67 research outputs found
Oscillations in the Sun with SONG: Setting the scale for asteroseismic investigations
Context. We present the first high-cadence multi-wavelength radial-velocity
observations of the Sun-as-a-star, carried out during 57 consecutive days using
the stellar \'echelle spectrograph at the Hertzsprung SONG Telescope operating
at the Teide Observatory. Aims. The aim was to produce a high-quality data set
and reference values for the global helioseismic parameters {\nu_{max}}, and
{\Delta \nu} of the solar p-modes using the SONG instrument. The obtained data
set or the inferred values should then be used when the scaling relations are
applied to other stars showing solar-like oscillations which are observed with
SONG or similar instruments. Methods. We used different approaches to analyse
the power spectrum of the time series to determine {\nu_{max}}; simple Gaussian
fitting and heavy smoothing of the power spectrum. {\Delta\nu} was determined
using the method of autocorrelation of the power spectrum. The amplitude per
radial mode was determined using the method described in Kjeldsen et al.
(2008). Results. We found the following values for the solar oscillations using
the SONG spectrograph: {\nu_{max}} = 3141 {\pm} 12 {\mu}Hz, {\Delta\nu} =
134.98 {\pm} 0.04 {\mu}Hz and an average amplitude of the strongest radial
modes of 16.6 {\pm} 0.4 cm/s. These values are consistent with previous
measurements with other techniques.Comment: 5 pages, 5 figures, letter accepted for A&
EPIC 219217635: A Doubly Eclipsing Quadruple System Containing an Evolved Binary
We have discovered a doubly eclipsing, bound, quadruple star system in the
field of K2 Campaign 7. EPIC 219217635 is a stellar image with that
contains an eclipsing binary (`EB') with d and a second EB with
d. We have obtained followup radial-velocity (`RV')
spectroscopy observations, adaptive optics imaging, as well as ground-based
photometric observations. From our analysis of all the observations, we derive
good estimates for a number of the system parameters. We conclude that (1) both
binaries are bound in a quadruple star system; (2) a linear trend to the RV
curve of binary A is found over a 2-year interval, corresponding to an
acceleration, cm s; (3) small
irregular variations are seen in the eclipse-timing variations (`ETVs')
detected over the same interval; (4) the orbital separation of the quadruple
system is probably in the range of 8-25 AU; and (5) the orbital planes of the
two binaries must be inclined with respect to each other by at least
25. In addition, we find that binary B is evolved, and the cooler and
currently less massive star has transferred much of its envelope to the
currently more massive star. We have also demonstrated that the system is
sufficiently bright that the eclipses can be followed using small ground-based
telescopes, and that this system may be profitably studied over the next decade
when the outer orbit of the quadruple is expected to manifest itself in the ETV
and/or RV curves.Comment: Accepted for publication in MNRA
Cold Jupiters and improved masses in 38 Kepler and K2 small planet systems from 3661 HARPS-N radial velocities. No excess of cold Jupiters in small planet systems
The exoplanet population characterized by relatively short orbital periods
( d) around solar-type stars is dominated by super-Earths and
sub-Neptunes. However, these planets are missing in our Solar System and the
reason behind this absence is still unknown. Two theoretical scenarios invoke
the role of Jupiter as the possible culprit: Jupiter may have acted as a
dynamical barrier to the inward migration of sub-Neptunes from beyond the water
iceline; alternatively, Jupiter may have reduced considerably the inward flux
of material (pebbles) required to form super-Earths inside that iceline. Both
scenarios predict an anti-correlation between the presence of small planets
(SPs) and that of cold Jupiters (CJs) in exoplanetary systems. To test that
prediction, we homogeneously analyzed the radial-velocity (RV) measurements of
38 Kepler and K2 transiting SP systems gathered over almost 10 years with the
HARPS-N spectrograph, as well as publicly available RVs collected with other
facilities. We detected five CJs in three systems, two in Kepler-68, two in
Kepler-454, and a very eccentric one in K2-312. We derived an occurrence rate
of for CJs with and 1-10 AU, which is
lower but still compatible at with that measured from RV surveys
for solar-type stars, regardless of the presence or absence of SPs. The sample
is not large enough to draw a firm conclusion about the predicted
anti-correlation between SPs and CJs; nevertheless, we found no evidence of
previous claims of an excess of CJs in SP systems. As an important by-product
of our analyses, we homogeneously determined the masses of 64 Kepler and K2
small planets, reaching a precision better than 5, 7.5 and 10 for 25,
13 and 8 planets, respectively. Finally, we release the 3661 HARPS-N radial
velocities used in this work to the scientific community. [Abridged]Comment: 21 pages, 10 figures, 10 tables, published in Astronomy and
Astrophysics. The updated version of the article takes into account the A&A
language editing and guidelines. Tables 1, A.1 and full Table 2 are available
at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/677/A3
Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here, we wish to determine the age and metallicity content of the open cluster NGC 2506. To this end, we investigated three detached eclipsing binaries (DEBs; V2032, V4, and V5) for which we determined their masses and radii, as well as four red giant branch stars for which we determined their effective temperatures, surface gravities, and metallicities. Three of the stars in the DEBs have masses close to the cluster turn-off mass, allowing for extremely precise age determination. Comparing the values for the masses and radii of the binaries to BaSTI (a Bag of Stellar Tracks and Isochrones) isochrones, we estimated a cluster age of 2.01 ± 0.10 Gyr. This does depend on the models used in the comparison, where we have found that the inclusion of convective core-overshooting is necessary to properly model the cluster. From red giant branch stars, we determined values for the effective temperatures, the surface gravities, and the metallicities. From these we find a cluster metallicity of −0.36 ± 0.10 dex. Using this value and the values for the effective temperatures, we determine the reddening to be E(b − y) = 0.057 ± 0.004 mag. Furthermore, we derived the distance to the cluster from Gaia parallaxes and found 3.101 ± 0.017 kpc, and we have performed a radial velocity membership determination for stars in the field of the cluster. Finally, we report on the detection of oscillation signals in γ Dor and δ Scuti members in data from the Transiting Exoplanet Survey Satellite (TESS) mission, including the possible detection of solar-like oscillations in two of the red giants.Funding for the Stellar
Astrophysics Centre is provided by The Danish National Research
Foundation (Grant agreement no.: DNRF106). ELS gratefully acknowledges support from the (U.S.) National Science Foundation
under grant AST 1817217. This work has made use of data from
the European Space Agency (ESA) mission Gaia (https://www.
cosmos.esa.int/gaia), processed by the Gaia Data Processing and
Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gai
a/dpac/consortium). Funding for the DPAC has been provided by
national institutions, in particular the institutions participating in
the Gaia Multilateral Agreement. This research has made use of
the VizieR catalogue access tool, CDS, Strasbourg, France
Cold Jupiters and improved masses in 38 Kepler and K2 small-planet systems from 3661 high-precision HARPS-N radial velocities. No excess of cold Jupiters in small-planet systems
The exoplanet population characterized by relatively short orbital periods
( d) around solar-type stars is dominated by super-Earths and
sub-Neptunes. However, these planets are missing in our Solar System and the
reason behind this absence is still unknown. Two theoretical scenarios invoke
the role of Jupiter as the possible culprit: Jupiter may have acted as a
dynamical barrier to the inward migration of sub-Neptunes from beyond the water
iceline; alternatively, Jupiter may have reduced considerably the inward flux
of material (pebbles) required to form super-Earths inside that iceline. Both
scenarios predict an anti-correlation between the presence of small planets
(SPs) and that of cold Jupiters (CJs) in exoplanetary systems. To test that
prediction, we homogeneously analyzed the radial-velocity (RV) measurements of
38 Kepler and K2 transiting SP systems gathered over almost 10 years with the
HARPS-N spectrograph, as well as publicly available RVs collected with other
facilities. We detected five CJs in three systems, two in Kepler-68, two in
Kepler-454, and a very eccentric one in K2-312. We derived an occurrence rate
of for CJs with and 1-10 AU, which is
lower but still compatible at with that measured from RV surveys
for solar-type stars, regardless of the presence or absence of SPs. The sample
is not large enough to draw a firm conclusion about the predicted
anti-correlation between SPs and CJs; nevertheless, we found no evidence of
previous claims of an excess of CJs in SP systems. As an important by-product
of our analyses, we homogeneously determined the masses of 64 Kepler and K2
small planets, reaching a precision better than 5, 7.5 and 10 for 25,
13 and 8 planets, respectively. Finally, we release the 3661 HARPS-N radial
velocities used in this work to the scientific community. [Abridged]Comment: 21 pages, 10 figures, 10 tables, published in Astronomy and
Astrophysics. The updated version of the article takes into account the A&A
language editing and guidelines. Tables 1, A.1 and full Table 2 are available
at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/677/A3
TOI-4641b: An Aligned Warm Jupiter Orbiting a Bright (V=7.5) Rapidly Rotating F-star
We report the discovery of TOI-4641b, a warm Jupiter transiting a rapidly
rotating F-type star with a stellar effective temperature of 6560 K. The planet
has a radius of 0.73 , a mass smaller than 3.87 ,
and a period of 22.09 days. It is orbiting a bright star (V=7.5 mag) on a
circular orbit with a radius and mass of 1.73 and 1.41 .
Follow-up ground-based photometry was obtained using the Tierras Observatory.
Two transits were also observed with the Tillinghast Reflector Echelle
Spectrograph (TRES), revealing the star to have a low projected spin-orbit
angle (= degrees). Such obliquity measurements
for stars with warm Jupiters are relatively few, and may shed light on the
formation of warm Jupiters. Among the known planets orbiting hot and
rapidly-rotating stars, TOI-4641b is one of the longest-period planets to be
thoroughly characterized. Unlike hot Jupiters around hot stars which are more
often misaligned, the warm Jupiter TOI-4641b is found in a well-aligned orbit.
Future exploration of this parameter space can add one more dimension to the
star-planet orbital obliquity distribution that has been well-sampled for hot
Jupiters.Comment: Accepted MNRA
Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
Accurate stellar parameters of stars in open clusters can help constrain
models of stellar structure and evolution. Here we wish to determine the age
and metallicity content of the open cluster NGC 2506. To this end we
investigated three detached eclipsing binaries (DEBs; V2032, V4, and V5) for
which we determined their masses and radii, as well as four red giant branch
stars for which we determined their effective temperatures, surface gravities,
and metallicities. Three of the stars in the DEBs have masses close to the
cluster turn-off mass, allowing for extremely precise age determination.
Comparing the values for the masses and radii of the binaries to BaSTI
isochrones we estimated a cluster age of Gyr. This does depend
on the models used in the comparison, where we have found that the inclusion of
convective core-overshooting is necessary to properly model the cluster. From
red giant branch stars we determined values for the effective temperatures, the
surface gravities, and the metallicities. From these we find a cluster
metallicity of dex. Using this value and the values for the
effective temperatures we determine the reddening to be E mag. Furthermore, we derived the distance to the cluster from Gaia
parallaxes and found kpc, and we have performed a radial
velocity membership determination for stars in the field of the cluster.
Finally, we report on the detection of oscillation signals in Dor and
Scuti members in data from the TESS mission, including the possible
detection of solar-like oscillations in two of the red giants.Comment: 30 pages, 16 figures, accepted for publication in MNRA
Revisiting the warm sub-Saturn TOI-1710b
The Transiting Exoplanet Survey Satellite (TESS) provides a continuous suite
of new planet candidates that need confirmation and precise mass determination
from ground-based observatories. This is the case for the G-type star TOI-1710,
which is known to host a transiting sub-Saturn planet
(28.34.7) in a long-period orbit
(P=24.28\,d). Here we combine archival SOPHIE and new and archival HARPS-N
radial velocity data with newly available TESS data to refine the planetary
parameters of the system and derive a new mass measurement for the transiting
planet, taking into account the impact of the stellar activity on the mass
measurement. We report for TOI-1710b a radius of
5.150.12, a mass of
18.44.5, and a mean bulk density of
0.730.18, which are consistent at
1.2, 1.5, and 0.7, respectively, with previous
measurements. Although there is not a significant difference in the final mass
measurement, we needed to add a Gaussian process component to successfully fit
the radial velocity dataset. This work illustrates that adding more
measurements does not necessarily imply a better mass determination in terms of
precision, even though they contribute to increasing our full understanding of
the system. Furthermore, TOI-1710b joins an intriguing class of planets with
radii in the range 4-8 that have no counterparts in the
Solar System. A large gaseous envelope and a bright host star make TOI-1710b a
very suitable candidate for follow-up atmospheric characterization.Comment: Accepted for publication in A&A. 21 pages, 14 figure
Physical properties and transmission spectrum of the WASP-74 planetary system from multi-band photometry
We present broad-band photometry of eleven planetary transits of the hot Jupiter WASP-74 b, using three medium-class telescopes and employing the telescope-defocussing technique. Most of the transits were monitored through I filters and one was simultaneously observed in five optical (U,g′,r′,i′,z′) and three near infrared (J, H, K) passbands, for a total of 18 light curves. We also obtained new high-resolution spectra of the host star. We used these new data to review the orbital and physical properties of the WASP-74 planetary system. We were able to better constrain the main system characteristics, measuring smaller radius and mass for both the hot Jupiter and its host star than previously reported in the literature. Joining our optical data with those taken with the HST in the near infrared, we built up an observational transmission spectrum of the planet, which suggests the presence of strong optical absorbers, as TiO and VO gases, in its atmosphere
High-precision photometry by telescope defocussing - VIII.WASP-22, WASP-41,WASP-42 andWASP-55
We present 13 high-precision and four additional light curves of four bright southernhemisphere transiting planetary systems: WASP-22, WASP-41, WASP-42 and WASP-55. In the cases of WASP-42 and WASP-55, these are the first follow-up observations since their discovery papers. We present refined measurements of the physical properties and orbital ephemerides of all four systems. No indications of transit timing variations were seen. All four planets have radii inflated above those expected from theoretical models of gas-giant planets; WASP-55 b is the most discrepant with a mass of 0.63MJup and a radius of 1.34 RJup. WASP-41 shows brightness anomalies during transit due to the planet occulting spots on the stellar surface. Two anomalies observed 3.1 d apart are very likely due to the same spot. We measure its change in position and determine a rotation period for the host star of 18.6 ± 1.5 d, in good agreement with a published measurement from spot-induced brightness modulation, and a sky-projected orbital obliquity of λ = 6 ± 11°. We conclude with a compilation of obliquity measurements from spot-tracking analyses and a discussion of this technique in the study of the orbital configurations of hot Jupiters
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