2,220 research outputs found
A vigorous activity cycle mimicking a planetary system in HD200466
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
HD200466, 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 Halpha 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
Halpha line indicator and the RV measurements identify the presence of a strong
activity cycle.Comment: Accepted on Astronomy and Astrophysics Main Journal 2014, 16 pages,
18 figure
The GAPS programme with HARPS-N@TNG IV: A planetary system around XO-2S
We performed an intensive radial velocity monitoring of XO-2S, the wide
companion of the transiting planet-host XO-2N, using HARPS-N at TNG in the
framework of the GAPS programme. The radial velocity measurements indicate the
presence of a new planetary system formed by a planet that is slightly more
massive than Jupiter at 0.48 au and a Saturn-mass planet at 0.13 au. Both
planetary orbits are moderately eccentric and were found to be dynamically
stable. There are also indications of a long-term trend in the radial
velocities. This is the first confirmed case of a wide binary whose components
both host planets, one of which is transiting, which makes the XO-2 system a
unique laboratory for understanding the diversity of planetary systems.Comment: 7 pages, 3 figures, accepted on A&A Lette
The GAPS Programme with HARPS-N@TNG IX. The multi-planet system KELT-6: detection of the planet KELT-6 c and measurement of the Rossiter-McLaughlin effect for KELT-6 b
Aims. For more than 1.5 years we monitored spectroscopically the star KELT-6
(BD+312447), known to host the transiting hot Saturn KELT-6b, because a
previously observed long-term trend in radial velocity time series suggested
the existence of an outer companion. Methods. We collected a total of 93 new
spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit of
KELT-6b was observed with HARPS-N, and simultaneous photometry was obtained
with the IAC-80 telescope. Results. We proved the existence of an outer planet
with a mininum mass Msini=3.710.21 M and a
moderately eccentric orbit () of period P3.5
years. We improved the orbital solution of KELT-6b and obtained the first
measurement of the Rossiter-McLaughlin effect, showing that the planet has a
likely circular, prograde, and slightly misaligned orbit, with a projected
spin-orbit angle =3611 degrees. We improved the KELT-6b
transit ephemeris from photometry, and we provided new measurements of the
stellar parameters. KELT-6 appears as an interesting case to study the
formation and evolution of multi-planet systems.Comment: Letter, 4 figures, accepted for publication in A&A. Some language
editing and numbering of the paper series changed (from X to IX
The GAPS Programme with HARPS-N@TNG XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets
We carried out a Bayesian homogeneous determination of the orbital parameters
of 231 transiting giant planets (TGPs) that are alone or have distant
companions; we employed DE-MCMC methods to analyse radial-velocity (RV) data
from the literature and 782 new high-accuracy RVs obtained with the HARPS-N
spectrograph for 45 systems over 3 years. Our work yields the largest sample of
systems with a transiting giant exoplanet and coherently determined orbital,
planetary, and stellar parameters. We found that the orbital parameters of TGPs
in non-compact planetary systems are clearly shaped by tides raised by their
host stars. Indeed, the most eccentric planets have relatively large orbital
separations and/or high mass ratios, as expected from the equilibrium tide
theory. This feature would be the outcome of high-eccentricity migration (HEM).
The distribution of , where and are the semi-major axis
and the Roche limit, for well-determined circular orbits peaks at 2.5; this
also agrees with expectations from the HEM. The few planets of our sample with
circular orbits and values may have migrated through disc-planet
interactions instead of HEM. By comparing circularisation times with stellar
ages, we found that hot Jupiters with au have modified tidal quality
factors are
required to explain the presence of eccentric planets at the same orbital
distance. As a by-product of our analysis, we detected a non-zero eccentricity
for HAT-P-29; we determined that five planets that were previously regarded to
have hints of non-zero eccentricity have circular orbits or undetermined
eccentricities; we unveiled curvatures caused by distant companions in the RV
time series of HAT-P-2, HAT-P-22, and HAT-P-29; and we revised the planetary
parameters of CoRoT-1b.Comment: 44 pages (16 pages of main text and figures), 11 figures, 5
longtables, published in Astronomy and Astrophysics, Volume 602, A107 (2017).
Tables with new HARPS-N and TRES radial-velocity data (Tables 1 and 2),
stellar parameters (Table 7), orbital parameters and RV jitter (Table 8), and
planet physical parameters (Table 9) are available as ancillary files
(sidebar on the right
Asteroseismology of Procyon A with SARG at TNG
We present high precision radial velocity measurements on the F5 IV star
alpha CMi obtained by the SARG spectrograph at TNG (Telescopio Nazionale
Galileo) exploiting the iodine cell technique. The time series of about 950
spectra of Procyon A taken during 6 observation nights are affected by an
individual error of 1.3 m/s. Thanks to the iodine cell technique, the
spectrograph contribution to the Doppler shift measurement error is quite
negligible and our error is dominated by the photon statistics Brown et al
1994. An excess of power between 0.5 and 1.5 mHz, detected also by Martic et
al. 2004 has been found. We determined a large separation frequency Delta nu0 =
56\pm 2 microHz, consistent with both theoretical estimates Chaboyer et al.
1999 and previous observations Martic et al. 2004.Comment: 4 pages, 5 figures, accepted to be published in A&A Letter
Discovery of a bipolar and highly variable mass outflow from the symbiotic binary StHa 190
A highly and rapidly variable bipolar mass outflow from StHa 190 has been
discovered, the first time in a yellow symbiotic star. Permitted emission lines
are flanked by symmetrical jet features and multi-component P-Cyg profiles,
with velocities up to 300 km/sec. Given the high orbital inclination of the
binary, if the jets leave the system nearly perpendicular to the orbital plane,
the de-projected velocity equals or exceeds the escape velocity (1000 km/sec).
StHa190 looks quite peculiar in many other respects: the hot component is an
O-type sub-dwarf without an accretion disk or a veiling nebular continuum and
the cool component is a G7 III star rotating at a spectacular 105 km/sec unseen
by a large margin in field G giants.Comment: Letter to the Editor, Astron.Astrophys, in pres
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
Oscillations in Procyon A: First results from a multi-site campaign
Procyon A is a bright F5IV star in a binary system. Although the distance,
mass and angular diameter of this star are all known with high precision, the
exact evolutionary state is still unclear. Evolutionary tracks with different
ages and different mass fractions of hydrogen in the core pass, within the
errors, through the observed position of Procyon A in the Hertzsprung-Russell
diagram. For more than 15 years several different groups have studied the
solar-like oscillations in Procyon A to determine its evolutionary state.
Although several studies independently detected power excess in the
periodogram, there is no agreement on the actual oscillation frequencies yet.
This is probably due to either insufficient high-quality data (i.e., aliasing)
or due to intrinsic properties of the star (i.e., short mode lifetimes). Now a
spectroscopic multi-site campaign using 10 telescopes world-wide (minimizing
aliasing effects) with a total time span of nearly 4 weeks (increase the
frequency resolution) is performed to identify frequencies in this star and
finally determine its properties and evolutionary state.Comment: 7 pages, 4 figures to be published in the proceedings of HELAS II
International Conference: Helioseismology, Asteroseismology and MHD
Connections published in the Journal of Physics: Conference Series. High
resolution colour figures can be provided on reques
SOXS: a wide band spectrograph to follow up transients
SOXS (Son Of X-Shooter) will be a spectrograph for the ESO NTT telescope
capable to cover the optical and NIR bands, based on the heritage of the
X-Shooter at the ESO-VLT. SOXS will be built and run by an international
consortium, carrying out rapid and longer term Target of Opportunity requests
on a variety of astronomical objects. SOXS will observe all kind of transient
and variable sources from different surveys. These will be a mixture of fast
alerts (e.g. gamma-ray bursts, gravitational waves, neutrino events), mid-term
alerts (e.g. supernovae, X-ray transients), fixed time events (e.g. close-by
passage of minor bodies). While the focus is on transients and variables, still
there is a wide range of other astrophysical targets and science topics that
will benefit from SOXS. The design foresees a spectrograph with a
Resolution-Slit product ~ 4500, capable of simultaneously observing over the
entire band the complete spectral range from the U- to the H-band. The limiting
magnitude of R~20 (1 hr at S/N~10) is suited to study transients identified
from on-going imaging surveys. Light imaging capabilities in the optical band
(grizy) are also envisaged to allow for multi-band photometry of the faintest
transients. This paper outlines the status of the project, now in Final Design
Phase.Comment: 12 pages, 14 figures, to be published in SPIE Proceedings 1070
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