130 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
CMBPol Mission Concept Study: Prospects for polarized foreground removal
In this report we discuss the impact of polarized foregrounds on a future
CMBPol satellite mission. We review our current knowledge of Galactic polarized
emission at microwave frequencies, including synchrotron and thermal dust
emission. We use existing data and our understanding of the physical behavior
of the sources of foreground emission to generate sky templates, and start to
assess how well primordial gravitational wave signals can be separated from
foreground contaminants for a CMBPol mission. At the estimated foreground
minimum of ~100 GHz, the polarized foregrounds are expected to be lower than a
primordial polarization signal with tensor-to-scalar ratio r=0.01, in a small
patch (~1%) of the sky known to have low Galactic emission. Over 75% of the sky
we expect the foreground amplitude to exceed the primordial signal by about a
factor of eight at the foreground minimum and on scales of two degrees. Only on
the largest scales does the polarized foreground amplitude exceed the
primordial signal by a larger factor of about 20. The prospects for detecting
an r=0.01 signal including degree-scale measurements appear promising, with 5
sigma_r ~0.003 forecast from multiple methods. A mission that observes a range
of scales offers better prospects from the foregrounds perspective than one
targeting only the lowest few multipoles. We begin to explore how optimizing
the composition of frequency channels in the focal plane can maximize our
ability to perform component separation, with a range of typically 40 < nu <
300 GHz preferred for ten channels. Foreground cleaning methods are already in
place to tackle a CMBPol mission data set, and further investigation of the
optimization and detectability of the primordial signal will be useful for
mission design.Comment: 42 pages, 14 figures, Foreground Removal Working Group contribution
to the CMBPol Mission Concept Study, v2, matches AIP versio
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
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
BU Canis Minoris -- the Most Compact Known Flat Doubly Eclipsing Quadruple System
We have found that the 2+2 quadruple star system BU CMi is currently the most
compact quadruple system known, with an extremely short outer period of only
121 days. The previous record holder was TIC 219006972 (Kostov et al. 2023),
with a period of 168 days. The quadruple nature of BU CMi was established by
Volkov et al. (2021), but they misidentified the outer period as 6.6 years. BU
CMi contains two eclipsing binaries (EBs), each with a period near 3 days, and
a substantial eccentricity of about 0.22. All four stars are within about 0.1
solar mass of 2.4 solar masses. Both binaries exhibit dynamically driven
apsidal motion with fairly short apsidal periods of about 30 years, thanks to
the short outer orbital period. The outer period of 121 days is found both from
the dynamical perturbations, with this period imprinted on the eclipse timing
variations (ETV) curve of each EB by the other binary, and by modeling the
complex line profiles in a collection of spectra. We find that the three
orbital planes are all mutually aligned to within 1 degree, but the overall
system has an inclination angle near 83.5 degrees. We utilize a complex
spectro-photodynamical analysis to compute and tabulate all the interesting
stellar and orbital parameters of the system. Finally, we also find an
unexpected dynamical perturbation on a timescale of several years whose origin
we explore. This latter effect was misinterpreted by Volkov et al. (2021) and
led them to conclude that the outer period was 6.6 years rather than the 121
days that we establish here.Comment: 19 pages, 8 pages, accepted to MNRA
Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death
Developing sympathetic neurons depend on nerve growth factor (NGF) for survival and die by apoptosis after NGF withdrawal. This process requires de novo gene expression but only a small number of genes induced by NGF deprivation have been identified so far, either by a candidate gene approach or in mRNA differential display experiments. This is partly because it is difficult to obtain large numbers of sympathetic neurons for in vitro studies. Here, we describe for the first time, how advances in gene microarray technology have allowed us to investigate the expression of all known genes in sympathetic neurons cultured in the presence and absence of NGF
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