177 research outputs found
Assay of riboflavin in sample wines by capillary zone electrophoresis and laser-induced fluorescence detection
To routinely assay the concentration of riboflavin (RF) in wines, a rapid and sensitive method was developed and evaluated. The method is based on a simple sample preparation, capillary zone electrophoretic separation and laser-induced fluorescence detection (CZE-LIF). Sample-preparation required only dilution and filtration. Under optimized conditions, the limit of detection of riboflavin was 0.5 mug/L, using a hydrodynamic sample introduction of 10 s at 54 mbar. The method was fully validated: the recovery of RF in wines was >95%. The concentrations of RF within the three sample types of Italian wines investigated here ranged from 69 to 151 mug/L with a mean value(+/-SD) of 112 +/- 25 mug/L, from 74 to 193 mug/L with a mean value of 115 +/- 45,ug/L, and from 156 to 292 mug/L with a mean value of 226 +/- 40 mug/L, for white, rose and red wines, respectively. Such an accurate and highly sensitive CZE-LIF method represents a powerful improvement over previous methods in terms of sensitivity, simplicity, and efficiency. It is well suited to satisfy the demands for accurate and sensitive detection with minimal sample preparation and cleanup
The multifunctional polydnavirus TnBVANK1 protein: impact on host apoptotic pathway
Toxoneuron nigriceps (Hymenoptera, Braconidae) is an endophagous parasitoid of the larval stages of the tobacco budworm, Heliothis virescens (Lepidoptera, Noctuidae). The bracovirus associated with this wasp (TnBV) is currently being studied. Several genes expressed in parasitised host larvae have been isolated and their possible roles partly elucidated. TnBVank1 encodes an ankyrin motif protein similar to insect and mammalian IκB, an inhibitor of the transcription nuclear factor κB (NF-κB). Here we show that, when TnBVank1 was stably expressed in polyclonal Drosophila S2 cells, apoptosis is induced. Furthermore, we observed the same effects in haemocytes of H. virescens larvae, after TnBVank1 in vivo transient transfection, and in haemocytes of parasitised larvae. Coimmunoprecipitation experiments showed that TnBVANK1 binds to ALG-2 interacting protein X (Alix/AIP1), an interactor of apoptosis-linked gene protein 2 (ALG-2). Using double-immunofluorescence labeling, we observed the potential colocalization of TnBVANK1 and Alix proteins in the cytoplasm of polyclonal S2 cells. When Alix was silenced by RNA interference, TnBVANK1 was no longer able to cause apoptosis in both S2 cells and H. virescens haemocytes. Collectively, these results indicate that TnBVANK1 induces apoptosis by interacting with Alix, suggesting a role of TnBVANK1 in the suppression of host immune response observed after parasitisation by T. nigricep
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XVII. Public Catalogue Release
In this paper we present the astro-photometric catalogues of 56 globular
clusters and one open cluster. Astrometry and photometry are mainly based on
images collected within the "HST Legacy Survey of Galactic Globular Clusters:
Shedding UV Light on Their Populations and Formation" (GO-13297, PI:~Piotto),
and the "ACS Survey of Galactic Globular Clusters" (GO-10775, PI:~Sarajedini).
For each source in the catalogues for which we have reliable proper motion we
also publish a membership probability for separation of field and cluster
stars. These new catalogues, which we make public in Mikulski Archive for Space
Telescopes, replace previous catalogues by Paper VIII of this series.Comment: 14 pages, 5 figures, 4 tables. Accepted for publication in MNRAS on
September 11, 2018. Astro-photometric catalogues, stacked and RGB images of
the clusters are publicly available at MAST as High Level Science Product at
https://archive.stsci.edu/prepds/hugs
Neutral Iron Emission Lines From The Day-side Of KELT-9b -- The GAPS Programme With HARPS-N At TNG XX
We present the first detection of atomic emission lines from the atmosphere
of an exoplanet. We detect neutral iron lines from the day-side of KELT-9b (Teq
4, 000 K). We combined thousands of spectrally resolved lines observed
during one night with the HARPS-N spectrograph (R 115, 000), mounted at
the Telescopio Nazionale Galileo. We introduce a novel statistical approach to
extract the planetary parameters from the binary mask cross-correlation
analysis. We also adapt the concept of contribution function to the context of
high spectral resolution observations, to identify the location in the
planetary atmosphere where the detected emission originates. The average
planetary line profile intersected by a stellar G2 binary mask was found in
emission with a contrast of 84 14 ppm relative to the planetary plus
stellar continuum (40 5 relative to the planetary continuum only).
This result unambiguously indicates the presence of an atmospheric thermal
inversion. Finally, assuming a modelled temperature profile previously
published (Lothringer et al. 2018), we show that an iron abundance consistent
with a few times the stellar value explains the data well. In this scenario,
the iron emission originates at the - bar level.Comment: Accepted for publication on ApJL; 19 pages, 4 figures, 3 table
X-ray and ultraviolet emission of the young planet-hosting star V1298 Tau from coordinated observations with XMM-Newton and Hubble Space Telescope
Atmospheric mass loss plays a major role in the evolution of exoplanets. This process is driven by the stellar high-energy irradiation, especially in the first hundreds of millions of years after dissipation of the proto-planetary disk. A major source of uncertainty in modeling atmospheric photoevaporation and photochemistry is due to the lack of direct measurements of the stellar flux at extreme-UV (EUV) wavelengths. Several empirical relationships have been proposed in the past to link EUV fluxes to emission levels in X-rays, but the stellar samples employed for this aim are heterogeneous, and the available scaling laws provide significantly different predictions, especially for very active stars. We present new far-UV and X-ray observations of V1298 Tau with Hubble Space Telescope/Cosmic Origins Spectrograph and XMM-Newton, aimed to determine more accurately the high-energy emission of this solar-mass pre-main-sequence star, which hosts four exoplanets. Spectroscopic data were employed to derive the plasma emission measure distribution versus temperature, from the chromosphere to the corona, and the possible variability of this irradiation on short and year-long timescales, due to magnetic activity. As a side result, we have also measured the chemical abundances of several elements in the outer atmosphere of V1298 Tau. We employ our results as a new benchmark point for the calibration of the X-ray to EUV scaling laws, and hence to predict the time evolution of the irradiation in the EUV band, and its effect on the evaporation of exo-atmospheres
The Hubble Space Telescope UV Legacy Survey of galactic globular clusters - II. The seven stellar populations of NGC 7089 (M2)
We present high-precision multiband photometry for the globular cluster (GC) M2. We combine the analysis of the photometric data obtained from the Hubble Space Telescope UV Legacy Survey of Galactic GCs GO-13297, with chemical abundances by Yong et al., and compare the photometry with models in order to analyse the multiple stellar sequences we identified in the colour–magnitude diagram. We find three main stellar components, composed of metal-poor, metal-intermediate, and metal-rich stars (hereafter referred to as population A, B, and C, respectively). The components A and B include stars with different s-process element abundances. They host six sub-populations with different light-element abundances, and exhibit an internal variation in helium up to ΔY ∼ 0.07 dex. In contrast with M22, another cluster characterized by the presence of populations with different metallicities, M2 contains a third stellar component, C, which shows neither evidence for sub-populations nor an internal spread in light-elements. Population C does not exhibit the typical photometric signatures that are associated with abundance variations of light elements produced by hydrogen burning at hot temperatures. We compare M2 with other GCs with intrinsic heavy-element variations and conclude that M2 resembles M22, but it includes an additional stellar component that makes it more similar to the central region of the Sagittarius galaxy, which hosts a GC (M54) and the nucleus of the Sagittarius galaxy itself.APM and HJ
acknowledge support by the Australian Research Council through
Discovery Project grant DP120100475. MZ acknowledges support
by Proyecto Fondecyt Regular 1110393, by the BASAL Center for
Astrophysics and Associated Technologies PFB-06, and by Project
IC120009 ‘Millennium Institute of Astrophysics (MAS)’ of Iniciativa
Cient´ıfica Milenio by the Chilean Ministry of Economy,
Development and Tourism
The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters - IX. The Atlas of multiple stellar populations
We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the 'Hubble Space Telescope (HST ) UV Legacy Survey of Galactic GCs', to identify and characterize their multiple stellar populations. For each cluster the pseudo-two-colour diagram (or 'chromosome map') is presented, built with a suitable combination of stellar magnitudes in the F275W, F336W, F438W, and F814W filters that maximizes the separation between multiple populations. In the chromosome map of most GCs (type-I clusters), stars separate in two distinct groups that we identify with the first (1G) and the second generation (2G). This identification is further supported by noticing that 1G stars have primordial (oxygen-rich, sodium-poor) chemical composition, whereas 2G stars are enhanced in sodium and depleted in oxygen. This 1G-2G separation is not possible for a few GCs where the two sequences have apparently merged into an extended, continuous sequence. In some GCs (type-II clusters) the 1G and/or the 2G sequences appear to be split, hence displaying more complex chromosome maps. These clusters exhibit multiple subgiant branches (SGBs) also in purely optical colour-magnitude diagrams, with the fainter SGB joining into a red RGB which is populated by stars with enhanced heavy-element abundance. We measure the RGB width by using appropriate colours and pseudo-colours. When the metallicity dependence is removed, the RGB width correlates with the cluster mass. The fraction of 1G stars ranges from ~8 per cent to ~67 per cent and anticorrelates with the cluster mass, indicating that incidence and complexity of the multiple population phenomenon both increase with cluster mass
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
We present high-precision multi-band photometry for the globular cluster (GC)
M2. We combine the analysis of the photometric data obtained from the Hubble
Space Telescope UV Legacy Survey of Galactic GCs GO-13297, with chemical
abundances by Yong et al.(2014), and compare the photometry with models in
order to analyze the multiple stellar sequences we identified in the
color-magnitude diagram (CMD). We find three main stellar components, composed
of metal-poor, metal-intermediate, and metal-rich stars (hereafter referred to
as population A, B, and C, respectively). The components A and B include stars
with different -process element abundances. They host six sub-populations
with different light-element abundances, and exhibit an internal variation in
helium up to Delta Y~0.07 dex. In contrast with M22, another cluster
characterized by the presence of populations with different metallicities, M2
contains a third stellar component, C, which shows neither evidence for
sub-populations nor an internal spread in light-elements. Population C does not
exhibit the typical photometric signatures that are associated with abundance
variations of light elements produced by hydrogen burning at hot temperatures.
We compare M2 with other GCs with intrinsic heavy-element variations and
conclude that M2 resembles M22, but it includes an additional stellar component
that makes it more similar to the central region of the Sagittarius galaxy,
which hosts a GC (M54) and the nucleus of the Sagittarius galaxy itself.Comment: 12 pages, 7 figures, accepted for publication in MNRA
The GAPS Programme at TNG : LI. Investigating the correlations between transiting system parameters and host chromospheric activity
Context. Stellar activity is the most relevant types of astrophysical noise that affect the discovery and characterization of extrasolar planets. On the other hand, the amplitude of stellar activity could hint at an interaction between the star and a close-in giant planet. Progress has been made in recent years in understanding how to deal with stellar activity and search for observational evidence of star-planet interactions.
Aims: The aim of this work is to characterize the chromospheric activity of stars hosting short-period exoplanets by studying the correlations between the chromospheric emission (CE) in the Ca II H&K and the planetary parameters.
Methods: We measured CE in the Ca II H&K lines using more than 1900 high-resolution spectra of a sample composed of 76 targets, observed with the HARPS-N spectrograph between 2012 and 2020. We transformed the fluxes into bolometric- and photospheric-corrected chromospheric emission ratios, R′HK. Furthermore, we completed the sample of hosts digging for data in previous works. Stellar parameters Teff, B-V, and V were retrieved homogeneously from the Gaia DR3. Then, M★, R★, and ages were determined from isochrone fitting. We retrieved planetary data from the literature and catalogs. The search for correlations between the log(R′HK) and planetary parameters have been performed through both Spearman's rank and its statistics as well as the more sophisticated Gaussian mixture model method.
Results: We found that the distribution of log(R′HK) for the transiting planet hosts is different from the distribution of field main-sequence and sub-giant stars. The log(R′HK) of planetary hosts is correlated with planetary parameters proportional to the planetary radius to the power of n (RPn, indicating a common origin for the correlations. The statistical analysis has also highlighted four clusters of host stars with different behavior in terms of their stellar activity with respect to the planetary surface gravity. Some of the host stars have a value of log(R′HK) that is lower than the basal level of activity for main sequence stars. The planets of these systems are very close to filling their Roche lobe, suggesting that they evaporate through hydrodynamic escape under the strong irradiation of the host star, creating shrouds that absorb the core of the chromospheric resonance lines
The GAPS programme at TNG XLV. A massive brown dwarf orbiting the active M dwarf TOI-5375
Context. Massive substellar companions orbiting active low-mass stars are
rare. They, however, offer an excellent opportunity to study the main
mechanisms involved in the formation and evolution of substellar objects. Aims.
We aim to unravel the physical nature of the transit signal observed by the
TESS space mission on the active M dwarf TOI-5375. Methods. We analysed the
available TESS photometric data as well as high-resolution (R 115000)
HARPS-N spectra. We combined these data to characterise the star TOI-5375 and
to disentangle signals related to stellar activity from the companion transit
signal in the light-curve data. We ran an MCMC analysis to derive the orbital
solution and apply state-of-the-art Gaussian process regression to deal with
the stellar activity signal. Results. We reveal the presence of a companion in
the brown dwarf / very-low-mass star boundary orbiting around the star
TOI-5375. The best-fit model corresponds to a companion with an orbital period
of 1.721564 10 d, a mass of 77 8 and a
radius of 0.99 0.16 . We derive a rotation period for the host
star of 1.9692 0.0004 d, and we conclude that the star is very close to
synchronising its rotation with the orbital period of the companion.Comment: Submitted to Astronomy & Astrophysics (under review
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