27 research outputs found
Flares in Open Clusters with K2. II. Pleiades, Hyades, Praesepe, Ruprecht 147, and M67
Flares, energetic eruptions on the surfaces of stars, are an unmistakable
manifestation of magnetically driven emission. Their occurrence rates and
energy distributions trace stellar characteristics such as mass and age. But
before flares can be used to constrain stellar properties, the flaring-age-mass
relation requires proper calibration. This work sets out to quantify flaring
activity of independently age-dated main sequence stars for a broad range of
spectral types using optical light curves obtained by the Kepler satellite.
Drawing from the complete K2 archive, we searched 3435 day long light
curves of 2111 open cluster members for flares using the open-source software
packages K2SC to remove instrumental and astrophysical variability from K2
light curves, and AltaiPony to search and characterize the flare candidates. We
confirmed a total of 3844 flares on high probability open cluster members with
ages from zero age main sequence (Pleiades) to 3.6 Gyr (M67). We extended the
mass range probed in the first study of this series to span from Sun-like stars
to mid-M dwarfs. We added the Hyades (690 Myr) to the sample as a comparison
cluster to Praesepe (750 Myr), the 2.6 Gyr old Ruprecht 147, and several
hundred light curves from the late K2 Campaigns in the remaining clusters. The
flare energy distribution was similar in the entire parameter space, following
a power law relation with exponent . The flaring rates
declined with age, and declined faster for higher mass stars. We found evidence
that a rapid decline in flaring activity occurred in M1-M2 dwarfs around
Hyades/Praesepe age, when these stars spun down to rotation periods of about 10
days, while higher mass stars had already transitioned to lower flaring rates,
and lower mass stars still resided in the saturated activity regime. (abridged)Comment: 27 pages, 13 figures. Accepted to A&
Newly identified compact hierarchical triple system candidates using Gaia DR3
Aims. We introduce a novel way to identify new compact hierarchical triple
stars by exploiting the huge potential of Gaia DR3 and also its future data
releases. We aim to increase the current number of compact hierarchical triples
significantly. Methods. We utilize several eclipsing binary catalogs from
different sky surveys totaling more than 1 million targets for which we search
for Gaia DR3 Non-single Star orbital solutions with periods substantially
longer than the eclipsing periods of the binaries. Those solutions in most
cases should belong to outer orbits of tertiary stars in those systems. We also
try to validate some of our best-suited candidates using TESS eclipse timing
variations. Results. We find 403 objects with suitable Gaia orbital solutions
of which 27 are already known triple systems. This makes 376 newly identified
hierarchical triple system candidates in our sample. We analyze the cumulative
probability distribution of the outer orbit eccentricities and find that it is
very similar to the ones found by earlier studies based on the observations of
the Kepler and OGLE missions. We found measurable non-linear eclipse timing
variations or third-body eclipses in the TESS data for 192 objects which we
also consider to be confirmed candidates. Out of these, we construct analytical
light-travel time effect models for the eclipse timing variations of 22 objects
with well-sampled TESS observations. We compare the outer orbital parameters
from our solutions with the ones from the Gaia solutions and find that the most
reliable orbital parameter is the orbital period, while the values of the other
parameters should be used with caution.Comment: 18 pages, 9 figures, 6 tables, Accepted for publication in Astronomy
& Astrophysic
Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)
We report the discovery of one newly confirmed planet ( days,
) and mass determinations of two previously
validated Kepler planets, Kepler-289 b ( days,
) and Kepler-289-c ( days,
), through their transit timing variations
(TTVs). We also exclude the possibility that these three planets reside in a
Laplace resonance. The outer planet has very deep (), high
signal-to-noise transits, which puts extremely tight constraints on its host
star's stellar properties via Kepler's Third Law. The star PH3 is a young
( Gyr as determined by isochrones and gyrochronology), Sun-like star
with , , and
K. The middle planet's large TTV amplitude (
hours) resulted either in non-detections or inaccurate detections in previous
searches. A strong chopping signal, a shorter period sinusoid in the TTVs,
allows us to break the mass-eccentricity degeneracy and uniquely determine the
masses of the inner, middle, and outer planets to be ,
, and , which we designate PH3 b, c, and
d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low
density, g/cm for a planet of its mass, requiring a
substantial H/He atmosphere of by mass, and joins a
growing population of low-mass, low-density planets.Comment: 21 pages, 10 figures, 5 tables, accepted into Ap
Planet Hunters X: Searching for Nearby Neighbors of 75 Planet and Eclipsing Binary Candidates from the K2 Kepler Extended Mission
We present high-resolution observations of a sample of 75 K2 targets from
Campaigns 1-3 using speckle interferometry on the Southern Astrophysical
Research (SOAR) telescope and adaptive optics (AO) imaging at the Keck II
telescope. The median SOAR -band and Keck -band detection limits at 1"
were ~mag and ~mag, respectively. This
sample includes 37 stars likely to host planets, 32 targets likely to be
eclipsing binaries (EBs), and 6 other targets previously labeled as likely
planetary false positives. We find nine likely physically bound companion stars
within 3" of three candidate transiting exoplanet host stars and six likely
EBs. Six of the nine detected companions are new discoveries; one of the six,
EPIC 206061524, is associated with a planet candidate. Among the EB candidates,
companions were only found near the shortest period ones ( days), which is
in line with previous results showing high multiplicity near short-period
binary stars. This high-resolution data, including both the detected companions
and the limits on potential unseen companions, will be useful in future planet
vetting and stellar multiplicity rate studies for planets and binaries.Comment: Accepted in A
Planet Hunters. VI: An Independent Characterization of KOI-351 and Several Long Period Planet Candidates from the Kepler Archival Data
We report the discovery of 14 new transiting planet candidates in the Kepler
field from the Planet Hunters citizen science program. None of these candidates
overlapped with Kepler Objects of Interest (KOIs) at the time of submission. We
report the discovery of one more addition to the six planet candidate system
around KOI-351, making it the only seven planet candidate system from Kepler.
Additionally, KOI-351 bears some resemblance to our own solar system, with the
inner five planets ranging from Earth to mini-Neptune radii and the outer
planets being gas giants; however, this system is very compact, with all seven
planet candidates orbiting AU from their host star. A Hill
stability test and an orbital integration of the system shows that the system
is stable. Furthermore, we significantly add to the population of long period
transiting planets; periods range from 124-904 days, eight of them more than
one Earth year long. Seven of these 14 candidates reside in their host star's
habitable zone.Comment: 27 pages, 6 figures, 5 tables, Accepted to AJ (in press) (updated
title from original astro-ph submission
Planet Hunters. VIII. Characterization of 41 Long-Period Exoplanet Candidates from Kepler Archival Data
The census of exoplanets is incomplete for orbital distances larger than 1
AU. Here, we present 41 long-period planet candidates in 38 systems identified
by Planet Hunters based on Kepler archival data (Q0-Q17). Among them, 17
exhibit only one transit, 14 have two visible transits and 10 have more than
three visible transits. For planet candidates with only one visible transit, we
estimate their orbital periods based on transit duration and host star
properties. The majority of the planet candidates in this work (75%) have
orbital periods that correspond to distances of 1-3 AU from their host stars.
We conduct follow-up imaging and spectroscopic observations to validate and
characterize planet host stars. In total, we obtain adaptive optics images for
33 stars to search for possible blending sources. Six stars have stellar
companions within 4". We obtain high-resolution spectra for 6 stars to
determine their physical properties. Stellar properties for other stars are
obtained from the NASA Exoplanet Archive and the Kepler Stellar Catalog by
Huber et al. (2014). We validate 7 planet candidates that have planet
confidence over 0.997 (3-{\sigma} level). These validated planets include 3
single-transit planets (KIC-3558849b, KIC-5951458b, and KIC-8540376c), 3
planets with double transits (KIC-8540376b, KIC-9663113b, and KIC-10525077b),
and 1 planet with 4 transits (KIC-5437945b). This work provides assessment
regarding the existence of planets at wide separations and the associated false
positive rate for transiting observation (17%-33%). More than half of the
long-period planets with at least three transits in this paper exhibit transit
timing variations up to 41 hours, which suggest additional components that
dynamically interact with the transiting planet candidates. The nature of these
components can be determined by follow-up radial velocity and transit
observations.Comment: Published on ApJ, 815, 127 Notations of validated planets are changed
in accordance with naming convention of NASA Exoplanet Archiv
A Population of Dipper Stars from the Transiting Exoplanet Survey Satellite Mission
Dipper stars are a classification of young stellar objects that exhibit
dimming variability in their light curves, dropping in brightness by 10-50%,
likely induced by occultations due to circumstellar disk material. This
variability can be periodic, quasi-periodic, or aperiodic. Dipper stars have
been discovered in young stellar associations via ground-based and space-based
photometric surveys. We present the detection and characterization of the
largest collection of dipper stars to date: 293 dipper stars, including 234 new
dipper candidates. We have produced a catalog of these targets, which also
includes young stellar variables that exhibit predominately bursting-like
variability and symmetric variability (equal parts bursting and dipping). The
total number of catalog sources is 414. These variable sources were found in a
visual survey of TESS light curves, where dipping-like variability was
observed. We found a typical age among our dipper sources of <5 Myr, with the
age distribution peaking at ~2 Myr, and a tail of the distribution extending to
ages older than 20 Myr. Regardless of the age, our dipper candidates tend to
exhibit infrared excess, which is indicative of the presence of disks. TESS is
now observing the ecliptic plane, which is rich in young stellar associations,
so we anticipate many more discoveries in the TESS dataset. A larger sample of
dipper stars would enhance the census statistics of light curve morphologies
and dipper ages.Comment: 19 pages, 11 figures, 1 table (included in latex source), accepted
for publication in ApJ
101 Eclipsing Quadruple Star Candidates Discovered in TESS Full Frame Images
We present our second catalog of quadruple star candidates, containing 101
systems discovered in TESS Full-Frame Image data. The targets were initially
detected as eclipsing binary stars with the help of supervised machine learning
methods applied to sectors Sectors 1 through 54. A dedicated team of citizen
scientists subsequently identified through visual inspection two sets of
eclipses following two different periods. All 101 systems presented here pass
comprehensive photocenter motion tests confirming that both sets of eclipses
originate from the target star. Some of the systems exhibit prominent eclipse
time variations suggesting dynamical interactions between the two component
binary stars. One target is an eclipsing quintuple candidate with a (2+1)+2
hierarchical configuration, such that the (2+1) subsystem produces eclipses on
the triple orbit as well. Another has recently been confirmed as the second
shortest period quadruple reported to date. This catalog provides ephemerides,
eclipse depths and durations, sample statistics, and highlights potentially
interesting targets for future studies.Comment: 38 pages, 21 figures, 2 tables. Table with targets available online
at MNRA
A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet
We report the discovery of a compact multi-planet system orbiting the
relatively nearby (78pc) and bright () K-star, K2-266 (EPIC248435473).
We identify up to six possible planets orbiting K2-266 with estimated periods
of P = 0.66, P = 6.1, P = 7.8, P = 14.7, P = 19.5, and
P = 56.7 days and radii of R = 3.3 R, 0.646
R, 0.705 R, 2.93 R, 2.73 R, and
0.90 R, respectively. We are able to confirm the planetary nature of
two of these planets (d & e) from analyzing their transit timing variations
( and ),
confidently validate the planetary nature of two other planets (b & c), and
classify the last two as planetary candidates (K2-266.02 & .06). From a
simultaneous fit of all 6 possible planets, we find that K2-266 b's orbit has
an inclination of 75.32 while the other five planets have
inclinations of 87-90. This observed mutual misalignment may indicate
that K2-266 b formed differently from the other planets in the system. The
brightness of the host star and the relatively large size of the sub-Neptune
sized planets d and e make them well-suited for atmospheric characterization
efforts with facilities like the Hubble Space Telescope and upcoming James Webb
Space Telescope. We also identify an 8.5-day transiting planet candidate
orbiting EPIC248435395, a co-moving companion to K2-266.Comment: 18 pages, 12 figures, 7 tables, Accepted for Publication in the
Astronomical Journa