91 research outputs found
The quest for Magrathea planets I: formation of second generation exoplanets around double white dwarfs
The evolution of binaries that become double white dwarf (DWD) can cause the
ejection of high amounts of dust and gas. Such material can give rise to
circumbinary discs and become the cradle of new planets, yet no studies so far
have focused on the formation of circumbinary planets around DWDs. These
binaries will be the main sources of gravitational waves (GWs) detectable by
the ESA Laser Interferometer Space Antenna (LISA) mission, opening the
possibility to detect circumbinary planets around short-period DWDs everywhere
in the Milky Way. We investigate the formation of Magrathea planets by
simulating multiple planet formation tracks to explore how seeds growing first
by pebble accretion, and then by gas accretion, are affected by the disc
environments surrounding DWDs. We present both planetary formation tracks
taking place in steady-state discs, and formation tracks taking place in discs
evolving with time. The time-dependent tracks account for both the disc
accretion rate onto the central binary and the disc photoevaporation rate
caused by stellar irradiation. Our results show that planetary formation in
circumbinary discs around DWDs can be possible. In particular, the extreme
planetary formation environment implies three main significant results: (i) the
accretion rate and the metallicity of the disc should be high in order to form
sub-stellar objects with masses up to 31 M, this is achieved only if planet
formation starts soon after the onset of the disc and if first generation seeds
are present in the disc; (ii) seeds formed within 0.1 Myr, or within 1 Myr,
from the onset of the disc can only produce sub-Neptune and Neptunian planets,
unless the disc accommodates first generation seeds with mass 10 M;
(iii) most of the planets are finally located within 1 au from the disc centre,
while they are still undergoing the gas accretion phase.Comment: Accepted for publication in A&A on 05/04/2023, abstract shortened, 28
pages, 11 figures, 14 table
DC-STAMP knock-down deregulates cytokine production and T-cell stimulatory capacity of LPS-matured dendritic cells
Contains fulltext :
96778.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: Dendritic cells (DCs) are the highly specialized antigen presenting cells of the immune system that play a key role in regulating immune responses. DCs can efficiently initiate immune responses or induce tolerance. Due to this dual function, DCs are studied in the context of immunotherapy for both cancer and autoimmune diseases. Characterization of DC-specific genes, leading to better understanding of DC immunobiology, will help to guide their use in clinical settings. We previously identified DC-STAMP, a multi-membrane spanning protein preferentially expressed by DCs. DC-STAMP resides in the endoplasmic reticulum (ER) of immature DCs and translocates towards the Golgi compartment upon maturation. In this study we knocked down DC-STAMP in mouse bone marrow-derived DCs (mBMDCs) to determine its function. RESULTS: We demonstrate that DC-STAMP knock-down mBMDCs secrete less IL-6, IL-12, TNF-alpha and IL-10 while IL-1 production is enhanced. Moreover, LPS-matured DC-STAMP knock-down mBMDCs show impaired T cell activation potential and induction of Th1 responses in an alloreaction. CONCLUSIONS: We show that DC-STAMP plays an important role in cytokine production by mBMDCs following LPS exposure. Our results reveal a novel function of DC-STAMP in regulating DC-initiated immune responses
Extended maceration of must improves phenolic composition and antioxidant potential of Touriga Nacional tropical wine
The Submédio do Vale do São Francisco (S.V.S.F.), located in the Brazilian Northeast, is an emerging winemaking region in South America. Touriga Nacional (T.N.) grapes originated in Portugal, thrive under the climatic conditions found in the S.V.S.F. The effects of extended maceration on different parameters of red wine must produced with T.N. grapes from two harvest years from S.V.S.F. were studied. Increased maceration time (16 to 20 days) resulted in greater total phenolic contents (40 to 85%) compared to eight days of maceration, along with higher antiradical activity (15 to 36%). Regardless of the harvest year, the antiradical activity was mostly related to the contents of resveratrol, (+)-catechin, isorhamnetin-3-O-glucosidase, and (?)-epigallocatechin gallate. In contrast, color intensity was not affected. The increase in the maceration period induced a positive effect on the phenolic composition, which was reflected in the higher antiradical activity of T.N. red wine
Characterisation of the upper atmospheres of HAT-P-32 b, WASP-69 b, GJ 1214 b, and WASP-76 b through their He I triplet absorption
Characterisation of atmospheres undergoing photo-evaporation is key to
understanding the formation, evolution, and diversity of planets. However, only
a few upper atmospheres that experience this kind of hydrodynamic escape have
been characterised. Our aim is to characterise the upper atmospheres of the hot
Jupiters HAT-P-32 b and WASP-69 b, the warm sub-Neptune GJ 1214 b, and the
ultra-hot Jupiter WASP-76 b through high-resolution observations of their HeI
triplet absorption. In addition, we also reanalyse the warm Neptune GJ 3470 b
and the hot Jupiter HD 189733 b. We used a spherically symmetric 1D
hydrodynamic model coupled with a non-local thermodynamic equilibrium model.
Comparing synthetic absorption spectra with observations, we constrained the
main parameters of the upper atmosphere of these planets and classify them
according to their hydrodynamic regime. Our results show that HAT-P-32 b
photo-evaporates at (13070)10 gs with a hot (12
4002900 K) upper atmosphere; WASP-69 b loses its atmosphere at
(0.90.5)10 gs and 5250750 K; and GJ 1214 b,
with a relatively cold outflow of 3750750 K, photo-evaporates at
(1.31.1)10 gs. For WASP-76 b, its weak absorption
prevents us from constraining its temperature and mass-loss rate significantly;
we obtained ranges of 6000-17 000\,K and 23.521.510
gs. Our reanalysis of GJ 3470 b yields colder temperatures, 3400350
K, but practically the same mass-loss rate as in our previous results. Our
reanalysis of HD 189733 b yields a slightly higher mass-loss rate,
(1.40.5)10 gs, and temperature, 12 700900 K
compared to previous estimates. Our results support that photo-evaporated
outflows tend to be very light
Exploring the link between star and planet formation with Ariel
The goal of the Ariel space mission is to observe a large and diversified population
of transiting planets around a range of host star types to collect information on their
atmospheric composition. The planetary bulk and atmospheric compositions bear the
marks of the way the planets formed: Arielâs observations will therefore provide
an unprecedented wealth of data to advance our understanding of planet formation
in our Galaxy. A number of environmental and evolutionary factors, however, can
affect the final atmospheric composition. Here we provide a concise overview of
which factors and effects of the star and planet formation processes can shape the
atmospheric compositions that will be observed by Ariel, and highlight how Arielâs
characteristics make this mission optimally suited to address this very complex
problem
Ariel stellar characterisation: I -- homogeneous stellar parameters of 187 FGK planet host stars Description and validation of the method
In 2020 the European Space Agency selected Ariel as the next mission to join
the space fleet of observatories to study planets outside our Solar System.
Ariel will be devoted to the characterisation of a thousand planetary
atmospheres, for understanding what exoplanets are made of, how they formed and
how they evolve. To achieve the last two goals all planets need to be studied
within the context of their own host stars, which in turn have to be analysed
with the same technique, in a uniform way. We present the spectro-photometric
method we have developed to infer the atmospheric parameters of the known host
stars in the Tier 1 of the Ariel Reference Sample. Our method is based on an
iterative approach, which combines spectral analysis, the determination of the
surface gravity from {\em Gaia} data, and the determination of stellar masses
from isochrone fitting. We validated our approach with the analysis of a
control sample, composed by members of three open clusters with well-known ages
and metallicities. We measured effective temperature, Teff, surface gravity,
logg, and the metallicity, [Fe/H], of 187 F-G-K stars within the Ariel
Reference Sample. We presented the general properties of the sample, including
their kinematics which allows us to separate them between thin and thick disc
populations. A homogeneous determination of the parameters of the host stars is
fundamental in the study of the stars themselves and their planetary systems.
Our analysis systematically improves agreement with theoretical models and
decreases uncertainties in the mass estimate (from 0.21+/-0.30 to 0.10+/-0.02
M_sun), providing useful data for the Ariel consortium and the astronomical
community at large.Comment: Accepted for publication in A&A, 13 pages, 14 figures, Tables A1 and
A2 in the Appendix will be available at CDS and can be requested by email to:
[email protected]
Defocused transmission spectroscopy: a potential detection of sodium in the atmosphere of WASP-12b
We report on a pilot study of a novel observing technique, defocused transmission spectroscopy, and its application to the study of exoplanet atmospheres using ground-based platforms. Similar to defocused photometry, defocused transmission spectroscopy has an added advantage over normal spectroscopy in that it reduces systematic errors due to flat-fielding, point spread function variations, slit-jaw imperfections and other effects associated with ground-based observations. For one of the planetary systems studied, WASP-12b, we report a tentative detection of additional Na absorption of 0.12 ± 0.03[+0.03]âperâcent during transit using a 2 Ă
wavelength mask. After consideration of a systematic that occurs mid-transit, it is likely that the true depth is actually closer to 0.15âperâcent. This is a similar level of absorption reported in the atmosphere of HD 209458b (0.135 ± 0.017âperâcent; Snellen et al. 2008). Finally, we outline methods that will improve the technique during future observations, based on our findings from this pilot study
A chemical survey of exoplanets with ARIEL
Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planetâs birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25â7.8 ÎŒm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10â100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed â using conservative estimates of mission performance and a full model of all significant noise sources in the measurement â using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL â in line with the stated mission objectives â will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems: Best Practices for Data Collection in Cycle 2 and Beyond
We present a set of recommended best practices for JWST data collection for
members of the community focussed on the direct imaging and spectroscopy of
exoplanetary systems. These findings and recommendations are based on the early
analysis of the JWST Early Release Science Program 1386, "High-Contrast Imaging
of Exoplanets and Exoplanetary Systems with JWST." Our goal is for this
information to be useful for observers in preparation of JWST proposals for
Cycle 2 and beyond. In addition to compiling a set of best practices from our
ERS program, in a few cases we also draw on the expertise gained within the
instrument commissioning programs, as well as include a handful of data
processing best practices. We anticipate that this document will be regularly
updated and resubmitted to arXiv.org to ensure that we have distributed our
knowledge of best-practices for data collection as widely and efficiently as
possible.Comment: Not yet submitted for publication. Intended only to be a community
resource for JWST Cycle 2 proposal
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