The Red Rectangle: Its Shaping Mechanism and its Source of Ultraviolet Photons

Adolf N. Witt; Uma P. Vijh; L. M. Hobbs; Jason P. Aufdenberg; Julie A. Thorburn; Donald G. York

doi:10.1088/0004-637X/693/2/1946

paper

The Red Rectangle: Its Shaping Mechanism and its Source of Ultraviolet Photons

arXiv:0812.2893 · doi:10.1088/0004-637X/693/2/1946

Abstract

The proto-planetary Red Rectangle nebula is powered by HD 44179, a spectroscopic binary (P = 318 d), in which a luminous post-AGB component is the primary source of both luminosity and current mass loss. Here, we present the results of a seven-year, eight-orbit spectroscopic monitoring program of HD 44179, designed to uncover new information about the source of the Lyman/far-ultraviolet continuum in the system as well as the driving mechanism for the bipolar outflow producing the current nebula. Our observations of the H-alpha line profile around the orbital phase of superior conjunction reveal the secondary component to be the origin of the fast (max. v~560 $k m s$ ^{-1} $) bi p o l a r o u t f l o w in t h e R e d R ec t an g l e . T h e v a r ia t i o n o f t o t a l H - a l p ha f l ux f r o m t h ece n t r a l H I I r e g i o n w i t h or bi t a l p ha se a l so i d e n t i f i es t h eseco n d a r y or i t ss u r r o u n d in g s a s t h eso u r ceo f t h e f a r - u l t r a v i o l e t i o ni z in g r a d ia t i o nin t h esy s t e m . T h ees t ima t e d ma sso f t h eseco n d a r y (0.94 M$ \sun $) an d t h es p ee d o f t h eo u t f l o w s ug g es tt ha tt hi sco m p o n e n t i s amain se q u e n ces t a r an d n o t a w hi t e d w a r f, a s p r e v i o u s l y s ug g es t e d . W e i d e n t i f y t h eso u r ceo f t h e L y man / f a r - u l t r a v i o l e t co n t in uu min t h esy s t e ma s t h e h o t, inn er r e g i o n (T$ _{max} \ge 17,000 $K) o f ana ccr e t i o n d i s k s u r r o u n d in g t h eseco n d a r y, f e d b y R oc h e l o b eo v er f l o w f r o m t h e p os t - A GB p r ima r y a t a r a t eo f ab o u t$ 2 - 5\times10^{-5} $M$ \sun $y r$ ^{-1} $. T h e t o t a l l u min os i t y o f t h e a ccr e t i o n d i s k a r o u n d t h eseco n d a r y i ses t ima t e d t o b e a tl e a s t 300 L$ \sun$, about 5% of the luminosity of the entire system. (abridged)

Accepted for publication in ApJ