Abstract
We report the discovery and characterization of TOI-1759 b, a temperate (400 K) sub-Neptune-sized exoplanet orbiting the M dwarf TOI-1759 (TIC 408636441). TOI-1759 b was observed by TESS to ...transit in Sectors 16, 17, and 24, with only one transit observed per sector, creating an ambiguity regarding the orbital period of the planet candidate. Ground-based photometric observations, combined with radial-velocity measurements obtained with the CARMENES spectrograph, confirm an actual period of 18.85019 ± 0.00014 days. A joint analysis of all available photometry and radial velocities reveals a radius of 3.17 ± 0.10
R
⊕
and a mass of 10.8 ± 1.5
M
⊕
. Combining this with the stellar properties derived for TOI-1759 (
R
⋆
= 0.597 ± 0.015
R
⊙
;
M
⋆
= 0.606 ± 0.020
M
⊙
;
T
eff
= 4065 ± 51 K), we compute a transmission spectroscopic metric (TSM) value of over 80 for the planet, making it a good target for transmission spectroscopy studies. TOI-1759 b is among the top five temperate, small exoplanets (
T
eq
< 500 K,
R
p
< 4
R
⊕
) with the highest TSM discovered to date. Two additional signals with periods of 80 days and >200 days seem to be present in our radial velocities. While our data suggest both could arise from stellar activity, the later signal’s source and periodicity are hard to pinpoint given the ∼200 days baseline of our radial-velocity campaign with CARMENES. Longer baseline radial-velocity campaigns should be performed in order to unveil the true nature of this long-period signal.
J. of Astronomical Telescopes, Instruments, and Systems, 5(1),
015001 (2018) We report the development of a 4-color simultaneous camera for the 1.52~m
Telescopio Carlos S\'anchez (TCS) in the Teide ...Observatory, Canaries, Spain.
The new instrument, named MuSCAT2, has a capability of 4-color simultaneous
imaging in $g$ (400--550 nm), $r$ (550--700 nm), $i$ (700--820 nm), and $z_s$
(820--920 nm) bands. MuSCAT2 equips four 1024$\times$1024 pixel CCDs, having a
field of view of 7.4$\times$7.4 arcmin$^2$ with a pixel scale of 0.44 arcsec
per pixel. The principal purpose of MuSCAT2 is to perform high-precision
multi-color exoplanet transit photometry. We have demonstrated photometric
precisions of 0.057%, 0.050%, 0.060%, and 0.076% as root-mean-square residuals
of 60~s binning in $g$, $r$, $i$ and $z_s$ bands, respectively, for a G0 V star
WASP-12 ($V=11.57\pm0.16$). MuSCAT2 has started science operations since
January 2018, with over 250 telescope nights per year. MuSCAT2 is expected to
become a reference tool for exoplanet transit observations, and will
substantially contribute to the follow-up of the TESS and PLATO space missions.
We report the development of a 4-color simultaneous camera for the 1.52~m Telescopio Carlos Sánchez (TCS) in the Teide Observatory, Canaries, Spain. The new instrument, named MuSCAT2, has a ...capability of 4-color simultaneous imaging in \(g\) (400--550 nm), \(r\) (550--700 nm), \(i\) (700--820 nm), and \(z_s\) (820--920 nm) bands. MuSCAT2 equips four 1024\(\times\)1024 pixel CCDs, having a field of view of 7.4\(\times\)7.4 arcmin\(^2\) with a pixel scale of 0.44 arcsec per pixel. The principal purpose of MuSCAT2 is to perform high-precision multi-color exoplanet transit photometry. We have demonstrated photometric precisions of 0.057%, 0.050%, 0.060%, and 0.076% as root-mean-square residuals of 60~s binning in \(g\), \(r\), \(i\) and \(z_s\) bands, respectively, for a G0 V star WASP-12 (\(V=11.57\pm0.16\)). MuSCAT2 has started science operations since January 2018, with over 250 telescope nights per year. MuSCAT2 is expected to become a reference tool for exoplanet transit observations, and will substantially contribute to the follow-up of the TESS and PLATO space missions.
Astron.Astrophys. 393 (2002) L85-L88 We report on the finding of the strongest H(alpha) emission -pseudoequivalent
width of 705 Angstrom- known so far in a young, late type dwarf. This object,
named ...as SOri71, is a substellar candidate member of the 1-8 Myr star cluster
sigma Orionis. Due to its overluminous location in color-magnitude diagrams,
SOri71 might be younger than other cluster members, or a binary of similar
components. Its mass is in the range 0.021-0.012 M(sun), depending on
evolutionary models and possible binarity. The broad H(alpha) line of SOri71
appears asymmetric, indicative of high velocity mass motions in the H(alpha)
forming region. The origin of this emission is unclear at the present time. We
discuss three possible scenarios: accretion from a disk, mass exchange between
the components of a binary system, and emission from a chromosphere.
We report on the finding of the strongest H(alpha) emission -pseudoequivalent width of 705 Angstrom- known so far in a young, late type dwarf. This object, named as SOri71, is a substellar candidate ...member of the 1-8 Myr star cluster sigma Orionis. Due to its overluminous location in color-magnitude diagrams, SOri71 might be younger than other cluster members, or a binary of similar components. Its mass is in the range 0.021-0.012 M(sun), depending on evolutionary models and possible binarity. The broad H(alpha) line of SOri71 appears asymmetric, indicative of high velocity mass motions in the H(alpha) forming region. The origin of this emission is unclear at the present time. We discuss three possible scenarios: accretion from a disk, mass exchange between the components of a binary system, and emission from a chromosphere.
The ESA space mission Euclid was launched on July 1st, 2023 and is undergoing its science verification phase. In this invited review we show that Euclid means a before and an after for our ...understanding of ultra-cool dwarfs and substellar-mass objects and their connections with stars, exoplanets and the Milky Way. Euclid enables the study with unprecedented statistical significance a very large ensemble of ultracool dwarfs, the identification of new types of substellar objects, and the determination of the substellar binary fraction and the Initial Mass Function (IMF) in diverse galactic environments from the nearest stellar nurseries to the ancient relics of Galactic formation.
We report the discovery and characterization of TOI-1759~b, a temperate (400 K) sub-Neptune-sized exoplanet orbiting the M~dwarf TOI-1759 (TIC 408636441). TOI-1759 b was observed by TESS to transit ...on sectors 16, 17 and 24, with only one transit observed per sector, creating an ambiguity on the orbital period of the planet candidate. Ground-based photometric observations, combined with radial-velocity measurements obtained with the CARMENES spectrograph, confirm an actual period of \(18.85019 \pm 0.00014\) d. A joint analysis of all available photometry and radial velocities reveal a radius of \(3.17 \pm 0.10\,R_\oplus\) and a mass of \(10.8 \pm 1.5\,M_\oplus\). Combining this with the stellar properties derived for TOI-1759 (\(R_\star = 0.597 \pm 0.015\,R_\odot\); \(M_\star = 0.606 \pm 0.020\,M_\odot\); \(T_{\textrm{eff}} = 4065 \pm 51\) K), we compute a transmission spectroscopic metric (TSM) value of over 80 for the planet, making it a good target for transmission spectroscopy studies. TOI-1759 b is among the top five temperate, small exoplanets (\(T_\textrm{eq} < 500\) K, \(R_p < 4 \,R_\oplus\)) with the highest TSM discovered to date. Two additional signals with periods of 80 d and \(>\) 200 d seem to be present in our radial velocities. While our data suggest both could arise from stellar activity, the later signal's source and periodicity are hard to pinpoint given the \(\sim 200\) d baseline of our radial-velocity campaign with CARMENES. Longer baseline radial-velocity campaigns should be performed in order to unveil the true nature of this long period signal.
VLT/FORS spectroscopy and 2MASS near-infrared photometry, together with
previously known data, have been used to establish the membership and the
properties of a sample of low-mass candidate members ...of the sigma Orionis
cluster with masses spanning from 1 Msun down to about 0.013 Msun (i.e.,
deuterium-burning mass limit). We have observed K-band infrared excess and
remarkably intense H(alpha) emission in various cluster members, which, in
addition to the previously detected forbidden emision lines and the presence of
LiI in absorption at 6708 A, have allowed us to tentatively classify sigma
Orionis members as classical or weak-line TTauri stars and substellar analogs.
Variability of the H(alpha) line has been investigated and detected in some
objects. Based on the K-band infrared excesses and the intensity of H(alpha)
emission, we estimate that the minimum disk frequency of the sigma Orionis
low-mass population is in the range 5-12%.
VLT/FORS spectroscopy and 2MASS near-infrared photometry, together with previously known data, have been used to establish the membership and the properties of a sample of low-mass candidate members ...of the sigma Orionis cluster with masses spanning from 1 Msun down to about 0.013 Msun (i.e., deuterium-burning mass limit). We have observed K-band infrared excess and remarkably intense H(alpha) emission in various cluster members, which, in addition to the previously detected forbidden emision lines and the presence of LiI in absorption at 6708 A, have allowed us to tentatively classify sigma Orionis members as classical or weak-line TTauri stars and substellar analogs. Variability of the H(alpha) line has been investigated and detected in some objects. Based on the K-band infrared excesses and the intensity of H(alpha) emission, we estimate that the minimum disk frequency of the sigma Orionis low-mass population is in the range 5-12%.
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