CONTEXT. Many O-type stars have nearby companions whose presence hamper their characterization through spectroscopy.
AIMS. We want to obtain spatially resolved spectroscopy of close O-type visual binaries to derive their spectral types.
METHODS. We use the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope (HST) to obtain long-slit blue-violet spectroscopy of eight Galactic O-type stars with nearby visual companions and use spatial-profile fitting to extract the separate spectra. We also use the ground-based Galactic O-Star Spectroscopic Survey (GOSSS) to study more distant visual components.
RESULTS. We spatially resolve seven of the eight systems, present spectra for their components, and obtain their spectral types. Those seven multiple systems are iota Ori Aa,Ab,B, 15 Mon Aa,Ab,C, tau CMa Aa,Ab,B,C,D,E, HD 206 267 Aa,Ab,C,D, HD 193 443 A,B, HD 16 429 Aa,Ab, and IU Aur A,B. This is the first time that spatially resolved spectroscopy of the close visual binaries of those systems is obtained. We establish the applicability of the technique as a function of the separation and magnitude difference of the binary.
We present UV spectra of the protoplanetary nebula (pPN) Hen3-1475 obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). Our deep, low-dispersion spectroscopy enables monochromatic imaging of Hen3-1475 in UV nebular emission lines, the first of such attempt ever made for a pPN. The high spatial resolution of STIS imaging allows an unprecedentedly sharp view of the S-shaped jet, especially the inner NW1 knot, which is resolved into four components in the MgII 2800 line emission. Through critical comparison with HST optical narrowband images, we…
The NIST database lists several Mn II lines that were observed in the laboratory but not classified. They cannot be used in spectrum synthesis because their atomic line data are unknown. These lines are concentrated in the 2380-2700 A interval. We aimed to assign energy levels and log gf values to these lines. Semi-empirical line data for Mn II computed by Kurucz were used to synthesize the ultraviolet spectrum of the slow-rotating, HgMn star HD 175640. The spectrum was compared with the high-resolution spectrum observed with the HST-STIS equipment. A UVES spectrum covering the 3050-10000 A re…
The B-emission line stars are rapid rotators that were probably spun up by mass and angular momentum accretion through mass transfer in an interacting binary. Mass transfer will strip the donor star of its envelope to create a small and hot subdwarf remnant. Here we report on Hubble Space Telescope/STIS far-ultraviolet spectroscopy of a sample of Be stars that reveals the presence of the hot sdO companion through the calculation of cross-correlation functions of the observed and model spectra. We clearly detect the spectral signature of the sdO star in 10 of the 13 stars in the sample, and the…
The multiple star system of delta Orionis is one of the closest examples of a system containing a luminous O-type, bright giant star (component Aa1). It is often used as a spectral-type standard and has the highest observed X-ray flux of any hot-star binary. The main component Aa1 is orbited by two lower mass stars, faint Aa2 in a 5.7 day eclipsing binary, and Ab, an astrometric companion with an estimated period of 346 years. Generally the flux from all three stars is recorded in ground-based spectroscopy, and the spectral decomposition of the components has proved difficult. Here we present …
We present the results of new spectral diagnostic investigations applied to high-resolution long-slit spectra of the RW Aur bipolar jet obtained with HST/STIS. The spectra include the forbidden doublets [O I] 6300,6363 Å, [S II] 6716,6731 Å, and [N II] 6548, 6583 Åthat we utilized to determine electron density, electron temperature, hydrogen ionisation fraction, total hydrogen density, radial velocity and the mass outflow rate. We were able to extract the parameters as far as 3".9 in the red- and 2".1 in the blueshifted beam. The RW Aur jet appears to be the second densest outflow from a T Tau…
The goal of the present study is twofold. First, we employ new HST/STIS spectra and photoionization modeling techniques to determine the progenitor masses of eight planetary nebulae (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, NGC 7662 and PB6). Second, for the first time we are able to compare each object's observed nebular abundances of helium, carbon and nitrogen with abundance predictions of these same elements by a stellar model that is consistent with each object's progenitor mass. Important results include the following: 1) the mass range of our objects' central stars matc…
We present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30x30 parsec^2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong HeII 1640 emission at very early ages (1-2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even …
We present the first ultraviolet spectrum of the peculiar, magnetic Of?p star HD 108 obtained in its spectroscopic low state. The new data, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope, reveal significant changes compared to IUE spectra obtained in the high state: N V 1240, Si IV 1400, and C IV 1550 present weaker P-Cygni profiles (less absorption) in the new data, while N IV 1718 absorption is deeper, without the clear wind signature evident in the high state. Such changes contrast with those found in other magnetic massive stars, where more abso…
Lyman-alpha (Lya) emission of neutral hydrogen (1215.67 Angström) is the main contributor to the ultraviolet flux of low-mass stars such as M dwarfs. It is also the main light source used in studies of the evaporating upper atmospheres of transiting extrasolar planets with ultraviolet transmission spectroscopy. However, there are very few observations of the Lya emissions of quiet M dwarfs, and none exist for those hosting exoplanets. Here, we present Lya observations of the hot-neptune host star GJ436 with the Hubble Space Telescope Imaging Spectrograph (HST/STIS). We detect bright emission i…
The sharp-line spectrum of the Bp star HR 6000 has peculiarities that distinguish it from those of the HgMn stars with which it is sometimes associated. The position of the star close to the center of the Lupus 3 molecular cloud, whose estimated age is on the order of 9.1 +/- 2.1 Myr, has lead to the hypothesis that the anomalous peculiarities of HR 6000 can be explained by the young age of the star. Observational material from HST provides the opportunity to extend the abundance analysis previously performed for the optical region and clarify the properties of this remarkable peculiar star. O…
CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. We used our own far-UV and visual photometric obs…
We present observations and initial analysis from an HST/STIS program to obtain the first co-spatial, UV-optical spectra of ten Galactic planetary nebulae (PNe). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented S/N and spatial resolution over UV-optical range, with the ultimate goal of quantifying the production of these elements in low- and intermediate-mass stars. Our sample was selected from PNe with a near-solar metallicity, but spanning a broad range in N/O. This study, the first of a series, concentrates on the observations and em…
Planetary nebulae (PNe) are expected to have a ~10$^{5}$ K interface layer between the $\geq$10$^{6}$ K inner hot bubble and the ~10$^{4}$ K optical nebular shell. The PN structure and evolution, and the X-ray emission depend critically on the efficiency of mixing of material at this interface layer. However, neither its location nor its spatial extent has ever been determined so far. Using high-spatial resolution HST STIS spectroscopic observations of the N V 1239,1243 lines in the Cat's Eye Nebula (NGC 6543), we have detected this interface layer and determined its location, extent, and phys…
Non-local Thermodynamic Equilibrium (NLTE) calculations of hot white dwarf (WD) model atmospheres are the cornerstone of modern flux calibrations for the Hubble Space Telescope (HST) and for the CALSPEC database. These theoretical spectral energy distributions (SEDs) provide the relative flux vs. wavelength, and only the absolute flux level remains to be set by reconciling the measured absolute flux of Vega in the visible with the Midcourse Space Experiment (MSX) values for Sirius in the mid-IR. The most recent SEDs calculated by the \textsc{tlusty} and \textsc{tmap} NLTE model atmosphere code…
Detailed abundances of the elements produced by r-process nucleosynthesis in various circumstances are our best observational clues to their origin, since the site(s) of r-element production is(are) still not known with certainty. A small fraction of extremely metal-poor (EMP) stars exhibit excesses of heavy neutron-capture elements produced in the r-process, and CS 31082-001 is among the 4 well-known r-process-enhanced EMP stars. Observations with HST/STIS provide abundances for elements observable only from the UV region. Here we aim to supplement the optical data with abundances from near-U…
The Space Telescope Imaging Spectrograph (STIS) has measured the spectral energy distributions (SEDs) for several stars of types O, B, A, F, and G. These absolute fluxes from the CALSPEC database are fit with a new spectral grid computed from the ATLAS-APOGEE ATLAS9 model atmosphere database using a chi-square minimization technique in four parameters. The quality of the fits are compared for complete LTE grids by Castelli & Kurucz (CK04) and our new comprehensive LTE grid (BOSZ). For the cooler stars, the fits with the MARCS LTE grid are also evaluated, while the hottest stars are also fit wi…
We present an atmospheric transmission spectrum of the ultra-hot Jupiter WASP-76 b by analyzing archival data obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The dataset spans three transits, two with a wavelength coverage between 2900 and 5700 Armstrong, and the third one between 5250 and 10300 Armstrong. From the one-dimensional, time dependent spectra we constructed white and chromatic light curves, the latter with typical integration band widths of ~200 Armstrong. We computed the wavelength dependent planet-to-star radii ratios takin…
We present observations of three protoplanetary disks in visible scattered light around M-type stars in the Upper Scorpius OB association using the STIS instrument on the Hubble Space Telescope. The disks around stars 2MASS J16090075-1908526, 2MASS J16142029-1906481 and 2MASS J16123916-1859284 have all been previously detected with ALMA, and 2MASS J16123916-1859284 has never previously been imaged at scattered light wavelengths. We process our images using Reference Differential Imaging, comparing and contrasting three reduction techniques - classical subtraction, Karhunen-Loeve Image Projecti…
Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the Hubble Space Telescope that show strong flickering in the UV continuum on time-scales of <~20 s, characteristic of an active accretion disk. Several UV lines with P…
We present an analysis of the visible through near infrared spectrum of Eta Carinae and its ejecta obtained during the "Eta Carinae Campaign with the UVES at the ESO VLT". This is a part of larger effort to present a complete Eta Carinae spectrum, and extends the previously presented analyses with the HST/STIS in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorpt…
CONTEXT: The second Gaia data release (DR2) took place on April 2018. DR2 included photometry for more than 1.3 10^9 sources in G, BP, and RP. Even though Gaia DR2 photometry is very precise, there are currently three alternative definitions of the sensitivity curves that show significative differences. AIMS: The aim of this paper is to improve the quality of the input calibration data to produce new compatible definitions of the three bands and to identify the reasons for the discrepancies between previous definitions. METHODS: We have searched the HST archive for STIS spectra with G430L+G750…
We present new Hubble Space Telescope observations of three a priori known starlight-scattering circumstellar debris systems (CDSs) viewed at intermediate inclinations around nearby close-solar analog stars: HD 207129, HD 202628, and HD 202917. Each of these CDSs possesses ring-like components that are more-massive analogs of our solar system's Edgeworth- Kuiper belt. These systems were chosen for follow-up observations to provide higher-fidelity and better sensitivity imaging for the sparse sample of solar-analog CDSs that range over two decades in systemic ages with HD 202628 and HD 202917 (…
The Weigelt knots, dense slow-moving ejecta near eta Car, are mysterious in structure as well as in origin. Using a special set of spectrograms obtained with the HST/STIS, we have partially resolved the ionization zones of one knot to an accuracy of about 10 mas. Contrary to simple models, higher ionization levels occur on the_outer_ side of the knot, i.e., farther from the star. They cannot represent a bow shock, and no truly satisfying explanation is yet available -- though we sketch one tentative possibility. We emphasize that STIS spectrograms provide far more reliable spatial measurements…
We determine abundances or upper limits for all of the 55 stable elements from copper to uranium for the A1 Vm star Sirius. The purpose of the study is to assemble the most complete picture of elemental abundances with the hope of revealing the chemical history of the brightest star in the sky, apart from the Sun. We also explore the relationship of this hot metallic-line (Am) star to its cooler congeners, as well as the hotter, weakly- or non-magnetic mercury-manganese (HgMn) stars. Our primary observational material consists of {\em Hubble Space Telescope} ($HST$) spectra taken with the Spac…
We derive the physical properties at the base of the jet from DG Tau both along and across the flow and as a function of velocity. We analysed seven optical spectra of the DG Tau jet, taken with the Hubble Space Telescope Imaging Spectrograph. The spectra were obtained by placing a long-slit parallel to the jet axis and stepping it across the jet width. The resulting position-velocity diagrams in optical forbidden emission lines allowed access to plasma conditions via calculation of emission line ratios. We find at the base of the jet high electron density, $n_e \sim $ 10$^5$, and very low ion…
Hubble Science in the 2030s White Paper: High-Contrast Optical and UV Spectroscopy with HST/STIS
Smith College（史密斯学院）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Texas - San Antonio（德克萨斯大学圣安东尼奥分校）；United States Naval Academy（美国海军学院）；Johns Hopkins University（约翰斯·霍普金斯大学）；Academia Sinica Institute of Astronomy & Astrophysics（中央研究院天文及天文物理研究所）；University of Hawai’i at Manoa（夏威夷大学马诺阿分校）；Amherst College（阿默斯特学院）
In late 2006, ground-based photometry of $η$ Car plus the Homunculus showed an unexpected decrease in its integrated apparent brightness, an apparent reversal of its long-term brightening. Subsequent HST/WFPC2 photometry of the central star in the near-UV showed that this was not a simple reversal. This multi-wavelength photometry did not support increased extinction by dust as the explanation for the decrease in brightness. A spectrum obtained with GMOS on the Gemini-South telescope, revealed subtle changes mid-way in $η$ Car's 5.5 yr spectroscopic cycle 0when compared with HST/STIS spectra a…
We present two new epochs of Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphic imaging, along with multi-epoch optical, near-IR, and radio monitoring, of the HD 163296 system. We find ansae features identified in earlier epoch HST imagery are a 4th ring, that resides at a semi-major axis distance of 3.25" (330 au). We determine the scale height of the dust is 64 au at a radial distance of 330 au. We observe surface brightness variations in the 4th ring on <3 month timescales, including large-scale, azimuthally asymmetric changes. This variability resembles earlier studi…
T Aurigae is an eclipsing old nova which exploded in 1891. At a Gaia EDR3 distance of 815-871 pc, it is a relatively nearby old nova. Through ultraviolet spectral modeling and using the new precise Gaia distance, we find that the HST/STIS spectrum of T Aurigae is consistent with an accretion disk with a mass transfer rate $\dot{M}$ of the order of $10^{-8}M_{\odot}$/yr, for a white dwarf mass of $M_{\rm wd} \approx 0.7 \pm 0.2 M_{\odot}$, an inclination of $i \sim 60^{\circ}$, and a Gaia distance of of $840_{-25}^{+31}$~pc. The sharp absorption lines of metals cannot form in the disk and are l…
The Space Telescope Imaging Spectrograph (STIS) has measured the flux for Sirius from 0.17--1.01~$μ$m on the \emph{HST} White Dwarf scale. Because of the cool debris disk around Vega, Sirius is commonly recommended as the primary IR flux standard. The measured STIS flux agrees well with predictions of a special Kurucz model atmosphere, adding confidence to the modeled IR flux predictions. The IR flux agrees to 2--3% with respect to the standard template of Cohen and to 2% with the MSX absolute flux measurements in the mid-IR. A weighted average of the independent visible and mid-IR absolute fl…
Data from transit light curves, radial velocity and transit timing observations can be used to probe the interiors of exoplanets beyond the mean density, by measuring the Love numbers $h_2$ and $k_2$. The first indirect estimate of $k_2$ for an exoplanet from radial velocity and transit timing variations observations has been performed by taking advantage of the years-spanning baseline. Not a single measurement of $h_2$ has been achieved from transit light curves, mostly because the photometric precision of current observing facilities is still too low. We show that the Imaging Spectrograph in…
We present an optical to near-infrared transmission spectrum of the hot Jupiter HAT-P-1b, based on HST observations, covering the spectral regime from 0.29 to 1.027μm with STIS, which is coupled with a recent WFC3 transit (1.087 to 1.687μm). We derive refined physical parameters of the HAT-P-1 system, including an improved orbital ephemeris. The transmission spectrum shows a strong absorption signature shortward of 0.55μm, with a strong blueward slope into the near-ultraviolet. We detect atmospheric sodium absorption at a 3.3σ significance level, but find no evidence for the potassium feature.…
