331 research outputs found
High precision radial velocities with GIANO spectra
Radial velocities (RV) measured from near-infrared (NIR) spectra are a
potentially excellent tool to search for extrasolar planets around cool or
active stars. High resolution infrared (IR) spectrographs now available are
reaching the high precision of visible instruments, with a constant improvement
over time. GIANO is an infrared echelle spectrograph at the Telescopio
Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution
spectra for accurate RV measurements of exoplanets and for chemical and
dynamical studies of stellar or extragalactic objects. No other high spectral
resolution IR instrument has GIANO's capability to cover the entire NIR
wavelength range (0.95-2.45 micron) in a single exposure. In this paper we
describe the ensemble of procedures that we have developed to measure high
precision RVs on GIANO spectra acquired during the Science Verification (SV)
run, using the telluric lines as wavelength reference. We used the Cross
Correlation Function (CCF) method to determine the velocity for both the star
and the telluric lines. For this purpose, we constructed two suitable digital
masks that include about 2000 stellar lines, and a similar number of telluric
lines. The method is applied to various targets with different spectral type,
from K2V to M8 stars. We reached different precisions mainly depending on the H
-magnitudes: for H ~ 5 we obtain an rms scatter of ~ 10 m s-1, while for H ~ 9
the standard deviation increases to ~ 50 - 80 m s-1. The corresponding
theoretical error expectations are ~4 m s-1 and 30 m s-1, respectively. Finally
we provide the RVs measured with our procedure for the targets observed during
GIANO Science Verification.Comment: 26 pages, 15 figures, 6 table
Modeling the Full Time-Dependent Phenomenology of Filled Rubber for Use in Anti-Vibration Design
Component design of rubber-based anti-vibration devices remains a challenge, since there is a lack of predictive models in the typical regimes encountered by anti-vibration devices that are deformed to medium dynamic strains (0.5 to 3.5) at medium strain rates (0.5/s to 10/s). An approach is proposed that demonstrates all non-linear viscoelastic effects such as hysteresis and cyclic stress softening. As it is based on a free-energy, it is fast and easily implementable. The fitting parameters behave meaningfully when changing the filler volume fraction. The model was implemented for use in the commercial finite element software ABAQUS. Examples of how to fit experimental data and simulations for a variety of carbon black filled natural rubber compounds are presented
Smooth Muscle Cell Phenotypic Switch Induced by Traditional Cigarette Smoke Condensate: A Holistic Overview
Cigarette smoke (CS) is a risk factor for inflammatory diseases, such as atherosclerosis. CS condensate (CSC) contains lipophilic components that may represent a systemic cardiac risk factor. To better understand CSC effects, we incubated mouse and human aortic smooth muscle cells (SMCs) with CSC. We evaluated specific markers for contractile [i.e., actin, aortic smooth muscle (ACTA2), calponin-1 (CNN1), the Kruppel-like factor 4 (KLF4), and myocardin (MYOCD) genes] and inflammatory [i.e., IL-1 beta, and IL-6, IL-8, and galectin-3 (LGALS-3) genes] phenotypes. CSC increased the expression of inflammatory markers and reduced the contractile ones in both cell types, with KLF4 modulating the SMC phenotypic switch. Next, we performed a mass spectrometry-based differential proteomic approach on human SMCs and could show 11 proteins were significantly affected by exposition to CSC (FC >= 2.7, p <= 0.05). These proteins are active in signaling pathways related to expression of pro-inflammatory cytokines and IFN, inflammasome assembly and activation, cy-toskeleton regulation and SMC contraction, mitochondrial integrity and cellular response to oxidative stress, proteostasis control via ubiquitination, and cell proliferation and epithelial-to-mesenchymal transition. Through specific bioinformatics resources, we showed their tight functional correlation in a close interaction niche mainly orchestrated by the interferon-induced double-stranded RNA-activated protein kinase (alternative name: protein kinase RNA-activated; PKR) (EIF2AK2/PKR). Finally, by combining gene expression and protein abundance data we obtained a hybrid network showing reciprocal integration of the CSC-deregulated factors and indicating KLF4 and PKR as the most relevant factors
The GAPS Programme with HARPS-N at TNG XV. A substellar companion around a K giant star identified with quasi-simultaneous HARPS-N and GIANO measurements
Context. Identification of planetary companions of giant stars is made
difficult because of the astrophysical noise, that may produce radial velocity
(RV) variations similar to those induced by a companion. On the other hand any
stellar signal is wavelength dependent, while signals due to a companion are
achromatic. Aims. Our goal is to determine the origin of the Doppler periodic
variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at
the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the
presence of a substellar companion. Methods. Several methods have been used to
exclude the stellar origin of the observed signal including detailed analysis
of activity indicators and bisector and the analysis of the photometric light
curve. Finally we have conducted an observational campaign to monitor the near
infrared (NIR) RV with GIANO at the TNG in order to verify whether the NIR
amplitude variations are comparable with those observed in the visible.
Results. Both optical and NIR RVs show consistent variations with a period at
101 days and similar amplitude, pointing to the presence of a companion
orbiting the target. The main orbital properties obtained for our giant star
with a derived mass of M=0.97+-0.03M_sun are
M_Psini=10.78+-0.12MJ;P=101.54+-0.05days;e=0.28+-0.01 and a=0.422+-0.009AU. The
chemical analysis shows a significant enrichment in the abundance of Nai, Mgi,
Ali and S i while the rest of analyzed elements are consistent with the solar
value demonstrating that the chemical composition corresponds with an old K
giant (age = 10.1 Gyr) belonging to local thick disk. Conclusions. We conclude
that the substellar companion hypothesis for this K giant is the best
explanation for the observed periodic RV variation. This study also shows the
high potential of multi-wavelength RV observations for the validation of planet
candidates.Comment: Accepted in Journal reference A&A 14/06/201
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
Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning
Context. Stellar activity is currently challenging the detection of young
planets via the radial velocity (RV) technique. Aims. We attempt to
definitively discriminate the nature of the RV variations for the young active
K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent
results on the existence of a substellar companion. Methods. We compare VIS
data with high precision RVs in the near infrared (NIR) range by using the
GIANO - B and IGRINS spectrographs. In addition, we present for the first time
simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS -
N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV
amplitude does not change at different wavelengths, while stellar activity
induces wavelength-dependent RV variations, which are significantly reduced in
the NIR range with respect to the VIS. Results. The NIR radial velocity
measurements from GIANO - B and IGRINS show an average amplitude of about one
quarter with respect to previously published VIS data, as expected when the RV
jitter is due to stellar activity. Coeval multi-band photometry surprisingly
shows larger amplitudes in the NIR range, explainable with a mixture of cool
and hot spots in the same active region. Conclusions. In this work, the claimed
massive planet around BD+20 1790 is ruled out by our data. We exploited the
crucial role of multi- wavelength spectroscopy when observing young active
stars: thanks to facilities like GIARPS that provide simultaneous observations,
this method can reach its maximum potential.Comment: 12 pages, 7 figure
A soft and transient ultraluminous X-ray source with 6-h modulation in the NGC 300 galaxy
We investigate the nature of CXOU J005440.5-374320 (J0054), a peculiar bright
( erg/s) and soft X-ray transient in the spiral galaxy
NGC 300 with a 6-hour periodic flux modulation that was detected in a 2014
Chandra observation. Subsequent observations with Chandra and XMM-Newton, as
well as a large observational campaign of NGC 300 and its sources performed
with the Swift Neil Gehrels Observatory, showed that this source exhibits
recurrent flaring activity: four other outbursts were detected across 8
years of monitoring. Using data from the Swift/UVOT archive and from the
XMM-Newton/OM and Gaia catalogues, we noted the source is likely associated
with a bright blue optical/ultraviolet counterpart. This prompted us to perform
follow-up observations with the Southern African Large Telescope in December
2019. With the multi-wavelength information at hand, we discuss several
possibilities for the nature of J0054. Although none is able to account for the
full range of the observed peculiar features, we found that the two most
promising scenarios are a stellar-mass compact object in a binary system with a
WolfRayet star companion, or the recurrent tidal stripping of a stellar
object trapped in a system with an intermediate-mass ( )
black hole.Comment: 13 pages, 11 Figures, 3 Tables (the Table in appendix A will be
available in the published version). Accepted for publication in A&
The GAPS programme at TNG XXII. The GIARPS view of the extended helium atmosphere of HD189733 b accounting for stellar activity
Exoplanets orbiting very close to their host star are strongly irradiated.
This can lead the upper atmospheric layers to expand and evaporate into space.
The metastable helium (HeI) triplet at 1083.3nm has recently been shown to be a
powerful diagnostic to probe extended and escaping exoplanetary atmosphere. We
perform high-resolution transmission spectroscopy of the transiting hot Jupiter
HD189733b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio
Nazionale Galileo, taking advantage of the simultaneous optical+near infrared
spectral coverage to detect HeI in the planet's extended atmosphere and to
gauge the impact of stellar magnetic activity on the planetary absorption
signal. Observations were performed during five transit events of HD189733b. By
comparison of the in- and out-of-transit GIANO-B observations we compute
high-resolution transmission spectra, on which we perform equivalent width
measurements and light-curves analyses to gauge the excess in-transit
absorption in the HeI triplet. We detect an absorption signal during all five
transits. The mean in-transit absorption depth amounts to 0.75+/-0.03%. We
detect night-to-night variations in the HeI absorption signal likely due to the
transit events occurring in presence of stellar surface inhomogeneities. We
evaluate the impact of stellar-activity pseudo-signals on the true planetary
absorption using a comparative analysis of the HeI and the H lines. We
interpret the time-series of the HeI absorption lines in the three nights not
affected by stellar contamination -exhibiting a mean in-transit absorption
depth of 0.77+/-0.04%- using a 3-d atmospheric code. Our simulations suggest
that the helium layers only fill part of the Roche lobe. Observations can be
explained with a thermosphere heated to 12000 K, expanding up to
1.2 planetary radii, and losing 1 g/s of metastable helium.Comment: 17 pages, 17 figures, accepted for publication in A&
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