33 research outputs found
Transmission spectroscopy of the ultra-hot Jupiter MASCARA-4 b: Disentangling the hydrostatic and exospheric regimes of ultra-hot Jupiters
Ultra-hot Jupiters (UHJs), rendering the hottest planetary atmospheres, offer
great opportunities of detailed characterisation with high-resolution
spectroscopy. MASCARA-4 b is a recently discovered close-in gas giant belonging
to this category. In order to refine system and planet parameters, we carried
out radial velocity measurements and transit photometry with the CORALIE
spectrograph and EulerCam at the Swiss 1.2m Euler telescope. We observed two
transits of MASCARA-4 b with the high-resolution spectrograph ESPRESSO at ESO's
Very Large Telescope. We searched for atomic, ionic, and molecular species via
individual absorption lines and cross-correlation techniques. These results are
compared to literature studies on UHJs characterised to date. With CORALIE and
EulerCam observations, we updated the mass of MASCARA-4 b (1.675 +/- 0.241
Jupiter masses) as well as other system and planet parameters. In the
transmission spectrum derived from ESPRESSO observations, we resolve excess
absorption by H, H, Na D1 & D2, Ca+ H & K, and a few strong
individual lines of Mg, Fe and Fe+. We also present the cross-correlation
detection of Mg, Ca, Cr, Fe and Fe+. The absorption strength of Fe+
significantly exceeds the prediction from a hydrostatic atmospheric model, as
commonly observed in other UHJs. We attribute this to the presence of Fe+ in
the exosphere due to hydrodynamic outflows. This is further supported by the
positive correlation of absorption strengths of Fe+ with the H line.
Comparing transmission signatures of various species in the UHJ population
allows us to disentangle the hydrostatic regime (as traced via the absorption
by Mg and Fe) from the exospheres (as probed by H and Fe+) of the
strongly irradiated atmospheres.Comment: 13 pages, 9 figures, accepted to A&
Transmission spectroscopy of the ultra-hot Jupiter MASCARA-4 b: disentangling the hydrostatic and exospheric regimes of ultra-hot Jupiters
Stars and planetary system
An ESPRESSO view of HD 189733 system. Broadband transmission spectrum, differential rotation, and system architecture
The development of state-of-the-art spectrographs has ushered in a new era in
the detection and characterization of exoplanetary systems. Our objective is to
utilize the high-resolution and precision capabilities of the ESPRESSO
instrument to detect and measure the broad-band transmission spectrum of HD
189733b's atmosphere. Additionally, we aim to employ an improved
Rossiter-McLaughlin model to derive properties related to the velocity fields
of the stellar surface and to constrain the orbital architecture.
Our results demonstrate a high degree of precision in fitting the observed
radial velocities during transit using the improved modeling of the
Rossiter-McLaughlin effect. We tentatively detect the effect of differential
rotation with a confidence level of when considering a rotation
period within the photometric literature values, and for a broader
range of rotation periods. For the former, the amplitude of differential
rotation ratio suggests an equatorial rotation period of days
and a polar period of . The addition of differential rotation breaks
the latitudinal symmetry, enabling us to measure the true spin-orbit angle and the stellar inclination axis angle . Moreover, we determine a
sub-solar amplitude of the convective blueshift velocity
ms, which falls within the expected range for
a K-dwarf host star and is compatible with both runs.
Finally, we successfully retrieved the transmission spectrum of HD 189733b
from the high-resolution ESPRESSO data. We observe a significant decrease in
radius with increasing wavelength, consistent with the phenomenon of
super-Rayleigh scattering
Analysis of natural variants of the hepatitis C virus internal ribosome entry site reveals that primary sequence plays a key role in cap-independent translation
The HCV internal ribosome entry site (IRES) spans a region of ∼340 nt that encompasses most of the 5′ untranslated region (5′UTR) of the viral mRNA and the first 24–40 nt of the core-coding region. To investigate the implication of altering the primary sequence of the 5′UTR on IRES activity, naturally occurring variants of the 5′UTR were isolated from clinical samples and analyzed. The impact of the identified mutations on translation was evaluated in the context of RLuc/FLuc bicistronic RNAs. Results show that depending on their location within the RNA structure, these naturally occurring mutations cause a range of effects on IRES activity. However, mutations within subdomain IIId hinder HCV IRES-mediated translation. In an attempt to explain these data, the dynamic behavior of the subdomain IIId was analyzed by means of molecular dynamics (MD) simulations. Despite the loss of function, MD simulations predicted that mutant G266A/G268U possesses a structure similar to the wt-RNA. This prediction was validated by analyzing the secondary structure of the isolated IIId RNAs by circular dichroism spectroscopy in the presence or absence of Mg2+ ions. These data strongly suggest that the primary sequence of subdomain IIId plays a key role in HCV IRES-mediated translation
Two long-period transiting exoplanets on eccentric orbits: NGTS-20 b (TOI-5152 b) and TOI-5153 b
Long-period transiting planets provide the opportunity to better understand
the formation and evolution of planetary systems. Their atmospheric properties
remain largely unaltered by tidal or radiative effects of the host star, and
their orbital arrangement reflects a different, and less extreme, migrational
history compared to close-in objects. The sample of long-period exoplanets with
well determined masses and radii is still limited, but a growing number of
long-period objects reveal themselves in the TESS data. Our goal is to vet and
confirm single transit planet candidates detected in the TESS space-based
photometric data through spectroscopic and photometric follow up observations
with ground-based instruments. We use the Next Generation Transit Survey (NGTS)
to photometrically monitor the candidates in order to observe additional
transits. We report the discovery of two massive, warm Jupiter-size planets,
one orbiting the F8-type star TOI-5153 and the other orbiting the G1-type star
NGTS-20 (=TOI-5152). From our spectroscopic analysis, both stars are metal-rich
with a metallicity of 0.12 and 0.15, respectively. Follow-up radial velocity
observations were carried out with CORALIE, CHIRON, FEROS, and HARPS. TOI-5153
hosts a 20.33 day period planet with a planetary mass of 3.26 (+-0.18) Mj, a
radius of 1.06 (+-0.04) Rj , and an orbital eccentricity of 0.091 (+-0.026).
NGTS-20 b is a 2.98 (+-0.16) Mj planet with a radius of 1.07 (+-0.04) Rj on an
eccentric (0.432 +- 0.023) orbit with an orbital period of 54.19 days. Both
planets are metal-enriched and their heavy element content is in line with the
previously reported mass-metallicity relation for gas giants. Both warm
Jupiters orbit moderately bright host stars making these objects valuable
targets for follow-up studies of the planetary atmosphere and measurement of
the spin-orbit angle of the system.Comment: 17 pages, 13 figures, accepted to A&
Three low-mass companions around aged stars discovered by TESS
We report the discovery of three transiting low-mass companions to aged
stars: a brown dwarf (TOI-2336b) and two objects near the hydrogen burning mass
limit (TOI-1608b and TOI-2521b). These three systems were first identified
using data from the Transiting Exoplanet Survey Satellite (TESS). TOI-2336b has
a radius of , a mass of and an orbital
period of 7.71 days. TOI-1608b has a radius of , a mass of
and an orbital period of 2.47 days. TOI-2521b has a radius
of , a mass of and an orbital period of
5.56 days. We found all these low-mass companions are inflated. We fitted a
relation between radius, mass and incident flux using the sample of known
transiting brown dwarfs and low-mass M dwarfs. We found a positive correlation
between the flux and the radius for brown dwarfs and for low-mass stars that is
weaker than the correlation observed for giant planets.Comment: 20 pages, 13 figures; submitted to MNRA
TOI-5678 b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS
A large sample of long-period giant planets has been discovered thanks to
long-term radial velocity surveys, but only a few dozen of these planets have a
precise radius measurement. Transiting gas giants are crucial targets for the
study of atmospheric composition across a wide range of equilibrium
temperatures and for shedding light on the formation and evolution of planetary
systems. Indeed, compared to hot Jupiters, the atmospheric properties and
orbital parameters of cooler gas giants are unaltered by intense stellar
irradiation and tidal effects. We identify long-period planets in the
Transiting Exoplanet Survey Satellite (TESS) data as duo-transit events. To
solve the orbital periods of TESS duo-transit candidates, we use the
CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability
period aliases in order to discard or confirm a transit event at a given
period. We also collect spectroscopic observations with CORALIE and HARPS in
order to confirm the planetary nature and measure the mass of the candidates.
We report the discovery of a warm transiting Neptune-mass planet orbiting
TOI-5678. After four non-detections corresponding to possible periods, CHEOPS
detected a transit event matching a unique period alias. Joint modeling reveals
that TOI-5678 hosts a 47.73 day period planet. TOI-5678 b has a mass of 20
(+-4) Me and a radius of 4.91 (+-0.08 Re) . Using interior structure modeling,
we find that TOI-5678 b is composed of a low-mass core surrounded by a large
H/He layer with a mass of 3.2 (+1.7, -1.3) Me. TOI-5678 b is part of a growing
sample of well-characterized transiting gas giants receiving moderate amounts
of stellar insolation (11 Se). Precise density measurement gives us insight
into their interior composition, and the objects orbiting bright stars are
suitable targets to study the atmospheric composition of cooler gas giants.Comment: 17 pages, 10 figures, accepted to A&
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant, in the transition between the super-Jupiters and brown-dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480+0.0004−0.0005 d, Mp = 12.74+1.01−1.01 MJ, Rp =1.026+0.065−0.067 RJ and e = 0.018+0.004−0.004 . In addition, the RV time series revealed a significant trend at the ∼ 350 m s−1 yr−1level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949+0.0003−0.0003 d, Mp =2.340+0.197−0.195 MJ, Rp = 1.030+0.050−0.050 RJ and e = 0.021+0.024−0.015 , making this object a new example of a growing population of transiting warm giant planets
Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS
While the sample of confirmed exoplanets continues to increase, the
population of transiting exoplanets around early-type stars is still limited.
These planets allow us to investigate the planet properties and formation
pathways over a wide range of stellar masses and study the impact of high
irradiation on hot Jupiters orbiting such stars. We report the discovery of
TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main
sequence, F-type stars. The planets were identified by the Transiting Exoplanet
Survey Satellite (TESS) and confirmed with complementary ground-based and
radial velocity observations. TOI-615b is a highly irradiated (1277
) and bloated Saturn-mass planet (1.69
and 0.43) in a 4.66 day orbit transiting a 6850 K
star. TOI-622b has a radius of 0.82 and a mass of
0.30~ in a 6.40 day orbit. Despite its high
insolation flux (600 ), TOI-622b does not show any evidence
of radius inflation. TOI-2641b is a 0.37 planet in a
4.88 day orbit with a grazing transit (b = 1.04) that
results in a poorly constrained radius of 1.61.
Additionally, TOI-615b is considered attractive for atmospheric studies via
transmission spectroscopy with ground-based spectrographs and .
Future atmospheric and spin-orbit alignment observations are essential since
they can provide information on the atmospheric composition, formation and
migration of exoplanets across various stellar types.Comment: 16 pages, 17 figures, submitted to A&
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two
long-period transiting substellar companions on low-eccentricity orbits around
TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space
mission. Ground-based photometric and spectroscopic follow-up from different
facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas
giant, in the transition between the super Jupiters and brown dwarfs mass
regime. From the joint analysis we derived the following orbital parameters: P
= 69.0480 d, Mp = 12.74 Mjup, Rp = 1.026 Rjup and e = 0.018. In addition, the
RV time series revealed a significant trend at the 350 m/s/yr level, which is
indicative of the presence of a massive outer companion in the system. TIC
4672985 b is a unique example of a transiting substellar companion with a mass
above the deuterium-burning limit, located beyond 0.1 AU and in a nearly
circular orbit. These planetary properties are difficult to reproduce from
canonical planet formation and evolution models. For TOI-2529 b, we obtained
the following orbital parameters: P = 64.5949 d, Mp = 2.340 Mjup, Rp = 1.030
Rjup and e = 0.021, making this object a new example of a growing population of
transiting warm giant planets.Comment: Accepted in A&