I develop a detailed empirical model for the chromosphere and wind of 31 Cyg based on a previously published analysis of IUE spectra from the 1993 eclipse and on the thermodynamics of how the wind must be driven. I then use this model to interpret observations of single supergiant stars and to assess the evidence that their winds are fundamentally different from those of supergiants in the binary systems. This model naturally predicts a certain level of clumping of the gas to balance the pressure that drives the wind. It also predicts that anisotropic turbulence, such as would result from transverse displacements of Alfven waves directed along radial magnetic flux lines, would not give the roughly Gaussian profiles of emission lines seen in cool giant stars. Furthermore, it implies that C II] may not tell us much at all about general conditions in chromospheres. Finally, I speculate that chaotic magnetic fields, in dynamical equilibrium with the gas of the wind, are the actual driving mechanism.
P Cygni is a prototype for understanding mass loss from massive stars. This textbook star is known first of all because of two great eruptions in the 17th century. In the first half of this century it has given its name to a class of stars which are characterized by spectral lines consisting of nearly undisplaced emissions accompanied by a blue-displaced absorption component. This characteristic P Cygni-type profile betrays the presence of a stellar wind, but P Cygni's wind is quite unlike that of other hot supergiants. P Cygni was the first star that showed the effects of stellar evoluton fro…
We have modeled nova light curves exceeding the Eddington luminosity. It has been suggested that a porous structure develops in nova envelopes during the super Eddington phase and the effective opacity is much reduced for such a porous atmosphere. Based on this reduced opacity model, we have calculated envelope structures and light curves of novae. The optically thick wind model is used to simulate nova winds. We find that the photospheric luminosity and the wind mass-loss rate increase inversely proportional to the reducing factor of opacities, but the wind velocity hardly changes. We also re…
We present a unified model for optical, ultraviolet (UV), and X-ray light curves of V1974 Cygni (Nova Cygni 1992). Based on an optically thick wind model of nova outbursts, we have calculated light curves and searched for the best fit model that is consistent with optical, UV, and X-ray observations. Our best fit model is a white dwarf (WD) of mass 1.05 M_\sun with a chemical composition of X=0.46, C+N+O=0.15, and Ne = 0.05 by mass weight. Both supersoft X-ray and continuum UV 1455 Ålight curves are well reproduced. Supersoft X-rays emerged on day ~ 250 after outburst, which is naturally expla…
The Hanle effect has been proposed as a new diagnostic of circumstellar magnetic fields for early-type stars, for which it is sensitive to field strengths in the 1-300 G range. In this paper we compute the polarized P-Cygni line profiles that result from the Hanle effect. For modeling the polarization, we employ a variant of the ``last scattering approximation''. For cases in which the Sobolev optical depths are greater than unity, the emergent line intensity is assumed to be unpolarized; while for smaller optical depths, the Stokes source functions for the Hanle effect with optically thin lin…
We show that the orbital variation in the UV P Cygni lines of the X-ray binary LMC X-4 results when X-rays photoionize nearly the entire region outside of the X-ray shadow of the normal star. We fit models to HST GHRS observations of N V and C IV P Cygni line profiles. Analytic methods assuming a spherically symmetric wind show that the wind velocity law is well-fit by v~(1-1/r)^beta, where beta is likely 1.4-1.6 and definitely <2.5. Escape probability models can fit the observed P Cygni profiles, and provide measurements of the stellar wind parameters. The fits determine Lx/Mdot=2.6+/-0.1 x10…
Recently, we correlated the inferred structure of the solar chromospheric plasma topography with solar wind velocity and composition data measured at 1AU. We now offer a physical justification of these relationships and present initial results of a empirical prediction model based on them. While still limited by the fundamentally complex physics behind the origins of the solar wind and how its structure develops in the magnetic photosphere and expands into the heliosphere, our model provides a near continuous range of solar wind speeds and composition quantities that are simply estimated from …
A continuous set of echelle spectra of TW Hya, taken with the MIKE spectrograph on the Magellan2/Clay telescope at Las Campanas Observatory in April 2006 reveals systematic variations in the flux, velocity, and profile of the H-alpha emission line which appear to be consistent with the photometric period of 2.8 days. Absorption features recur at high outflow velocities in the wind. This behavior suggests that: (a) accretion is not uniformly distributed over the stellar hemisphere in view; (b) stable structures are present in the chromosphere, most likely due to the stellar magnetic field confi…
We have examined radial velocities and fluxes of ultraviolet emission lines at different epochs, deduced from archival IUE and GRHS/HST spectra. The line fluxes give electron densities and were in addition used to calculate emission measures, suggesting line formation in regions rather smaller than the binary separation. Examination of the radial velocities led to us to find a systematic redshift of the high ionization resonance lines with respect to the intercombination, and HeII lines. Possible explanations of the redshift and the high resolution GHRS CIV profile are discussed. We favour tha…
We present a grid of nova models that have an extremely large number of species treated in non-LTE, and apply it to the analysis of an extensive time series of ultraviolet spectroscopic data for Nova Cygni 1992. We use ultraviolet colors to derive the time development of the effective temperature of the expanding atmosphere during the fireball phase and the first ten days of the optically thick wind phase. We find that the nova has a pure optically thick wind spectrum until about 10 days after the explosion. During this interval, we find that synthetic spectra based on our derived temperature …
We have determined the spectral energy distribution at wavelengths between 6 cm and 0.85 mm for the proto-typical S(stellar)-type symbiotic star, CI Cygni, during quiescence. Data were obtained simultaneously with the Very Large Array and the SCUBA sub-millimetre (sub-mm) camera on the James Clerk Maxwell Telescope. The data have allowed us to determine the free-free turnover frequency of the ionised component, facilitating a model-dependent estimate of the binary separation to compare with the known orbital parameters of CI Cug and to critically test the known models for radio emission from s…
We have fitted the Chandra Low Energy Transmission Grating spectrum of SS Cygni in outburst with a single temperature blackbody suffering the photoelectric opacity of a neutral column density and the scattering opacity of an outflowing wind. We find that this simple model is capable of reproducing the essential features of the observed spectrum with the blackbody temperature T_bl = 250+/-50 kK, hydrogen column density N_H = 5.0^{+2.9}_{-1.5} x 10^{19} cm^{-2}, fractional emitting area f = 5.6^{+60}_{-4.5} x 10^{-3}, boundary layer luminosity L_bl = 5^{+18}_{-3} x 10^{33} erg/s, wind velocity v…
We have detected the (0,11c,0)J=3-2 and (0,0,0)J=8-7 transitions of HCN towards the S star {chi} Cygni. The excitation requirements of these transitions are too high to be satisfied in the outer envelope of the star, and the emission must originate within {solar}20 stellar radii, ie. the molecule must be forming close to the star. This conclusion is supported by a model for AGB stars in which molecules including HCN form in a shocked wind close to the stellar surface.
We report on new data, including four vacuum ultraviolet spectropolarimetric observations by the Wisconsin Ultraviolet Photo-Polarimeter Experiment ("WUPPE") on the Astro-1 (one observation) and Astro-2 (three observations) shuttle missions, and 15 new visible-wavelength observations obtained by the HPOL CCD spectropolarimeter at the Pine Bluff Observatory of the University of Wisconsin. This includes three HPOL observations made within 12 hours of each of the three Astro-2 WUPPE observations, giving essentially simultaneous observations extending from 1500 to 10500 Angstroms. An analysis of t…
I discuss the role of short-duration eruptive mass loss in the evolution of very massive stars. Giant eruptions of Luminous Blue Variables (LBVs) like the 19th century event of $η$ Carinae can remove large quantities of mass almost instantaneously, making them significant in stellar evolution. They can potentially remove more mass from the star than line-driven winds, especially if winds are clumped such that O star mass-loss rates need to be revised downward. When seen in other galaxies as ``supernova impostors'', these eruptions typically last for less than a decade, and they can remove of o…
The luminous X-ray binary Circinus X-1 has been observed twice near zero orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS) onboard Chandra. The source was in a high-flux state during a flare for the first observation, and it was in a low-flux state during a dip for the second. Spectra from both flux states show clear P Cygni lines, predominantly from H-like and He-like ion species. These indicate the presence of a high-velocity outflow from the Cir X-1 system which we interpret as an equatorial accretion-disk wind, and from the blueshifted resonance absorption lines…
Chandra High Energy Transmission Grating Spectrometer (HETGS) observations of the extremely luminous and violent X-ray binary Cir X-1 reveal many X-ray emission lines showing broad P Cygni profiles. These are from H-like and He-like ions of Ne, Mg, Si, S, Ar, and Fe. The lines originate in a high-velocity (up to 2000 km s^-1) outflow, which may be an accretion disk wind. Cir X-1 has a radio jet, and during some periastron passages of the neutron star (orbital phase = 0.0), it flares at radio, infrared and X-ray wavelengths. The X-ray P Cygni profiles were observed during this phase, where we a…
Most symbiotic stars consist of a white dwarf accreting material from the wind of a red giant. An increasing number of these objects have been found to produce jets. Analysis of archival Chandra data of the symbiotic system CH Cygni reveals faint extended emission to the south, aligned with the optical and radio jets seen in earlier HST and VLA observations. CH Cygni thus contains only the second known white dwarf with an X-ray jet, after R Aquarii. The X-rays from symbiotic-star jets appear to be produced when jet material is shock-heated following collision with surrounding gas, as with the …
Context. In 1985, at the end of the active phase 1977-1986, a broad (4000 km/s) Ly alpha line appeared in the symbiotic system CH Cygni that had never been observed previously. Aims. In this work we investigate the origin of this anomalous broad Ly alpha line. Methods. We suggest a new interpretation of the broad Ly alpha based on the theory of charge transfer reactions between ambient hydrogen atoms and post-shock protons at a strong shock front. Results. We have found that the broad Ly alpha line originated from the blast wave created by the outburst, while the contemporary optical and UV li…
Context. We analyse the line and continuum spectra of the symbiotic system CH Cygni. Aims. To show that the colliding-wind model is valid to explain this symbiotic star at different phases. Methods. Peculiar observed features such as flickering, radio variation, X-ray emission, as well as the distribution of the nebulae and shells throughout the system are investigated by modelling the spectra at different epochs. The models account consistently for shock and photoionization and are constrained by absolute fluxes. Results. We find that the reverse shock between the stars leads to the broad lin…
A conceptually novel model - one in which stimulated (i.e. induced) resonance Rayleigh scattering causes ions of select species to become accelerated to very high terminal velocities in the solar winds of OB-type stars - is proposed to explain the general appearance of so-called P Cygni profiles that often dominate the vacuum ultraviolet (VUV) spectra of such stars. The high rate of stimulated scattering enables ions of the resonant species in the solar wind to become accelerated to terminal velocities as high as 1000 km/sec. Since stimulated scattering processes are characterized by pump powe…
We present the high resolution spectra of the D type symbiotic stars V1016 Cygni and HM Sagittae obtained with the Bohyunsan Optical Echelle Spectrograph (BOES), and investigate the double-peaked asymmetric profiles of the Raman scattered O VI 6825. By adopting a wind accretion disk model, we assume that the O VI emission region is described by a Keplerian thin disk. The Raman scattering occurs in a neutral region near the giant, taking in the form of a slow stellar wind, part of which is ionized by the strong UV radiation from the hot white dwarf. Using a Monte Carlo technique, we compute the…
Cataclysmic variables (CVs) are interacting binary systems where a cool, rapidly rotating secondary star passes material to a white dwarf. If this mass loss is to continue then there must be continuous angular momentum loss from the system. By analogy with the Sun and other cool stars, it has been assumed that magnetic braking is responsible, angular momentum being carried away by an ionised wind from the secondary star, threading a dynamo-generated magnetic field. We have discovered TiO absorption in the spectrum of SS Cyg, whose secondary star should be too hot to show such features. The mos…
We present the first grating-resolution X-ray spectra of the X-ray binary Cir X-1, obtained with the High Energy Transmission Grating Spectrometer on Chandra. These reveal a rich set of lines from H-like and/or He-like Ne, Mg, Si, S and Fe detected with a high signal-to-noise ratio. The lines are broad (+/- 2000 km/s) and show P Cygni profiles. The absorption components of the lines extend to low velocity, and they have about the same widths and strengths as the corresponding emission components. The widths of the X-ray P Cygni lines are comparable to that of the broad component of the strong,…
VLA surface brightness and spectral index maps of the evolving extended emission of the triple symbiotic star CH Cygni are presented. These are derived from observations at 4.8, 8.4 and 14GHz between 1985 and 1999. The maps are dominated by thermal emission around the central bright peak of the nebula, but we also find unambiguous non-thermal emission associated with the extended regions. Our observations confirm that this is a jet. The central region has been associated with the stellar components through HST imaging. If the jets are due to ejection events at outburst, expansion velocities ar…
Narrow Line Seyfert 1 galaxies are generally accreting at high fractions of the Eddington limit. They can show complex X-ray spectra, with a strong `soft excess' below 2 keV and a sharp drop at ~7 keV. There is strong evidence linking the soft excess to either reflection or absorption from relativistic, partially ionized material close to the black hole. The reflection models can also simultaneously produce the 7 keV feature from fluorescent iron Ka line emission from the disc. Here we show that absorption can also produce a sharp feature at 7 keV from the P Cygni profile which results from ab…
We present moderate and high-dispersion 1-2.5 micron spectra of the 10 arcsec nebula around P Cygni, dominated by bright emission lines of [Fe II]. Observed [Fe II] line ratios disagree with theoretical transition rates in the literature, so we use the spectrum of P Cygni's nebula to constrain the atomic data for low-lying levels of [Fe II]. Of particular interest is the ratio [Fe II] 12567/16435, often used as a reddening indicator, for which we empirically derive an intrinsic value of 1.49, which is 10--40 per cent higher than previous estimates. High-dispersion spectra of [Fe II] 16435 cons…
Deep, wide-field, continuum-subtracted, images in the light of the Halpha+[NII] 6548 & 6584 A and [O III] 5007 A nebular emission lines have been obtained of the environment of the Luminous Blue Variable (LBV) star P Cygni. A previously discovered, receding, nebulous filament along PA 50 deg has now been shown to extend up to 12' from this star. Furthermore, in the light of [O III] 5007 A, a southern counterpart is discovered as well as irregular filaments on the opposite side of P Cygni. Line profiles from this nebulous complex indicate that this extended nebulosity is similar to that associa…
We show that a strong P-Cygni feature seen in the far-UV spectra of some very hot (Teff >~ 85 kK) central stars of planetary nebulae (CSPN), which has been previously identified as CIII lambda 977, actually originates from NeVII lambda 973. Using stellar atmospheres models, we reproduce this feature seen in the spectra of two [WR]-PG 1159 type CSPN, Abell 78 and NGC 2371, and in one PG 1159 CSPN, K 1-16. In the latter case, our analysis suggests an enhanced neon abundance. Strong neon features in CSPN spectra are important because an overabundance of this element is indicative of processed mat…
As part of the Red MSX Source Survey of Massive Young Stellar Objects (MYSOs) we have conducted multi-wavelength follow up observations of the well-known object V645 Cygni. We present our data on this object, whose near-infrared spectrum is exceptional and place these in context with previous observations. Our observations of V645 Cyg included near/mid infrared imaging observations, 13CO 2-1 line observations and high signal-to-noise velocity resolved near-infrared spectroscopy. The spectrum shows P-Cygni hydrogen Brackett emission, consistent with a high velocity stellar wind. A red-shifted e…
We compare the predictions of hydrodynamic models of the LMC X-4 X-ray binary system with observations of UV P Cygni lines with the GHRS and STIS spectrographs on the Hubble Space Telescope. The hydrodynamic model determines density and velocity fields of the stellar wind, wind-compressed disk, accretion stream, Keplerian accretion disk, and accretion disk wind. We use a Monte Carlo code to determine the UV P Cygni line profiles by simulating the radiative transfer of UV photons that originate on the star and are scattered in the wind. The qualitative orbital variation predicted is similar to …
BZ Cam is the first cataclysmic variable star with an accretion disk wind evident in its optical spectrum. The wind was found by Thorstensen, who discovered intermittent P Cygni profiles occurring simultaneously in He I 5876 Angstroms and H alpha. We have since obtained spectra with 0.4-Angstroms/pixel dispersion and 60-s time resolution. We find a wind much faster and more rapidly variable than the radiatively accelerated winds of OB stars, Wolf-Rayet stars, or luminous blue variables. Instead of showing blob ejection, the whole wind of BZ Cam appears to turn on and off. We use this to measur…
The ultraviolet spectra of all "weak emission line central stars of planetary nebulae" (WELS) with available IUE data is analyzed. We found that the WELS can be divided in three different groups regarding their UV: (1) Strong P-Cygni profiles (mainly in C IV 1549); (2) Weak P-Cygni features and (3) Absence of P-Cygni profiles. We have measured wind terminal velocities for all objects presenting P-Cygni profiles in N V 1238 and/or C IV 1549. The results obtained were compared to the UV data of the two prototype stars of the [WC]-PG 1159 class, namely, A30 and A78. They indicate that WELS are di…
We obtained Halpha diffraction limited data of the LBV star P Cyg using the ONERA Adaptive Optics (AO) facility BOA at the OHP 1.52m telescope on October 1997. Taking P Cyg and the reference star 59 Cyg AO long exposures we find that P Cyg clearly exhibits a large and diffuse intensity distribution compared to the 59 Cyg's point-like source. A deconvolution of P Cyg using 59 Cyg as the Point Spread Function was performed by means of the Richardson-Lucy algorithm. P Cyg clearly appears as an unresolved star surrounded by a clumped envelope. The reconstructed image of P Cyg is compared to simila…
The physics of the Hanle effect is briefly reviewed, and its application as a diagnostic of hot star magnetic fields is described. Emphasis is given to the practicalities of using spectropolarimetry of resolved wind emission lines to infer information about the circumstellar magnetic field strength and its geometry. A model for a weakly magnetized wind from "WCFields" theory is used as the backdrop for investigating polarized line profile effects for P Cygni resonance lines using a kind of "last scattering approximation". Model results are presented for a typical P Cygni line that forms in a s…
The ultraviolet spectra of all ``weak emission line central stars of planetary nebulae'' (WELS) with available IUE data are presented and discussed. We performed line identifications, equivalent width and flux measurements for several features in their spectra. We found that the WELS can be divided in three different groups regarding their UV: i) Strong P-Cygni profiles (mainly in CIV 1549); ii) Weak P-Cygni features and iii) Absence of P-Cygni profiles. The last group encompasses stars with a featureless UV spectrum or with intense emission lines and a weak continuum, which are most likely of…
We report the detection of N V 1239 A transition region emission in HST/GHRS spectra of the A7 V stars, Alpha Aql and Alpha Cep. Our observations provide the first direct evidence of 1-3 x 10^5 K material in the atmospheres of normal A-type stars. For both stars, and for the mid-A--type star Tau3 Eri, we also report the detection of chromospheric emission in the Si III 1206 A line. At a B-V color of 0.16 and an effective temperature of 8200 K, Tau3 Eri becomes the hottest main sequence star known to have a chromosphere and thus an outer convection zone. We see no firm evidence that the Si III …
(Shortened) Ultraviolet observations of the black hole X-ray binary Cygnus X-1 were obtained using the STIS on HSTubble. We detect P Cygni line features show strong, broad absorption components when the X-ray source is behind the companion star and noticeably weaker absorption when the X-ray source is between us and the companion star. We fit the P Cygni profiles using the SEI method applied to a spherically symmetric stellar wind subject to X-ray photoionization from the black hole. The Si IV doublet provides the most reliable estimates of the parameters of the wind and X-ray illumination. Th…
HST high resolution spectra of metal-deficient field giants more than double the stars in previous studies, span about 3 magnitudes on the red giant branch, and sample an abundance range [Fe/H]= -1 to -3. These stars, in spite of their age and low metallicity, possess chromospheric fluxes of Mg II (2800 Angstrom) that are within a factor of 4 of Population I stars, and give signs of a dependence on the metal abundance at the lowest metallicities. The Mg II k-line widths depend on luminosity and correlate with metallicity. Line profile asymmetries reveal outflows that occur at lower luminositie…
Spectroscopic data in wavelengths 900--3000A have been obtained in a low flux state of the nucleus of the Seyfert 1 galaxy NGC 3516. The line profiles show P Cygni characteristics, particularly in O VI 1032A, and are compared with data from an earlier higher state. The profiles are suggestive of, and consistent with, an accelerating wind driven by a disk continuum source, in which the ionisation radii have changed. This scenario may apply to the formation of other broad emission lines in AGN.
Resonance lines that are sensitive to the Hanle effect are prominent in the UV spectra of early-type stars. To understand the differences from the solar application of the Hanle effect, we focus on the formation of P-Cygni lines both as a scattering process, and as one that allows a spectral isolation of sectors in the wind. Some complications occuring in the solar case are found to be absent for the Hanle effect for hot stars. Rocket observations from the Far Ultraviolet SpectroPolarimeter (FUSP) experiment should allow for a determination of fields in the dynamically interesting range from 1…
We present the results of a photometric monitoring campaign of three well studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken at Maidanak Observatory between 1981 and 2003. When combined with photometric data in the literature, this database provides a valuable resource for searching for short timescale variability - both periodic and aperiodic - as well as for studying the secular evolution of these systems. In the case of V1057 Cyg (which is the system exhibiting the largest changes in brightness since it went into outburst) we compare the photometric data with ti…
We present results obtained from near-infrared JHK spectroscopic observations of novae V2491 Cyg and V597 Pup in the early declining phases of their 2007 and 2008 outbursts respectively. In both objects, the spectra displayed emission lines of HI, OI, HeI and NI. In V597 Pup, the HeI lines were found to strengthen rapidly with time. Based on the observed spectral characteristics, both objects are classified as He/N novae. We have investigated the possibility of V2491 Cyg being a recurrent nova as has been suggested. By studying the temporal evolution of the line widths in V2491 Cyg it appears …
We have analyzed a time series of spectra in the hydrogen Lyman lines and the Lyman continuum obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the SOlar Heliospheric Observatory (SOHO). The time series of about 2 hours and 22 minutes was obtained on 1999 March 9 in a quiet region near the center of the solar disk. For our analysis, we have selected a Lyman continuum window around 907 A, and the five Lyman lines: Ly5 (937.8 A), Ly7 (926.2 A), Ly9 (920.9 A), Ly11 (918.1 A), and Ly15 (915.3 A). A Fast Fourier analysis has been performed in the spatial do…
We present new spectroscopic observations of the He I $λ$10830 line in R Coronae Borealis (RCB) stars which provide the first strong evidence that most, if not all, RCB stars have winds. It has long been suggested that when dust forms around an RCB star, radiation pressure accelerates the dust away from the star, dragging the gas along with it. The new spectra show that nine of the ten stars observed have P-Cygni or asymmetric blue-shifted profiles in the He I $λ$10830 line. In all cases, the He I line indicates a mass outflow - with a range of intensity and velocity. Around the RCB stars, it …
Aims: To investigate magnetic reconnection rates during the coalescence of two current loops in the solar chromosphere, by altering the neutral-hydrogen to proton density ratio, ioniziation/recombination coefficients, collision frequency and relative helicity of the loops. Methods: 2.5D numerical simulations of the chromosphere were conducted using a newly developed two-fluid (ion-neutral) numerical code. Developed from the Artificial Wind scheme, the numerical code includes the effects of ion-neutral collisions, ionization/recombination, thermal/resistive diffusivity and collisional/resistive…
We present H alpha emission line spectra of 7 post-AGB stars. Typically, they have a P-Cygni type profile with a very strong emission component and a relatively narrow absorption component. These lines are formed in the fast post-AGB wind which in most cases has a velocity of around 100 km/s. Hence the emission originates close to the central star and the absorption occurs in the fast wind itself or in the region where the fast wind sweeps up the slow wind. The emission profile has very broad wings. It is still unclear what causes these wings.
We report the detection with FUSE of strong, highly blue-shifted absorption features appearing in the absorption troughs of practically all major P Cygni profiles in the presumably single Wolf-Rayet star WR135. These features also appear in the shock-sensitive OVI 1032/38 Ådoublet, coincident both in time and velocity space with the rest of the lower-ionization species. Choosing between two alternative interpretations: large-scale, coherent structures vs. localized, random shocks, we favor the latter. The absolute value of velocity, as well as velocity dispersion in the shocked region, the den…
We present a unified picture of outflowing gas from the X-ray binary system Hercules X-1/HZ Herculis. We suggest that the outflowing gas (a wind) causes UV emission seen in mid-eclipse, narrow UV absorption lines, and broad UV P Cygni lines. Observations with the FOS and STIS spectrographs on the Hubble Space Telescope (HST) show UV emission lines in the middle of X-ray eclipse, when the X-ray heated atmosphere of the normal star and accretion disk should be entirely hidden from view. Narrow absorption lines (FWHM~50 km/s) blueshifted by 500 km/s during observations in 1998 and by 400 km/s dur…
Spectroscopy of the infrared He I (10830A) line with KECK/NIRSPEC and IRTF/CSHELL, and of the ultraviolet C III (977A) and O VI (1032A) emission with FUSE reveals that the classical T Tauri star TW Hydrae exhibits P Cygni profiles, line asymmetries, and absorption indicative of a continuous, fast (~400 km/s), hot (~300,000 K) accelerating outflow with a mass loss rate \~10^-11 - 10^-12 solar masses per year, or larger. Spectra of T Tauri N appear consistent with such a wind. The source of the emission and outflow seems restricted to the stars themselves. Although the mass accretion rate is an …
We discuss the development of the new radiative transfer code Wind3D. It solves the non-LTE radiative transport problem in moving stellar atmosphere models in three geometric dimensions. The code accepts arbitrary 3D velocity fields in Cartesian geometry without assumptions of axial symmetry. Wind3D is currently implemented as a fully parallelized (exact) accelerated lambda iteration scheme with a two level atom formulation. The numerical transfer scheme is efficient and very accurate to trace small variations of local velocity gradients on line opacity in strongly scattering dominated extende…
We present our spectroscopic data around H$β$ of the symbiotic star V1016 Cyg obtained with the Bohyunsan Echelle Spectrograph, in order to secure the broad emission feature at around 4850Å, which is formed through Raman scattering of He II $λ$ 972. The total cross section around Ly$γ$ is approximately given by $σ(λ)\simeq 1.7\times 10^{-28}[λ_{Lyγ}/(λ-λ_{Lyγ})]^2{\rm cm^2}$, with $λ_{Lyγ}$ being the line centre wavelength of Ly$γ$. We find a centre shift redward by an amount $Δλ= +0.64{\rm Å}$ in the Raman scattered He II $λ$ 4850. This redward centre shift is exactly analogous to the effect …
We present photometric and spectroscopic observations of two luminous blue variable (LBV) stars in two extremely metal-deficient blue compact dwarf (BCD) galaxies, DDO 68 with 12+logO/H = 7.15 and PHL 293B with 12+logO/H = 7.72. These two BCDs are the lowest-metallicity galaxies where LBV stars have been detected, allowing to study the LBV phenomenon in the extremely low metallicity regime, and shedding light of the evolution of the first generation of massive stars born from primordial gas. We find that the strong outburst of the LBV star in DDO 68 occurred sometime between February 2007 and …
We have analyzed high spatial, moderate spectral resolution observations of Eta Carinae obtained with the STIS from 1998.0 to 2004.3. The spectra show prominent P-Cygni lines in H I, Fe II and He I which are complicated by blends and contamination by nebular emission and absorption along the line-of-sight toward the observer. All lines show phase and species dependent variations in emission and absorption. For most of the cycle the He I emission is blueshifted relative to the H I and Fe II P-Cygni emission lines, which are approximately centered at system velocity. The blueshifted He I absorpt…
Infrared observations of hot massive stars and their environments provide a detailed picture of mass loss histories, dust formation, and dynamical interactions with the local stellar medium that can be unique to the thermal regime. We have acquired new infrared spectroscopy and imaging with the sensitive instruments onboard the Spitzer Space Telescope in guaranteed and open time programs comprised of some of the best known examples of hot stars with circumstellar nebulae, supplementing with unpublished Infrared Space Observatory spectroscopy. Here we present highlights of our work on the envir…
We present infrared spectroscopy of the low-mass X-ray binary GX 1+4/V2116 Oph. This symbiotic binary consists of a 2-min accretion-powered pulsar and an M5 III red giant. A strong He I 1.083 micron emission line with a pronounced P Cygni profile was observed. From the blue edge of this feature, we infer an outflow velocity of 250(50) km/s. This is an order of magnitude faster than a typical red giant wind, and we suggest that radiation from the accretion disk or the neutron star may contribute to the acceleration of the outflow. We infer a wind mass loss rate of around 10^-6 Msun/yr. Accretio…
Outflows in the form of fast winds from the accretion disk appear in nearly all high accretion rate cataclysmic variables (CVs), both novalikes (NLs) and dwarf novae in outburst (DN). The primary signatures of CV winds are broad, blueshifted absorption features and P Cygni profiles that appear in the ionized metal lines of lower inclination systems and the broad emission lines that appear in eclipsing systems. Much progress has been made in our understanding of the structure and behavior of CV outflows based on data obtained with X-ray, EUV, and UV telescopes and the kinematical models develop…
We present a spectrum of the symbiotic star V1016 Cyg observed with the 3.6 m Canada-France-Hawaii Telescope, in order to illustrate a method to measure the covering factor of the neutral scattering region around the giant component with respect to the hot emission region around the white dwarf component. In the spectrum, we find broad wings around H$α$ and a broad emission feature around 6545${\rm Å}$ that is blended with the [N II]$ λ$ 6548 line. These two features are proposed to be formed by Raman scattering by atomic hydrogen, where the incident radiation is proposed to be UV continuum ra…
A review of spectroscopic results obtained from Chandra High Energy Transmission Grating Spectrometer and XMM-Newton Reflection Grating Spectrometer observations of several wind-fed high-mass X-ray binaries (HMXBs) is presented. These observations allow us to study the structure of the stellar wind in more detail and provide, for the first time, a dyanmical view of the X-ray photoionized wind that surrounds the compact object. At the same time, however, they are also providing us with numerous puzzles that cannot be explained in terms of simple models. For example, simple spherically-symmetric…
Thermal and ionization structures of self-similar, magnetically-driven disk winds obtained in a companion paper \cite{Garcia2001a} are used to compute a series of jet synthetic observations. These include spatially resolved forbidden line emission maps, long-slit spectra, as well as line ratios. Line profiles and jet widths appear to be good tracers of the wind dynamics and collimation, whereas line ratios essentially trace gas excitation conditions. All the above diagnostics are confronted to observations of T Tauri star microjets. Convolution by the observing beam is shown to be essential fo…
We study a possibility of detection of circumstellar absorption lines of Na I D$_{1,2}$ and Ca II H,K in spectra of type IIP supernovae at the photospheric epoch. The modelling shows that the circumstellar lines of Na I doublet will not be seen in type IIP supernovae for moderate wind density, e.g., characteristic of SN 1999em, whereas rather pronounced Ca II lines with P Cygni profile should be detectable. A similar model is used to describe Na I and Ca II circumstellar lines seen in SN 1998S, type IIL with a dense wind. We show that line intensities in this supernova are reproduced, if one a…
