5 research outputs found
Fluctuation Study of the Specific Heat of MgB2
The specific heat of polycrystalline MgB has been measured with
high resolution ac calorimetry from 5 to 45 K at constant magnetic fields. The
excess specific heat above T is discussed in terms of Gaussian
fluctuations and suggests that MgB is a bulk superconductor with
Ginzburg-Landau coherence length \AA . The transition-width
broadening in field is treated in terms of lowest-Landau-level (LLL)
fluctuations. That analysis requires that \AA . The underestimate
of the coherence length in field, along with deviations from 3D LLL
predictions, suggest that there is an influence from the anisotropy of B
between the c-axis and the a-b plane.Comment: Phys. Rev. B 66, 134515 (2002
Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops
peer reviewedHIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R (HIP 9618 b) and 3.343 ± 0.039 R (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M for HIP 9618 b, which, according to our interior structure models, corresponds to a 6.8 ± 1.4 per cent gas fraction. HIP 9618 c appears to have a lower mass than HIP 9618 b, with a 3-sigma upper limit of 50 d, opening the door for the atmospheric characterization of warm (Teq < 750 K) sub-Neptunes
Applying next generation sequencing with microdroplet PCR to determine the disease-causing mutations in retinal dystrophies
Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076
Context: TOI-2076 is a transiting three-planet system of sub-Neptunes
orbiting a bright (G = 8.9 mag), young ( Myr) K-type star. Although a
validated planetary system, the orbits of the two outer planets were
unconstrained as only two non-consecutive transits were seen in TESS
photometry. This left 11 and 7 possible period aliases for each.
Aims: To reveal the true orbits of these two long-period planets, precise
photometry targeted on the highest-probability period aliases is required.
Long-term monitoring of transits in multi-planet systems can also help
constrain planetary masses through TTV measurements.
Methods: We used the MonoTools package to determine which aliases to follow,
and then performed space-based and ground-based photometric follow-up of
TOI-2076 c and d with CHEOPS, SAINT-EX, and LCO telescopes.
Results: CHEOPS observations revealed a clear detection for TOI-2076 c at
d, and allowed us to rule out three of the
most likely period aliases for TOI-2076 d. Ground-based photometry further
enabled us to rule out remaining aliases and confirm the
d alias. These observations also improved the radius precision of all three
sub-Neptunes to , , and
. Our observations also revealed a clear anti-correlated TTV signal
between planets b and c likely caused by their proximity to the 2:1 resonance,
while planets c and d appear close to a 5:3 period commensurability, although
model degeneracy meant we were unable to retrieve robust TTV masses. Their
inflated radii, likely due to extended H-He atmospheres, combined with low
insolation makes all three planets excellent candidates for future comparative
transmission spectroscopy with JWST
TESS and CHEOPS discover two warm sub-Neptunes transiting the bright K-dwarf HD 15906
peer reviewedWe report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461, TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet, HD 15906 c, showed only two transits separated by ∼ 734 d, leading to 36 possible values of its period. We performed follow-up observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the radius precision of the two planets. From TESS, CHEOPS, and additional ground-based photometry, we find that HD 15906 b has a radius of 2.24 ± 0.08 R and a period of 10.924709 ± 0.000032 d, whilst HD 15906 c has a radius of 2.93+−000607 R and a period of 21.583298+−00000055000052 d. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 ± 13 K and 532 ± 10 K, respectively. The HD 15906 system has become one of only six multiplanet systems with two warm (700 K) sub-Neptune sized planets transiting a bright star (G ≤ 10 mag). It is an excellent target for detailed characterization studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution