Modeling MWC 297’s Complex Circumstellar Structure with Magnetically Supported Outflows Open Access

Abstract

Motivated by the different properties of Herbig Be and Herbig Ae stars, we adapt a Monte Carlo Radiative Transfer code that has been successfully used to explain the observational data from Herbig Ae stars, in order to model magneto-rotationally driven dusty outflows around these objects. The adaptations we make generalize this approach to examine the Spectral Energy Distribution (SED) of MWC 297, a higher luminosity Herbig Be star. Furthermore, we developed an algorithm to produce Near Infra-Red (NIR) images of the target at a variety of different inclinations, which allows us to compare the simulations to existing NIR images of MWC 297 whose inclination is poorly constrained. We find that while dusty magnetically driven outflows alone can produce the observed NIR excess, high mass outflow rates are needed, a condition that worsens at higher inclinations. Consequently, we also examine the effects of several physically and observationally motivated modifications to the model. Namely, we consider the presence of an optically thick inner accretion disk (supported by multiple previous studies of MWC 297 and other Herbig Be sources), and setting the sublimation radius closer to the star. Though neither of these models with non-stellar emissions within the sublimation radius are fully consistently implemented, our data shows that both of their effects complement that of the dusty wind, and together they may play important roles in shaping the NIR emission of higher luminosity stars. Furthermore, their inclusion makes the inferred mass outflow rates more consistent with the literature. More work is needed to better model all these components consistently.

Table of Contents

1 Introduction ............................................................................. 1

1.1 MWC297 ............................................................................ 2

2 Outflow Models ........................................................................ 6

2.1 DiskWinds ......................................................................... 6

2.2 Model Setup and Parameters ............................................... 7

2.2.1 Gas density profile ...................................................... 7

2.2.2 Passive Disk and dust properties .................................. 9

2.2.3 Sublimation radius Rsub ............................................. 10

2.2.4 Non-Stellar Emissions within Rsub .............................. 11

2.2.5 An inner accretion disk ............................................... 11

2.2.6 A smaller Rsub ........................................................... 12

3 Methodology ........................................................................... 14

3.1 Monte Carlo Radiative Transfer .......................................... 14

3.2 Adding an inner disk to the Spectral Energy Distribution ..... 15

3.3 Image Creation ................................................................. 16

4 Results and Discussion ............................................................. 21

4.1 Spectral Energy Distributions ............................................. 21

4.2 Best Models....................................................................... 26

4.2.1 Model WD ................................................................. 28

4.2.2 Model WD+Acc .......................................................... 30

4.2.3 Model WD-R .............................................................. 32

4.3 Discussion ......................................................................... 33

4.3.1 Future Work ............................................................... 35

Bibliography ................................................................................ 37

About this Honors Thesis

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School	Emory College
Department	Physics
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Physics, Astronomy and Astrophysics Physics, General
Keyword	Herbig Be Monte Carlo Radiative Transfer Spectral Energy Distribution Young Stellar Object Circumstellar disk
Committee Chair / Thesis Advisor	Alissa Bans, Emory University
Committee Members	Merida Batiste, Emory University James Nagy, Emory University

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