Engineering topics

Nichols, Joy

Publications and source records attributed to Nichols, Joy.

5 records

NASA NTRS2013

The Chandra Delta Ori Large Project: Occultation Measurements of the Shocked Gas tn the Nearest Eclipsing O-Star Binary

Delta Ori is the nearest massive, single-lined eclipsing binary (O9.5 II + B0.5III). As such it serves as a fundamental calibrator of the mass-radius-luminosity relation in the upper HR diagram. It is also the only eclipsing O-type binary system which is bright enough to be observable with the CHANDRA gratings in a reasonable exposure. Studies of resolved X-ray line complexes provide tracers of wind mass loss rate and clumpiness; occultation by the X-ray dark companion of the line emitting region can provide direct spatial information on the location of the X-ray emitting gas produced by shocks embedded in the wind of the primary star. We obtained phase-resolved spectra with Chandra in order to determine the level of phase-dependent vs. secular variability in the shocked wind. Along with the Chandra observations we obtained simultaneous photometry from space with the Canadian MOST satellite to help understand the relation between X-ray and photospheric variability.

eclipsing binary↗

NASA NTRS2004

Study of Elongated Superbubble around CYG OB1

OB association superbubbles and supernova remnants are believed to be the primary sources of the hot component of the interstellar medium. Super- bubbles are also thought to "blow out" of the galactic plane and are thus the potential source of galactic coronal gas. Quantifying the energetics and accurately modeling the evolution of superbubbles is thus an important task in the understanding of the evolution of our Galaxy. The superbubble surrounding the Cyg OB1 association is an excellent example for study of the early stages of superbubble evolution. This superbubble, discovered in IRAS data, is an elongated structure 2 x 5 degrees (26 x 65 pc at distance=1.5 kpc), with at least 2 known supernova remnants believed to be associated with the superbubble. The elongated shape is more extended than can be explained by differential galactic rotation. A major problem in understanding the evolution of the Cyg OB1 superbubble is the discrepancy between the age of the superbubble and the derived age of the parent star association. The superbubble is believed to be no more than 1 Myr old, while the association is about 4-5 Myr old.

Sonneborn, George↗

NASA NTRS2002

A Multi-Wavelength Study of the Hot Component of the Interstellar Medium

The goals of this research are as follows: (1) Using the large number of lines of sight available in the ME database, identify the lines of sight with high-velocity components in interstellar lines, from neutral species through Si VI, C IV, and N V; (2) Compare the column density of the main components (i.e. low velocity components) of the interstellar lines with distance, galactic longitude and latitude, and galactic radial position. Derive statistics on the distribution of components in space (e.g. mean free path, mean column density of a component). Compare with model predictions for the column densities in the walls of old SNR bubbles and superbubbles, in evaporating cloud boundaries and in turbulent mixing layers; (3) For the lines of sight associated with multiple high velocity, high ionization components, model the shock parameters for the associated superbubble and SNR to provide more accurate energy input information for hot phase models and galactic halo models. Thus far 49 lines of sight with at least one high velocity component to the C IV lines have been identified; and (4) Obtain higher resolution data for the lines of sight with high velocity components (and a few without) to further refine these models.

Nichols, Joy↗

NASA NTRS2002

Shocks in Dense Clouds in the Vela Supernova Remnant: FUSE

We have obtained 8 LWRS FUSE spectra to study a recently identified interaction of the Vela supernova remnant with a dense cloud region along its western edge. The goal is to quantify the temperature, ionization, density, and abundance characteristics associated with this shock/dense cloud interface by means of UV absorption line studies. Our detection of high-velocity absorption line C I at +90 to +130 km/s with IUE toward a narrow region interior to the Vela SNR strongly suggests the Vela supernova remnant is interacting with a dense ISM or molecular cloud. The shock/dense cloud interface is suggested by (1) the rarity of detection of high-velocity C I seen in IUE spectra, (2) its very limited spatial distribution in the remnant, and (3) a marked decrease in X-ray emission in the region immediately west of the position of these stars where one also finds a 100 micron emission ridge in IRAS images. We have investigated the shock physics and general properties of this interaction region through a focussed UV absorption line study using FUSE spectra. We have FUSE data on OVI absorption lines observed toward 8 stars behind the Vela supernova remnant (SNR). We compare the OVI observations with IUE observations of CIV absorption toward the same stars. Most of the stars, which are all B stars, have complex continua making the extraction of absorption lines difficult. Three of the stars, HD 72088, HD 72089 and HD 72350, however, are rapid rotators (v sin i less than 100 km/s) making the derivation of absorption column densities much easier. We have measured OVI and CIV column densities for the "main component" (i.e. the low velocity component) for these stars. In addition, by removing the H2 line at 1032.35A (121.6 km/s relative to OVI), we find high velocity components of OVI at approximately 150 km/s that we attribute to the shock in the Vela SNR. The column density ratios and magnitudes are compared to both steady shock models and results of hydrodynamical SNR modeling. We find that the models require the shock to be relatively slow (approximately 100 - 170 km/s) to match the FUSE data. We discuss the implications of our results for models of the evolution of the Vela SNR.

Nichols, Joy↗

NASA NTRS2001

A Multi-Wavelength Study of the Hot Component Of The Interstellar Medium

This research focuses on the kinematics and evolution of the hot phase of the interstellar medium in the Galaxy. The plan is to measure the UV spectra for all hot stars observed with International Ultraviolet Explorer (IUE), in order to identify and measure the main component and any high velocity components to the interstellar lines. A total of 1200 stars are candidates for inclusion in this study.

Nichols, Joy↗