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Fuelled by space photometry, asteroseismology is vastly benefitting the study of cool main-sequence stars, which exhibit convection-driven solar-like oscillations. Even so, the tiny oscillation amplitudes in K dwarfs continue to pose a challenge to space-based asteroseismology. A viable alternative is offered by the lower stellar noise over the oscillation timescales in Doppler observations. In this letter we present the definite detection of solar-like oscillations in the bright K5 dwarf $\epsilon$ Indi based on time-intensive observations collected with the ESPRESSO spectrograph at the VLT, thus making it the coolest seismic dwarf ever observed. We measured the frequencies of a total of 19 modes of degree $\ell=0$--2 along with $\nu_{\rm max}=5305\pm176\:{\rm \mu Hz}$ and $\Delta\nu=201.25\pm0.16\:{\rm \mu Hz}$. The peak amplitude of radial modes is $2.6\pm0.5\:{\rm cm\,s^{-1}}$, or a mere ${\sim} 14\%$ of the solar value. Measured mode amplitudes are ${\sim} 2$ times lower than predicted from a nominal $L/M$ scaling relation and favour a scaling closer to $(L/M)^{1.5}$ below ${\sim} 5500\:{\rm K}$, carrying important implications for our understanding of the coupling efficiency between pulsations and near-surface convection in K dwarfs. This detection conclusively shows that precise asteroseismology of cool dwarfs is possible down to at least the mid-K regime using next-generation spectrographs on large-aperture telescopes, effectively opening up a new domain in observational asteroseismology., Comment: Accepted for publication in Astronomy & Astrophysics Letters

High-contrast eclipsing binaries with low mass M-dwarf secondaries are precise benchmark stars to build empirical mass-radius relationships for fully convective low-mass ($\rm M_{*} < 0.35\,M_{\rm sun}$) dwarf stars. The contributed light of the M-dwarf in such binaries is usually much less than one~per~cent at optical wavelengths. This enables the detection of circumbinary planets from precise radial velocity measurements. High-resolution cross-correlation techniques are typically used to detect exoplanet atmospheres. One key aspect of these techniques is the post-processing, which includes the removal of telluric and spectral lines of the host star. We introduce the application of such techniques to optical high-resolution spectra of the circumbinary planet-host TOI-1338/BEBOP-1, turning it effectively into a double-lined eclipsing binary. By using simulations, we further explore the impact of post-processing techniques for high-contrast systems. We detect the M-dwarf secondary with a significance of 11-$\sigma$ and measure absolute dynamical masses for both components. Compared to previous model-dependent mass measurements, we obtain a four times better precision. We further find that the post-processing results in negligible systematic impact on the radial velocity precision for TOI-1338/BEBOP-1 with more than $96.6\,$per~cent (1-$\sigma$) of the M-dwarf's signal being conserved. We show that these methods can be used to robustly measure dynamical masses of high-contrast single-lined binaries providing important benchmark stars for stellar evolution particularly near the bottom of the main sequence. We also demonstrate how to retrieve the phase curve of an exoplanet with high-resolution spectroscopy using our data., Comment: Accepted for publication in MNRAS, 17 pages, 13 images

We present solar low-degree rotational splitting values based on a new analysis of Sun-as-a-star observations from the Birmingham Solar Oscillations Network, covering a 16,425-day period from 1976 December 31--2021 December 20 with a duty cycle of 57 per cent. The splitting values are estimated from the power spectrum using a Markov Chain Monte Carlo sampling method, and we also present for comparison the results from an analysis of 100 realizations of synthetic data with the same resolution and gap structure. Comparison of the scatter in the results from the synthetic realizations with their estimated uncertainties suggests that for this data set the formal uncertainty estimates are about 30 per cent too small. An upward bias in the splittings at frequencies above 2200 microHz, where the components are not fully resolved, is seen in both the observed and synthetic data. When this bias is taken into account our results are consistent with a frequency-independent synodic rotational splitting value of 400 nHz., Comment: 13 pages, 14 figures, accepted by MNRAS 4th September 2023

The asteroseismic analysis of stellar power density spectra is often computationally expensive. The models used in the analysis may use several dozen parameters to accurately describe features in the spectra caused by oscillation modes and surface granulation. Many parameters are often highly correlated, making the parameter space difficult to quickly and accurately sample. They are, however, all dependent on a smaller set of parameters, namely the fundamental stellar properties. We aim to leverage this to simplify the process of sampling the model parameter space for the asteroseismic analysis of solar-like oscillators, with an emphasis on mode identification. Using a large set of previous observations, we applied principal component analysis to the sample covariance matrix to select a new basis on which to sample the model parameters. Selecting the subset of basis vectors that explains the majority of the sample variance, we redefine the model parameter prior probability density distributions in terms of a smaller set of latent parameters. We are able to reduce the dimensionality of the sampled parameter space by a factor of two to three. The number of latent parameters needed to accurately model the stellar oscillation spectra cannot be determined exactly but is likely only between four and six. Using two latent parameters, the method is able to describe the bulk features of the oscillation spectrum, while including more latent parameters allows for a frequency precision better than $\approx10\%$ of the small frequency separation for a given target. We find that sampling a lower-rank latent parameter space still allows for accurate mode identification and parameter estimation on solar-like oscillators over a wide range of evolutionary stages. This allows for the potential to increase the complexity of spectrum models without a corresponding increase in computational expense., Comment: Accepted for publication in Astronomy & Astrophysics. 11 pages. 10 figures

Using the coalescence model we compute the multiplicity of $Z_{cs} (3985)^-$ (treated as a compact tetraquark) at the end of the quark gluon plasma phase in heavy ion collisions. Then we study the time evolution of this state in the hot hadron gas phase. We calculate the thermal cross sections for the collisions of the $Z_{cs} (3985)^-$ with light mesons using effective Lagrangians and form factors derived from QCD sum rules for the vertices $Z_{cs}\bar{D}_{s }^* D $ and $Z_{cs} \bar{D}_{s} D^{*}$. We solve the kinetic equation and find how the $Z_{cs} (3985)^-$ multiplicity is affected by the considered reactions during the expansion of the hadronic matter. A comparison with the statistical hadronization model predictions is presented. Our results show that the tetraquark yield increases by a factor of about $2-3$ from the hadronization to the kinetic freeze-out. We also make predictions for the dependence of the $Z_{cs} (3985)^-$ yield on the centrality, the center-of-mass energy and the charged hadron multiplicity measured at midrapidity $ \left[ d N_{ch} / d \eta (\eta < 0.5)\right]$., Comment: 9 pages, 8 figures

We study the production of heavy multiquark states in the heavy ion collisions performed at the LHC. We assume that they are produced at the end of the quark-gluon plasma phase and then interact with light hadrons during the hadron gas phase. We use the coalescence model to compute the initial multiplicities and effective Lagrangians to describe the interactions. We find that the initial multiplicity of molecules is two orders of magnitude larger than that of tetraquarks. The interactions in the hadron gas reduce the number of molecules and increase the number of tetraquarks by a factor two in each case. At kinetic freeze-out, the difference is still very large., Comment: Talk presented at QCD22 (04-07/07/20222, Montpellier - FR). 4 pages, 3 figures

We examine the solar-cycle variation of the power in the low-degree helioseismic modes by looking at binned power spectra from 45 years of observations with the Birmingham Solar Oscillations Network, which provides a more robust estimate of the mode power than that obtained by peak fitting. The solar-cycle variation of acoustic mode power in the five-minute band is clearly seen. Unusually, even though Cycle 24 was substantially weaker in terms of surface magnetic activity than Cycle 23, the reduction in mode power at solar maximum is very similar for the two cycles, suggesting that the relationship between mode power and magnetic activity is more complex than has previously been thought. This is in contrast to the mode frequencies, which show a strong correlation with activity with only subtle differences between in the response across different solar cycles., Comment: 8 pages, 6 figures, accepted by MNRAS 27-5-22

Current and future space-based observatories such as the Transiting Exoplanet Survey Satellite (TESS) and PLATO are set to provide an enormous amount of new data on oscillating stars, and in particular stars that oscillate similar to the Sun. Solar-like oscillators constitute the majority of known oscillating stars and so automated analysis methods are becoming an ever increasing necessity to make as much use of these data as possible. Here we aim to construct an algorithm that can automatically determine if a given time series of photometric measurements shows evidence of solar-like oscillations. The algorithm is aimed at analyzing data from the TESS mission and the future PLATO mission, and in particular stars in the main-sequence and subgiant evolutionary stages. The algorithm first tests the range of observable frequencies in the power spectrum of a TESS light curve for an excess that is consistent with that expected from solar-like oscillations. In addition, the algorithm tests if a repeating pattern of oscillation frequencies is present in the time series, and whether it is consistent with the large separation seen in solar-like oscillators. Both methods use scaling relations and observations which were established and obtained during the CoRoT, Kepler, and K2 missions. Using a set of test data consisting of visually confirmed solar-like oscillators and nonoscillators observed by TESS, we find that the proposed algorithm can attain a $94.7\%$ true positive rate and a $8.2\%$ false positive rate at peak accuracy. However, by applying stricter selection criteria, the false positive rate can be reduced to $\approx2\%$, while retaining an $80\%$ true positive rate., Comment: Accepted for publication in A&A. 13 pages, 9 figures

We investigate the absorption and production processes of this new state in a hadronic medium, considering the reactions $T_{cc}^+ \pi, T_{cc}^+ \rho \rightarrow D^{(*)} D^{(*)} $ and the corresponding inverse reactions. We use effective field Lagrangians to account for the couplings between light and heavy mesons, and give special attention to the form factors in the vertices. We calculate here for the first time the $ T_{cc}^+ - D - D^*$ form factor derived from QCD sum rules. The results are also obtained by testing widely utilized empirical form factors. The absorption cross sections are found to be larger than the production ones. We compare our results with the only existing estimate of these quantities, presented in a work of J.~Hong, S.~Cho, T.~Song and S.~H.~Lee, in which the authors employed the quasi-free approximation. We find cross sections which are one order of magnitude smaller., Comment: 10 pages; 6 figures; v2: added a new Section and two Subsections with a comprehensive study of the influence of form factors on the results; empirical formulas have been tested and compared with those derived from QCD sum rules; the $ T_{cc}^+ - D - D^*$ form factor has been calculated with QCD sum rules for the first time

Supersymmetric Light Front Holographic QCD is a holographic theory, which not only describes the spectroscopy of mesons and baryons, but also predicts the existence and spectroscopy of tetraquarks. A discussion of the limitations of the theory is also presented., Comment: one reference added

Asteroseismology is an exceptional tool for studying stars by using the properties of observed modes of oscillation. So far the process of performing an asteroseismic analysis of a star has remained somewhat esoteric and inaccessible to non-experts. In this software paper we describe PBjam, an open-source Python package for analyzing the frequency spectra of solar-like oscillators in a simple but principled and automated way. The aim of PBjam is to provide a set of easy-to-use tools to extract information about the radial and quadrupole oscillations in stars that oscillate like the Sun, which may then be used to infer bulk properties such as stellar mass, radius and age or even structure. Asteroseismology and its data analysis methods are becoming increasingly important as space-based photometric observatories are producing a wealth of new data, allowing asteroseismology to be applied in a wide range of contexts such as exoplanet, stellar structure and evolution, and Galactic population studies., Comment: 12 Pages, 4 figures. Accepted for publication in AJ. Associated software available at https://doi.org/10.5281/zenodo.4300079

Since the discovery of a flux of high-energy astrophysical neutrinos, searches for their origins have focused primarily at TeV-PeV energies. Compared to sub-TeV searches, high-energy searches benefit from an increase in the neutrino cross section, improved angular resolution on the neutrino direction, and a reduced background from atmospheric neutrinos and muons. However, the focus on high energy does not preclude the existence of sub-TeV neutrino emission where IceCube retains sensitivity. Here we present the first all-flavor search from IceCube for transient emission of low-energy neutrinos, focusing on the energy region of 5.6-100 GeV using three years of data obtained with the IceCube-DeepCore detector. We find no evidence of transient neutrino emission in the data, thus leading to a constraint on the volumetric rate of astrophysical transient sources in the range of $\sim 705-2301\, \text{Gpc}^{-3}\, \text{yr}^{-1}$ for sources following a subphotospheric energy spectrum with a mean energy of 100 GeV and a bolometric energy of $10^{52}$ erg., Comment: 16 pages, 10 figures. Update from previous arXiv version reflects a change to the title, minor text edits, and additional description of the statistical derivation of the results, which were all part of the JCAP review process

The Transiting Exoplanet Survey Satellite (TESS) is observing bright known planet-host stars across almost the entire sky. These stars have been subject to extensive ground-based observations, providing a large number of radial velocity (RV) measurements. In this work we use the new TESS photometric observations to characterize the star $\lambda^2$ Fornacis, and following this to update the parameters of the orbiting planet $\lambda^2$ For b. We measure the p-mode oscillation frequencies in $\lambda^2$ For, and in combination with non-seismic parameters estimate the stellar fundamental properties using stellar models. Using the revised stellar properties and a time series of archival RV data from the UCLES, HIRES and HARPS instruments spanning almost 20 years, we refit the orbit of $\lambda^2$ For b and search the RV residuals for remaining variability. We find that $\lambda^2$ For has a mass of $1.16\pm0.03$M$_\odot$ and a radius of $1.63\pm0.04$R$_\odot$, with an age of $6.3\pm0.9$Gyr. This and the updated RV measurements suggest a mass of $\lambda^2$ For b of $16.8^{+1.2}_{-1.3}$M$_\oplus$, which is $\sim5$M$_\oplus$ less than literature estimates. We also detect a periodicity at 33 days in the RV measurements, which is likely due to the rotation of the host star. While previous literature estimates of the properties of $\lambda^2$ are ambiguous, the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase. Typically only short time series of photometric data are available from TESS, but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground. This prompts a reexamination of archival RV data from the past few decades to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible., Comment: Accepted for publication in A&A. 12 pages, 11 figures

The economic value of a photovoltaic installation depends upon both its lifetime and power conversion efficiency. Progress towards the latter includes mechanisms to circumvent the Shockley- Queisser limit, such as tandem designs and multiple exciton generation (MEG). Here we explain how both silicon tandem and MEG enhanced silicon cell architectures result in lower cell operating temperatures, increasing the device lifetime compared to standard c-Si cells. Also demonstrated are further advantages from MEG enhanced silicon cells: (i) the device architecture can completely circumvent the need for current-matching; and (ii) upon degradation, tetracene, a candidate singlet fission (a form of MEG) material, is transparent to the solar spectrum. The combination of (i) and (ii) mean that the primary silicon device will continue to operate with reasonable efficiency even if the singlet fission layer degrades. The lifespan advantages of singlet fission enhanced silicon cells, from a module perspective, are compared favorably alongside the highly regarded perovskite/silicon tandem and conventional c-Si modules., Comment: 16 pages, 4 figures

We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = $-$19.95 $\pm$ 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H$\alpha$ are also unusually high with the blue edge tracing the fastest moving gas initially at 20000 km s$^{-1}$, and then declining approximately linearly to 15000 km s$^{-1}$ over $\sim$100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H$\alpha$ absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry., Comment: 25 pages, 17 figures, Published by MNRAS. Re-uploaded to reflect published version. Changes made to Figures 1,8,11 to give more information, new figure 15 added. Changes to text to improve clarity and add additional information and analysis requested by the referee

By combining ground-based spectrographic observations of variability in the chromospheric emission from Sun-like stars with the variability seen in their eigenmode frequencies, it is possible to relate the changes observed at the surfaces of these stars to the changes taking place in the interior. By further comparing this variability to changes in the relative flux from the stars, one can obtain an expression for how these activity indicators relate to the energy output from the stars. Such studies become very pertinent when the variability can be related to stellar cycles as they can then be used to improve our understanding of the solar cycle and its effect on the energy output from the Sun. Here we present observations of chromospheric emission in 20 Sun-like stars obtained over the course of the nominal 4-year Kepler mission. Even though 4 years is too short to detect stellar equivalents of the 11-year solar cycle, observations from the Kepler mission can still be used to analyse the variability of the different activity indicators thereby obtaining information of the physical mechanism generating the variability. The analysis reveals no strong correlation between the different activity indicators, except in very few cases. We suggest that this is due to the sparse sampling of our ground-based observations on the one hand and that we are likely not tracing cyclic variability on the other hand. We also discuss how to improve the situation., Comment: accepted for publication in MNRAS

Asteroseismology has undergone a profound transformation as a scientific field following the CoRoT and Kepler space missions. The latter is now yielding the first measurements of latitudinal differential rotation obtained directly from oscillation frequencies. Differential rotation is a fundamental mechanism of the stellar dynamo effect. Our goal is to measure the amount of differential rotation in the solar analogues 16 Cyg A and B, which are the components of a binary system. These stars are the brightest observed by Kepler and have therefore been extensively observed, with exquisite precision on their oscillation frequencies. We modelled the acoustic power spectrum of 16 Cyg A and B using a model that takes into account the contribution of differential rotation to the rotational frequency splitting. The estimation was carried out in a Bayesian setting. We then inverted these results to obtain the rotation profile of both stars under the assumption of a solar-like functional form. We observe that the magnitude of latitudinal differential rotation has a strong chance of being solar-like for both stars, their rotation rates being higher at the equator than at the pole. The measured latitudinal differential rotation, defined as the difference of rotation rate between the equator and the pole, is $320\pm269$ nHz and $440^{+363}_{-383}$ nHz for 16 Cyg A and B, respectively, confirming that the rotation rates of these stars are almost solar-like. Their equatorial rotation rates are $535\pm75$ nHz and $565_{-129}^{+150}$ nHz. Our results are in good agreement with measurements obtained from spectropolarimetry, spectroscopy, and photometry. We present the first conclusive measurement of latitudinal differential rotation for solar analogues. Their rotational profiles are very close to those of the Sun. These results depend weakly on the uncertainties of the stellar parameters., Comment: Accepted in A&A

During the solar magnetic activity cycle the emergence latitudes of sunspots change, leading to the well-known butterfly diagram. This phenomenon is poorly understood for other stars as starspot latitudes are generally unknown. The related changes in starspot rotation rates caused by latitudinal differential rotation can however be measured. Using the set of 3093 Kepler stars with activity cycles identified by Reinhold et al. (2017), we aim to study the temporal change in starspot rotation rates over magnetic activity cycles, and how this relates to the activity level, mean rotation rate, and effective temperature of the star. We measure the photometric variability as a proxy for the magnetic activity and the spot rotation rate in each quarter over the duration of the Kepler mission. We phase-fold these measurements with the cycle period. We perform averages over stars with comparable mean rotation rates and effective temperature at fixed activity-cycle phases. We detect a clear correlation between the variation of activity level and the variation of the starspot rotation rate. The sign and amplitude of this correlation depends on the mean stellar rotation and, to a lesser extent, on the effective temperature. For slowly rotating stars (with periods between 15-28 days) the starspot rotation rates are clearly anti-correlated with the level of activity during the activity cycles. A transition is seen at periods of 10-15 days, where stars with effective temperature above 4200K instead show positive correlation. Our results can be interpreted in terms of a stellar "butterfly diagram", but these appear different from the Sun's as the starspot rotation rates are either in phase or anti-phase with the activity level. Alternatively, the activity cycles seen by Kepler are short (around 2.5 years) and may therefore be secondary cycles, perhaps analogous to the solar quasi-biennial oscillations., Comment: Accepted for publication in Astronomy & Astrophysics. 11 pages, 8 figures

Microlensing events can be used to directly measure the masses of single field stars to a precision of $\sim$1-10\%. The majority of direct mass measurements for stellar and sub-stellar objects typically only come from observations of binary systems. Hence microlensing provides an important channel for direct mass measurements of single stars. The Gaia satellite has observed $\sim$1.7 billion objects, and analysis of the second data release has recently yielded numerous event predictions for the next few decades. However, the Gaia catalog is incomplete for nearby very-low-mass objects such as brown dwarfs for which mass measurements are most crucial. We employ a catalog of very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens stars, and we use the objects from Gaia data release 2 (GDR2) as potential source stars. We then search for future microlensing events up to the year 2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any that are present in both catalogs. This leaves a sample of 1,718 possible lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry to estimate their masses. We then compute their paths on the sky, along with the paths of the GDR2 source objects, until the year 2070, and search for potential microlensing events. Source-lens pairs that will produce a microlensing signal with an astrometric amplitude of greater than 0.131 mas, or a photometric amplitude of greater than 0.4 mmag, are retained., Comment: 25 pages, 6 PNG figures. Accepted for publication in Acta Astronomica

Stellar magnetic fields are poorly understood but are known to be important for stellar evolution and exoplanet habitability. They drive stellar activity, which is the main observational constraint on theoretical models for magnetic field generation and evolution. Starspots are the main manifestation of the magnetic fields at the stellar surface. In this study we measure the variation of their latitude with time, called a butterfly diagram in the solar case, for the solar analogue HD 173701 (KIC 8006161). To that effect, we use Kepler data, to combine starspot rotation rates at different epochs and the asteroseismically determined latitudinal variation of the stellar rotation rates. We observe a clear variation of the latitude of the starspots. It is the first time such a diagram is constructed using asteroseismic data., Comment: 8 pages, 4 figures, accepted in A&A Letters

The differentially rotating outer layers of stars are thought to play a role in driving their magnetic activity, but the underlying mechanisms that generate and sustain differential rotation are poorly understood. We report the measurement of latitudinal differential rotation in the convection zones of 40 Sun-like stars using asteroseismology. For the most significant detections, the stars' equators rotate approximately twice as fast as their mid-latitudes. The latitudinal shear inferred from asteroseismology is much larger than predictions from numerical simulations., Comment: 45 pages, 11 figures, 4 tables, published in Science

We present an early-phase $g$-band light curve and visual-wavelength spectra of the normal Type Ia supernova (SN) 2013gy. The light curve is constructed by determining the appropriate S-corrections to transform KAIT natural-system $B$- and $V$-band photometry and Carnegie Supernova Project natural-system $g$-band photometry to the Pan-STARRS1 $g$-band natural photometric system. A Markov Chain Monte Carlo calculation provides a best-fit single power-law function to the first ten epochs of photometry described by an exponent of $2.16^{+0.06}_{-0.06}$ and a time of first light of MJD 56629.4$^{+0.1}_{-0.1}$, which is $1.93^{+0.12}_{-0.13}$ days (i.e., $<48$~hr) before the discovery date (2013 December 4.84 UT) and $-19.10^{+0.12}_{-0.13}$ days before the time of $B$-band maximum (MJD 56648.5$\pm0.1$). The estimate of the time of first light is consistent with the explosion time inferred from the evolution of the Si II $\lambda$6355 Doppler velocity. Furthermore, discovery photometry and previous nondetection limits enable us to constrain the companion radius down to $R_c \leq 4\,R_{\odot}$. In addition to our early-time constraints, we use a deep +235 day nebular-phase spectrum from Magellan/IMACS to place a stripped H-mass limit of $< 0.018\,M_{\odot}$. Combined, these limits effectively rule out H-rich nondegenerate companions.

In this work we study the interactions of bottom mesons which lead to $\Upsilon$ production and absorption in hot hadronic matter. We use effective Lagrangians to calculate the $\Upsilon$ production cross section in processes such as $ \bar{B}^{(*)} + B^{(*)} \to \Upsilon + (\pi, \rho)$ and also the $\Upsilon$ absorption cross section in the corresponding inverse processes. We update and extend previous calculations by Lin and Ko, introducing anomalous interactions. The obtained cross sections are used as input to solve the rate equation which allows us to follow the time evolution of the $\Upsilon$ multiplicity. In contrast to previous conjectures, our results suggest that the interactions in the hadron gas phase strongly reduce the $\Upsilon$ abundance., Comment: 11 pages, 8 figures. arXiv admin note: text overlap with arXiv:1712.06019; text overlap with arXiv:1708.02913 by other authors

Using Gaia data release 2 (GDR2), we present an almanac of 2,509 predicted microlensing events, caused by 2,130 unique lens stars, that will peak between 25th July 2026 and the end of the century. This work extends and completes a thorough search for future microlensing events initiated by Bramich (2018) and Nielsen & Bramich (2018) using GDR2. The almanac includes 161 lenses that will cause at least two microlensing events each. A few highlights are presented and discussed, including: (i) an astrometric microlensing event with a peak amplitude of ~9.7 mas, (ii) an event that will probe the planetary system of a lens with three known planets, and (iii) an event (resolvable from space) where the blend of the lens and the minor source image will brighten by a detectable amount (~2 mmag) due to the appearance of the minor source image. All of the predicted microlensing events in the almanac will exhibit astrometric signals that are detectable by observing facilities with an angular resolution and astrometric precision similar to, or better than, that of the Hubble Space Telescope (e.g. NIRCam on the James Webb Space Telescope), although the events with the most extreme source-to-lens contrast ratios may be challenging. Ground-based telescopes of at least 1 m in diameter can be used to observe many of the events that are also expected to exhibit a photometric signal., Comment: Accepted AcA. Almanac available on request. arXiv admin note: text overlap with arXiv:1805.10630

In relativistic heavy ion collisions, after the quark gluon plasma (QGP) phase there is a hadron gas (HG) phase. In both phases $J/\psi$ may be formed and destroyed. In this note we study the $J/\psi$ interactions with other mesons in the hadron gas phase. Making use of effective field Lagrangians we obtain the cross sections for the production and absorption processes. With respect to the existing calculations, the improvements introduced here are the inclusion of $K$ and $K^*$'s in the effective Lagrangian approach and the inclusion of processes involving the new exotic charmonium states $Z_c(3900)$ and $Z_c(4025)$. We conclude that the interactions between $J/\psi$ and all the considered mesons reduce the original $J/\psi$ abundance ( determined at the end of the quark gluon plasma phase ) by 20 \% and 24 \% in RHIC and LHC collisions respectively. Consequently, any really significant change in the $J/\psi$ abundance comes from dissociation and regeneration processes in the QGP phase., Comment: 4 pages, 2 figures. Contribution to the Proceedings of the XIV HADRON PHYSICS, 2018, MARCH 18-23, FLORIANOPOLIS, BRAZIL

Oscillation properties are usually measured by fitting symmetric Lorentzian profiles to the power spectra of Sun-like stars. However the line profiles of solar oscillations have been observed to be asymmetrical for the Sun. The physical origin of this line asymmetry is not fully understood, although it should depend on the depth dependence of the source of wave excitation (convective turbulence) and details of the observable (velocity or intensity). For oscillations of the Sun, it has been shown that neglecting the asymmetry leads to systematic errors in the frequency determination. This could subsequently affects the results of seismic inferences of the solar internal structure. Using light curves from the {\it Kepler} spacecraft we have measured mode asymmetries in 43 stars. We confirm that neglecting the asymmetry leads to systematic errors that can exceed the $1\sigma$ confidence intervals for seismic observations longer than one year. Therefore, the application of an asymmetric Lorentzian profile is to be favoured to improve the accuracy of the internal stellar structure and stellar fundamental parameters. We also show that the asymmetry changes sign between cool Sun-like stars and hotter stars. This provides the best constraints to date on the location of the excitation sources across the Hertzsprung-Russel diagram., Comment: 8 pages, 7 Figures, 1 Table, Accepted to ApJ

In this manuscript we discuss the results of our recent study on $\Xi$ resonances. We have studied meson-baryon interaction with strangeness $-2$ by solving scattering equations in a coupled channel approach and found that the dynamics gives rise to the development of two poles in the complex plane close to the real axis. The corresponding narrow states have isospin half and spin half in one case and spin 3/2 in the other case. We find that the properties of the isospin and spin 1/2 state are strikingly similar to $\Xi(1690)$, while the state with spin 3/2 can be related to $\Xi(2120)$. We find that our results on $\Xi(1690)$ are in good agreement with the data available from the BELLE and BABAR Collaborations. Our formalism consists of treating pseudoscalar-baryon and vector-baryon channels on an equal footing. Since the thresholds of such channels are distributed over a relatively larger energy range, we obtain all interaction kernels needed to solve the Bethe-Salpeter equation without resorting to any nonrelativistic approximation even though the amplitudes are calculated at low energies., Comment: Conference proceedings for Hadron 2017 (Salamanca, Spain)

In heavy ion collisions after the quark-gluon plasma there is a hadronic gas phase. Using effective Lagrangians we study the interactions of charmed mesons which lead to $J/\psi$ production and absorption in this gas. We update and extend previous calculations introducing strange meson interactions and also including the interactions mediated by the recently measured exotic charmonium resonances $Z(3900)$ and $Z(4025)$. These resonances open new reaction channels for the $J/\psi$, which could potentially lead to changes in its multiplicity. We compute the $J/\psi$ production cross section in processes such as $D_{(s)}^{(*)} + \bar{D}^{(*)} \to J/\psi + (\pi, \rho, K, K^{\ast})$ and also the $J/\psi$ absorption cross section in the corresponding inverse processes. Using the obtained cross sections as input to solve the rate equation, we conclude that the interactions in the hadron gas phase do not significantly affect the $J/\Psi$ abundance. In other words, there is neither a charmonium suppression nor charmonium regeneration from light mesons in the hadronic phase., Comment: Corrections in the text and in the references, 14 pages 6 figures

In this work we investigate the $Z_b (10610)$ (called simply $Z_b$) abundance in the hot hadron gas produced in the late stage of heavy ion collisions. We use effective Lagrangians to calculate the thermally averaged cross sections of $Z_b $ production in processes such as $B^{(*)} + \bar{B}^{(*)} \to \pi + Z_b (10610)$ and also of its absorption in the corresponding inverse processes. We then solve the rate equation to follow the time evolution of the $Z_b$ multiplicity, and the results remarkably suggest that this quantity is not significantly affected by the considered reactions. The number of $Z_b$'s produced at the end of the quark-gluon plasma phase remains constant during the hadron phase., Comment: 6 pages, 6 figures

The most powerful tests of stellar models come from the brightest stars in the sky, for which complementary techniques, such as astrometry, asteroseismology, spectroscopy, and interferometry can be combined. The K2 Mission is providing a unique opportunity to obtain high-precision photometric time series for bright stars along the ecliptic. However, bright targets require a large number of pixels to capture the entirety of the stellar flux, and bandwidth restrictions limit the number and brightness of stars that can be observed. To overcome this, we have developed a new photometric technique, that we call halo photometry, to observe very bright stars using a limited number of pixels. Halo photometry is simple, fast and does not require extensive pixel allocation, and will allow us to use K2 and other photometric missions, such as TESS, to observe very bright stars for asteroseismology and to search for transiting exoplanets. We apply this method to the seven brightest stars in the Pleiades open cluster. Each star exhibits variability; six of the stars show what are most-likely slowly pulsating B-star (SPB) pulsations, with amplitudes ranging from 20 to 2000 ppm. For the star Maia, we demonstrate the utility of combining K2 photometry with spectroscopy and interferometry to show that it is not a 'Maia variable', and to establish that its variability is caused by rotational modulation of a large chemical spot on a 10 d time scale., Comment: Published in Monthly Notices of the Royal Astronomical Society. 20 pages, 10 figures and 10 tables

We have computed the isospin and spin averaged cross sections of the processes $\pi K^*\to \rho K$ and $\rho K^*\to \pi K$, which are crucial in the determination of the abundances of $K^*$ and $K$ in heavy ion collisions. Improving previous calculations, we have considered several mechanisms which were missing, such as the exchange of axial and vector resonances ($K_1(1270)$, $K^*_2(1430)$, $h_1(1170)$, etc...) and also other processes such as $\pi K^*\to \omega K, \phi K$ and $\omega K^*,\,\phi K^*\to \pi K$. We find that some of these mechanisms give important contributions to the cross section. Our results also suggest that, in a hadron gas, $K^*$ production might be more important than its absorption.