The Fourth Positive System of Carbon Monoxide in the Hubble Space Telescope Spectra of Comets

The rich structure of the Fourth Positive System (A-X) of carbon monoxide accounts for many of the spectral features seen in long slit HST-STIS observations of comets 153P/Ikeya-Zhang, C/2001 Q4 (NEAT), and C/2000 WM1 (LINEAR), as well as in the HST-GHRS spectrum of comet C/1996 B2 Hyakutake. A detailed CO fluorescence model is developed to derive the CO abundances in these comets by simultaneously fitting all of the observed A-X bands. The model includes the latest values for the oscillator strengths and state parameters, and accounts for optical depth effects due to line overlap and self-absorption. The model fits yield radial profiles of CO column density that are consistent with a predominantly native source for all the comets observed by STIS. The derived CO abundances relative to water in these comets span a wide range, from 0.44% for C/2000 WM1 (LINEAR), 7.2% for 153P/Ikeya-Zhang, 8.8% for C/2001 Q4 (NEAT) to 20.9% for C/1996 B2 (Hyakutake). The subtraction of the CO spectral features using this model leads to the first identification of a molecular hydrogen line pumped by solar HI Lyman-beta longward of 1200A in the spectrum of comet 153P/Ikeya-Zhang. (Abridged)Comment: 12 pages, 11 figures, ApJ accepte

Multiwavelength analysis as a probe of accretion and radiative processes in LINERs

We study the multiwavelength properties of an optically selected sample of Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to determine the accretion mechanism powering their central engine. We show how their X-ray spectral characteristics, and their spectral energy distribution compare to luminous AGN, and briefly discuss their connection to their less massive counter-parts galactic black-hole X-ray binaries.Comment: 2 Pages. Proceedings of IAUS 290 "Feeding Compact Objects: Accretion on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.

Manni Zhang, soprano and Anna Carl, piano, April 21, 2018

This is the concert program of the Manni Zhang, soprano and Anna Carl, piano performance on Saturday, April 21, 2018 at 8:00 p.m., at the Concert Hall, 855 Commonwealth Avenue. Works performed were La Promessa by Gioachino Rossini, Fiocca La Neve nu Pietro Cimara, Stornello by P. Cimara, Perchè dolce, caro bene by Stefano Donaudy, Ganymed Op. 19, No. 3 D. 544 by Franz Schubert, Liebhaber in allen Gestalten D. 558 by F. Schubert, Im Abendroth D. 799 by F. Schubert, Die Forelle Op. 32 D. 550 by F. Schubert, Vorrei spiegarvi, O Dio by Wolfgang Amadeus Mozart, Fêtes galantes by Claude Debussy, En Sourdine by C. Debussy, Fantoches by C. Debussy, Clair De Lune by C. Debussy, Love by Vittorio Giannini, Tell me, Oh blue blue Sky! by V. Giannini, Sing to My Heart a Song by V. Giannini, and Spring Nostalgia by Huang Zi. Digitization for Boston University Concert Programs was supported by the Boston University Humanities Library Endowed Fund

A Search for N2+ in Spectra of Comet C/2002C1 (Ikeya-Zhang)

We report low- and high-resolution spectra of comet C/2002 C1 (Ikeya-Zhang) from McDonald Observatory. The comet had a well-developed ion tail including CO+, CO2+, CH+, and H2O+. We used our high-resolution spectra to search for N2+. None was detected and we placed upper limits on N2+/CO+ of 5.4 times 10^{-4}. N2+ was detected in the low-resolution spectra but we show that this emission was probably telluric in origin (if cometary, we derive N2+/CO+ = 5.5 times 10^{-3}, still very low). We discuss the implications for the conditions in the early solar nebula of the non-detection of N2+. These depend on whether the H2O ice was deposited in the amorphous or crystalline form. If H2O was deposited in its crystalline form, the detection of CO+ but not N2+ has implications for H2O/H2 in the early solar nebula.Comment: Accepted for publication in ApJ (Letters) - 10 Sept 200