54 research outputs found
Constraints on pulsar magnetospheric and wind parameters for the compact nebulae of Vela and PSR B1706-44
We present a new model for the synchrotron compact nebular emissions for Vela
and PSR B1706-44, and derive fundamental pulsar/plerion parameters such as the
pair production multiplicity, M, and wind magnetization parameter, sigma. The
pair cascade above the pulsar polar cap, combined with the energy from the
pulsar wind, injects a pair plasma into the surrounding environment. This wind,
consisting of particles and fields, is shocked by the environment, resulting in
synchrotron emission from "thermalized" pairs in a compact nebula. The broad
band nebular spectrum depends crucially on the spindown power, distance, pair
multiplicity, pulsar wind shock radius and sigma at this shock. We construct
such a model for the particle spectra in the compact X-ray nebula of Vela and
PSR B1706-44. Fits to the multiwavelength spectra of these sources indicate
that 300<M<1000, whereas 0.05<sigma<0.5 for Vela. The same sigma interval (as
for Vela) was independently derived from the radial gradients of the X-ray
compact nebular emission from both Vela and PSR B1706-44, giving us confidence
in our results. The M we derive for Vela is too small to be explained by
curvature losses in the open magnetoshere of Vela, but the presence of optical
pulsed photons could modify the predicted multiplicity.Comment: 29 pages, 4 figures, accepted for publication in Ap
NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf
We report the discovery of NGTS-21b, a massive hot Jupiter orbiting a
low-mass star as part of the Next Generation Transit Survey (NGTS). The planet
has a mass and radius of M, and
R, and an orbital period of 1.543 days. The host is a K3V (, K) metal-poor (, dex) dwarf
star with a mass and radius of , M,and , R. Its age and rotation period of , Gyr
and , d respectively, are in accordance with the observed
moderately low stellar activity level. When comparing NGTS-21b with currently
known transiting hot Jupiters with similar equilibrium temperatures, it is
found to have one of the largest measured radii despite its large mass.
Inflation-free planetary structure models suggest the planet's atmosphere is
inflated by , while inflationary models predict a radius consistent
with observations, thus pointing to stellar irradiation as the probable origin
of NGTS-21b's radius inflation. Additionally, NGTS-21b's bulk density (, g/cm) is also amongst the largest within the population of
metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper
boundary in metallicity-planet density parameter space that is in concordance
with core accretion formation models. The discovery of rare planetary systems
such as NGTS-21 greatly contributes towards better constraints being placed on
the formation and evolution mechanisms of massive planets orbiting low-mass
stars.Comment: 12 pages, 13 figures, accepted for publication in MNRA
TESS Discovery of Twin Planets near 2:1 Resonance around Early M-Dwarf TOI 4342
With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase
improvements to the MIT Quick-Look Pipeline (QLP) through the discovery and
validation of a multi-planet system around M-dwarf TOI 4342 (,
, , K,
pc). With updates to QLP, including a new multi-planet search, as well as
faster cadence data from TESS' First Extended Mission, we discovered two
sub-Neptunes ( and ; = 5.538 days and = 10.689 days)
and validated them with ground-based photometry, spectra, and speckle imaging.
Both planets notably have high transmission spectroscopy metrics (TSMs) of 36
and 32, making TOI 4342 one of the best systems for comparative atmospheric
studies. This system demonstrates how improvements to QLP, along with faster
cadence Full-Frame Images (FFIs), can lead to the discovery of new multi-planet
systems.Comment: accepted for publication in A
TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association
Young (<500 Myr) planets are critical to studying how planets form and evolve. Among these young planetary systems, multiplanet configurations are particularly useful, as they provide a means to control for variables within a system. Here, we report the discovery and characterization of a young planetary system, TOI-1224. We show that the planet host resides within a young population we denote as MELANGE-5. By employing a range of age-dating methods—isochrone fitting, lithium abundance analysis, gyrochronology, and Gaia excess variability—we estimate the age of MELANGE-5 to be 210 ± 27 Myr. MELANGE-5 is situated in close proximity to previously identified younger (80–110 Myr) associations, Crius 221 and Theia 424/Volans-Carina, motivating further work to map out the group boundaries. In addition to a planet candidate detected by the TESS pipeline and alerted as a TESS object of interest, TOI-1224 b, we identify a second planet, TOI-1224 c, using custom search tools optimized for young stars (Notch and LOCoR). We find that the planets are 2.10 ± 0.09 R⊕ and 2.88 ± 0.10 R⊕ and orbit their host star every 4.18 and 17.95 days, respectively. With their bright (K = 9.1 mag), small (R* = 0.44 R⊙), and cool (Teff = 3326 K) host star, these planets represent excellent candidates for atmospheric characterization with JWST
TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association
Young (<500 Myr) planets are critical to studying how planets form and evolve. Among these young planetary systems, multiplanet configurations are particularly useful, as they provide a means to control for variables within a system. Here, we report the discovery and characterization of a young planetary system, TOI-1224. We show that the planet host resides within a young population we denote as MELANGE-5. By employing a range of age-dating methods—isochrone fitting, lithium abundance analysis, gyrochronology, and Gaia excess variability—we estimate the age of MELANGE-5 to be 210 ± 27 Myr. MELANGE-5 is situated in close proximity to previously identified younger (80–110 Myr) associations, Crius 221 and Theia 424/Volans-Carina, motivating further work to map out the group boundaries. In addition to a planet candidate detected by the TESS pipeline and alerted as a TESS object of interest, TOI-1224 b, we identify a second planet, TOI-1224 c, using custom search tools optimized for young stars (Notch and LOCoR). We find that the planets are 2.10 ± 0.09 R⊕ and 2.88 ± 0.10 R⊕ and orbit their host star every 4.18 and 17.95 days, respectively. With their bright (K = 9.1 mag), small (R* = 0.44 R⊙), and cool (Teff = 3326 K) host star, these planets represent excellent candidates for atmospheric characterization with JWST
Eclipses During the 2010 Eruption of the Recurrent Nova U Scorpii
The eruption of the recurrent nova U Scorpii on 28 January 2010 is now the
all-time best observed nova event. We report 36,776 magnitudes throughout its
67 day eruption, for an average of one measure every 2.6 minutes. This unique
and unprecedented coverage is the first time that a nova has any substantial
amount of fast photometry. With this, two new phenomena have been discovered:
the fast flares in the early light curve seen from days 9-15 (which have no
proposed explanation) and the optical dips seen out of eclipse from days 41-61
(likely caused by raised rims of the accretion disk occulting the bright inner
regions of the disk as seen over specific orbital phases). The expanding shell
and wind cleared enough from days 12-15 so that the inner binary system became
visible, resulting in the sudden onset of eclipses and the turn-on of the
supersoft X-ray source. On day 15, a strong asymmetry in the out-of-eclipse
light points to the existence of the accretion stream. The normal optical
flickering restarts on day 24.5. For days 15-26, eclipse mapping shows that the
optical source is spherically symmetric with a radius of 4.1 R_sun. For days
26-41, the optical light is coming from a rim-bright disk of radius 3.4 R_sun.
For days 41-67, the optical source is a center-bright disk of radius 2.2 R_sun.
Throughout the eruption, the colors remain essentially constant. We present 12
eclipse times during eruption plus five just after the eruption.Comment: ApJ in press. 60 pages, 17 figure
VaTEST III : validation of 8 potential super-earths from TESS data
Funding: The ULiege’s contribution to SPECULOOS has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) (grant Agreement n◦ 336480/SPECULOOS). This research is in part funded by the European Union’s Horizon 2020 research and innovation programme (grants agreements n◦ 803193/BEBOP), and from the Science and Technology Facilities Council (STFC; grant n◦ ST/S00193X/1, and ST/W000385/1).NASA’s all-sky survey mission, the Transiting Exoplanet Survey Satellite (TESS), is specifically engineered to detect exoplanets that transit bright stars. Thus far, TESS has successfully identified approximately 400 transiting exoplanets, in addition to roughly 6 000 candidate exoplanets pending confirmation. In this study, we present the results of our ongoing project, the Validation of Transiting Exoplanets using Statistical Tools (VaTEST). Our dedicated effort is focused on the confirmation and characterisation of new exoplanets through the application of statistical validation tools. Through a combination of ground-based telescope data, high-resolution imaging, and the utilisation of the statistical validation tool known as TRICERATOPS, we have successfully discovered eight potential super-Earths. These planets bear the designations: TOI-238b (1.61 +0.09−0.10 R ⊕ ), TOI-771b (1.42 +0.11−0.09 R ⊕ ), TOI-871b (1.66 +0.11−0.11 R ⊕ ), TOI-1467b (1.83 +0.16−0.15 R ⊕ ), TOI-1739b (1.69 +0.10−0.08 R ⊕ ), TOI-2068b (1.82 +0.16−0.15 R ⊕ ), TOI-4559b (1.42 +0.13−0.11 R ⊕ ), and TOI-5799b (1.62 +0.19−0.13 R ⊕ ). Among all these planets, six of them fall within the region known as ‘keystone planets’, which makes them particularly interesting for study. Based on the location of TOI-771b and TOI-4559b below the radius valley we characterised them as likely super-Earths, though radial velocity mass measurements for these planets will provide more details about their characterisation. It is noteworthy that planets within the size range investigated herein are absent from our own solar system, making their study crucial for gaining insights into the evolutionary stages between Earth and Neptune.Peer reviewe
NGTS-28Ab:a short period transiting brown dwarf
We report the discovery of a brown dwarf orbiting a M1 host star. We first identified the brown dwarf within the Next Generation Transit Survey data, with supporting observations found in TESS sectors 11 and 38. We confirmed the discovery with follow-up photometry from the South African Astronomical Observatory, SPECULOOS-S, and TRAPPIST-S, and radial velocity measurements from HARPS, which allowed us to characterize the system. We find an orbital period of ∼1.25 d, a mass of 69.0+5.3-4.8 MJ, close to the hydrogen burning limit, and a radius of 0.95 ± 0.05 RJ. We determine the age to be >0.5 Gyr, using model isochrones, which is found to be in agreement with spectral energy distribution fitting within errors. NGTS-28Ab is one of the shortest period systems found within the brown dwarf desert, as well as one of the highest mass brown dwarfs that transits an M dwarf. This makes NGTS-28Ab another important discovery within this scarcely populated region.</div
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