The GAPS programme with HARPS-N at TNG Covino, E; Esposito, M; Barbieri, M ...
Astronomy and astrophysics (Berlin),
06/2013, Letnik:
554
Journal Article
Recenzirano
Odprti dostop
Our understanding of the formation and evolution of planetary systems is still fragmentary because most of the current data provide limited information about the orbital structure and dynamics of ...these systems. The knowledge of the orbital properties for a variety of systems and at different ages yields information on planet migration and on star-planet tidal interaction mechanisms. In this context, a long-term, multi-purpose, observational programme has started with HARPS-N at TNG and aims to characterise the global architectural properties of exoplanetary systems. The goal of this first paper is to fully characterise the orbital properties of the transiting system Qatar-1 as well as the physical properties of the star and the planet. We find that the system is well aligned and fits well within the general lambda versus Tsubeff trend. We can definitely rule out any significant orbital eccentricity. The evolutionary status of the system is inferred based on gyrochronology, and the present orbital configuration and timescale for orbital decay are discussed in terms of star-planet tidal interactions.
HADES RV Programme with HARPS-N at TNG González-Álvarez, E.; Micela, G.; Maldonado, J. ...
Astronomy and astrophysics (Berlin),
04/2019, Letnik:
624
Journal Article
Recenzirano
Odprti dostop
Aims.
We extend the relationship between X-ray luminosity (
L
x
) and rotation period (
P
rot
) found for main-sequence FGK stars, and test whether it also holds for early M dwarfs, especially in the ...non-saturated regime (
L
x
∝
P
rot
−2
) which corresponds to slow rotators.
Methods.
We use the luminosity coronal activity indicator (
L
x
) of a sample of 78 early M dwarfs with masses in the range from 0.3 to 0.75
M
⊙
from the HArps-N red Dwarf Exoplanet Survey (HADES) radial velocity (RV) programme collected from ROSAT and
XMM-Newton
. The determination of the rotation periods (
P
rot
) was done by analysing time series of high-resolution spectroscopy of the Ca
II
H & K and H
α
activity indicators. Our sample principally covers the slow rotation regime with rotation periods from 15 to 60 days.
Results.
Our work extends to the low mass regime the observed trend for more massive stars showing a continuous shift of the
L
x
∕
L
bol
versus
P
rot
power law towards longer rotation period values, and includes a more accurate way to determine the value of the rotation period at which the saturation occurs (
P
sat
) for M dwarf stars.
Conclusions.
We conclude that the relations between coronal activity and stellar rotation for FGK stars also hold for early M dwarfs in the non-saturated regime, indicating that the rotation period is sufficient to determine the ratio
L
x
∕
L
bol
.
The GAPS Programme at TNG Scandariato, G.; Borsa, F.; Sicilia, D. ...
Astronomy and astrophysics (Berlin),
02/2021, Letnik:
646
Journal Article
Recenzirano
Odprti dostop
Context.
The analysis of exoplanetary atmospheres by means of high-resolution spectroscopy is an expanding research field which provides information on the chemical composition, thermal structure, ...atmospheric dynamics, and orbital velocity of exoplanets.
Aims.
In this work, we aim to detect the light reflected by the exoplanet 51 Peg b by employing optical high-resolution spectroscopy.
Methods.
To detect the light reflected by the planetary dayside, we used optical High Accuracy Radial velocity Planet Searcher and High Accuracy Radial velocity Planet Searcher for the Northern hemisphere spectra taken near the superior conjunction of the planet, when the flux contrast between the planet and the star is maximum. To search for the weak planetary signal, we cross-correlated the observed spectra with a high signal-to-noise ratio stellar spectrum.
Results.
We homogeneously analyze the available datasets and derive a 10
−5
upper limit on the planet-to-star flux contrast in the optical.
Conclusions.
The upper limit on the planet-to-star flux contrast of 10
−5
translates into a low albedo of the planetary atmosphere (
A
g
≲ 0.05−0.15 for an assumed planetary radius in the range of 1.5−0.9
R
Jup
, as estimated from the planet’s mass).
Abstract
We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD 79210 and HD 79211, two M0V members of a gravitationally bound binary system. We detect a planet ...candidate with a period of
24.421
−
0.017
+
0.016
days around HD 79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES, and RVs spanning a total of 25 yr, we further refine the planet candidate parameters to
P
= 24.422 ± 0.014 days,
K
= 3.19 ± 0.27 m s
−1
,
M
sin
i
= 10.6 ± 1.2
M
⊕
, and
a
= 0.142 ± 0.005 au. We do not find any additional planet candidate signals in the data of HD 79211, nor do we find any planet candidate signals in HD 79210. This system adds to the number of exoplanets detected in binaries with M-dwarf members and serves as a case study for planet formation in stellar binaries.
ABSTRACT We present the discovery of three super-Earth candidates orbiting HD 48948, a bright K-dwarf star with an apparent magnitude of $m_V$ = 8.58 mag. As part of the HARPS-N Rocky Planet Search ...programme, we collect 189 high-precision radial velocity measurements using the HARPS-N spectrograph from 2013 October 6, to 2023 April 16. Various methodologies are applied to extract the radial velocities from the spectra, and we conduct a comprehensive comparative analysis of the outcomes obtained through these diverse extraction techniques. To ensure the robustness of our findings, we employ several methods to address stellar variability, with a focus on Gaussian Process regression. To account for the impact of stellar variability and correlated noise in the radial velocity data set, we include activity indicators, such as $\log R^{^{\prime }}_{\mathrm{HK}}$ and bisector span, in the multidimensional Gaussian Process regression. Our analysis reveals three planetary candidates with orbital periods of 7.3, 38, and 151 d, and minimum masses estimated at $4.88 \pm 0.21$ M$_{\oplus }$, $7.27 \pm 0.70$ M$_{\oplus }$, and $10.59 \pm 1.00$ M$_{\oplus }$, respectively. The outermost planet resides within the (temperate) habitable zone, positioned at a projected distance of $0.029\,{\rm arcsec}$ from its star. Given the close proximity of this planetary system, situated at a distance of 16.8 parsecs, HD 48498 emerges as a promising target (closest super-Earth around FGK stars) for future high-contrast direct imaging and high-resolution spectroscopic studies.
We present iron abundance analysis for 23 wide binaries with main sequence components in the temperture range 4900–6300 K, taken from the sample of the pairs currently included in the radial velocity ...planet search on going at the Telescopio Nazionale Galileo (TNG) using the high resolution spectrograph SARG. The use of a line-by-line differential analysis technique between the components of each pair allows us to reach errors of about 0.02 dex in the iron content difference. Most of the pairs have abundance differences lower than 0.02 dex and there are no pairs with differences larger than 0.07 dex. The four cases of differences larger than 0.02 dex may be spurious because of the larger error bars affecting pairs with large temperature difference, cold stars and rotating stars. The pair HD 219542, previously reported by us to have a different composition, here is shown to be normal. For non-rotating stars warmer than 5500 K, characterized by a thinner convective envelope and for which our analyis appears to be of higher accuracy, we are able to exclude in most cases the consumption of more than 1 Earth Mass of iron (about 5 Earth masses of meteoritic material) during the main sequence lifetime of the stars, placing more stringent limits (about 0.4 Earth masses of iron) in five cases of warm stars. This latter limit is similar to the estimates of rocky material accreted by the Sun during its main sequence lifetime. Combining the results of the present analysis with those for the Hyades and Pleiades, we conclude that the hypothesis that pollution by planetary material is the only mechanism responsible for the highest metallicity of the stars with planets may be rejected at more than 99% level of confidence if the incidence of planets in these samples is as high as 8% and similar to the field stars included in current radial velocity surveys. However, the significance of this result drops considerably if the incidence of planets around stars in binary systems and clusters is less than a half of that around normal field stars.
The GAPS Programme with HARPS-N at TNG Barbato, D.; Sozzetti, A.; Biazzo, K. ...
Astronomy and astrophysics (Berlin),
01/2019, Letnik:
621
Journal Article
Recenzirano
Odprti dostop
Context.
Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity stars, while no such correlation is evident for lower ...mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence
f
p
is an important element in providing support to models of planet formation.
Aims.
We present results from the HARPS-N search for giant planets orbiting metal-poor (− 1.0 ≤Fe/H ≤−0.5 dex) stars in the northern hemisphere, complementing a previous HARPS survey on southern stars in order to update the estimate of
f
p
.
Methods.
High-precision HARPS-N observations of 42 metal-poor stars were used to search for planetary signals to be fitted using differential evolution Markov chain Monte Carlo single-Keplerian models. We then joined our detections to the results of the previous HARPS survey on 88 metal-poor stars to provide a preliminary estimate of the two-hemisphere
f
p
.
Results.
We report the detection of two new giant planets around HD 220197 and HD 233832. The first companion has Msin
i
= 0.20
−0.04
+0.07
M
Jup
and an orbital period of 1728
−80
+162
days, and for the second companion, we find two solutions of equal statistical weight with periods of 2058
−40
+47
and 4047
−117
+91
days and minimum masses of 1.78
−0.06
+0.08
and 2.72
−0.23
+0.23
M
Jup
, respectively. Joining our two detections with the three from the southern survey, we obtain a preliminary and conservative estimate of the global frequency of
f
p
= 3.84
−1.06
+2.45
% for giant planets around metal-poor stars.
Conclusions.
The two new giant planets orbit dwarf stars at the metal-rich end of the HARPS-N metal-poor sample. This corroborates previous results that suggested that giant planet frequency is still a rising function of the host star Fe/H. We also note that all detections in the overall sample are giant long-period planets.
Low-resolution spectroscopy obtained with FORS2 at the Very Large Telescope (VLT) has been used for the measurement of individual metal abundances (Fe/H) for 110 variable stars, including 107 RR ...Lyrae stars and one anomalous Cepheid, and to trace the metal distribution of the oldest stellar component in the Sculptor dwarf spheroidal galaxy. The RR Lyrae stars are spread over a 15 × 15 arcmin2 area around the galaxy centre. Their metallicities have an average value of Fe/H = −1.83 ± 0.03 (rms = 0.26 dex) and cover the metallicity range −2.40 < Fe/H < −0.85 (on the scale of Zinn & West), but there is only one variable that has Fe/H > −1.3. The star-to-star scatter is larger than typical errors on individual metallicities (±0.15–0.16 dex), indicating a real spread in metal abundances. The radial velocities measured from the RR Lyrae spectra have a dispersion of 12.9 km s−1. This value is consistent with the dispersion derived by Tolstoy et al. for metal-poor red giants associated with the blue horizontal branch stars in Sculptor. Along with the metallicity distribution these results suggest that most of the RR Lyrae stars in Sculptor arise from the same burst of stellar formation that produced the metal-poor component, originating the galaxy blue horizontal branch. The metal-rich red horizontal branch population found to be centrally concentrated only produced a few (if any) of the RR Lyrae stars in our sample. The spectroscopic metallicities were used along with the apparent luminosities to study the luminosity—metallicity relation followed by the RR Lyrae stars in Sculptor, for which we derive a shallow slope of 0.09 mag dex−1. This result can be due to a high level of evolution off the zero-age horizontal branch of the RR Lyrae stars in this galaxy, again in agreement with their origin from the blue horizontal branch population.
Stellar activity can be a source of radial velocity (RV) noise and can reproduce periodic RV variations similar to those produced by an exoplanet. We present the vigorous activity cycle in the ...primary of the visual binary HD 200466, a system made of two almost identical solar-type stars with an apparent separation of 4.6 arcsec at a distance of 44 ± 2 pc. High precision RV over more than a decade, adaptive optics (AO) images, and abundances have been obtained for both components. A linear trend in the RV is found for the secondary. We assumed that it is due to the binary orbit and once coupled with the astrometric data, it strongly constrains the orbital solution of the binary at high eccentricities (e ~ 0.85) and quite small periastron of ~21 AU. If this orbital motion is subtracted from the primary radial velocity curve, a highly significant (false alarm probability <0.1%) period of about 1300 d is obtained, suggesting in a first analysis the presence of a giant planet, but it turned out to be due to the stellar activity cycle. Since our spectra do not include the Ca II resonance lines, we measured a chromospheric activity indicator based on the Hα line to study the correlation between activity cycles and long-term activity variations. While the bisector analysis of the line profile does not show a clear indication of activity, the correlation between the Hα line indicator and the RV measurements identify the presence of a strong activity cycle.
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