24 research outputs found
A Pilot Survey of an M Dwarf Flare Star with Swift's UV Grism
The near-ultraviolet (NUV) spectral region is a useful diagnostic for stellar
flare physics and assessing the energy environment of young exoplanets,
especially as relates to prebiotic chemistry. We conducted a pilot NUV
spectroscopic flare survey of the young M dwarf AU Mic with the Neil Gehrels
Swift Observatory's UltraViolet and Optical Telescope. We detected four flares
and three other epochs of significantly elevated count rates during the 9.6
hours of total exposure time, consistent with a NUV flare rate of 0.5
hour. The largest flare we observed released a minimum energy of
610 erg between 1730-5000 \r{A}. All flares had durations longer
than the 14-17 minute duration of each Swift visit, making measuring
total flare energy and duration infeasible.Comment: Published in Research Notes of the AAS (RNAAS
Wisep j060738.65+242953.4: A Nearby Pole-on L8 Brown Dwarf With Radio Emission
We present a simultaneous, multi-wavelength campaign targeting the nearby (7.2 pc) L8/L9 (optical/near-infrared) dwarf WISEP J060738.65+242953.4 in the mid-infrared, radio, and optical. Spitzer Space Telescope observations show no variability at the 0.2% level over 10 hours each in the 3.6 and 4.5 micron bands. Kepler K2 monitoring over 36 days in Campaign 0 rules out stable periodic signals in the optical with amplitudes great than 1.5% and periods between 1.5 hours and 2 days. Non-simultaneous Gemini optical spectroscopy detects lithium, constraining this L dwarf to be less than ∼ 2 Gyr old, but no Balmer emission is observed. The low measured projected rotation velocity (v sin i < 6 km s−1) and lack of variability are very unusual compared to other brown dwarfs, and we argue that this substellar object is likely viewed pole-on. We detect quiescent (non-bursting) radio emission with the VLA. Amongst radio detected L and T dwarfs, it has the lowest observed Lν and the lowest v sin i. We discuss the implications of a pole-on detection for various proposed radio emission scenarios.Astronom
Two Warm Super-Earths Transiting the Nearby M Dwarf TOI-2095
We report the detection and validation of two planets orbiting TOI-2095 (TIC
235678745). The host star is a 3700K M1V dwarf with a high proper motion. The
star lies at a distance of 42 pc in a sparsely populated portion of the sky and
is bright in the infrared (K=9). With data from 24 Sectors of observation
during TESS's Cycles 2 and 4, TOI-2095 exhibits two sets of transits associated
with super-Earth-sized planets. The planets have orbital periods of 17.7 days
and 28.2 days and radii of 1.30 and 1.39 Earth radii, respectively. Archival
data, preliminary follow-up observations, and vetting analyses support the
planetary interpretation of the detected transit signals. The pair of planets
have estimated equilibrium temperatures of approximately 400 K, with stellar
insolations of 3.23 and 1.73 times that of Earth, placing them in the Venus
zone. The planets also lie in a radius regime signaling the transition between
rock-dominated and volatile-rich compositions. They are thus prime targets for
follow-up mass measurements to better understand the properties of warm,
transition radius planets. The relatively long orbital periods of these two
planets provide crucial data that can help shed light on the processes that
shape the composition of small planets orbiting M dwarfs.Comment: Submitted to AAS Journal