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Stars which are rapidly rotating are expected to show high levels of activity according to the activity-rotation relation. However, previous TESS studies have found Ultra Fast Rotating (UFR) M dwarfs with periods less than one day…

Solar and Stellar Astrophysics · Physics 2022-03-02 Lauren Doyle , Stefano Bagnulo , Gavin Ramsay , Gerry Doyle , Pasi Hakala

According to activity-rotation relations, rapid rotators are expected to show high levels of magnetic activity. However, recent studies with TESS have found Ultra Fast Rotating (UFR) M dwarfs with periods $<1$ d displaying low levels of…

Solar and Stellar Astrophysics · Physics 2026-04-10 Lauren Doyle , George W. King , Gavin Ramsay , Lía R. Corrales , Stefano Bagnulo , J. Gerry Doyle , Pasi Hakala

We characterize the magnetic activity of M dwarfs to provide the planet community with information on the energy input from the star; in particular, in addition to the frequency of optical flares directly observed with TESS, we aim at…

Solar and Stellar Astrophysics · Physics 2022-09-14 B. Stelzer , M. Bogner , E. Magaudda , St. Raetz

We present a study of photometric flares on 154 low-mass ($\leq 0.2 \textrm{M}_{\odot}$) objects observed by the SPECULOOS-South Observatory from 1st June 2018 to 23rd March 2020. In this sample we identify 85 flaring objects, ranging in…

We use 1-m class telescopes and the Transiting Exoplanet Survey Satellite (TESS) to explore the photometric variability of all known rapidly rotating ($v\sin{i}\gtrsim30$ km\,s$^{-1}$) ultra-cool ($\geq$M7) dwarfs brighter than…

Solar and Stellar Astrophysics · Physics 2023-02-01 Paulo A. Miles-Páez , Stanimir A. Metchev , Benjamin George

In our previous study of low mass stars using TESS, we found a handful which show a periodic modulation on a period <1 d but also displayed no flaring activity. Here we present the results of a systematic search for Ultra Fast Rotators…

Solar and Stellar Astrophysics · Physics 2020-07-22 G. Ramsay , J. G. Doyle , L. Doyle

M dwarfs are magnetically active stars that frequently produce flares, which have implications for both stellar evolution and exoplanet studies. Flare occurrence rates and activity levels of M dwarfs correlate with stellar characteristics…

Solar and Stellar Astrophysics · Physics 2025-11-20 Benjamin K. Capistrant , Jason Dittmann

We present a comprehensive analysis of a Transiting Exoplanet Survey Satellite (TESS) high-quality light curve for a young brown dwarf, MHO~4 having spectral type M7.0, in the Taurus star-forming region. We investigate the rotation periods…

Solar and Stellar Astrophysics · Physics 2023-09-06 Rajib Kumbhakar , Soumen Mondal , Samrat Ghosh , Diya Ram , Sudip Pramanik

Observations made using TESS revealed a sample of low mass stars which show a periodic modulation on a period $<0.2$~d. Surprisingly many of these Ultra Fast Rotating (UFR) stars showed no evidence of flare activity which would be expected…

Solar and Stellar Astrophysics · Physics 2022-02-23 Gavin Ramsay , Pasi Hakala , J. Gerry Doyle , Lauren Doyle , Stefano Bagnulo

This study presents the results of a search for rotation signature in 250 Gaia DR3 Ultra-Cool Dwarfs (UCDs) with TESS light curves. We identified 71 targets with unambiguous periodicities, of which 61 present rotation signatures and a…

Photometric space missions like Kepler and TESS continuously discover new exoplanets and advance the search for a second habitable world. The light curves recorded by these telescopes also reveal signs of magnetic activity, such as star…

Solar and Stellar Astrophysics · Physics 2021-11-16 Mirjam Bogner , Beate Stelzer , Stefanie Raetz

We present a study of flare rates, rotation periods, and spectroscopic activity indicators of 125 single stars within 15 parsecs and with masses between 0.1$-$0.3 $M_\odot$ observed during the first year of the TESS mission, with the goal…

Solar and Stellar Astrophysics · Physics 2021-01-06 Amber A. Medina , Jennifer G. Winters , Jonathan M. Irwin , David Charbonneau

We perform a study of stellar flares for the 24,809 stars observed with 2 minute cadence during the first two months of the TESS mission. Flares may erode exoplanets' atmospheres and impact their habitability, but might also trigger the…

We investigate the flare-frequency distributions of 5 M-dwarfs that experienced superflares with energies in excess of $10^{33}$ erg detected by ASAS-SN. We use K2 and TESS short-cadence observations along with archival ASAS-SN data to…

Stellar flares are intense bursts of radiation caused by magnetic reconnection on active stars. They are especially frequent on M dwarfs, where they can significantly influence the habitability of orbiting planets. Flare frequency…

Solar and Stellar Astrophysics · Physics 2026-04-22 Julien Poyatos , Octavi Fors , José Maria Gómez Cama

We report the white light flare rates for 10 ultracool dwarfs (UCDs) using \textit{Kepler K2} short cadence data. Among our sample stars, two have spectral type M6, three are M7, three are M8 and two are L0. Most of our targets are old low…

Solar and Stellar Astrophysics · Physics 2018-06-06 Rishi R. Paudel , John E. Gizis , D. J. Mullan , Sarah J. Schmidt , Adam J. Burgasser , Peter K. G. Williams , Edo Berger

We apply multi-algorithm machine learning models to TESS 2-minute survey data from Sectors 1-72 to identify stellar flares. Models trained with Deep Neural Network, Random Forest, and XGBoost algorithms, respectively, utilized four flare…

Solar and Stellar Astrophysics · Physics 2024-10-24 Chia-Lung Lin , Daniel Apai , Mark S. Giampapa , Wing-Huen Ip

We present $I$-band time-series photometric variability studies of three known nearby ($\sim$ 140 pc) and young ( $\sim$ 1 Myr) brown dwarfs (BD) in the Taurus star-forming region in the Perseus Molecular Cloud. From 10 nights of…

Solar and Stellar Astrophysics · Physics 2025-02-28 Samrat Ghosh , Soumen Mondal , Somnath Dutta , Rajib Kumbhakar , Ramkrishna Das , Santosh Joshi , Sneh Lata

Over the past few years monitoring programs have shown ultra cool dwarfs (UCDs) to be photometrically variable. Of the 60 sources monitored in the field and some 120 monitored in clusters, about 40% show variability in both cases. For mid…

Astrophysics · Physics 2007-05-23 C. A. L. Bailer-Jones

Most M dwarfs show higher chromospheric activity, often exceeding solar levels. Characterizing stellar activity is essential, particularly since these stars are prime targets in the search for habitable exoplanets. We investigate the…

Solar and Stellar Astrophysics · Physics 2026-01-14 A. S. Rajpurohit , V. Kumar , K. Srivastava Mudit , L. Labadie , K. Rajpurohit , J. G. Fernandez-Trincado
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