We present the metallicity results from the ARGOS spectroscopic survey of the Galactic bulge. Our aim is to understand the formation of the Galactic bulge: did it form via mergers, as expected from Λ ...cold dark matter theory, or from disc instabilities, as suggested by its boxy/peanut shape, or both? Our stars are mostly red clump giants, which have a well-defined absolute magnitude from which distances can be determined. We have obtained spectra for 28 000 stars at a spectral resolution of R = 11 000. From these spectra, we have determined stellar parameters and distances to an accuracy of <1.5 kpc. The stars in the inner Galaxy span a large range in Fe/H, −2.8 ≤ Fe/H ≤ +0.6. From the spatial distribution of the red clump stars as a function of Fe/H, we propose that the stars with Fe/H > −0.5 are part of the boxy/peanut bar/bulge. We associate the lower metallicity stars (Fe/H < −0.5) with the thick disc, which may be puffed up in the inner region, and with the inner regions of the metal-weak thick disc and inner halo. For the bulge stars with Fe/H > −0.5, we find two discrete populations: (i) stars with Fe/H −0.25 which provide a roughly constant fraction of the stars in the latitude interval b = −5° to −10°, and (ii) a kinematically colder, more metal-rich population with mean Fe/H +0.15 which is more prominent closer to the plane. The changing ratio of these components with latitude appears as a vertical abundance gradient of the bulge. We attribute both of these bulge components to instability-driven bar/bulge formation from the thin disc. We associate the thicker component with the stars of the early less metal-rich thin disc, and associate the more metal-rich population concentrated to the plane with the colder more metal-rich stars of the early thin disc, similar to the colder and younger more metal-rich stars seen in the thin disc in the solar neighbourhood today. We do not exclude a weak underlying classical merger-generated bulge component, but see no obvious kinematic association of any of our bulge stars with such a classical bulge component. The clear spatial and kinematic separation of the two bulge populations (i) and (ii) makes it unlikely that any significant merger event could have affected the inner regions of the Galaxy since the time when the bulge-forming instabilities occurred.
Context. With seven planets, the TRAPPIST-1 system has among the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its ...planets orbit in the habitable zone of the ultracool M dwarf. Aims. We aim to determine interior structures for each planet and estimate the temperatures of their rock mantles due to a balance between tidal heating and convective heat transport to assess their habitability. We also aim to determine the precision in mass and radius necessary to determine the planets’ compositions. Methods. Assuming the planets are composed of uniform-density noncompressible materials (iron, rock, H2O), we determine possible compositional models and interior structures for each planet. We also construct a tidal heat generation model using a single uniform viscosity and rigidity based on each planet’s composition. Results. The compositions for planets b, c, d, and e remain uncertain given the error bars on mass and radius. With the exception of TRAPPIST-1c, all have densities low enough to indicate the presence of significant H2O. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have surface eruptions of silicate magma, potentially detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are twenty times higher than Earth’s mean heat flow. Conclusions. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is ≳0.3. Determining the planet’s masses within ~0.1–0.5 Earth masses would confirm or rule out the presence of H2O and/or iron. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.
We present the kinematic results from our ARGOS spectroscopic survey of the Galactic bulge of the Milky Way. Our aim is to understand the formation of the Galactic bulge. We examine the kinematics of ...about 17 400 stars in the bulge located within 3.5 kpc of the Galactic Centre, identified from the 28 000 star ARGOS survey. We aim to determine if the formation of the bulge has been internally driven from disc instabilities as suggested by its boxy shape, or if mergers have played a significant role as expected from lambda cold dark matter simulations. From our velocity measurements across latitudes b = −5°, − 7
5 and −10° we find the bulge to be a cylindrically rotating system that transitions smoothly out into the disc. From observations of 3 fields at b = +10, the kinematics of the bulge show North-South symmetry about the major axis. Within the bulge, we find a kinematically distinct metal-poor population (Fe/H < −1.0) that is not rotating cylindrically. The 5 per cent of our stars with Fe/H < −1.0 are a slowly rotating spheroidal population, which we believe are stars of the metal-weak thick disc and halo which presently lie in the inner Galaxy. The kinematics of the two bulge components that we identified in ARGOS Paper III (mean Fe/H −0.25 and Fe/H +0.15, respectively) demonstrate that they are likely to share a common formation origin and are distinct from the more metal-poor populations of the thick disc and halo which are co-located inside the bulge. We do not exclude an underlying merger generated bulge component but our results favour bulge formation from instabilities in the early thin disc.
The inflammation is an important biological response induced by various harmful stimuli, like viruses, bacterial infections, toxins, toxic compounds, tissue injury. During inflammation inflammatory ...cytokines and reactive oxygen species are produced. Inflammatory cytokines act on various receptors present on the plasma membrane of target cells. To initiate signaling cascade, and activate transcription factors, receptors should be internalized and enter the early endosomes, where the members of the signaling cascade can meet. The further cytoplasmic fate of the receptor plays crucial role in the progression and the course of inflammation. Usually acute inflammation removes injurious stimuli and helps to regain the normal healthy status of the organism. In contrast to this the uncontrolled chronic inflammation-stimulating other than immune cells, inducing transdifferentiation-can provide base of various serious diseases. This paper draws the attention of the long-lasting consequence of chronic inflammation, pointing out that one of the most important step in medication is to identify in time the factors initiating and maintaining inflammation.
Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and ...removal of tidal heat by solid-state convection. Aims. Here we compute the heat flux due to insolation and tidal heating for the inner four planets. Methods. We apply a Maxwell viscoelastic rheology to compute the tidal response of the planets using the volume-weighted average of the viscosities and rigidities of the metal, rock, high-pressure ice, and liquid water/ice I layers. Results. We show that TRAPPIST-1d and e can avoid entering a runaway greenhouse state. Planet e is the most likely to support a habitable environment, with Earth-like surface temperatures and possibly liquid water oceans. Planet d also avoids a runaway greenhouse, if its surface reflectance is at least as high as that of the Earth. Planets b and c, closer to the star, have heat fluxes high enough to trigger a runaway greenhouse and to support volcanism on the surfaces of their rock layers, rendering them too warm for life. Planets f, g, and h are too far from the star to experience significant tidal heating, and likely have solid ice surfaces with possible subsurface liquid water oceans.
Most aspects of stellar evolution proceed far too slowly to be directly observable in a single star on human timescales. The thermally pulsing asymptotic giant branch (AGB) is one exception. The ...combination of state-of-the-art modeling techniques with data assimilated from observations collected by amateur astronomers over many decades provide, for the first time, the opportunity to identify a star occupying this precise evolutionary stage. In this study, we show that the rapid pulsation period change and the associated reduction in radius in the bright, northern variable star T Ursae Minoris are caused by the recent onset of a thermal pulse (TP). We demonstrate that T UMi transitioned into a double-mode pulsation state, and we exploit its asteroseismic features to constrain its fundamental stellar parameters. We use evolutionary models from MESA and linear pulsation models from GYRE to track simultaneously the structural and oscillatory evolution of models with varying mass, and we apply a sophisticated iterative sampling scheme to achieve time resolution ≤10 yr at the onset of the relevant TPs. We report an initial mass of 2.0 0.15 M and an age of 1.17 0.21 Gyr for T UMi. This is the most precise mass and age determination for a single AGB star ever obtained. The ultimate test of our models will be the continued observation of its evolution in real time: we predict that the pulsation periods in T UMi will continue shortening for a few decades before they rebound and begin to lengthen again, as the star expands in radius.
We present fully covered phased light curves for 56 Jovian Trojan asteroids as observed by the K2 mission of the Kepler space telescope. This set of objects has been monitored during Campaign 6 and ...represents a nearly unbiased subsample of the population of small solar system bodies. We derived precise periods and amplitudes for all Trojans, and found their distributions to be compatible with the previous statistics. We point out, however, that ground-based rotation periods are often unreliable above 20 h, and we find an overabundance of rotation periods above 60 h compared with other minor planet populations. From amplitude analysis we derive a rate of binarity of 20 ± 5%. Our spin rate distribution confirms the previously obtained spin barrier of ~5 h and the corresponding ~0.5 g cm-3 cometary-like density limit, also suggesting a high internal porosity for Jovian Trojans. One of our targets, asteroid 65227 exhibits a double rotation period, which can either be due to binarity or the outcome of a recent collision.
Context. Because the second reaction wheel failed, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 mission, the telescope is staring at the plane ...of the Ecliptic. Thousands of solar system bodies therefore cross the K2 fields and usually cause additional noise in the highly accurate photometric data. Aims. We here follow the principle that some person’s noise is another person’s signal and investigate the possibility of deriving continuous asteroid light curves. This is the first such endeavor. In general, we are interested in the photometric precision that the K2 mission can deliver on moving solar system bodies. In particular, we investigate space photometric optical light curves of main-belt asteroids. Methods. We studied the K2 superstamps that cover the fields of M35, and Neptune together with Nereid, which were observed in the long-cadence mode (29.4 min sampling). Asteroid light curves were generated by applying elongated apertures. We used the Lomb-Scargle method to determine periodicities that are due to rotation. Results. We derived K2 light curves of 924 main-belt asteroids in the M35 field and 96 in the path of Neptune and Nereid. The light curves are quasi-continuous and several days long. K2 observations are sensitive to longer rotational periods than typical ground-based surveys. Rotational periods are derived for 26 main-belt asteroids for the first time. The asteroid sample is dominated by faint objects (>20 mag). Owing to the faintness of the asteroids and the high density of stars in the M35 field, only 4.0% of the asteroids with at least 12 data points show clear periodicities or trends that signal a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach ~60% to successfully recover rotational periods.
Despite the existence of many short-period hot Jupiters, there is not one hot Neptune with an orbital period less than 2.5 days. Here, we discuss a cluster analysis of the currently known 106 ...transiting exoplanets to investigate a possible explanation for this observation. We find two distinct clusters in the mass-density space, one with hot Jupiters with a wide range of orbital periods (0.8-114 days) and a narrow range of planet radii (1.2 ? 0.2 RJ ) and another one with a mixture of super-Earths, hot Neptunes, and hot Jupiters, exhibiting a surprisingly narrow period distribution (3.7 ? 0.8 days). These two clusters follow strikingly different distributions in the period-radius parameter plane. The branch of sub-Jupiter mass exoplanets is censored by the orbital period at the large-radius end: no planets with mass between 0.02 and 0.8 MJ or with radius between 0.25 and 1.0 RJ are known with P orb < 2.5 days. This clustering is not predicted by current theories of planet formation and evolution, which we also review briefly.
ABSTRACT Kepler-13Ab (KOI-13) is an exoplanet orbiting a rapidly rotating A-type star. The system shows a significant spin–orbit misalignment and a changing transit duration most probably caused by ...the precession of the orbit. Here, we present a self-consistent analysis of the system combining Kepler and Transiting Exoplanet Survey Satellite (TESS) observations. We model the light curves assuming a planet transits a rotating oblate star that has a strong surface temperature gradient due to rotation-induced gravity darkening. The transit chord moves slowly as an emergent feature of orbital precession excited by the oblate star with a decline rate in the impact parameter of db/dt = −0.011 yr−1, and with an actual value of b = 0.19 for the latest TESS measurements. The changing transit duration that was measured from Kepler Q2 and Q17 quarters and the TESS measurements indicates a linear drift of the impact parameter. The solutions for the stellar spin axis suggest a nearly orthogonal aspect, with inclination around 100°.
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