35 research outputs found
A ground-based NUV secondary eclipse observation of KELT-9b
KELT-9b is a recently discovered exoplanet with a 1.49 d orbit around a
B9.5/A0-type star. The unparalleled levels of UV irradiation it receives from
its host star put KELT-9b in its own unique class of ultra-hot Jupiters, with
an equilibrium temperature > 4000 K. The high quantities of dissociated
hydrogen and atomic metals present in the dayside atmosphere of KELT-9b bear
more resemblance to a K-type star than a gas giant. We present a single
observation of KELT-9b during its secondary eclipse, taken with the Wide Field
Camera on the Isaac Newton Telescope (INT). This observation was taken in the
U-band, a window particularly sensitive to Rayleigh scattering. We do not
detect a secondary eclipse signal, but our 3 upper limit of 181 ppm on
the depth allows us to constrain the dayside temperature of KELT-9b at
pressures of ~30 mbar to 4995 K (3). Although we can place an
observational constraint of 0.14, our models suggest that the actual
value is considerably lower than this due to H opacity. This places KELT-9b
squarely in the albedo regime populated by its cooler cousins, almost all of
which reflect very small components of the light incident on their daysides.
This work demonstrates the ability of ground-based 2m-class telescopes like the
INT to perform secondary eclipse studies in the NUV, which have previously only
been conducted from space-based facilities.Comment: Accepted in ApJL. 7 pages, 3 figure
Extreme asteroids in the Pan-STARRS 1 Survey
Using the first 18 months of the Pan-STARRS 1 survey we have identified 33
candidate high-amplitude objects for follow-up observations and carried out
observations of 22 asteroids. 4 of the observed objects were found to have
observed amplitude mag. We find that these high amplitude
objects are most simply explained by single rubble pile objects with some
density-dependent internal strength, allowing them to resist mass shedding even
at their highly elongated shapes. 3 further objects although below the cut-off
for 'high-amplitude' had a combination of elongation and rotation period which
also may require internal cohesive strength, depending on the density of the
body. We find that none of the 'high-amplitude asteroids' identified here
require any unusual cohesive strengths to resist rotational fission. 3
asteroids were sufficiently observed to allow for shape and spin pole models to
be determined through light curve inversion. 45864 was determined to have
retrograde rotation with spin pole axes and asteroid 206167 was found to have best fit spin
pole axes , . An additional
object not initially measured with mag, 49257, was determined to
have a shape model which does suggest a high-amplitude object. Its spin pole
axes were best fit for values .
In the course of this project to date no large super-fast rotators ( h) have been identified.Comment: 31 pages; accepted by A
Spectroscopic Transit Search: a self-calibrating method for detecting planets around bright stars
We search for transiting exoplanets around the star Pictoris using
high resolution spectroscopy and Doppler imaging that removes the need for
standard star observations. These data were obtained on the VLT with UVES
during the course of an observing campaign throughout 2017 that monitored the
Hill sphere transit of the exoplanet Pictoris b. We utilize line
profile tomography as a method for the discovery of transiting exoplanets. By
measuring the exoplanet distortion of the stellar line profile, we remove the
need for reference star measurements. We demonstrate the method with white
noise simulations, and then look at the case of Pictoris, which is a
Scuti pulsator. We describe a method to remove the stellar pulsations
and perform a search for any transiting exoplanets in the resultant data set.
We inject fake planet transits with varying orbital periods and planet radii
into the spectra and determine the recovery fraction. In the photon noise
limited case we can recover planets down to a Neptune radius with an 80%
success rate, using an 8 m telescope with a spectrograph and 20
minutes of observations per night. The pulsations of Pictoris limit our
sensitivity to Jupiter-sized planets, but a pulsation removal algorithm
improves this limit to Saturn-sized planets. We present two planet candidates,
but argue that their signals are most likely caused by other phenomena. We have
demonstrated a method for searching for transiting exoplanets that (i) does not
require ancillary calibration observations, (ii) can work on any star whose
rotational broadening can be resolved with a high spectral dispersion
spectrograph and (iii) provides the lowest limits so far on the radii of
transiting Jupiter-sized exoplanets around Pictoris with orbital
periods from 15 days to 200 days with >50% coverage.Comment: Accepted for publication in A&A, 8 pages, 8 figures. The Github
repository can be found at
https://github.com/lennartvansluijs/Spectroscopic-Transit-Searc
An M dwarf accompanied by a close-in giant orbiter with SPECULOOS
In the last decade, a dozen close-in giant planets have been discovered
orbiting stars with spectral types ranging from M0 to M4, a mystery since known
formation pathways do not predict the existence of such systems. Here, we
confirm TOI-4860 b, a Jupiter-sized planet orbiting an M4.5 host, a star at the
transition between fully and partially convective interiors. First identified
with TESS data, we validate the transiting companion's planetary nature through
multicolour photometry from the TRAPPIST-South/North, SPECULOOS, and MuSCAT3
facilities. Our analysis yields a radius of for
the planet, a mass of for the star, and an orbital period of
1.52 d. Using the newly commissioned SPIRIT InGaAs camera at the
SPECULOOS-South Observatory, we collect infrared photometry in zYJ that spans
the time of secondary eclipse. These observations do not detect a secondary
eclipse, placing an upper limit on the brightness of the companion. The
planetary nature of the companion is further confirmed through high-resolution
spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which
we measure a mass of . Based on its overall
density, TOI-4860 b appears to be rich in heavy elements, like its host star.Comment: Accepted for publication in MNRAS Letter
A massive hot Jupiter orbiting a metal-rich early-M star discovered in the TESS full frame images
Observations and statistical studies have shown that giant planets are rare
around M dwarfs compared with Sun-like stars. The formation mechanism of these
extreme systems remains under debate for decades. With the help of the TESS
mission and ground based follow-up observations, we report the discovery of
TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so
far with a radius of and a mass of ,
about 5 times heavier than most other giant planets around M dwarfs. It also
has the highest planet-to-star mass ratio () among such
systems. The host star is an early-M dwarf with a mass of $0.61\pm0.02\
M_{\odot}0.63\pm0.02\ R_{\odot}0.52\pm 0.08$ dex). However, interior
structure modeling suggests that its planet TOI-4201b is metal-poor, which
challenges the classical core-accretion correlation of stellar-planet
metallicity, unless the planet is inflated by additional energy sources.
Building on the detection of this planet, we compare the stellar metallicity
distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We
find that hot/warm Jupiters show a similar metallicity dependence around G-type
stars. For M dwarf host stars, the occurrence of hot Jupiters shows a much
stronger correlation with iron abundance, while warm Jupiters display a weaker
preference, indicating possible different formation histories.Comment: 21 pages, 11 figures, 4 tables, submitted to A
An ultrahot Neptune in the Neptune desert
About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (Râ), or apparently rocky planets smaller than 2âRâ. Such lack of planets of intermediate size (the âhot Neptune desertâ) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6âRâ and a mass of 29âMâ, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite revealed transits of the bright Sun-like star LTT 9779 every 0.79âdays. The planetâs mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(â2.9)% of the total mass. With an equilibrium temperature around 2,000âK, it is unclear how this âultrahot Neptuneâ managed to retain such an envelope. Follow-up observations of the planetâs atmosphere to better understand its origin and physical nature will be facilitated by the starâs brightness (V_(mag)â=â9.8)
TOI-836 : a super-Earth and mini-Neptune transiting a nearby K-dwarf
Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1.We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (âŒ200 mas yrâ1), low metallicity ([Fe/H]ââ0.28) K-dwarf with a mass of 0.68 ± 0.05 Mâ and a radius of 0.67 ± 0.01 Râ. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 Râ super-Earth in a 3.82 day orbit, placing it directly within the so-called âradius valleyâ. The outer planet, TOI-836 c, is a 2.59 ± 0.09 Râ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 Mâ, while TOI-836 c has a mass of 9.6 ± 2.6 Mâ. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.Publisher PDFPeer reviewe
TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf
We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364)
using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (
mag), high proper motion ( mas yr), low metallicity
([Fe/H]) K-dwarf with a mass of M and a
radius of R. We obtain photometric follow-up
observations with a variety of facilities, and we use these data-sets to
determine that the inner planet, TOI-836 b, is a R
super-Earth in a 3.82 day orbit, placing it directly within the so-called
'radius valley'. The outer planet, TOI-836 c, is a R
mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that
TOI-836 b has a mass of M , while TOI-836 c has a mass
of M. Photometric observations show Transit Timing
Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are
no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by
an undetected exterior planet
A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1.We report the discovery and characterization of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in the Transiting Exoplanet Survey Satellite (TESS) photometry. To characterize the system, we performed and retrieved the CHaracterising ExOPlanets Satellite (CHEOPS), TESS, and ground-based photometry, the High Accuracy Radial velocity Planet Searcher (HARPS) high-resolution spectroscopy, and Gemini speckle imaging. We characterize the host star and determine Teff,â=4734±67Kâ , Râ=0.726±0.007Rââ , and Mâ=0.748±0.032Mââ . We present a novel detrending method based on point spread function shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of Pb = 6.44387 ± 0.00003 d, a radius of Rb = 2.59 ± 0.04 Râ, and a mass of Mb=13.5+1.7â1.8 Mâ, whilst TOI-1064 c has an orbital period of Pc=12.22657+0.00005â0.00004 d, a radius of Rc = 2.65 ± 0.04 Râ, and a 3Ï upper mass limit of 8.5 Mâ. From the high-precision photometry we obtain radius uncertainties of âŒ1.6 per cent, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterized sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further radial velocities are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of massâradius space, and it allow us to identify a trend in bulk densityâstellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets.Publisher PDFPeer reviewe
Three new brown dwarfs and a massive hot Jupiter revealed by TESS around early-type stars
Context. The detection and characterization of exoplanets and brown dwarfs around massive AF-type stars is essential to investigate and constrain the impact of stellar mass on planet properties. However, such targets are still poorly explored in radial velocity (RV) surveys because they only feature a small number of stellar lines and those are usually broadened and blended by stellar rotation as well as stellar jitter. As a result, the available information about the formation and evolution of planets and brown dwarfs around hot stars is limited.
Aims. We aim to increase the sample and precisely measure the masses and eccentricities of giant planets and brown dwarfs transiting early-type stars detected by the Transiting Exoplanet Survey Satellite (TESS).
Methods. We followed bright (V 6200 K that host giant companions (R > 7 Râ) using ground-based photometric observations as well as high precision radial velocity measurements from the CORALIE, CHIRON, TRES, FEROS, and MINERVA-Australis spectrographs.
Results. In the context of the search for exoplanets and brown dwarfs around early-type stars, we present the discovery of three brown dwarf companions, TOI-629b, TOI-1982b, and TOI-2543b, and one massive planet, TOI-1107b. From the joint analysis of TESS and ground-based photometry in combination with high precision radial velocity measurements, we find the brown dwarfs have masses between 66 and 68 MJup, periods between 7.54 and 17.17 days, and radii between 0.95 and 1.11 RJup. The hot Jupiter TOI-1107b has an orbital period of 4.08 days, a radius of 1.30 RJup, and a mass of 3.35 MJup. As a by-product of this program, we identified four low-mass eclipsing components (TOI-288b, TOI-446b, TOI-478b, and TOI-764b).
Conclusions. Both TOI-1107b and TOI-1982b present an anomalously inflated radius with respect to the age of these systems. TOI-629 is among the hottest stars with a known transiting brown dwarf. TOI-629b and TOI-1982b are among the most eccentric brown dwarfs. The massive planet and the three brown dwarfs add to the growing population of well-characterized giant planets and brown dwarfs transiting AF-type stars and they reduce the apparent paucity