45 research outputs found
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
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
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
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
Photodynamical analysis of the triply eclipsing hierarchical triple system EPIC 249432662
Using Campaign 15 data from the K2 mission, we have discovered a triply eclipsing triple star system: EPIC 249432662. The inner eclipsing binary system has a period of 8.23 d, with shallow ∼3 per cent eclipses. During the entire 80-d campaign, there is also a single eclipse event of a third body in the system that reaches a depth of nearly 50 per cent and has a total duration of 1.7 d, longer than for any previously known third-body eclipse involving unevolved stars. The binary eclipses exhibit clear eclipse timing variations. A combination of photodynamical modeling of the light curve, as well as seven follow-up radial velocity measurements, has led to a prediction of the subsequent eclipses of the third star with a period of 188 d. A campaign of follow-up ground-based photometry was able to capture the subsequent pair of third-body events as well as two further 8-d eclipses. A combined photo-spectro-dynamical analysis then leads to the determination of many of the system parameters. The 8-d binary consists of a pair of M stars, while most of the system light is from a K star around which the pair of M stars orbits
Confirmation and Characterization of the Eccentric, Warm Jupiter TIC 393818343 b with a Network of Citizen Scientists
NASA’s Transiting Exoplanet Survey Satellite (TESS) has identified over 7000 candidate exoplanets via the transit method, with gas giants among the most readily detected due to their large radii. Even so, long intervals between TESS observations for much of the sky lead to candidates for which only a single transit is detected in one TESS sector, leaving those candidate exoplanets with unconstrained orbital periods. Here, we confirm the planetary nature of TIC 393818343 b, originally identified via a single TESS transit, using radial velocity data and ground-based photometric observations from citizen scientists with the Unistellar Network and Exoplanet Watch. We determine a period of P = 16.24921 −0.00011+0.00010 days, a mass M P = 4.34 ± 0.15 M J, and semimajor axis a = 0.1291 −0.0022+0.0021 au, placing TIC 393818343 b in the “warm Jupiter” population of exoplanets. With an eccentricity e = 0.6058 ± 0.0023, TIC 393818343 b is the most eccentric warm Jupiter to be discovered by TESS orbiting less than 0.15 au from its host star and therefore an excellent candidate for follow-up, as it may inform our future understanding of how hot and warm Jupiter populations are linked
The Random Transiter - EPIC 249706694/HD 139139
We have identified a star, EPIC 249706694 (HD 139139), that was observed
during K2 Campaign 15 with the Kepler extended mission that appears to exhibit
28 transit-like events over the course of the 87-day observation. The unusual
aspect of these dips, all but two of which have depths of ppm, is
that they exhibit no periodicity, and their arrival times could just as well
have been produced by a random number generator. We show that no more than four
of the events can be part of a periodic sequence. We have done a number of data
quality tests to ascertain that these dips are of astrophysical origin, and
while we cannot be absolutely certain that this is so, they have all the
hallmarks of astrophysical variability on one of two possible host stars (a
likely bound pair) in the photometric aperture. We explore a number of ideas
for the origin of these dips, including actual planet transits due to multiple
or dust emitting planets, anomalously large TTVs, S- and P-type transits in
binary systems, a collection of dust-emitting asteroids, `dipper-star'
activity, and short-lived starspots. All transit scenarios that we have been
able to conjure up appear to fail, while the intrinsic stellar variability
hypothesis would be novel and untested.Comment: 12 pages, 6 figures, and 7 tables; Accepted for publication in MNRA