Evidence for a double coronal cycle in the young solar analog iota Hor

Activity cycles are commonly found among late type stars through the chromospheric Ca II emission. Their coronal counterpart, however, remains elusive in most cases, despite of the clear X-ray cycle observed in the solar corona, spanning as much as 1.7 dex in L x . The recent discovery of a Ca II cycle in iota Hor of just 1.6 yr, the shortest to date, offered us a unique opportunity to monitor its X-ray counterpart in short time. The star offers also two more interesting properties: a planet of ~1.9 MJ orbits the star at 0.9 a.u., and with an age of only ~600 Myr and spectral type F8V, ι Hor represents a young solar analog, so its cycle might be the paradigm of the first activity cycles in the life of a solar-like star. Our XMM-Newton observations show the first coronal cycle in a single star. In good agreement with Ca II contemporaneous observations, the long term XMM-Newton light curve suggests also a long-term trend that seems to modulate the 1.6 yr cycle. Iota Hor may offer us the unique possibility to observe for the first time a double coronal cycle similar to those observed in the chromosphere of other stars

Las coronas estelares de los sistemas binarios activos

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Astrofísica y Ciencias de la Atmósfera, leída el 19-10-2001El lanzamiento del satélite espacial EUVE ha permitido por primera vez obtener espectros de alta resolución en el rango del Extremo Ultravioleta (EUV) para una amplia muestra de estrellas. En este trabajo se han incluido todos los datos disponibles de 30 estrellas de últimos tipos, observadas durante 9 años con EUVE. Los espectros obtenidos han permitido el estudio pormenorizado e la estructura coronal en 22 sistemas binarios activos y 6 estrellas aisladas. Para ello se han utilizado los espectros de estas estrellas para deducir la densidad electrónica, la distribución de la Medida de Emisión (EMD) y las escalas de tamaño de los volúmenes emisiores. El estudio de las curvas de luz ha mostrado la presencia de frecuentes fulguraciones, algunas con varios días de duración, además de la existencia de eclipses en luz EUV y modulación rotacional durante algunas fulguraciones. Se ha observado en todas las estrellas de la muestra una densidad electrónica de log Ne(cm-3)=11.5-13.5, medidos a log T(K)=7, con una tendencia al aumento de la densidad durante las fulguraciones, que también produce un incremento general de toda la EMD. El análisis de la EMD conjunta con líneas de EUEVE y IUE cubre un rango de log T(K)=4.2-7.8 y ha demostrado la presencia de una estrecha elevación en torno a log T (K)=6.9, que de forma sorprendente se encuentra en la mayoría de las estrellas, independientemente de factores como la clase de luminosidad, el periodo de rotación o la edad de la estrella, y que permanece en la misma posición incluso durante las fulguraciones. La forma de la EMD es interpretada en función del balance de dos o tres tipos de bucles coronales que podrían justificar parcialmente la EMD observada, y abre muchas cuestiones interesantes para futuros estudios teóricosDepto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu

The Coronae of AR Lac

We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma. Line widths interpreted in terms of Doppler broadening suggest that both binary stellar components are active. From line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. A strong maximum was found in the differential emission measure, characterized by peaks at log T = 6.9 and 7.4, together with a weak but significant cooler maximum near log T=6.2, and a moderately strong hot tail from log T= 7.6-8.2. Coronal abundances have a broad distribution and show no simple correlation with first ionization potential. While the resulting model spectrum generally agrees very well with the observed spectrum, there are some significant discrepancies, especially among the many Fe L-lines. Both the emission measure and abundance distributions are qualitatively similar to prior determinations from other X-ray and ultraviolet spectra, indicating some long-term stability in the overall coronal structure.Comment: 31 pages, 8 figures, 3 tables; Accepted for publication in the Astrophysical Journal (tentatively October 1, 2003

Hydrodynamic atmospheric escape in HD 189733 b: Signatures of carbon and hydrogen measured with the Hubble Space Telescope

One of the most well-studied exoplanets to date, HD 189733 b, stands out as an archetypal hot Jupiter with many observations and theoretical models aimed at characterizing its atmosphere, interior, host star, and environment. We report here on the results of an extensive campaign to observe atmospheric escape signatures in HD 189733 b using the Hubble Space Telescope and its unique ultraviolet capabilities. We have found a tentative, but repeatable in-transit absorption of singly-ionized carbon (C II, $5.2\% \pm 1.4\%$) in the epoch of June-July/2017, as well as a neutral hydrogen (H I) absorption consistent with previous observations. We model the hydrodynamic outflow of HD 189733 b using an isothermal Parker wind formulation to interpret the observations of escaping C and O nuclei at the altitudes probed by our observations. Our forward models indicate that the outflow of HD 189733 b is mostly neutral within an altitude of $\sim 2$ R$_\mathrm{p}$ and singly ionized beyond that point. The measured in-transit absorption of C II at 133.57 nm is consistent with an escape rate of $\sim 1.1 \times 10^{11}$ g$\,$s$^{-1}$, assuming solar C abundance and outflow temperature of $12\,100$ K. Although we find a marginal neutral oxygen (O I) in-transit absorption, our models predict an in-transit depth that is only comparable to the size of measurement uncertainties. A comparison between the observed Lyman-$\alpha$ transit depths and hydrodynamics models suggests that the exosphere of this planet interacts with a stellar wind at least one order of magnitude stronger than solar.Comment: 22 pages, 14 figures, 5 tables. Accepted for publication in the Astronomical Journa

Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b

Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, affecting their physical and chemical evolution. Studies of atmospheric escape from exoplanets have mostly relied on space-based observations of the hydrogen Lyman-{\alpha} line in the far ultraviolet which is strongly affected by interstellar absorption. Using ground-based high-resolution spectroscopy we detect excess absorption in the helium triplet at 1083 nm during the transit of the Saturn-mass exoplanet WASP-69b, at a signal-to-noise ratio of 18. We measure line blue shifts of several km/s and post transit absorption, which we interpret as the escape of part of the atmosphere trailing behind the planet in comet-like form. [Additional notes by authors: Furthermore, we provide upper limits for helium signals in the atmospheres of the exoplanets HD 209458b, KELT-9b, and GJ 436b. We investigate the host stars of all planets with detected helium signals and those of the three planets we derive upper limits for. In each case we calculate the X-ray and extreme ultraviolet flux received by these planets. We find that helium is detected in the atmospheres of planets (orbiting the more active stars and) receiving the larger amount of irradiation from their host stars.]Comment: Submitted to Science on 14 March 2018; Accepted by Science on 16 November 2018; Published by Science on 6 December 2018. This is the author's version of the work. It is posted here by permission of the AAAS for personal use. The definitive version was published in Science, on 6 December 2018 - Report: pages 21 (preprint), 4 figures - Supplementary materials: 22 pages, 10 figures, 3 table

The HST PanCET Program:Hints of Na I and Evidence of a Cloudy Atmosphere for the Inflated Hot Jupiter WASP-52b

We present an optical to near-infrared transmission spectrum of the inflated hot Jupiter WASP-52b using three transit observations from the Space Telescope Imaging Spectrograph (STIS) mounted on the Hubble Space Telescope, combined with Spitzer/Infrared Array Camera (IRAC) photometry at 3.6 microns and 4.5 microns. Since WASP-52 is a moderately active (log(Lx/Lbol) = -4.7) star, we correct the transit light curves for the effect of stellar activity using ground-based photometric monitoring data from the All-Sky Automated Survey for Supernovae (ASAS-SN) and Tennessee State University's Automatic Imaging Telescope (AIT). We bin the data in 38 spectrophotometric light curves from 0.29 to 4.5 microns and measure the transit depths to a median precision of 90 ppm. We compare the transmission spectrum to a grid of forward atmospheric models and find that our results are consistent with a cloudy spectrum and evidence of sodium at 2.3-sigma confidence, but no observable evidence of potassium absorption even in the narrowest spectroscopic channel. We find that the optical transmission spectrum of WASP-52b is similar to that of the well-studied inflated hot Jupiter HAT-P-1b, which has comparable surface gravity, equilibrium temperature, mass, radius, and stellar irradiation levels. At longer wavelengths, however, the best fitting models for WASP-52b and HAT-P-1b predict quite dissimilar properties, which could be confirmed with observations at wavelengths longer than ~1 micron. The identification of planets with common atmospheric properties and similar system parameters will be insightful for comparative atmospheric studies with the James Webb Space Telescope.Comment: 35 pages, 16 figures, accepted for publication in A

Hubble PanCET: an isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab

We present a thermal emission spectrum of the bloated hot Jupiter HAT-P-32Ab from a single eclipse observation made in spatial scan mode with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST). The spectrum covers the wavelength regime from 1.123 to 1.644 μm which is binned into 14 eclipse depths measured to an averaged precision of 104 parts-per million. The spectrum is unaffected by a dilution from the close M-dwarf companion HAT-P-32B, which was fully resolved. We complemented our spectrum with literature results and performed a comparative forward and retrieval analysis with the 1D radiative-convective ATMO model. Assuming solar abundance of the planet atmosphere, we find that the measured spectrum can best be explained by the spectrum of a blackbody isothermal atmosphere with Tp = 1995 ± 17 K, but can equally well be described by a spectrum with modest thermal inversion. The retrieved spectrum suggests emission from VO at the WFC3 wavelengths and no evidence of the 1.4 μm water feature. The emission models with temperature profiles decreasing with height are rejected at a high confidence. An isothermal or inverted spectrum can imply a clear atmosphere with an absorber, a dusty cloud deck or a combination of both. We find that the planet can have continuum of values for the albedo and recirculation, ranging from high albedo and poor recirculation to low albedo and efficient recirculation. Optical spectroscopy of the planet\u27s day-side or thermal emission phase curves can potentially resolve the current albedo with recirculation degeneracy

The Hubble Space Telescope PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab

We present a 0.3-5 μm transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 Å, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planet's atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of $1248^{+92}_{-92}K$, a thick cloud deck, enhanced Rayleigh scattering, and ∼10× solar $H_2O$ abundance. We find log($Z/Z_☉$) = $2.41^{+0.06}_{-0.07}$, and compare this measurement with the mass-metallicity relation derived for the solar system

Protective effects of halite to vacuum and vacuum-ultraviolet radiation: A potential scenario during a young sun superflare

Halite (NaCl mineral) has exhibited the potential to preserve microorganisms for millions of years on Earth. This mineral was also identified on Mars and in meteorites. In this study, we investigated the potential of halite crystals to protect microbial life-forms on the surface of an airless body (e.g., meteorite), for instance, during a lithopanspermia process (interplanetary travel step) in the early Solar System. To investigate the effect of the radiation of the young Sun on microorganisms, we performed extensive simulation experiments by employing a synchrotron facility. We focused on two exposure conditions: vacuum (low Earth orbit, 10-4 Pa) and vacuum-ultraviolet (VUV) radiation (range 57.6-124 nm, flux 7.14 W/m2), with the latter representing an extreme scenario with high VUV fluxes comparable to the amount of radiation of a stellar superflare from the young Sun. The stellar VUV parameters were estimated by using the very well-studied solar analog of the young Sun, κ1 Cet. To evaluate the protective effects of halite, we entrapped a halophilic archaeon (Haloferax volcanii) and a non-halophilic bacterium (Deinococcus radiodurans) in laboratory-grown halite. Control groups were cells entrapped in salt crystals (mixtures of different salts and NaCl) and non-trapped (naked) cells, respectively. All groups were exposed either to vacuum alone or to vacuum plus VUV. Our results demonstrate that halite can serve as protection against vacuum and VUV radiation, regardless of the type of microorganism. In addition, we found that the protection is higher than provided by crystals obtained from mixtures of salts. This extends the protective effects of halite documented in previous studies and reinforces the possibility to consider the crystals of this mineral as potential preservation structures in airless bodies or as vehicles for the interplanetary transfer of microorganisms.X.C.A. acknowledges CNPEM for the beamtime grantedto the proposal TGM—16126 (LNLS), FAPESP postdoc-toral fellowship (years 2013–2014) (Processo nro: 2012/20106-5), Brazil, and funding from PIP—CONICET 0754,Argentina. M.L. and P.O. acknowledge the Austrian ScienceFund (FWF): P30949-N36, I5711-N for supporting thisproject. J.E.H. acknowledges the financial support of FAPESP (Sao Paulo State) and CNPQ (Brazil) financingagencies. G.F.P.M. acknowledges grant 474972/2009-7from CNPq/Brazil.Peer reviewe