−9 and ΓTESS ≃ 0.6 × 10−9 star–1 day–1, respectively. The microlensing optical depth decreases with increasing CTL priority, whereas the efficiency for detecting their microlensing signals enhances with priority. Additionally, we simulate microlensing events from TESS Full Frame Image (FFI) stars extracted from the TESS-SPOC pipeline. The optical depth and event rate for these stars are on average ≃1–3 × 10−9, and ΓTESS ≃ 1–4 × 10−9 star–1 day–1, and their highest values occur for Sector 12. The total number of microlensing events for the CTL stars is N e,tot ∼ 0.03, whereas for the FFI stars the number of events per star during the 27.4 day observing windows is Nˆe,tot≃1.4×10−6 . Based on four criteria we extract the detectable microlensing events and evaluate the detection efficiencies. The highest efficiency for detecting microlensing events from the TESS data occurs for lens masses of log10[Ml(M⊙)]∈[−4.5 , −2.5], i.e., super-Earths to Jupiter-mass free floating planets. The detectable microlensing events from the TESS stars are significantly affected by both finite-source and parallax effects.

We investigate whether there is a variation in the orbital period of the short-period brown dwarf-mass KELT-1 b, which is one of the best candidates to observe orbital decay. We obtain 19 high-precision transit light curves of the target using six different telescopes. We add all precise and complete transit light curves from open databases and the literature, as well as the available Transiting Exoplanet Survey Satellite (TESS) observations from sectors 17 and 57, to form a transit timing variation (TTV) diagram spanning more than 10 yr of observations. The analysis of the TTV diagram, however, is inconclusive in terms of a secular or periodic variation, hinting that the system might have synchronized. We update the transit ephemeris and determine an informative lower limit for the reduced tidal quality parameter of its host star of Q$_{\star }^{\prime } \gt (8.5 \pm 3.9) \times 10^{6}$ assuming that the stellar rotation is not yet synchronized. Using our new photometric observations, published light curves, the TESS data, archival radial velocities, and broadband magnitudes, we also update the measured parameters of the system. Our results are in good agreement with those found in previous analyses.

We report the first discovery of a transiting circumbinary planet detected from a single sector of Transiting Exoplanet Survey Satellite (TESS) data. During Sector 21, the planet TIC 172900988b transited the primary star and then five days later it transited the secondary star. The binary is itself eclipsing, with a period P ≈ 19.7 days and an eccentricity e ≈ 0.45. Archival data from ASAS-SN, Evryscope, KELT, and SuperWASP reveal a prominent apsidal motion of the binary orbit, caused by the dynamical interactions between the binary and the planet. A comprehensive photodynamical analysis of the TESS, archival and follow-up data yields stellar masses and radii of M 1 = 1.2384 ±0.0007 M ⊙ and R 1 = 1.3827 ± 0.0016 R ⊙ for the primary and M 2 = 1.2019 ± 0.0007 M ⊙ and R 2 = 1.3124 ±0.0012 R ⊙ for the secondary. The radius of the planet is R 3 = 11.25 ± 0.44 R ⊕ (1.004 ± 0.039R Jup). The planet’s mass and orbital properties are not uniquely determined—there are six solutions with nearly equal likelihood. Specifically, we find that the planet’s mass is in the range of 824 ≲ M 3 ≲ 981 M ⊕ (2.65 ≲ M 3 ≲ 3.09M Jup), its orbital period could be 188.8, 190.4, 194.0, 199.0, 200.4, or 204.1 days, and the eccentricity is between 0.02 and 0.09. At V = 10.141 mag, the system is accessible for high-resolution spectroscopic observations, e.g., the Rossiter–McLaughlin effect and transit spectroscopy.