Warren Hack

First Hubble Space Telescope Observations of Mira AB Wind-accreting Binary System

The Mira AB system belongs to a class of detached binaries in which a compact object accretes mass from the wind of a cool giant or supergiant. This system provides a unique laboratory for detailed study of the characteristics of the wind accretion processes because it can be spatially resolved with the Hubble Space Telescope (HST) and the components can be studied individually at UV and optical wavelengths. We resolved the components of this binary using HST Faint Object Camera (FOC) images and obtained spectra of each component separately for the first time. The multiwavelength FOC images combined with the spectra provide a unique perspective on this accreting system and its components at wavelengths ranging from 150 to 550 nm. We determined the spectral energy distribution of each component unambiguously at UV and optical wavelengths and obtained the first high spatial resolution images of Mira A and Mira B at UV wavelengths. We detected significant asymmetries in the giants atmosphere and found evidence for possible interaction with its companion.

A Large X-Ray Outburst in Mira A*

We report the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We have resolved the system for the first time in X-rays. Using Chandra and Hubble Space Telescope images, we determine that the unprecedented outburst is likely associated with the cool asymptotic giant branch (AGB) star, Mira A, the prototype of the Mira class of variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total X-ray luminosity of the system is several times higher than the luminosity estimated using previous XMM-Newton and ROSAT observations. The outburst may be caused by a giant flare in Mira A associated with a mass ejection or a jet and may have long-term consequences on the system.

The Intrinsic Absorber in QSO 2359–1241: Keck and Hubble Space Telescope Observations

We present detailed analyses of the absorption spectrum seen in QSO 2359-1241 (NVSS J235953-124148). Keck HIRES data reveal absorption from 20 transitions arising from He I, Mg I, Mg II, Ca II, and Fe II. Hubble Space Telescope data show broad absorption lines (BALs) from Al III ?1857, C IV ?1549, Si IV ?1397, and N V??1240. Absorption from excited Fe II states constrains the temperature of the absorber to 2000 T 10,000 K and puts a lower limit of 105 cm-3 on the electron number density. Saturation diagnostics show that the real column densities of He I and Fe II can be determined, allowing us to derive meaningful constraints on the ionization equilibrium and abundances in the flow. The ionization parameter is constrained by the iron, helium, and magnesium data to -3.0 log(U) -2.5, and the observed column densities can be reproduced without assuming departure from solar abundances. From comparison of the He I and Fe II absorption features, we infer that the outflow seen in QSO 2359-1241 is not shielded by a hydrogen ionization front and therefore that the existence of low-ionization species in the outflow (e.g., Mg II, Al III, Fe II) does not necessitate the existence of such a front. We find that the velocity width of the absorption systematically increases as a function of ionization and to a lesser extent with abundance. Complementary analyses of the radio and polarization properties of the object are discussed in a companion paper (Brotherton et al.).

QSO 2359(1241: A BRIGHT, HIGHLY POLARIZED, RADIO-MODERATE, REDDENED, LOW-IONIZATION BROAD ABSORPTION LINE QUASAR

We report the discovery of a bright quasar (E = 15.8, z = 0.868) associated with the flat-spectrum radio source NVSS J235953-124148. This quasar, which we designate QSO 2359-1241, possesses a rare combination of extreme properties that make it of special interest. These properties include intrinsic high-velocity outflow seen in absorption for both high- and low-ionization species, high optical polarization (~5%), significant radio emission, and dust reddening. The dereddened absolute magnitude of QSO 2359-1241 places it among the three most optically luminous quasars known at z < 1. High-resolution spectroscopy and a detailed analysis of the optical/ultraviolet absorption features will be given in a companion paper.

The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion

We present an analysis of photometric and spectroscopic observations of the symbiotic binary system RX Pup with the aims of developing a reliable binary model for the system and identifying mechanisms responsible for its spectacular activity. The binary is composed of a long-period Mira variable surrounded by a thick dust shell and a hot ∼ 0.8M ⊙ white dwarf companion. The hot component produces practically all activity observed in the UV, optical and radio range, while variable obscuration of the Mira by circumstellar dust is responsible for long-term changes in the near-infrared magnitudes. The observations show RX Pup underwent a nova-like eruption during the last three decades. The hot component contracted in radius at roughly constant luminosity from 1975 to 1986, and was the source of a strong stellar wind which prevented it from accreting material lost in the Mira wind. Around 1988/9 the hot component turned over in the HR diagram and by 1991 its luminosity had faded by a factor of ∼ 30 with respect to the maximum plateau value and the hot wind had practically ceased. By 1995 the nova remnant started to accrete material from the Mira wind, as indicated by a general increase in intensity of the optical continuum and H i emission. The quiescent spectrum resembles the quiescent spectra of symbiotic recurrent novae, and its intensity indicates the hot component must accrete as much as ∼ 1 per cent of the Mira wind, which is more or less the amount predicted by Bondi-Hoyle theory. The earliest observational records from the 1890s suggest that another nova-like eruption of RX Pup occurred around 1894.

Calibration of spatially phase-shifted DSPI for measurement of large structures

We present a method for the calibration of a spatially phase-shifted digital speckle pattern interferometer (SPS-DSPI), which was designed and built for the purpose of testing the James Webb space telescope (JWST) optical structures and related technology development structures. The need to measure dynamic deformations of large, diffuse structures to nanometer accuracy at cryogenic temperature is paramount in the characterization of a large diameter space and terrestrial based telescopes. The techniques described herein apply to any situation, in which high accuracy measurement of diffuse structures are required. The calibration of the instrument is done using a single-crystal silicon gauge. The gauge has four islands of different heights that change in a predictable manner as a function of temperature. The SPS-DSPI is used to measure the relative piston between the islands as the temperature of the gauge is changed. The measurement results are then compared with the theoretical changes in the height of the gauge islands. The maximum deviation of the measured rate of change of the relative piston in nm/K from the expected value is 3.3%.

In-flight performance of the Faint Object Camera of the Hubble Space Telescope: II

This paper gives an update on the performance of the Faint Object Camera--launched with the Hubble Space Telescope--since the last report two years ago. The primary camera, the f/96 relay, continues to work well, but the f/48 relay has recently developed serious problems. The stability of the f/96 relay has been very good with the only change being a small apparent decrease in UV sensitivity. Preliminary results for the f/48 DQE are presented. In-orbit UV flat fields have been obtained and the f/96 objective prisms and polarizers have been calibrated.

Spatially phase-shifted digital speckle pattern interferometry (SPS-DSPI) and cryogenic structures: recent improvements

The Spatially Phase Shifted Digital Speckle Pattern Interferometer (SPS-DSPI) is a speckle pattern interferometer in which the four phase-shifted interferograms are captured simultaneously in a single image. Designed to measure thermal distortions of large matte-surfaced structures for the James Webb Space Telescope (JWST) program, this metrology instrument has been used in two major cryo-distortion tests. This report will describe how differences in the vibrational motions of the test objects necessitated changes in basic algorithms. The authors also report operational upgrades, quantification of uncertainty, and improvement of the software operability with a graphic interface. Results from the tests of the JWST test structures are discussed as illustration.

Development of electronic speckle pattern interferometry for testing JWST composite structures

The stability requirements for the James Webb Space Telescope (JWST) optical metering structure are driven by the science objectives of the mission. This structure, JWST Optical Telescope Element (OTE) primary mirror backplane, has to be stable over time at cryogenic temperatures. Successful development of the large, lightweight, deployable, cryogenic metering structure requires verification of structural deformations to nanometer level accuracy in representative test articles at cryogenic temperature. An instantaneous acquisition phase shifting speckle interferometer was designed and built to support the development of JWST Optical Telescope Element (OTE) primary mirror backplane. This paper discusses characterization of the Electronic Speckle Pattern Interferometer (SPS-DSPI) developed for JWST to verify its capabilities to measure structural deformations in large composite structures at cryogenic temperature. Interferometer performance during the Backplane Stability Test Article (BSTA) test that completed the TRL-6 (Technology Readiness Level-6) demonstration of Large Precision Cryogenic Structures will also be discussed.

Detection of H2 Emission from Mira B in Ultraviolet Spectra from the Hubble Space Telescope

We present ultraviolet spectra of Miras companion star from the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope (HST). The companion is generally assumed to be a white dwarf surrounded by an accretion disk fed by Miras wind, which dominates the UV emission from the system. The STIS UV spectrum is dominated by numerous, narrow H2 lines fluoresced by H I Ly-alpha, which were not detected in any of the numerous observations of Mira B by the International Ultraviolet Explorer (IUE). The high temperature lines detected by IUE (e.g., C IV 1550) still exist in the STIS spectrum but with dramatically lower fluxes. The continuum fluxes in the STIS spectra are also much lower, being more than an order of magnitude lower than ever observed by IUE, and also an order of magnitude lower than fluxes observed in more recent HST Faint Object Camera objective prism spectra from 1995. Thus, the accretion rate onto Mira B was apparently much lower when STIS observed the star, and this change altered the character of Mira Bs UV spectrum.