The Factory and the Beehive. IV. A Comprehensive Study of the Rotation X-Ray Activity Relation in Praesepe and the Hyades

X-ray observations of low-mass stars in open clusters are critical to understanding the dependence of magnetic activity on stellar properties and their evolution. Praesepe and the Hyades, two of the nearest, most-studied open clusters, are among the best available laboratories for examining the dependence of magnetic activity on rotation for stars with masses 21 M . We present an updated study of the rotation-X-ray activity relation in the two clusters. We updated membership catalogs that combine pre-Gaia catalogs with new catalogs based on Gaia Data Release 2. The resulting catalogs are the most inclusive ones for both clusters: 1739 Praesepe and 1315 Hyades stars. We collected X-ray detections for cluster members, for which we analyzed, re-analyzed, or collated data from ROSAT, the Chandra X-ray Observatory, the Neil Gehrels Swift Observatory, and XMM-Newton. We have detections for 326 Praesepe and 462 Hyades members, of which 273 and 164, respectively, have rotation periods - an increase of 6× relative to what was previously available. We find that at ≈700 Myr, only M dwarfs remain saturated in X-rays, with only tentative evidence for supersaturation. We also find a tight relation between the Rossby number and fractional X-ray luminosity L X/L bol in unsaturated single members, suggesting a power-law index between -3.2 and -3.9. Lastly, we find no difference in the coronal parameters between binary and single members. These results provide essential insight into the relative efficiency of magnetic heating of the stars' atmospheres, thereby informing the development of robust age-rotation-activity relations

Three K2 campaigns yield rotation periods for 1013 stars in Praesepe

We use three campaigns of K2 observations to complete the census of rotation in low-mass members of the benchmark, ≈670 Myr old open cluster Praesepe. We measure new rotation periods (Prot) for 220≲1.3 M☉ Praesepe members and recovery periods for 97% (793/812) of the stars with a Prot in the literature. Of the 19 stars for which we do not recover a Prot, 17 were not observed by K2. As K2’s three Praesepe campaigns took place over the course of 3 yr, we test the stability of our measured Prot for stars observed in more than one campaign. We measure Prot consistent to within 10% for >95% of the 331 likely single stars with ≥2 high-quality observations; the median difference in Prot is 0.3%, with a standard deviation of 2%. Nearly all of the exceptions are stars with discrepant Prot measurements in Campaign 18, K2’s last, which was significantly shorter than the earlier two (≈50 days rather than ≈75 days). This suggests that, despite the evident morphological evolution we observe in the light curves of 38% of the stars, Prot measurements for low-mass stars in Praesepe are stable on timescales of several years. A Prot can therefore be taken to be representative even if measured only once

KELT-25 b and KELT-26 b: A Hot Jupiter and a Substellar Companion Transiting Young A Stars Observed by TESS

We present the discoveries of KELT-25 b (TIC 65412605, TOI-626.01) and KELT-26 b (TIC 160708862, TOI-1337.01), two transiting companions orbiting relatively bright, early A stars. The transit signals were initially detected by the KELT survey and subsequently confirmed by Transiting Exoplanet Survey Satellite (TESS) photometry. KELT-25 b is on a 4.40 day orbit around the V = 9.66 star CD-24 5016 (Teff=8280-180+440 K, M ∗ = 2.18-0.11+0.12 M o˙), while KELT-26 b is on a 3.34 day orbit around the V = 9.95 star HD 134004 (Teff = 8640-240+500 K, M ∗ = 1.93-0.16+0.14 M o˙), which is likely an Am star. We have confirmed the substellar nature of both companions through detailed characterization of each system using ground-based and TESS photometry, radial velocity measurements, Doppler tomography, and high-resolution imaging. For KELT-25, we determine a companion radius of R P = 1.64-0.043+0.039 R J and a 3σ upper limit on the companion's mass of ∼64 M J. For KELT-26 b, we infer a planetary mass and radius of M P = 1.41-0.51+0.43MJ and R P = 1.94-0.058+0.060 R J. From Doppler tomographic observations, we find KELT-26 b to reside in a highly misaligned orbit. This conclusion is weakly corroborated by a subtle asymmetry in the transit light curve from the TESS data. KELT-25 b appears to be in a well-aligned, prograde orbit, and the system is likely a member of the cluster Theia 449

The Mass of the Milky Way from the H3 Survey

The mass of the Milky Way is a critical quantity that, despite decades of research, remains uncertain within a factor of two. Until recently, most studies have used dynamical tracers in the inner regions of the halo, relying on extrapolations to estimate the mass of the Milky Way. In this paper, we extend the hierarchical Bayesian model applied in Eadie & Juri to study the mass distribution of the Milky Way halo; the new model allows for the use of all available 6D phase-space measurements. We use kinematic data of halo stars out to 142 kpc, obtained from the H3 survey and Gaia EDR3, to infer the mass of the Galaxy. Inference is carried out with the No-U-Turn sampler, a fast and scalable extension of Hamiltonian Monte Carlo. We report a median mass enclosed within 100 kpc of (68% Bayesian credible interval), or a virial mass of , in good agreement with other recent estimates. We analyze our results using posterior predictive checks and find limitations in the model's ability to describe the data. In particular, we find sensitivity with respect to substructure in the halo, which limits the precision of our mass estimates to ∼15%. © 2022. The Author(s). Published by the American Astronomical Society..Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Orbital Clustering Identifies the Origins of Galactic Stellar Streams

The origins of most stellar streams in the Milky Way are unknown. With improved proper motions provided by Gaia EDR3, we show that the orbits of 23 Galactic stellar streams are highly clustered in orbital phase space. Based on their energies and angular momenta, most streams in our sample can plausibly be associated with a specific (disrupted) dwarf galaxy host that brought them into the Milky Way. For eight streams we also identify likely globular cluster progenitors (four of these associations are reported here for the first time). Some of these stream progenitors are surprisingly far apart, displaced from their tidal debris by a few to tens of degrees. We identify stellar streams that appear spatially distinct, but whose similar orbits indicate they likely originate from the same progenitor. If confirmed as physical discontinuities, they will provide strong constraints on the mass loss from the progenitor. The nearly universal ex situ origin of existing stellar streams makes them valuable tracers of galaxy mergers and dynamical friction within the Galactic halo. Their phase-space clustering can be leveraged to construct a precise global map of dark matter in the Milky Way, while their internal structure may hold clues to the small-scale structure of dark matter in their original host galaxies. © 2021. The American Astronomical Society. All rights reserved..Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy

We report the discovery of Specter, a disrupted ultrafaint dwarf galaxy revealed by the H3 Spectroscopic Survey. We detected this structure via a pair of comoving metal-poor stars at a distance of 12.5 kpc, and further characterized it with Gaia astrometry and follow-up spectroscopy. Specter is a 25° × 1° stream of stars that is entirely invisible until strict kinematic cuts are applied to remove the Galactic foreground. The spectroscopic members suggest a stellar age τ ≳ 12 Gyr and a mean metallicity 〈 [ Fe / H ] 〉 = − 1.84 − 0.18 + 0.16 , with a significant intrinsic metallicity dispersion σ [ Fe / H ] = 0.37 − 0.13 + 0.21 . We therefore argue that Specter is the disrupted remnant of an ancient dwarf galaxy. With an integrated luminosity M V ≈ −2.6, Specter is by far the least-luminous dwarf galaxy stream known. We estimate that dozens of similar streams are lurking below the detection threshold of current search techniques, and conclude that spectroscopic surveys offer a novel means to identify extremely low surface brightness structures. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Discovery of magellanic stellar debris in the H3 survey

We report the discovery of 15 stars in the H3 survey that lie, in projection, near the tip of the trailing gaseous Magellanic Stream (MS). The stars have Galactocentric velocities <−155 km s−1, Galactocentric distances of ≈40 to 80 kpc (increasing along the MS), and [Fe/H] consistent with that of stars in the Small Magellanic Cloud. These 15 stars comprise 94% (15 of 16) of the H3 observed stars to date that have RGAL > 37.5 kpc, −350 km s−1 < VGSR < −155 km s−1, and are not associated with the Sagittarius Stream. They represent a unique portion of the Milky Way's outer halo phase space distribution function and confirm that unrelaxed structure is detectable even at radii where H3 includes only a few hundred stars. Due to their statistical excess, their close association with the MS and HI compact clouds in the same region, both in position and velocity space, and their plausible correspondence with tidal debris in a published simulation, we identify these stars as debris of past Magellanic Cloud encounters. These stars are evidence for a stellar component of the tidal debris field far from the Clouds themselves and provide unique constraints on the interaction. © 2020. The American Astronomical Society. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A deep proper-motion survey of the nearby open cluster Blanco 1ltlink href

We provide two comprehensive catalogues of positions and proper motions in the area of open cluster Blanco 1. The main catalogue, CtlgM, contains 6271 objects down to V∼ 18.5 and covers a circular ∼11 deg 2 area. The accuracy of CtlgM proper motions, at about 0.3-0.5masyr -1 for well-measured stars, permits an excellent segregation between the cluster and field stars. The vector-point diagram of proper motions indicates an estimated total of ∼165 cluster members among the stars in our sample, while 314 stars with σ μ < 2.5masyr -1 have membership probabilities P μ≥ 1 per cent. We also explored the astrometric potential of the Catalogue of Objects and Measured Parameters from All Sky Surveys (COMPASS) data base in order to obtain additional proper motions for fainter stars in the area of Blanco 1. This effort produced the second catalogue of proper motions, CtlgD, containing 11598 objects down to V∼ 21. A total of 4273 objects are common between the two catalogues. The accuracy of proper motions in CtlgD ranges from 1.0 to 6masyr -1. A combination of both proper-motion catalogues was instrumental in confirming that Blanco 1 contains a large population of M dwarfs (∼150 down to M5V - the limit of our survey). In many respects, Blanco 1 is a scaled down 'twin' of the Pleiades. The noted discrepancy between the distance from a new Hipparcos parallax of Blanco 1 and the cluster's photometric distance, at least partially, might be due to the apparent correlation between parallax and proper motion in right ascension for the ensemble of cluster members. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Two planets straddling the habitable zone of the nearby K dwarf Gl 414A

We present the discovery of two planets orbiting the nearby (D = 11.9 pc) K7 dwarf Gl 414A. Gl 414A b is a sub- Neptune mass planet with = Mb sin ib 7.60+2.44-2.19 M⊗ and a semimajor axis of 0.23 ± 0.01 au. Gl 414A c is a sub-Saturn mass planet with = Mc sin ic 53.83+9.18-8.58M⊗ and a semimajor axis of 1.43 ± 0.06 au. We jointly analyzed radial velocity data from Keck/HIRES and the Automated Planet Finder at Lick Observatory, as well as photometric data from KELT, to detect the two planets and two additional signals related to the rotationally modulated activity and the long-term magnetic activity cycle of the star. The outer planet in this system may be a potential candidate for future direct-imaging missions. © 2021. The American Astronomical Society. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Effects of diclofenac and dexamethasone on horse experimental endotoxemia Efeitos do diclofenaco e da dexametasona na endotoxemia experimental em eqüinos

Fifteen healthy Mangalarga horses, aged two to three years were used to evaluate the possible beneficial effects of dexamethasone and sodium diclofenac administration during experimental endotoxemia in horses. They were divided into three groups with five animals each: control (C), sodium diclofenac (SD) and dexamethasone (DM). All groups were given 0.1µg of Escherichia coli O55:B5 endotoxin/kg of body weight, intravenous, over 15 minutes, and one of the following preparations: group C - 20ml of 0.9% saline intravenous, 30 minutes before endoxin infusion; group SD - 2.2mg/kg, per os, 60 minutes before endotoxin infusion and group DM - 1.1 mg/kg, intravenous, 30 minutes before endotoxin infusion. No increase in rectal temperature was observed in the SD or DM treated groups. SD did not prevent the significant leukopenia, neutropenia and lymphopenia induced three hours after LPS injection, but DM attenuated these changes. No significant changes in plasma and peritoneal fluid total protein, inorganic phosphorus or glucose concentrations and in total nucleated cell count in peritoneal fluid were observed. SD was effective to prevent the fever and changes in intestinal borborygmi and DM blocked the cellular changes induced by experimental endotoxemia.<br>Quinze eqüinos machos, da raça Mangalarga, com idades entre dois e três anos, foram utilizados para se avaliar os possíveis efeitos clínicos benéficos da administração de dexametasona ou diclofenaco sódico durante a endotoxemia experimental em eqüinos. Os animais foram divididos em três grupos de cinco animais cada: controle (C), diclofenaco sódico (SD) e dexametasona (DM). Todos os grupos receberam 0,1µg/kg de lipopolissarídeo de Escherichia coli 055:B5, durante 15 minutos, por via intravenosa mais: grupo SD - 2,2mg/kg de SD, por via oral, 60 minutos antes da infusão da endotoxina; grupo DM - 1,1mg/kg, por via intravenosa, 30 minutos antes da endotoxina; grupo C - 20ml de NaCl 0,9%, por via intravenosa, 30 minutos antes da endotoxina. O SD não preveniu a leucopenia, neutropenia e linfopenia ocorridas três horas após a indução da endotoxemia, porém a DM atenuou essas alterações. As taxas de proteínas plasmática e peritoneal, a concentração de glicose e de fósforo inorgânico e a contagem de células nucleadas totais peritoneais mantiveram-se inalteradas. O diclofenaco foi eficaz na prevenção da febre e alterações nos borborigmos intestinais enquanto que a dexametasona bloqueou as alterações no número de células inflamatórias em relação ao grupo controle