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Among the solar proxies, κ1 Cet, stands out as potentially having a mass very close to solar and a young age. We report magnetic field measurements and planetary habitability consequences around this star, a proxy of the young Sun when life arose on Earth. Magnetic strength was determined from spectropolarimetric observations and we reconstruct the large-scale surface magnetic field to derive the magnetic environment, stellar winds, and particle flux permeating the interplanetary medium around κ1 Cet. Our results show a closer magnetosphere and mass-loss rate 50 times larger than the current solar wind mass-loss rate when Life arose on Earth, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions.

The search for Earth-like planets around late-type stars using ultrastable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard's Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5yr and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1yr and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (H alpha, CaiiHK, and Nai D), as well as the full width at half-maximum (FWHM), of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 +/- 15d, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1ms(-1). We also find evidence of a long-term cycle of 10 +/- 2yr that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.© 2019 The Author(s).Published by Oxford University Press on behalf of the Royal Astronomical Society, This work has been financed by the Spanish Ministry of Science, Innovation and Universities (MICIU) through the grant AYA2017-86389-P. BTP acknowledges Fundacion La Caixa for the financial support received in the form of a Ph.D. contract. JIGH acknowledges financial support from the Spanish MICIU under the 2013 Ramon y Cajal program MICIU RYC-2013-14875. ASM acknowledges financial support from the Swiss National Science Foundation (SNSF). The IAA-CSIC and UCM teams acknowledge support by the Spanish Ministry of Economy and Competitiveness (MINECO) through grants AYA2016-79425-C3-1-P, AYA2016-79425-C3-2-P, AYA2016-79425-C3-3-P, ESP2014-54362P, and ESP2017-87143R. IR, JCM, MP, and EHacknowledge support from the Spanish MINECO and the Fondo Europeo de Desarrollo Regional (FEDER) through grant ESP2016-80435-C2-1-R, as well as the support of the Generalitat de Catalunya/CERCA program. GAE research is funded via the STFC Consolidated Grants ST/P000592/1, and a Perren foundation grant. The results of this paper were based on observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF-Fundacion Galileo Galilei at the Roque de Los Muchachos Observatory of the Instituto de Astrofisica de Canarias (IAC); observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory (Chile); observations made with the CARMENES instrument at the 3.5 m telescope of the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain), funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union, and the CARMENES Consortium members. This paper made use of the IAC Supercomputing facility HTCondor (http://research.cs.wisc.edu/htcondor/), partly financed by the Ministry of Economy and Competitiveness with FEDER funds, code IACA13-3E-2493. We are grateful to all the observers of the projects whose data we are using for the following spectrographs: HARPS (072.C-0488, 183.C-0437, 191.C-0505, 099.C-0880), HARPS-N (CAT14A_43, A27CAT_83, CAT13B_136, CAT16A_109, CAT17A_38, CAT17A_58), CARMENES (CARMENES GTO survey), HIRES (U11H, U11H, N12H, N10H, A264Hr, A288Hr, C168Hr, C199Hr, C205Hr, C202Hr, C232Hr, C240Hr, C275Hr, C332Hr, H174Hr, H218Hr, H238Hr, H224Hr, H244Hr, H257Hr, K01H, N007Hr, N014Hr, N024, N054Hr, N05H, N06H, N085Hr, N086Hr, N095Hr, N108Hr, N10H, N112Hr, N118Hr, N125Hr, N129HR, N12H, N12H, N131Hr, N131Hr, N136Hr, N141Hr, N145Hr, N148Hr, N14H, N157Hr, N15H, N168Hr, N19H, N20H, N22H, N28H, N32H, N50H, N59H, U014Hr, U01H, U023Hr, U027Hr, U027Hr, U030Hr, U052Hr, U058Hr, U05H, U064Hr, U077Hr, U078Hr, U07H, U082Hr, U084Hr, U08H, U10H, U115Hr, U11H, U12H, U131Hr, U142Hr, U66H, Y013Hr, Y065Hr, Y283Hr, Y292Hr), UVES (65.L-0428, 66.C-0446, 267.C-5700, 68.C0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C0495, 173.C-0606, 078.C-0829), APF (LCES/APF planet survey), and PFS (Carnegie-California survey).

Context. Compact hierarchical systems are important because the effects caused by the dynamical interaction among its members occur ona human timescale. These interactions play a role in the formation of close binaries through Kozai cycles with tides. One such system is ξ Tauri: it has three hierarchical orbits: 7.14 d (eclipsing components Aa, Ab), 145 d (components Aa+Ab, B), and 51 yr (components Aa+Ab+B, C).Aims. We aim to obtain physical properties of the system and to study the dynamical interaction between its components.Methods. Our analysis is based on a large series of spectroscopic photometric (including space-borne) observations and long-baseline optical and infrared spectro-interferometric observations. We used two approaches to infer the system properties: a set of observation-specific models, where all components have elliptical trajectories, and an N -body model, which computes the trajectory of each component by integrating Newton’s equations of motion.Results. The triple subsystem exhibits clear signs of dynamical interaction. The most pronounced are the advance of the apsidal line and eclipse-timing variations. We determined the geometry of all three orbits using both observation-specific and N -body models. The latter correctly accounted for observed effects of the dynamical interaction, predicted cyclic variations of orbital inclinations, and determined the sense of motion of all orbits. Using perturbation theory, we demonstrate that prominent secular and periodic dynamical effects are explainable with a quadrupole interaction. We constrained the basic properties of all components, especially of members of the inner triple subsystem and detected rapid low-amplitude light variations that we attribute to co-rotating surface structures of component B. We also estimated the radius of component B. Properties of component C remain uncertain because of its low relative luminosity. We provide an independent estimate of the distance to the system.Conclusions. The accuracy and consistency of our results make ξ Tau an excellent test bed for models of formation and evolution of hierarchical systems.

We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around Kappa1~Cet. Our results show a closer magnetosphere and mass-loss rate of Mdot = 9.7 x 10^{-13} Msol/yr, i.e., a factor 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planet's habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions, 6 pages, 5 figures, Published at the Astrophysical Journal Letters (ApJL): Manuscript #LET33582

With the launch of NASA's Kepler mission, stellar astrophysics in general, and the eclipsing binary star field in particular, has witnessed a surge in data quality, interpretation possibilities, and the ability to confront theoretical predictions with observations. The unprecedented data accuracy and an essentially uninterrupted observing mode of over 2000 eclipsing binaries is revolutionizing the field. Amidst all this excitement, we came to realize that our best models to describe the physical and geometric properties of binaries are not good enough. Systematic errors are evident in a large range of binary light curves, and the residuals are anything but Gaussian. This is crucial because it limits us in the precision of the attained parameters. Since eclipsing binary stars are prime targets for determining the fundamental properties of stars, including their ages and distances, the penalty for this loss of accuracy affects other areas of astrophysics as well. Here, we propose to substantially revamp our current models by applying the lessons learned while reducing, modeling, and analyzing Kepler data.

Context. Several binaries with masses anomalously small for their observed spectral types have been discussed in the astronomical literature and interpreted as the result of envelope ejection. V379 Cep is one of these objects. Aims. We obtained new series of electronic spectra and UBV photometry of V379 Cep and analysed them in an effort to check whether the conclusion about its anomalous masses may not be premature. Methods. Reduction of new spectra was carried out in the IRAF and SPEFO programs. New photometry was reduced and transformed to the standard system using the HEC22 program. Orbital elements were derived with the FOTEL program and via disentangling with the program KOREL. The final combined solution was obtained with the program PHOEBE. Some initial period searches were carried out using the phase dispersion minimalization technique. Results. We found that the second system of spectral lines seen in the spectra of V379 Cep does not belong to the secondary but to the primary of another binary Ba + Bb (orbital period of 158 d .71 ± 0 d .17), which constitutes a quadruple system with the narrow-lined 99 d .7638 ± 0 d .0006 eclipsing binary Aa + Ab (for which we report probable detection of the secondary and derive improved period and orbital elements). The mutual motion of the two binaries A + B around the common centre of gravity is also observable, and the probable orbital period is (7878 ± 77) days. Our result shows that the components Aa and Ba are somewhat evolved but removes the reported discrepancy of anomalously small masses. Conclusions. We find that V379 Cep is an astrophysically interesting quadruple system for which a future combination of interferometry, spectroscopy, and photometry can provide individual masses of all four bodies.

Previous interpretations of the Pioneer Venus mass spectrometer data of the deuterium to hydrogen ( D / H ) ratio of 1.9 × 10 - 2 or 120 ± 40 times the terrestrial value indicate that Venus may have had at least an H 2 O content of the order of about 0.3% of a terrestrial ocean (TO), and even much more during and shortly after the accretion period of ⩽ 300 Myr , depending on the unknown ratio of a continuous supply of H 2 O by comets to a hydrogen blow-off loss and impact erosion of the early atmosphere. In view of the low H 2 O abundance in the present atmosphere, several studies suggest that the planet should have lost most of its H 2 O during the early high X-ray, EUV and solar wind period of the active young Sun. Because oxygen did not accumulate in Venus’ atmosphere it is commonly believed that a part of the oxygen from dissociated H 2 O vapor was dragged off to space along with the escaping hydrogen during a blow-off period, or could have oxidized the surface minerals to produce FeO and Fe 2 O 3 to the depths of a few kilometers to tens of kilometers depending on the initial amount of H 2 O . We use in the present study, for the first time, multi-wavelength X-ray and EUV (XUV) observations by the ASCA, ROSAT, EUVE, FUSE and IUE satellites and stellar winds inferred from mass loss observations by the Hubble Space Telescope of solar proxies with ages 4.6 Gyr for the investigation of how efficiently the radiation and particle environment of the young Sun could have influenced the evolution of the early Venusian atmosphere and its H 2 O inventory due to the removal of oxygen picked up by the solar wind. For modelling the Venusian thermosphere over the planetary history we apply a diffusive-gravitational equilibrium and thermal balance model and investigate the heating of the early thermosphere by photodissociation and ionization processes, due to exothermic chemical reactions and cooling by CO 2 IR emission in the 15 μ m band. Our model simulations result in expanded thermospheres with exobase levels between about 200 km at present and about 2200 km 4.5 Gyr ago. Moreover, our results yield high exospheric temperatures during the active phase of the young Sun even if we assume a “dry” CO 2 atmosphere with similar composition that is observed on present Venus of more than 8000 K after the Sun arrived at the zero-age-main-sequence (ZAMS). Exospheric temperatures above about 4000 K lead to diffusion-limited escape and high loss rates for atomic hydrogen. The duration of this blow-off phase for atomic hydrogen essentially depends on the mixing ratios of CO 2 , N 2 and H 2 O in the early Venusian atmosphere and could last between about 150 to several hundred Myr, which could result in a large thermal loss of hydrogen from Venus. For studying how much of the H 2 O -related oxygen could have been lost to space by the ion pick up process due to the stronger solar wind and higher XUV fluxes of the young Sun we used our modelled atmospheric density profiles and studied the loss of O + ion pick up from the upper atmosphere of Venus over the planet's history by applying a numerical test particle model. Depending on the used solar wind parameters, our model simulations show that ion pick up by a strong early solar wind on a non-magnetized Venus could erode during 4.6 Gyr more than about 250 bar of O + ions, that corresponds to an equivalent amount of one terrestrial ocean. Finally, we discuss the implications of our findings for the formation of the Venusian atmosphere and discuss our results in the frame of previous studies.

We obtained new series of electronic spectra and UBV photometry of V379 Cep and analyzed them in an effort to check whether the conclusion about its anomalous masses is not premature. We found that the second system of spectral lines seen in the spectra of V379 Cep does not belong to the secondary but to the primary of another binary Ba+Bb (orbital period of 159d0) which constitutes a quadruple system with the narrow-lined 99d76 eclipsing binary Aa+Ab (for which we report probable detection of the secondary and derive improved period and orbital elements). The mutual motion of the two binaries A+B around the common centre of gravity is also observable and the probable orbital period is some 7878 days. Our result shows that the components Aa and Ba are somewhat evolved but removes the reported discrepancy of anomalously small masses. We find that V379 Cep is an astrophysically interesting quadruple system for which a future combination of interferometry, spectroscopy and photometry can provide individual masses of all four bodies.

We derive the properties of spotted regions in late-type active stars from V - and B -band photometric data. Specifically, we compare the amplitudes of spot-induced light and color variations with model amplitudes, which depend on the area, temperature and distribution of spotted regions over the stellar surface. Our analysis is applied to three well-known chromospherically active K dwarf stars: DX Leonis, AB Doradus and LQ Hydrae, and indicates that all three stars show significant variations of the average spot temperature from epoch to epoch. The observed temporal variations of the starspot temperatures are best explained as arising from the contemporary presence on the stellar photosphere of two-component (two-temperature) active regions. These consist of either dark spots and hot faculae and/or dark umbrae and penumbrae and the variations over time arise from change of their areal ratio.

International audience; We study the interaction between the planetary magnetosphere and atmosphere of the close-in extrasolar planets HD 209458b and OGLE-TR-56b with the stellar wind during the evolution of their host stars. Recent astrophysical observations of solar-like stars indicate that the radiation and particle environments of young stars are orders of magnitudes larger than for stars with ages comparable to the sun (∼4.6 Gyr). We model the interaction for the present and for early evolutionary stages, showing that it is possible that "Hot Jupiters" have an ionosphere-stellar wind interaction like Venus. Our study suggests that the internal magnetic field of exoplanets orbiting close to their host stars may be very weak due to tidal locking. The magnetic moments can be less than one tenth of the value presently observed for the rapidly rotating planet Jupiter. We find that the stronger stellar wind of younger solar-type stars compresses the magnetosphere to a standoff distance at which the ionized part of the upper atmosphere, hydrodynamically expanded by the XUV-flux, builds an obstacle. Because of a much larger stellar wind particle flux during the first ∼0.5 Gyr after the host stars arrived on the Zero-Age-Main-Sequence, "Hot Jupiters" may have not been protected by their intrinsic magnetic fields, even if one neglects the effect of tidal locking. In such a case, the unshielded upper atmosphere will be affected by different ionization and non-thermal ion loss processes. This contributes to the estimated neutral hydrogen loss rates of about ≥10 10 g/s of the observed expanded exosphere of HD 209458b (Vidal-Madjar et al. 2003) and will be an ionized part of the estimated upper energy-limited neutral hydrogen loss rates of about 10 12 g/s (Lammer et al. 2003a).

The Andromeda Galaxy (M31) is potentially a crucial calibrator for the Cosmic Distance Scale, and thus for determining the age and evolution of the Universe. Yet, currently the M31 distance is known to no better than ∼15%. We have demonstrated in our work on the LMC distance that double-line eclipsing binaries can serve as excellent “standard candles.” Distances derived from eclipsing binaries are basically geometric and essentially free from many assumptions and uncertainties that plague other less direct methods. We present the extension of our program of using eclipsing binaries as standard candles to determine an accurate distance to M31. The photometric observations that yield the light curves are underway with the Isaac Newton Telescope at the ING (La Palma). Spectrophotometric observations will be conducted with the HST, and large telescopes (for example Gemini or GTC) are necessary to acquire the spectra for the radial velocity curves because of the faintness of the target stars ( V ∼19–20). Based on our previous experience, we expect to reduce the uncertainty of the M31 distance to better than 5%, thereby firmly calibrating the Cosmic Distance Scale.

Past studies addressing the thermal atmospheric escape of hydrogen from hot Jupiters have been based on the planet's effective temperature, which, as we show here, is not physically relevant for loss processes. In consequence, these studies led to significant underestimations of the atmospheric escape rate (≤103 g s-1) and to the conclusion of long-term atmospheric stability. From more realistic exospheric temperatures, determined from X-ray and extreme-ultraviolet (XUV) irradiation and thermal conduction in the thermosphere, we find that energy-limited escape and atmospheric expansion arise, leading to much higher estimations for the loss rates (≈1012 g s-1). These fluxes are in good agreement with recent determinations for HD 209458b based on observations of its extended exosphere. We also show that for young solar-type stars, which emit stronger XUV fluxes, the inferred loss rates are significantly higher. Thus, hydrogen-rich giant exoplanets under such strong XUV irradiances may evaporate down to their core sizes or shrink to levels at which heavier atmospheric constituents may prevent hydrodynamic escape. These results could explain the apparent paucity of exoplanets so far detected at orbital distances less than 0.04 AU.

The maximum amplitude (A m a x ) of spot-induced brightness variations from long-term V-band photometry and the ratio L x /L ? o l between X-ray and bolometric luminosities are suitable indicators of the level of magnetic activity in the photosphere and in the corona of late-type stars, respectively. By using these activity indicators we investigate the dependence of coronal X-ray emission on the level of photospheric starspot activity in a homogeneous sample of low mass main sequence field and cluster stars of different ages (IC 2602, IC 4665, IC 2391, a Persei, Pleiades and Hyades). First, the activity-rotation connection at the photospheric level is re-analysed, as well as its dependence on spectral type and age. The upper envelope of A m a x increases monotonically with decreasing rotational period (P) and Rossby number (R 0 ) showing a break around 1.1 d that separates two rotation regimes where the starspot activity shows different behaviours. The A m a x -P and A m a x -R 0 relations are fitted with linear, exponential and power laws to look for the function which best represents the trend of the data. The highest values of A m a x are found among K-type stars and at the ages of α Persei and Pleiades. We also analyse the activity-rotation connection at the coronal level as well as its dependence on spectral type. The level of X-ray emission increases with increasing rotation rate up to a saturation level. The rotational period at which saturation occurs is colour-dependent and increases with advancing spectral type. Also the Lx/L b o l -P and Lx/L b o l -R 0 relations are fitted with linear, exponential and power laws to look for the best fitting function. Among the fastest rotating stars (P ≤ 0.3 d) there is evidence of super-saturation. Also the highest values of L x /L b o l are found among K-type stars. Finally, the photospheric-coronal activity connection is investigated by using for the first time the largest ever sample of light curve amplitudes as indicators of the magnetic filling factor. The activity parameters L x /L b o l and A m a x are found to be correlated with each other, thus confirming the dependence of coronal activity on photospheric magnetic fields. More precisely, the L x /L b o l -A m a x distribution shows the presence of an upper envelope, which is constant at the L x /L b o l ≃ -3.0 saturation level, and of a lower envelope. The best fit to the lower envelope is given by a power law with steepness decreasing from F-G to M spectral types. However, it is considered a tentative result, since the fit reduced chi-squares are large. Such spectral-type dependence may be related to a colour dependence of A m a x on the total starspot filling factor, as well as to the coronal emission being possibly more sensitive to starspot activity variations in F- and G-type than in M-type stars. The L x /L b o l -A m a x mean values for each cluster in our sample decrease monotonically with increasing age, showing that the levels of photospheric and coronal activity evolve in time according to a single power law till the Sun's age.

The evolution of the martian atmosphere with regard to its H 2 O inventory is influenced by thermal loss processes of H, H 2 , nonthermal atmospheric loss processes of H + , H 2 + , O, O + , CO 2 , and O 2 + into space, as well as by chemical weathering of the surface soil. The evolution of thermal and nonthermal escape processes depend on the history of the intensity of the solar XUV radiation and the solar wind density. Thus, we use actual data from the observation of solar proxies with different ages from the Sun in Time program for reconstructing the Sun's radiation and particle environment from the present to 3.5 Gyr ago. The correlation between mass loss and X-ray surface flux of solar proxies follows a power law relationship, which indicates a solar wind density up to 1000 times higher at the beginning of the Sun's main sequence lifetime. For the study of various atmospheric escape processes we used a gas dynamic test particle model for the estimation of the pick up ion loss rates and considered pick up ion sputtering, as well as dissociative recombination. The loss of H 2 O from Mars over the last 3.5 Gyr was estimated to be equivalent to a global martian H 2 O ocean with a depth of about 12 m, which is smaller than the values reported by previous studies. If ion momentum transport, a process studied in detail by Mars Express is significant on Mars, the water loss may be enhanced by a factor of about 2. In our investigation we found that the sum of thermal and nonthermal atmospheric loss rates of H and all nonthermal escape processes of O to space are not compatible with a ratio of 2:1, and is currently close to about 20:1. Escape to space cannot therefore be the only sink for oxygen on Mars. Our results suggest that the missing oxygen (needed for the validation of the 2:1 ratio between H and O) can be explained by the incorporation into the martian surface by chemical weathering processes since the onset of intense oxidation about 2 Gyr ago. Based on the evolution of the atmosphere-surface-interaction on Mars, an overall global surface sink of about 2×10 42 oxygen particles in the regolith can be expected. Because of the intense oxidation of inorganic matter, this process may have led to the formation of considerable amounts of sulfates and ferric oxides on Mars. To model this effect we consider several factors: (1) the amount of incorporated oxygen, (2) the inorganic composition of the martian soil and (3) meteoritic gardening. We show that the oxygen incorporation has also implications for the oxidant extinction depth, which is an important parameter to determine required sampling depths on Mars aimed at finding putative organic material. We found that the oxidant extinction depth is expected to lie in a range between 2 and 5 m for global mean values.

Intensive long-term photometric Q1 observations of the archetypical young G2 IIIe stellar object SU Aurigae are analyzed to determine many of its photometric and physical properties. Combining nearly 2000 Stromgren uvby measures obtained using the 0.8 m Four College Automatic Photoelectric Telescope, previously published photometry, and recently obtained high-resolution echelle spectra has led to the deter- mination of its effective temperature, surface gravity, luminosity, mass, age, rotation period, and absolute radius. Since the disk of SU Aur is seen at a high inclination angle (i.e., nearly edge-on), this complicates the observations with significant (DVDyd0:80 mag), and apparently random, drops in observed mean light. These are possibly due to the transits of protoplanetary bodies, protocomets, or associated accretion halos. In this study, an effort has been made to separate the contributions of the circumstellar disk from the intrinsic properties of the stellar core itself. Furthermore, photometry has been simultaneously obtained for the nearby young A0 Vpe stellar companion AB Aurigae. Analysis has shown that SU Aur and AB Aur are a coeval proper-motion pair. Also included are certain photometric and physical properties of AB Aur. Q2

We have determined the fundamental properties and distance of a fourth eclipsing binary (EB) system in the Large Magellanic Cloud, HV 5936 (~B0.5 V + ~B2 III). As in our previous studies, we combine "classical" EB light-curve and radial velocity curve analyses with modeling of the UV/optical spectral energy distribution of HV 5936 to produce a detailed characterization of the system. In this paper, we also include an analysis of the high-resolution optical absorption line spectra of the binary components. We find HV 5936 to be an Algol-class system, in which the masses of the primary and secondary stars have evolved via mass transfer to their current values of 11.6 and 4.7 M☉, respectively. The properties of the primary star are indistinguishable from those of a "normal" star of the same current mass. The secondary is found to be overluminous for its current mass and exhibits a factor of 2 enhancement in its surface He abundance. These results are compatible with case A mass exchange occurring during the core hydrogen-burning phase of the current secondary. The distance derived to the system, 43.2 ± 1.8 kpc, implies a distance of ~44.3 kpc to the optical center of the LMC. This is several kiloparsecs closer than found in our analyses of other systems, and we suggest that HV 5936 lies "above" the LMC disk. This is supported by the very low interstellar H I column density and low E(B-V) found for the system—both of which are consistent with expected Milky Way foreground material—and may be associated with HV 5936's location near the LMC supergiant shell LMC 4.

A long-term photometric monitoring of a selected sample of solar analogues has been carried out since early nineties as part of The Sun in time project, which is aimed at a multiwavelength study of stars with solar-like global properties, but with dierent ages and thus at dierent stages of their evolution. The extended time sequence of ground-based observations collected over more than a decade as part of this program has revealed the existence of starspot cycles. Also from these data it is possible to investigate surface dierential rotation of the stars. In this paper we present the photometry collected to date and report on cycles search for a selected subsample of five young single G0-G5V stars with ages between'130 Myr and 700 Myr: EK Dra, 1 UMa, HN Peg, k 1 Cet and BE Cet. Also we include in this study the Pleiades-age (' 130 Myr) K0V star DX Leo (HD 82443). All the cited stars show activity cycles whose period is, furthermore, the first determined from photometric data. They are compared to those activity cycles derived from CaII HK ii) the range in the observed cycle lengths seems to converge with stellar age from a maximum dispersion around the Pleiades' age towards the solar cycle value at the Sun's age; iii) the overall short- and long-term photometric variability increases with inverse Rossby number with very high correlation degree, indicating that the level of magnetic activity at least in photosphere is still controlled by the stellar rotation even on the longest time scales; iiii) the increase with inverse Rossby number of the long-term overall photometric variability seems to level o at the highest rotation rate, which may be interpreted as due to a saturation in the level of photospheric magnetic activity around the activity maximum.

We have determined the distance to a second eclipsing binary (EB) system in the Large Magellanic Cloud, HV 982 (DB1 IVV ) DB1 IVV). The measurement of the distanceamong other properties of the systemis based on optical photometry and spectroscopy and space-based UV/optical spectropho- tometry. The analysis combines the ii classical ˇˇ EB study of light and radial velocity curves, which yields the stellar masses and radii, with a new analysis of the observed energy distribution, which yields the eUective temperature, metallicity, and reddening of the system plus the distance ii attenuation factor,ˇˇ essentially (radius/distance)2. Combining the results gives the distance to HV 982, which is 50.2 ^ 1.2 kpc. This distance determination consists of a detailed study of well-understood objects (B stars) in a well-understood evolutionary phase (core H burning). The results are entirely consistent withbut do not depend onstellar evolution calculations. There are no ii zero-point ˇˇ uncertainties as, for example, with the use of Cepheid variables. Neither is the result subject to sampling biases, as may aUect tech- niques that utilize whole stellar populations, such as red giant branch stars. Moreover, the analysis is insensitive to stellar metallicity (although the metallicity of the stars is explicitly determined), and the eUects of interstellar extinction are determined for each object studied. After correcting for the location of HV 982, we —nd an implied distance to the optical center of the LMCs bar of kpc. d LMC \ 50.7 ^ 1.2 This result diUers by nearly 5 kpc from our earlier result for the EB HV 2274, which implies a bar distance of 45.9 kpc. These results may either re—ect marginally compatible measures of a unique LMC distance or, alternatively, suggest a signi—cant depth to the stellar distribution in the LMC. Some evi- dence for this latter hypothesis is discussed. Subject headings: binaries: eclipsingdistance scaleMagellanic Cloudsstars: distances ¨ stars: fundamental parametersstars: individual (HV 982)

We present a NASA-DLR SOFIA-Echelon Cross Echelle Spectrograph (EXES) and NASA Infrared Telescope Facility-Texas Echelon Cross Echelle Spectrograph (TEXES) mid-IR R ≃ 50,000 spectral study of forbidden Fe II transitions in the early-type M supergiants, Betelgeuse (α Ori: M2 Iab) and Antares (α Sco: M1 Iab + B3 V). With EXES, we spectrally resolve the ground term [Fe II] 25.99 μm ( a 6DJ= 7/2-9/2: Eup = 540 K) emission from Betelgeuse. We find a small centroid blueshift of 1.9 ± 0.4 km s-1 that is a significant fraction (20%) of the current epoch wind speed, with a FWHM of 14.3 ± 0.1 km s-1. The TEXES observations of [Fe II] 17.94 μm (a 4FJ= - 7/2 9/2: Eup = 3400 K) show a broader FWHM of 19.1 ± 0.2 km s-1, consistent with previous observations, and a small redshift of 1.6 ± 0.6 km s-1 with respect to the adopted stellar center-ofmass velocity of VCoM = 20.9 ± 0.3 km s-1. To produce [Fe II] 25.99 μm blueshifts of 20% wind speed requires that the emission arises closer to the star than existing thermal models for α Ori's circumstellar envelope predict. This implies a more rapid wind cooling to below 500 K within 10R∗ (q∗ = 44 mas, dist = 200 pc) of the star, where the wind has also reached a significant fraction of the maximum wind speed. The line width is consistent with the turbulence in the outflow being close to the hydrogen sound speed. EXES observations of [Fe II] 22.90 μm ( a 4DJ= 5/2-7/2: Eup = 11,700 K) reveal no emission from either star. These findings confirm the dominance of cool plasma in the mixed region where hot chromospheric plasma emits copiously in the UV, and they also constrain the wind heating produced by the poorly understood mechanisms that drive stellar outflows from these low variability and weak-dust signature stars.

In this paper we present the results of a different approach in the study of the so-called rotation-activity connection , which is a well established correlation between rotation and magnetic activity at chromospheric and outer atmospheric levels. The present study concerns the photospheric level and was carried out by using V -band photometric light curve amplitudes as indicators of starspot coverage and of magnetic activity. A high degree of correlation between the envelope of maximum V -band light curve amplitudes and the rotation period is found for the active star members of young open clusters (IC 2602, IC 2391, Alpha Persei, Pleiades and Hyades), as well as for active field stars. This correlation shows a diffe rent behaviour in two different rotation period ranges. Moreover, some evidence of a possible activity "saturation"is found among the most rapidly rotating stars of the sample. Additional correlations between photospheric and other magnetic activity indicators in the chromosphere, transition region and corona are also investigated. The results presented here can be considered as an extension of the well established rotation-activity connection valid from the corona, transition region and chromosphere, down to the photosphere.

Our collaboration involves groups in Denmark, the U.S.A. Spain and of course New Zealand. Combining ground-based and satellite (IUE and HST) observations we aim to determine accurate and precise stellar fundamental parameters for the components of Magellanic Cloud Eclipsing Binaries as well as the distances to these systems and hence the parent galaxies themselves. This poster presents our latest progress.

We present the wind velocity and UV luminosity variations in the Wolf-Rayet system HD 5980 obtained over a time span during which one of the stars of the system was transformed into a luminous blue variable and underwent an eruption. We are able to separate the velocity components of the two stars in the system: a stable velocity component at -1700 km s-1 is associated with the nonerupting star, while the variable wind with velocities ranging from -500 to -3000 km s-1 corresponds to the eruptor. The development of a fast wind following the slow wind eruptive phase is observed. Under the assumption of radiatively driven winds, these changing velocities indicate that the radius of the photosphere gradually increased during at least 12 years prior to the 1994 eruption, decreasing rapidly thereafter. An estimate of the stellar parameters indicates that the erupting star is massive (M > 40 M☉) and very luminous (L > 106 L☉), and that during the eruption its radius extended beyond the binary orbit (R* > 100 R☉).

In this work we have studied CM Draconis, one of the least massive eclipsing binaries known. Its components are very similar, with masses and radii of about 0.23 M⊙ and 0.25 R⊙. We have analysed light curves in the R and I bands to calculate the fundamental properties of this system with accuracies better than 1%. With these results we plan to carry out a thorough test of the models, which have been found to predict smaller radii and larger effective temperatures than observed for these low-mass stars. This will also be especially interesting in the case of CM Dra since the mechanism driving magnetic activity is thought to be different from that of more massive stars. In addition, the extended time-span of the observations has led to the detection of apsidal motion. This provides a further check on models through the determination of the internal structure of the stars.

Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornestones to critical tests of stellar evolution theory for massive stars. Yet, the determination of the basic physical properties is less accurate than it could be given the existing number of spectral and photometric observations. Our goal is to analyze all these data simultaneously with the new dedicated series of our own spectral and photometric observations from observatories widely separated in longitude. We obtained new series of UBV observations at three observatories separated in local time to obtain complete light curves of Y Cyg for its orbital period close to 3 days. This new photometry was reduced and carefully transformed to the standard UBV system using the HEC22 program. We also obtained new series of red spectra secured at two observatories and re-analyzed earlier obtained blue electronic spectra. Our analyses provide the most accurate so far published value of the apsidal period of 47.805 +/- 0.030 yrs and the following physical elements: M1=17.72+/-0.35$ Msun, M2=17.73+/-0.30 Msun, R1=5.785+/-0.091 Rsun, and R2=5.816+/-0.063 Rsun. The disentangling thus resulted in the masses, which are somewhat higher than all previous determinations and virtually the same for both stars, while the light curve implies a slighly higher radius and luminosity for star 2. The above empirical values imply the logarithm of the internal structure constant log k2 = -1.937. A comparison with Claret's stellar interior models implies an age close to 2 millions yrs for both stars. The claimed accuracy of modern element determination of 1-2 per cent seems still a bit too optimistic and obtaining new high-dispersion and high-resolution spectra is desirable., Comment: 13 pages; accepted for publication in Astronomy and Astrophysics

The X-ray observations of three classical Cepheids produce a surprising result. At approximately the phase of maximum radius there is a sharp increase in X-ray flux above the normal “quiescent” level. The relation of this new upper atmosphere diagnostic to other phenonena above the photosphere is discussed.

The RCT 1.3-meter telescope, formerly known as the Kitt Peak National Observatory (KPNO) 50-inch telescope, has been refurbished as a fully robotic telescope, using an autonomous scheduler to take full advantage of the observing site without the requirement of a human presence. Here we detail the current configuration of the RCT, and present as a demonstration of its high-priority science goals, the broadband {\it UBVRI} photometric calibration of the optical facility. In summary, we find the linear color transformation and extinction corrections to be consistent with similar optical KPNO facilities, to within a photometric precision of 10% (at $1\sigma$). While there were identified instrumental errors likely adding to the overall uncertainty, associated with since-resolved issues in engineering and maintenance of the robotic facility, a preliminary verification of this calibration gave good indication that the solution is robust, perhaps to a higher precision than this initial calibration implies. The RCT has been executing regular science operations since 2009, and is largely meeting the science requirements set in its acquisition and re-design., Comment: 14 pages, 10 figures. Accepted by the Astronomical Journal

Measurements of rates of period change of Classical Cepheids probe stellar physics and evolution. Additionally, better understanding of Cepheid structure and evolution provides greater insight into their use as standard candles and tools for measuring the Hubble constant. Our recent study of the period change of the nearest Cepheid, Polaris, suggested that it is undergoing enhanced mass loss when compared to canonical stellar evolution model predictions. In this work, we expand the analysis to rates of period change measured for about 200 Galactic Cepheids and compare them to population synthesis models of Cepheids including convective core overshooting and enhanced mass loss. Rates of period change predicted from stellar evolution models without mass loss do not agree with observed rates whereas including enhanced mass loss yields predicted rates in better agreement with observations. This is the first evidence that enhanced mass loss as suggested previously for Polaris and delta Cephei must be a ubiquitous property of Classical Cepheids., 6 pages, 4 figures, Accepted for publication in ApJ Letters

Polaris is one of the most observed stars in the night sky, with recorded observations spanning more than 200 years. From these observations, one can study the real-time evolution of Polaris via the secular rate of change of the pulsation period. However, the measurements of the rate of period change do not agree with predictions from state-of-the-art stellar evolution models. We show that this may imply that Polaris is currently losing mass at a rate of $\dot{M} \approx 10^{-6} M_\odot$ yr$^{-1}$ based on the difference between modeled and observed rates of period change, consistent with pulsation-enhanced Cepheid mass loss. A relation between the rate of period change and mass loss has important implications for understanding stellar evolution and pulsation, and provides insight into the current Cepheid mass discrepancy., 5 pages, 4 figures, compiled using emulateapj, Accepted for publication in ApJ Letters. Fixed correction in title

The long-period (P = 27.1 years) peculiar eclipsing binary e Aur, which has recently completed its two year-long primary eclipse, has perplexed astronomers for over a century. The eclipse arises from the transit of a huge, cool and opaque, disk across the face of the F0 Iab star. One of the principal problems with understanding this binary is that the very small parallax of p = (1.53 ± 1.29) mas, implying a distance range of d ∼ (0.4−4.0) kpc, returned by a revised reduction of the Hipparcos satellite observations, is so uncertain that it precludes a trustworthy estimate of the luminosities and masses of the binary components. A reliable distance determination would help solve the nature of this binary and distinguish between competing models. A new approach is discussed here: we estimate the distance to e Aur from the calibration of reddening and interstellar-medium gas absorption in the direction of the system. The distance to e Aur is estimated from its measured E(B −V) and the strength of the diffuse interstellar band 6613.56 A. Spectroscopy and UBV photometry of several B- and A-type stars (

We aim at determining the rotational and magnetic-related activity properties of stars at different stages of evolution. We focus our attention primarily on members of young stellar associations of known ages. Specifically, we extend our previous analysis in Paper I (Messina et al. 2010, A&A 520, A15) to 3 additional young stellar associations beyond 100 pc and with ages in the range 6-40 Myr: epsilon Chamaeleontis (~6 Myr), Octans (~20 Myr), and Argus (~40 Myr). Additional rotational data of eta Chamaeleontis and IC2391 clusters are also considered. Rotational periods were determined from photometric time-series data obtained by the All Sky Automated Survey (ASAS) and the Wide Angle Search for Planets (SuperWASP) archives. With the present study we have completed the analysis of the rotational properties of the late-type members of all known young loose associations in the solar neighborhood. Considering also the results of Paper I, we have derived the rotation periods of 241 targets: 171 confirmed, 44 likely, 26 uncertain. The period of the remaining 50 stars known to be part of loose associations still remains unknown. This rotation period catalogue, and specifically the new information presented in this paper at ~6, 20, and 40 Myr, contributes significantly to a better observational description of the angular momentum evolution of young stars., Accepted by Astronomy & Astrophysics. Onlines figures will be available at CDS

Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 $M_\odot$ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip., 2 pages, 1 figure, Poster presented at IAU307: New windows on massive stars: asteroseismology, interferometry, and spectropolarimetry, Editors: G. Meynet, C. Georgy, J.H. Groh & Ph. Stee

We have been carrying out a study of stellar magnetic activity, dynamos, atmospheric physics, and spectral irradiances from a sample of solar-type G0-5 V stars with different ages. One of the major goals of this program is to study the evolution of the Sun's X-ray through NUV spectral irradiances with age. Of particular interest is the determination of the young Sun's elevated levels of high-energy fluxes because of the critical roles that X-ray through FUV emissions play on the photochemical and photoionization evolution of early, young planetary atmospheres and ionospheres. Motivated by the current exoplanetary search missions that are hunting for earth-size planets in the habitable zones of nearby main-sequence G-M stars, we are expanding our program to cooler, less luminous, but much more numerous main-sequence K-type stars, such as alpha Centauri B. The long life (2-3x longer than our Sun) and slow evolution of K stars provide nearly constant energy sources for possible hosted planets. Presented here are X-ray, UV, and recently acquired FUV observations of the K1 V star alpha Cen B. These combined high-energy measures provide a more complete look into the nature of alpha Cen B's magnetic activity and X-UV radiances. We find that alpha Cen B has exhibited significant long-term variability in X-ray through NUV emission fluxes, indicating a solar-like long-term activity cycle of P_cycle = 8.84 years. In addition, analysis of the short-term rotational modulation of mean light due to the effects of magnetically active regions has yielded a well-determined rotation period of P_rotation = 36.2 days. alpha Cen B is the only old main-sequence K star with a reliably determined age and rotation period, and for early K-stars, is an important calibrator for stellar age/rotation/activity relations.

Distance determinations to Local Group galaxies conform the basic rungs of the cosmological distance scale. The chief goal of our project is obtaining direct and accurate distance determinations to M 31 from two important stellar populations: eclipsing binaries and Cepheids. A variability survey in the North–Eastern quadrant of M 31 was performed (in B and V passbands) with the Isaac Newton Telescope (La Palma) to identify suitable targets. The resulting catalog of 3,964 variable stars contains 437 eclipsing binaries and 416 Cepheids with ∼ 250 epochs per filter. The selection of the 68 Cepheids less affected by blending were selected to determine a distance to M 31 of (m − M)0 = 24. 32 ± 0. 12 mag. At the same time, the analysis of the eclipsing binary sample (with the acquisition of Gemini/GMOS spectroscopy) has provided two direct distance determinations to M 31: (m − M)0 = 24. 44 ± 0. 12 mag and (m − M)0 = 24. 46 ± 0. 19 mag. All the obtained distances are in complete agreement and provide a direct and accurate distance determination to M 31. The combination of these results with additional data could well reduce the distance uncertainty to M 31 to better than 4%.

A review of IAU Symposium 151 on Interacting Binary Stars is given along with discussions of the present and future prospects of research in close binary stars.

We present the first results of a continuous monitoring of Algol with IUE along 1.5 orbital period (4 1/3 days). A total of 32 high resolution spectra were obtained. Algol represents the final slow stage of mass transfer. The spectra show the presence of high ionization lines (NV, SiIV, CIV) due to the heating of the gas that impacts the accreting star. The depth of the primary eclipse is larger at shorter wavelengths and the shape of the continuum out of the eclipse is compatible with a B star, ruling out the presence of an extra light source at these wavelengths.

We present results from a multi-wavelength campaign to monitor the 2005 outburst of the low-mass young star V1118 Ori. Although our campaign covers the X-ray, optical, infrared, and radio regimes, we focus in this Letter on the properties of the X-ray emission in V1118 Ori during the first few months after the optical outburst. Chandra and XMM-Newton detected V1118 Ori at three epochs in early 2005. The X-ray flux and luminosity stayed similar within a factor of two, and at the same level as in a pre-outburst observation in 2002. The hydrogen column density showed no evidence for variation from its modest pre-outburst value of $N_\mathrm{H} \sim 3 \times 10^{21}$ cm$^{-2}$. However, a spectral change occurred from a dominant hot plasma ($\sim 25$ MK) in 2002 and in January 2005 to a cooler plasma ($\sim 8$ MK) in February 2005 and in March 2005. We hypothesize that the hot magnetic loops high in the corona were disrupted by the closing in of the accretion disk due to the increased accretion rate during the outburst, whereas the lower cooler loops were probably less affected and became the dominant coronal component., Accepted for publication in ApJ Letters

We report on the results of the Sun in Time multi-wavelength program (X-rays to the UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter goal, which has the ultimate purpose of providing the spectral irradiance evolution of solar-type stars to be used in the study and modeling of planetary atmospheres. The results from the Sun in Time program suggest that the coronal X-ray-EUV emissions of the young main-sequence Sun were ~100-1000 times stronger than those of the present Sun. Similarly, the transition region and chromospheric FUV-UV emissions of the young Sun are expected to be 20-60 and 10-20 times stronger, respectively, than at present. When considering the integrated high-energy emission from 1 to 1200 A, the resulting relationship indicates that the solar high-energy flux was about 2.5 times the present value 2.5 Gyr ago and about 6 times the present value about 3.5 Gyr ago (when life supposedly arose on Earth). The strong radiation emissions inferred should have had major influences on the thermal structure, photochemistry, and photoionization of planetary atmospheres and also played an important role in the development of primitive life in the Solar System. Some examples of the application of the Sun in Time results on exoplanets and on early Solar System planets are discussed., Comment: 20 pages, 8 figures, accepted for publication in ApJ

The Andromeda Galaxy (M31), with its large and diverse stellar population and chemical history and galactic structure similar to that of the Milky Way, is potentially a crucial calibrator for the Cosmic Distance Scale and thus for determining the age and evolution of the Universe. We have demonstrated in our work on the LMC distance that double-line eclipsing binaries can serve as excellent “standard candles”. Also, the resulting accurate fundamental properties (M, R, T eff) of the two binary components yield an empirical determination of the mass-luminosity law and permit critical tests of stellar structure and evolution models.

We discuss the potential of using extragalactic eclipsing binaries with well-determined physical properties as standard candles to improve the extragalactic distance scale. The advent of high quantum efficient/low noise CCDs has now made it possible to obtain high precision light and radial velocity curves for the more luminous OB-type eclipsing binaries in the Magellanic Clouds with even small to moderate size (l–2m) telescopes. This can now lead to the determination of distance modulii (m — M)o to the LMC and SMC with precisions of about 0m.15 for individual binaries. These distances are essentially free from the assumptions made using other distance indicators

Thanks to OGLE, Kepler, CoRoT and planned new ambitious survey projects, the eclipsing binary (EB) community is beginning to experience a long-predicted data deluge. Beyond the analysis of the many fascinating individual objects yielded by these programs, these complete datasets themselves should yield further insights. Because objects in such datasets are characterized by many parameters, tools that assist in understanding high-dimensional data are acquiring increasing relevance. Chiefly among these are new Advanced Visualization (AV) tools and various methods of clustering data, both approaches complementing each other naturally. We illustrate the use of these tools as applied to OGLE II LMC EB data and respective EBAI light curve solutions.

The distance to the Large Magellanic Cloud (LMC) is crucial for the calibration of the Cosmic Distance Scale. We derive a distance to the LMC based on an analysis of ground-based photometry and HST-based spectroscopy and spectrophotometry of the LMC eclipsing binary system HV2274. Analysis of the optical light curve and HST/GHRS radial velocity curve provides the masses and radii of the binary components. Analysis of the HST/FOS UV/optical spectrophotometry provides the temperatures of the component stars and the interstellar extinction of the system. When combined, these data yield a distance to the binary system. After correcting for the location of HV2274 with respect to the center of the LMC, we find d(LMC) = 45.7 +/- 1.6 kpc or DM(LMC) = 18.30 +/- 0.07 mag. This result, which is immune to the metallicity-induced zero point uncertainties that have plagued other techniques, lends strong support to the ``short'' LMC distance scale as derived from a number of independent methods., 6 pages, including 2 pages of figures. Newly available optical (B and V) photometry has revealed -- and allowed the elimination of -- a systematic error in the previously reported determination of E(B-V) for HV2274. The new result is E(B-V) = 0.12 mag (as compared to the value of 0.083 reported in the original submission) and produces a DECREASE in the distance modulus of HV2274 by 0.12 mag. ApJ Letters, in press

We present results of IUE observations (λλ1200-3200) of the erupting system HD 5980 obtained in 1994 November and December. The 1994 spectrum presents emission lines from ions such as N III, Si II-III and Al III which were absent in 1991. There is a systematic tendency towards higher degrees of ionization over the 44 days covered by the present observations. At the start of the observations on HJD 2449674 the UV continuum flux at 1850 A is a factor of ~2 larger than in 1991, declining by 30% in 18 days, followed by a tendency to once again increase. FES magnitudes indicate a rapid decline in visual brightness after maximum in the eruption. Wind speeds as high as ~1700 km s-1 are measured although the P Cygni absorption components are highly peculiar, containing several emission-like "bumps," the most prominent of which lies at 920 km s-1. We conclude that the eruption occurred in the primary star of the 19.3 day orbital pair, the one classified as WN4 by Breysacher et al. and which now is displaying an LBV-type event. The phenomena in HD 5980 provide evidence supporting evolutionary scenarios in which pulsationally unstable, H-rich WN stars precede the LBV phase.

We have conducted an observing campaign to study the Blazhko effect in RR Lyrae, using ground-based photometry and spectroscopy, along with low-resolution ultraviolet spectra with the International Ultraviolet Explorer (IUE). Observations were taken which followed a complete pulsation cycle, at a variety of Blazhko phases. The IUE observing shifts also provided a detailed V light curve, from measurements with IUE’s Fine Error Sensor (FES). These data are analyzed using Fourier decomposition techniques.