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A variety of on-orbit imaging and spectroscopic observations are used to characterize the Charge Transfer Efficiency (CTE) of the Charge-Coupled Device (CCD) of the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope. A set of formulae is presented to correct observations of point sources for CTE-related loss of signal. For data taken in imaging mode, the CTE loss is parametrized in terms of the location of the source on the CCD, the source signal level within the measurement aperture, the background level, and the time of observation. For spectroscopic data, it is found that one additional parameter is needed to provide an adequate calibration of the CTE loss, namely the signal in the point spread function located between the signal extraction box and the read-out amplifier. The effect of the latter parameter is significant for spectra taken using the G750L or G750M gratings of STIS. The algorithms presented here correct flux calibration inaccuracies due to CTE losses as large as 30% to within ~ 1.5% RMS throughout the wavelength range covered by the STIS CCD modes. This uncertainty is similar to the Poisson noise associated with a source detected at a signal level of about 2500 electrons per resolution element. Using bi-directional CCD readouts, centroid shifts incurred due to CTE loss are also derived. A tight correlation is found between the CTE loss and the centroid shift (both for imaging and spectroscopic modes), thus enabling one to correct for both effects of imperfect charge transfer to STIS CCD observations.

The unfiltered Space Telescope Imaging Spectrograph (STIS) CCD in tandem with focal plane wedges and a Lyot stop provides a simple white‐light coronagraph with a bandpass of 0.2–1.0 μm, which has been used since late 1998 to image nebulosity around stars in the ranges \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $0.34\leq V\leq 14$ \end{document} and \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \use...

The calculation and use of molecular hydrogen optical depth templates to quickly identify and model molecular hydrogen absorption features longward of the Lyman edge at 912 Angstroms are described. Such features are commonly encountered in spectra obtained by the Far Ultraviolet Spectroscopic Explorer and also in spectra obtained by the Space Telescope Imaging Spectrograph, albeit less commonly. Individual templates are calculated containing all the Lyman and Werner transitions originating from a single rotational state (J'') of the 0th vibrational level (v'') of the ground electronic state. Templates are provided with 0.01 Angstrom sampling for doppler parameters ranging from 2, 20 pages, 2 tables, 6 figures, submitted to PASP 02-04-2003 Accepted for publication on 03-05-2003 with revisions, including modified fg1, modifed fg6 to become fg2 to support improved error discussion. To appear in the June 2003 issue of the PASP

Using what is known about the physical and chemical structure of the CCD detector on the Space Telescope Imaging Spectrograph (STIS) and over 50 calibration images taken with different wavelength mappings onto the detector, we have devised a model function that allows us to predict the fringing of any spectral image taken with the STIS CCD. This function is especially useful for spectra taken without a slit with the G750L grating. The STIS parallel observing program uses this “slitless spectroscopy” mode extensively. The arbitrary mapping of wavelength versus position that results from each source's chance position in the field renders direct calibration of the fringe amplitudes in this mode impossible. However, we find that correcting observed data using our semiempirical fringing model produces a substantial reduction in the fringe amplitudes. Tests using the flux calibration white dwarf standard G191‐B2B show that we can reduce the fringe amplitude in the 9000–10000 A region from about 20% pea...

We present deep Hubble Space Telescope optical imaging observations of two Galactic globular clusters, 47 Tuc and M15, using the Space Telescope Imaging Spectrograph (STIS) longpass (LP) filter and the Wide Field and Planetary Camera 2 (WFPC2) F606W and F814W filters. These globular clusters have very different metallicities ([Fe/H] = -0.7 dex for 47 Tuc, and [Fe/H] = -2.2 dex for M15), essentially spanning the metallicity distribution of the entire Milky Way globular cluster system, and were chosen to investigate the relationship between magnitudes in the non-standard STIS LP system and the better characterized WFPC2 magnitudes. We determine this relationship by combining our new STIS data with archival WFPC2 data, taking care to provide a robust and reliable transformation. Examining the 47 Tuc and M15 data separately, there is no evidence for a metallicity dependence in the transformation relations. This allows us to combine the data for both clusters, and also include the stars in the Small Magellanic Cloud that lie within the field of view of the 47 Tuc images, to determine final transformations that are valid for main sequence stars with colors in the range 0.3 < V606-I814 < 1.8. These final relations predict STIS magnitudes within 0.05 mag (1 sigma) of those measured for stars in both clusters. In an appendix, we discuss the differences between our empirical transformation relations and those predicted by synthetic photometry.

An ultraviolet and optical spectral atlas of 15 O stars in the Small Magellanic Cloud (SMC) is presented and described. The echelle data have resolving powers of order 104; they were obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph in the UV, and at the Anglo‐Australian Telescope or the European Southern Observatory 3.6 m in the optical. The ultimate objective is to develop metal‐deficient templates for the interpretation of distant starbursts, but here we discuss interesting new properties of the SMC stars themselves, revealed by the high quality of these data. The SMC metal deficiency produces anomalously weak stellar‐wind profiles along the entire O main sequence, as well as at intermediate luminosities; the first intermediate Si iv λ1400 wind profile in the SMC is shown. The second known Of star in the SMC displays wind peculiarities that are identical to those of its spectral classmate, again likely due to the low systemic metallicity. Several objects display mar...

On‐orbit data characteristics of the Space Telescope Imaging Spectrograph (STIS) CCD aboard the Hubble Space Telescope have been explored with early calibrations in a number of limiting conditions. At a gain of 4 e− DN−1, STIS CCD data show excellent linearity at high count levels, even for extreme oversaturation of individual central pixels. At low count levels we interpret a position‐ and intensity‐dependent nonlinearity in terms of charge transfer (in)efficiency in the parallel clocking direction and provide a simple model that accounts for this. A short time series of spectra was acquired at short‐exposure times and high signal‐to‐noise ratio (S/N) on the binary system α Cen A and B enabling the shutter repeatability to be quantified at 0.0002 s. A direct demonstration of near‐Poisson–limited time series with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp...

The planetary nebula M94--20 in the Large Magellanic Cloud was serendipitously observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope as part of the Hubble Space Telescope Archival Pure Parallel Program. We present spatially resolved imaging and spectral data of the nebula and compare them with ground based data, including detection of several emission lines from the nebula and the detection of the central star. We find the total H alpha + [NII] flux = 7.3e-15 erg s^-1 cm^-2 and we estimate the magnitude of the central star to be m_V = 26.0 +/- 0.2. Many other H alpha sources have been found in M31, M33 and NGC 205 as well. We discuss the use of the parallel observations as a versatile tool for planetary nebula surveys and for other fields of astronomical research., Latex, 14 pages, 2 JPEG figures, 2 tables. PASP Research Note, June 1999, in press

The Space Telescope Imaging Spectrograph (STIS) instrument was installed on the Hubble Space Telescope (HST) during the second servicing mission, in 1997 February. Four bands cover the wavelength range of 115–1000 nm, with spectral resolving powers between 26 and 200,000. Camera modes are used for target acquisition and deep imaging. Correction for HST's spherical aberration and astigmatism is included. The 115–170 nm range is covered by a CsI MAMA (Multianode Microchannel Array) detector and the 165–310 nm range by a Cs2Te MAMA, each with a format of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cy...

The Space Telescope Imaging Spectrograph (STIS) was designed as a versatile spectrograph for the Hubble Space Telescope (HST) capable of maintaining or exceeding the spectroscopic capabilities of both the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS) over the broad bandpass extending from the ultraviolet (115 nm) through the visible (1 μm). STIS achieves performance gains over the aforementioned first‐generation HST instruments primarily through the use of large ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6}...

We present a new technique of decontaminating Swift UVOT grism spectra for transient objects. We describe the template image requirements and image processing steps necessary to successfully implement the empirical decontamination technique. We demonstrate the accuracy of the flux and wavelength calibrations for decontaminated spectra by comparing a spectrum of SN 2011fe with a well-calibrated, long-slit ultraviolet spectrum from the Hubble Space Telescope's Space Telescope Imaging Spectrograph. We also show how the decontamination removes spurious emission lines from spectra of iPTF14bdn which otherwise could be misinterpreted as coming from the supernova. The software which implements this technique is briefly discussed and is made available to the community., Comment: 26 pages, 11 figures, accepted to PASP. Astrophysics Source Code Library: 2015ascl.soft09005S

In February, 1997, the second Space Shuttle servicing mission to the Hubble Observatory installed the Space Telescope Imaging Spectrograph (STIS). This new instrument will greatly enhance the spectroscopic capabilities of the Hubble Space Telescope by providing a longslit format and CCD detector technology. STIS can also be used as an imager, providing an alternative to the Wide Field Planetary Camera 2. The optical filter set of STIS is limited and does not contain standard bandpasses, but we show here that this does not preclude useful two-color broad band photometry. Because the STIS bandpasses reach ~ 1.5 magnitudes deeper than WFPC2, the STIS photometric system may be preferable for many applications where a faint limiting magnitude and fine spatial resolution are overriding considerations. The two optical wide-band choices on STIS are a clear aperture and a longpass (λ > 5500A) filter. We define an effective short-pass filter from the difference of these, making two-color photometry possible with STIS. We present preliminary transformations between the STIS system and Cousins BVRI bandpasses, showing that these transformations are very well-behaved over almost all temperatures, luminosities, and abundances for normal stars. In an 8-orbit cycle, STIS will be able to reach signal-to-noise of ~ 5-10 at V = 30.0 in its clear and longpass imaging modes, a significant increase in the power of HST to address a number of fundamental issues out of reach of current instrumentation capabilities on the ground or in spac.