Off-axis Synchrotron Light Curves from Full-time-domain Moving-mesh Simulations of Jets from Massive Stars

AbstractUsing three-dimensional, moving-mesh simulations, we investigate the future evolution of the recently discovered gas cloud G2 traveling through the galactic center. From our simulations we expect an average feeding rate onto Sgr A* in the range of (5−19) × 10−8M⊙ yr−1 beginning in 2014. This accretion varies by less than a factor of three on timescales ∼ 1 month, and shows no more than a factor of 10 difference between the maximum and minimum observed rates within any given model. These rates are comparable to the current estimated accretion rate in the immediate vicinity of Sgr A*, although they represent only a small (< 10%) increase over the current expected feeding rate at the effective inner boundary of our simulations (racc = 750 RS ∼ 1015 cm). We also explore multiple possible equations of state to describe the gas. In examining the Br-γ light curves produced from our simulations, we find that all of our isothermal models predict significant (factor of 10) enhancements in the luminosity of G2 as it approaches pericenter, in conflict with observations. Models that instead allow the cloud to heat as it is compressed do better at matching observations.

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Contact binaries of spectral type O

Symposium - International Astronomical Union ◽

10.1017/s0074180900013589 ◽

1979 ◽

Vol 83 ◽

pp. 265-269 ◽

Cited By ~ 1

Author(s):

Kam-Ching Leung ◽

Donald P. Schneider

Keyword(s):

Direct Measurement ◽

Spectral Type ◽

Time Scale ◽

Massive Stars ◽

Eclipsing Binaries ◽

Light Curves ◽

Consistent Model ◽

Contact Binaries ◽

Primary Attraction ◽

V729 Cyg

The eclipsing binaries UW CMa, AO Cas, and V729 Cyg have been systems of great interest for over fifty years. The light curves are complex and suffer significant changes on a time scale of months, but the primary attraction of these systems is that both components have O-type spectra; thus they present us with some of the few possibilities for direct measurement of absolute dimensions of very massive stars. Much effort has been expended on these systems, but no really consistent model has emerged.

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Identification of the Velocity, Thickness, and Interfacial Roughness of Coating Using Full Time-Domain URCPS: Cross-Correlation-Based Inverse Problem

Journal of Nondestructive Evaluation Diagnostics and Prognostics of Engineering Systems ◽

10.1115/1.4042177 ◽

2019 ◽

Vol 2 (1) ◽

Author(s):

Zhiyuan Ma ◽

Li Lin ◽

Shijie Jin ◽

Mingkai Lei

Keyword(s):

Time Domain ◽

Measurement Errors ◽

Cross Correlation ◽

Inversion Method ◽

Full Time ◽

Interfacial Roughness ◽

Measured Velocity ◽

Detection Frequency ◽

Relative Errors ◽

Good Agreement

Aiming at characterizing interfacial roughness of thin coatings with unknown sound velocity and thickness, we derive a full time-domain ultrasonic reflection coefficient phase spectrum (URCPS) as a function of interfacial roughness based on the phase screen approximation theory. The constructed URCPS is used to determine the velocity, thickness, and interfacial roughness of specimens through the cross-correlation algorithm. The effect of detection frequency on the roughness measurement is investigated through the finite element method. A series of simulations were implemented on Ni-coating specimens with a thickness of 400 μm and interfacial roughness of 1.9–39.8 μm. Simulation results indicated that the measurement errors of interfacial roughness were less than 10% when the roughness satisfies the relationship of Rq = 1.6–10.0%λ. The measured velocity and thicknesses were in good agreement with those imported in simulation models with less than 9.3% error. Ultrasonic experiments were carried out on two Ni-coating specimens through a flat transducer with an optimized frequency of 15 MHz. Compared with the velocities measured by time-of-flight (TOF) method, the relative errors of inversed velocities were all less than 10%. The inversed thicknesses were in good agreement with those observed by optical microscopy with less than 10.9% and 7.6% error. The averaged interfacial roughness determined by the ultrasonic inversion method was 16.9 μm and 30.7 μm, respectively. The relative errors were 5.1% and 2.0% between ultrasonic and confocal laser scanning microscope (CLSM) method, respectively.

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Supernova Abundance Generation

Symposium - International Astronomical Union ◽

10.1017/s007418090022723x ◽

1991 ◽

Vol 145 ◽

pp. 21-38

Author(s):

K. Nomoto ◽

T. Shigeyama ◽

T. Tsujimoto

Keyword(s):

Heavy Element ◽

Massive Stars ◽

Theoretical Models ◽

Light Curves ◽

Maximum Brightness ◽

Sn 1987A ◽

New Models ◽

Decline Rate ◽

Type Ia ◽

Supernova Explosions

Theoretical models of supernova explosions of various types are reviewed to obtain heavy element yields from supernovae. We focus on new models for SN 1987A, and Type Ia, Ib, and Ic supernovae. Maximum brightness and decline rate of their light curves suggest that 12–18 M⊙ stars produce larger amount of 56Ni than more massive stars. We discuss relative roles of various types of supernovae in the chemical evolution of galaxies.

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Two optical emission components with different variability in V404 Cygni

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317000011 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 43-44

Author(s):

Yutaro Tachibana ◽

Taketoshi Yoshii ◽

Nobuyuki Kawai

Keyword(s):

Spectral Index ◽

Power Law ◽

Time Domain ◽

Optical Emission ◽

Time Domain Analysis ◽

Blackbody Radiation ◽

Light Curves ◽

Variable Component ◽

Single Temperature ◽

The Time Domain

AbstractV404 Cygni went into an outburst again on June 15, 2015 after 26 years of quietness. Soon after the notifications, we started intense optical observation campaign of this source. The spectral index between RC and IC-band was stable over the outburst, whereas that between g′ and RC-band varied violently. With the time domain analysis of the multi-color optical light curves, we successfully decomposed optical variations into three components: highly-variable component (HVC), little-variable component (LVC). The loci of the LVC in the color-color diagram is consistent with that of a single temperature blackbody radiation or a multi-color blackbody radiation from a standard accretion disk, while those of the HVC trace that of power-law spectra.

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Time-domain-induced polarization: Full-decay forward modeling and 1D laterally constrained inversion of Cole-Cole parameters

Geophysics ◽

10.1190/geo2011-0217.1 ◽

2012 ◽

Vol 77 (3) ◽

pp. E213-E225 ◽

Cited By ~ 73

Author(s):

Gianluca Fiandaca ◽

Esben Auken ◽

Anders Vest Christiansen ◽

Aurélie Gazoty

Keyword(s):

Time Domain ◽

Mineral Exploration ◽

Induced Polarization ◽

Significant Loss ◽

Step Response ◽

Model Parameters ◽

Full Time ◽

Inversion Algorithm ◽

Modeling Tools ◽

Polarization Response

Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use of time-domain-induced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function, to reconstruct the distribution of the Cole-Cole parameters of the earth. The accurate modeling of the transmitter waveform had a strong influence on the forward response, and we showed that the difference between a solution using a step response and a solution using the accurate modeling often is above 100%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D laterally constrained inversion algorithm that extracts the spectral content of the induced polarization phenomenon in terms of the Cole-Cole parameters. Synthetic examples and field examples from Denmark showed a significant improvement in the resolution of the parameters that control the induced polarization response when compared to traditional integral chargeability inversion. The quality of the inversion results has been assessed by a complete uncertainty analysis of the model parameters; furthermore, borehole information confirm the outcomes of the field interpretations. With this new accurate code in situ time-domain-induced polarization measurements give access to new applications in environmental and hydrogeophysical investigations, e.g., accurate landfill delineation or on the relation between Cole-Cole and hydraulic parameters.

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Modelling the photometric variability of magnetic massive stars with the Analytical Dynamical Magnetosphere model

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2904 ◽

2019 ◽

Author(s):

M S Munoz ◽

G A Wade ◽

Y Nazé ◽

J Puls ◽

S Bagnulo ◽

...

Keyword(s):

Magnetic Field ◽

Electron Scattering ◽

Massive Star ◽

Massive Stars ◽

Mass Density ◽

Magellanic Clouds ◽

Light Curves ◽

Photometric Variability ◽

P Type ◽

The Magnetic Field

Abstract In this paper, we investigate the photometric variability of magnetic O-type stars. Such stars possess oblique, predominantly dipolar magnetic fields that confine their winds roughly axisymmetrically about the magnetic equator, thus forming a magnetosphere. We interpret their photometric variability as phase-dependent magnetospheric occultations. For massive star winds dominated by electron scattering opacity in the optical and NIR, we can compute synthetic light curves from simply knowing the magnetosphere’s mass density distribution. We exploit the newly-developed Analytical Dynamical Magnetosphere model (ADM) in order to obtain the predicted circumstellar density structures of magnetic O-type stars. The simplicity in our light curve synthesis model allows us to readily conduct a parameter space study. For validation purposes, we first apply our algorithm to HD 191612, the prototypical Of?p star. Next, we attempt to model the photometric variability of the Of?p-type stars identified in the Magellanic Clouds using OGLE photometry. We evaluate the compatibility of the ADM predictions with the observed photometric variations, and discuss the magnetic field properties that are implied by our modelling.

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Radio variability from corotating interaction regions threading Wolf–Rayet winds

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2014 ◽

2020 ◽

Vol 497 (1) ◽

pp. 1127-1134

Author(s):

Richard Ignace ◽

Nicole St-Louis ◽

Raman K Prinja

Keyword(s):

Light Curve ◽

Phenomenological Model ◽

Massive Stars ◽

Light Curves ◽

Parameter Study ◽

Detailed Structure ◽

Corotating Interaction Regions ◽

X Ray ◽

Cent Level ◽

Interaction Regions

ABSTRACT The structured winds of single massive stars can be classified into two broad groups: stochastic structure and organized structure. While the former is typically identified with clumping, the latter is typically associated with rotational modulations, particularly the paradigm of corotating interaction regions (CIRs). While CIRs have been explored extensively in the ultraviolet band, and moderately in the X-ray and optical, here we evaluate radio variability from CIR structures assuming free–free opacity in a dense wind. Our goal is to conduct a broad parameter study to assess the observational feasibility, and to this end, we adopt a phenomenological model for a CIR that threads an otherwise spherical wind. We find that under reasonable assumptions, it is possible to obtain radio variability at the 10 per cent level. The detailed structure of the folded light curve depends not only on the curvature of the CIR, the density contrast of the CIR relative to the wind, and viewing inclination, but also on wavelength. Comparing light curves at different wavelengths, we find that the amplitude can change, that there can be phase shifts in the waveform, and the entire waveform itself can change. These characterstics could be exploited to detect the presence of CIRs in dense, hot winds.

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