Search

An upgrade of the COSINE-100 experiment, COSINE-100U, has been prepared for installation at Yemilab, a new underground laboratory in Korea, following 6.4 years of operation at the Yangyang Underground Laboratory. The COSINE-100 experiment aimed to investigate the annual modulation signals reported by the DAMA/LIBRA but observed a null result, revealing a more than 3$\sigma$ discrepancy. COSINE-100U seeks to explore new parameter spaces for dark matter detection using NaI(Tl) detectors. All eight NaI(Tl) crystals, with a total mass of 99.1 kg, have been upgraded to improve light collection efficiency, significantly enhancing dark matter detection sensitivity. This paper describes the detector upgrades, performance improvements, and the enhanced sensitivity to low-mass dark matter detection in the COSINE-100U experiment., Comment: 14 pages, 17 figures

For over 25 years, the DAMA/LIBRA collaboration has claimed to observe an annual modulation signal, suggesting the existence of dark matter interactions. However, no other experiments have replicated their result using different detector materials. To address this puzzle, the COSINE-100 collaboration conducted a model-independent test using 106 kg of sodium iodide as detectors, the same target material as DAMA/LIBRA. Analyzing data collected over 6.4 years, with improved energy calibration and time-dependent background description, we found no evidence of an annual modulation signal, challenging the DAMA/LIBRA result with a confidence level greater than 3$\sigma$. This finding represents a significant step toward resolving the long-standing debate surrounding DAMA/LIBRA's dark matter claim, indicating that the observed modulation is unlikely to be caused by dark matter interactions.

COSINE-100 is a direct dark matter search experiment, with the primary goal of testing the annual modulation signal observed by DAMA/LIBRA, using the same target material, NaI(Tl). In previous analyses, we achieved the same 1 keV energy threshold used in the DAMA/LIBRA's analysis that reported an annual modulation signal with 11.6$\sigma$ significance. In this article, we report an improved analysis that lowered the threshold to 0.7 keV, thanks to the application of Multi-Layer Perception network and a new likelihood parameter with waveforms in the frequency domain. The lower threshold would enable a better comparison of COSINE-100 with new DAMA results with a 0.75 keV threshold and account for differences in quenching factors. Furthermore the lower threshold can enhance COSINE-100's sensitivity to sub-GeV dark matter searches.

COSINE-100 aims to conclusively test the claimed dark matter annual modulation signal detected by DAMA/LIBRA collaboration. DAMA/LIBRA has released updated analysis results by lowering the energy threshold to 0.75 keV through various upgrades. They have consistently claimed to have observed the annual modulation. In COSINE-100, it is crucial to lower the energy threshold for a direct comparison with DAMA/LIBRA, which also enhances the sensitivity of the search for low-mass dark matter, enabling COSINE-100 to explore this area. Therefore, it is essential to have a precise and quantitative understanding of the background spectrum across all energy ranges. This study expands the background modeling from 0.7 to 4000 keV using 2.82 years of COSINE-100 data. The modeling has been improved to describe the background spectrum across all energy ranges accurately. Assessments of the background spectrum are presented, considering the nonproportionality of NaI(Tl) crystals at both low and high energies and the characteristic X-rays produced by the interaction of external backgrounds with materials such as copper. Additionally, constraints on the fit parameters obtained from the alpha spectrum modeling fit are integrated into this model. These improvements are detailed in the paper.

We report on the critical influence of small-scale flow structures (e.g., fronts, vortices, and waves) that immediately arise in hot-exoplanet atmosphere simulations initialized with a resting state. A hot, 1:1 spin-orbit synchronized Jupiter is used here as a clear example; but, the phenomenon is generic and important for any type of hot synchronized planet--gaseous, oceanic, or telluric. When the early-time structures are not captured in simulations (due to, e.g., poor resolution and/or too much dissipation), the flow behavior is markedly different at later times--in an observationally significant way; for example, the flow at large-scale is smoother and much less dynamic. This results in the temperature field, and its corresponding thermal flux, to be incorrectly predicted in numerical simulations, even when the quantities are spatially averaged., Comment: 9 pages, 4 figures, submitted to ApJ Letters

We present a comprehensive study of the nonproportionality of NaI(Tl) scintillation detectors within the context of dark matter search experiments. Our investigation, which integrates COSINE-100 data with supplementary $\gamma$ spectroscopy, measures light yields across diverse energy levels from full-energy $\gamma$ peaks produced by the decays of various isotopes. These $\gamma$ peaks of interest were produced by decays supported by both long and short-lived isotopes. Analyzing peaks from decays supported only by short-lived isotopes presented a unique challenge due to their limited statistics and overlapping energies, which was overcome by long-term data collection and a time-dependent analysis. A key achievement is the direct measurement of the 0.87 keV light yield, resulting from the cascade following electron capture decay of $^{22}$Na from internal contamination. This measurement, previously accessible only indirectly, deepens our understanding of NaI(Tl) scintillator behavior in the region of interest for dark matter searches. This study holds substantial implications for background modeling and the interpretation of dark matter signals in NaI(Tl) experiments., Comment: 12 pages, 7 figures

COSINE-100 is a dark matter direct detection experiment with 106 kg NaI(Tl) as the target material. 210Pb and daughter isotopes are a dominant background in the WIMP region of interest and are detected via beta decay and alpha decay. Analysis of the alpha channel complements the background model as observed in the beta/gamma channel. We present the measurement of the quenching factors and Monte Carlo simulation results and activity quantification of the alpha decay components of the COSINE-100 NaI(Tl) crystals. The data strongly indicate that the alpha decays probabilistically undergo two possible quenching factors but require further investigation. The fitted results are consistent with independent measurements and improve the overall understanding of the COSINE-100 backgrounds. Furthermore, the half-life of 216Po has been measured to be 143.4 +/- 1.2 ms, which is consistent with and more precise than recent measurements.

Most current models of hot-exoplanet atmospheres assume shallow heating, a strong day-night differential heating near the top of the atmosphere. Here we investigate the effects of energy deposition at differing depths in a model tidally locked gas-giant exoplanet. We perform high-resolution atmospheric flow simulations of hot-exoplanet atmospheres forced with idealized thermal heating representative of shallow and deep heating (i.e., stellar irradiation strongly deposited at $\sim 10^3$ Pa and $\sim 10^5$ Pa pressure levels, respectively). Unlike with shallow heating, the flow with deep heating exhibits a new dynamic equilibrium state, characterized by repeated generation of giant cyclonic storms that move away westward once formed. The formation is accompanied by a burst of heightened turbulence, leading to the production of small-scale flow structures and large-scale mixing of temperature on a timescale of $\sim 3$ planetary rotations. Significantly, while effects that could be important (e.g., coupled radiative flux and convectively excited gravity waves) are not included, over a timescale of several hundred days the simulations robustly show that the emergent thermal flux depends strongly on the heating type and is distinguishable by current observations., Comment: Published in Physical Review Letters

We investigate modons on tidally synchronised extrasolar planets. Modons are highly dynamic, coherent flow structures composed of a pair of storms with opposite signs of vorticity. They are important because they divert flows on the large-scale; and, powered by the intense irradiation from the host star, they are planetary-scale sized and exhibit quasi-periodic life-cycles -- chaotically moving around the planet, breaking and reforming many times over long durations (e.g. thousands of planet days). Additionally, modons transport and mix planetary-scale patches of hot and cold air around the planet, leading to high-amplitude and quasi-periodic signatures in the disc-averaged temperature flux. Hence, they induce variations of the "hot spot" longitude to either side of the planet's sub-stellar point -- consistent with observations at different epoch. The variability behaviour in our simulations broadly underscores the importance of accurately capturing vortex dynamics in extrasolar planet atmosphere modelling, particularly in understanding current observations., Comment: Accepted for publication in MNRAS

Observations of hot-Jupiter atmospheres show large variations in the location of the hot spot and the amplitude of spectral features. Atmospheric flow simulations using the commonly-employed forcing and initialization have generally produced a large, monolithic patch of stationary hot area located eastward of the substellar point at $\sim 3\!\times\! 10^{-3}$ MPa pressure level. Here we perform high-resolution (up to T682) pseudospectral simulations that accurately capture small-scale eddies and waves, inherent in hot-Jupiter atmospheres due to ageostrophy. The atmospheres contain a large number of intense storms over a wide range of scales, including the planetary-scale. The latter sized storms dictate the large-scale spatial distribution and temporal variability of hot, as well as cold, regions over the planet. In addition, the large storms exhibit quasi-periodic life cycles within multiple equilibrium states -- all identifiable in the disk-integrated time series of the temperature flux., Comment: Accepted for publication in ApJ Letters

We review the recent progress in understanding the jet structures on exoplanets as well as on and inside the Sun. The emphasis is on the more robust aspects of observation and numerical modeling that relate directly to jets. For the exoplanets, the primary focus is on hot-Jupiters since many more observations are available for them presently than other types of exoplanets. Because not much is known about the morphology and strength of the jets on exoplanets, there is currently not much agreement. In contrast, the picture is very different for the Sun. In fact, the jet structure of the Sun is arguably one of the best known jet structures of all the planets and stars, due to the fact that Sun's disk is resolved and its interior can be probed with helioseismology. A discussion of several critical issues pertaining to the modeling of jets on exoplanets and the Sun is presented, along with a brief outlook on the subject.

We perform an extensive study of numerical convergence for hot-Jupiter atmospheric flow solutions in simulations employing a setup commonly-used in extrasolar planet studies, a resting state thermally forced to a prescribed temperature distribution on a short time-scale at high altitudes. Convergence is assessed rigorously with: (i) a highly-accurate pseudospectral model which has been explicitly verified to perform well under hot-Jupiter flow conditions and (ii) comparisons of the kinetic energy spectra, instantaneous (unaveraged) vorticity fields and temporal evolutions of the vorticity field from simulations which are numerically equatable. In the simulations, the (horizontal and vertical) resolutions, dissipation operator order and viscosity coefficient are varied with identical physical and initial setups. All of the simulations are compared against a fiducial, reference simulation at high horizontal resolution and dissipation order (T682 and $\nabla^{16}$, respectively) -- as well as against each other. Broadly, the reference solution features a dynamic, zonally (east-west) asymmetric jet with a copious amount of small-scale vortices and gravity waves. Here we show that simulations converge to the reference simulation only at T341 resolution and with $\nabla^{16}$ dissipation order. Below this resolution and order, simulations either do not converge or converge to unphysical solutions. The general convergence behaviour is independent of the vertical range of the atmosphere modelled, from $\sim\! 2\!\times\! 10^{-3}$ MPa to $\sim\! 2\!\times\! 10^1$ MPa. Ramifications for current extrasolar planet atmosphere modelling and observations are discussed., Comment: 17 pages, 9 figures, accepted for publication in MNRAS

We revisit the issue of sensitivity to initial flow and intrinsic variability in hot-Jupiter atmospheric flow simulations, originally investigated by Cho et al. (2008) and Thrastarson & Cho (2010). The flow in the lower region (~1 to 20 MPa) `dragged' to immobility and uniform temperature on a very short timescale, as in Liu & Showman (2013), leads to effectively a complete cessation of variability as well as sensitivity in three-dimensional (3D) simulations with traditional primitive equations. Such momentum (Rayleigh) and thermal (Newtonian) drags are, however, ad hoc for 3D giant planet simulations. For 3D hot-Jupiter simulations, which typically already employ strong Newtonian drag in the upper region, sensitivity is not quenched if only the Newtonian drag is applied in the lower region, without the strong Rayleigh drag: in general, both sensitivity and variability persist if the two drags are not applied concurrently in the lower region. However, even when the drags are applied concurrently, vertically-propagating planetary waves give rise to significant variability in the ~0.05 to 0.5 MPa region, if the vertical resolution of the lower region is increased (e.g. here with 1000 layers for the entire domain). New observations on the effects of the physical setup and model convergence in `deep' atmosphere simulations are also presented., Comment: 9 pages, 6 figures, accepted for publication in MNRAS

Strong ionization on close-in extrasolar giant planets suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive MHD that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an upper ionosphere dominated by ionization of H and He and a lower ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter the energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments [abridged]., Comment: 16 pages, 22 figures, accepted by ApJ

Data from the Galileo Probe, collected during its descent into Jupiter's atmosphere, is used to obtain a vertical profile of the zonal wind from $\mathbf{\sim 0.5}$ bar (upper troposphere) to $\mathbf{\sim 0.1\, \mu{bar}}$ (lower thermosphere) at the probe entry site. This is accomplished by constructing a map of gravity wave Lomb-Scargle periodograms as a function of altitude. The profile obtained from the map indicates that the wind speed above the visible cloud deck increases with height to $\mathbf{\sim 150}$ m\,s$\mathbf{^{-1}}$ and then levels off at this value over a broad altitude range. The location of the turbopause, as a region of wide wave spectrum, is also identified from the map. In addition, a cross-equatorial oscillation of a jet, which has previously been linked to the quasi-quadrennial oscillation in the stratosphere, is suggested by the profile., Comment: 5 pages, 4 figures. Accepted for publication in GRL

A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO -the Exoplanet Characterisation Observatory- is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. EChO will simultaneously observe a broad enough spectral region -from the visible to the mid-IR- to constrain from one single spectrum the temperature structure of the atmosphere and the abundances of the major molecular species. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules to retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures Teq up to 2000 K, to those of a few Earth masses, with Teq ~300 K. We have baselined a dispersive spectrograph design covering continuously the 0.4-16 micron spectral range in 6 channels (1 in the VIS, 5 in the IR), which allows the spectral resolution to be adapted from several tens to several hundreds, depending on the target brightness. The instrument will be mounted behind a 1.5 m class telescope, passively cooled to 50 K, with the instrument structure and optics passively cooled to ~45 K. EChO will be placed in a grand halo orbit around L2. We have also undertaken a first-order cost and development plan analysis and find that EChO is easily compatible with the ESA M-class mission framework., Comment: Accepted for publication in Experimental Astronomy, 23 pages, 15 figures

We present an analysis of seven primary transit observations of the hot Neptune GJ436b at 3.6, 4.5 and $8~\mu$m obtained with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. After correcting for systematic effects, we fitted the light curves using the Markov Chain Monte Carlo technique. Combining these new data with the EPOXI, HST and ground-based $V, I, H$ and $K_s$ published observations, the range $0.5-10~\mu$m can be covered. Due to the low level of activity of GJ436, the effect of starspots on the combination of transits at different epochs is negligible at the accuracy of the dataset. Representative climate models were calculated by using a three-dimensional, pseudo-spectral general circulation model with idealised thermal forcing. Simulated transit spectra of GJ436b were generated using line-by-line radiative transfer models including the opacities of the molecular species expected to be present in such a planetary atmosphere. A new, ab-initio calculated, linelist for hot ammonia has been used for the first time. The photometric data observed at multiple wavelengths can be interpreted with methane being the dominant absorption after molecular hydrogen, possibly with minor contributions from ammonia, water and other molecules. No clear evidence of carbon monoxide and dioxide is found from transit photometry. We discuss this result in the light of a recent paper where photochemical disequilibrium is hypothesised to interpret secondary transit photometric data. We show that the emission photometric data are not incompatible with the presence of abundant methane, but further spectroscopic data are desirable to confirm this scenario., Comment: 19 pages, 10 figures, 1 table, Astrophysical Journal in press

We report the results of de-Haas-van-Alphen (dHvA) measurements in Cd doped CeCoIn$_5$ and LaCoIn$_5$. Cd doping is known to induce an antiferromagnetic order in the heavy fermion superconductor CeCoIn$_5$, whose effect can be reversed with applied pressure. We find a slight but systematic change of the dHvA frequencies with Cd doping in both compounds, reflecting the chemical potential shift due to the addition of holes. The frequencies and effective masses are close to those found in the nominally pure compounds with similar changes apparent in the Ce and La compounds with Cd substitution. We observe no abrupt changes to the Fermi surface in the high field paramagnetic state for $x \sim x_c$ corresponding to the onset of antiferromagnetic ordering at H=0 in CeCo(In$_{1-x}$Cd$_x$)$_5$. Our results rule out $f-$electron localization as the mechanism for the tuning of the ground state in CeCoIn$_5$ with Cd doping.

The Super-Earth Explorer is an Off-Axis Space Telescope (SEE-COAST) designed for high contrast imaging. Its scientific objective is to make the physico-chemical characterization of exoplanets possibly down to 2 Earth radii >. For that purpose it will analyze the spectral and polarimetric properties of the parent starlight reflected by the planets, in the wavelength range 400-1250 nm, Comment: Accepted in Experimental Astronomy

We discuss atmosphere models of HD209458b in light of the recent day-side flux measurement of HD209458b's secondary eclipse by Spitzer-MIPS at 24 microns. In addition, we present a revised secondary eclipse IRTF upper limit at 2.2 microns which places a stringent constraint on the adjacent H2O absorption band depths. These two measurements are complementary because they are both shaped by H2O absorption and because the former is on the Wien tail of the planet's thermal emission spectrum and the latter is near the thermal emission peak. A wide range of models fit the observational data, confirming our basic understanding of hot Jupiter atmospheric physics. Although a range of models are viable, some models at the hot and cold end of the plausible temperature range can be ruled out. One class of previously unconsidered hot Jupiter atmospheric models that fit the data are those with C/O >~ 1 (as Jupiter may have), which have a significant paucity of H2O compared to solar abundance models with C/O = 0.5. The models indicate that HD209458b is in a situation intermediate between pure in situ reradiation and very efficient redistribution of heat; one which will require a careful treatment of atmospheric circulation. We discuss how future wavelength-dependent and phase-dependent observations will further constrain the atmospheric circulation regime. In the shorter term, additional planned measurements for HD209458b, especially Spitzer IRAC photometry, should lift many of the model degeneracies. Multiwavelength IR observations constrain the atmospheric structure and circulation properties of hot Jupiters and thus open a new chapter in quantitative extrasolar planetology., Comment: 12 pages, 4 figures, submitted to ApJ