scholarly journals SN 2018zd: an unusual stellar explosion as part of the diverse Type II Supernova landscape

2020 ◽  
Vol 498 (1) ◽  
pp. 84-100 ◽  
Author(s):  
Jujia Zhang ◽  
Xiaofeng Wang ◽  
Vinkó József ◽  
Qian Zhai ◽  
Tianmeng Zhang ◽  
...  
Keyword(s):  
Temperature Rise ◽  
Stellar Wind ◽  
Radioactive Decay ◽  
Vital Role ◽  
Asymptotic Giant Branch ◽  
Expansion Velocity ◽  
Spectral Features ◽  
Asymptotic Giant Branch Star ◽  
Significant Temperature ◽  
Transition Event

ABSTRACT We present extensive observations of SN 2018zd covering the first ∼450 d after the explosion. This SN shows a possible shock-breakout signal ∼3.6 h after the explosion in the unfiltered light curve, and prominent flash-ionization spectral features within the first week. The unusual photospheric temperature rise (rapidly from ∼12 000 to above 18 000 K) within the earliest few days suggests that the ejecta were continuously heated. Both the significant temperature rise and the flash spectral features can be explained by the interaction of the SN ejecta with the massive stellar wind ($0.18^{+0.05}_{-0.10}\, \rm M_{\odot }$), which accounts for the luminous peak ($L_{\rm max} = [1.36\pm 0.63] \times 10^{43}\, \rm erg\, s^{-1}$) of SN 2018zd. The luminous peak and low expansion velocity (v ≈ 3300 km s−1) make SN 2018zd like a member of the LLEV (luminous SNe II with low expansion velocities) events originating due to circumstellar interaction. The relatively fast post-peak decline allows a classification of SN 2018zd as a transition event morphologically linking SNe IIP and SNe IIL. In the radioactive-decay phase, SN 2018zd experienced a significant flux drop and behaved more like a low-luminosity SN IIP both spectroscopically and photometrically. This contrast indicates that circumstellar interaction plays a vital role in modifying the observed light curves of SNe II. Comparing nebular-phase spectra with model predictions suggests that SN 2018zd arose from a star of $\sim 12\, \rm M_{\odot }$. Given the relatively small amount of 56Ni ($0.013\!-\!0.035 \rm M_{\odot }$), the massive stellar wind, and the faint X-ray radiation, the progenitor of SN 2018zd could be a massive asymptotic giant branch star that collapsed owing to electron capture.

scholarly journals The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr

2019 ◽  
Vol 484 (2) ◽  
pp. 1865-1888 ◽  
Author(s):  
D T Hoai ◽  
P T Nhung ◽  
P Tuan-Anh ◽  
P Darriulat ◽  
P N Diep ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Equatorial Region ◽  
Data Cube ◽  
Asymptotic Giant Branch ◽  
Expansion Velocity ◽  
Circumstellar Envelope ◽  
Low Velocity ◽  
Loss Mechanism ◽  
Asymptotic Giant Branch Star

ABSTRACT ALMA observations of CO(1–0) and CO(2–1) emissions of the circumstellar envelope of EP Aqr, an oxygen-rich asymptotic giant branch star, are reported. A thorough analysis of their properties is presented using an original method based on the separation of the data cube into a low-velocity component associated with an equatorial outflow and a faster component associated with a bipolar outflow. A number of important and new results are obtained concerning the distribution in space of the effective emissivity, the temperature, the density, and the flux of matter. A mass-loss rate of (1.6 ± 0.4)×10−7 solar masses per year is measured. The main parameters defining the morphology and kinematics of the envelope are evaluated and uncertainties inherent to de-projection are critically discussed. Detailed properties of the equatorial region of the envelope are presented including a measurement of the line width and a precise description of the observed inhomogeneity of both morphology and kinematics. In particular, in addition to the presence of a previously observed spiral enhancement of the morphology at very small Doppler velocities, a similarly significant but uncorrelated circular enhancement of the expansion velocity is revealed, both close to the limit of sensitivity. The results of the analysis place significant constraints on the parameters of models proposing descriptions of the mass-loss mechanism, but cannot choose among them with confidence.

scholarly journals Formation of Interstellar Bubble: A Time Dependent Numerical Simulation

1970 ◽  
Vol 6 (6) ◽  
pp. 8-15
Author(s):  
B Aryal ◽  
A Devkota ◽  
R Weinberger
Keyword(s):  
Interstellar Medium ◽  
Stellar Wind ◽  
Planetary Nebula ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Star ◽  
Scientific World ◽  
Three Phase ◽  
Good Environment ◽  
Branch Star

We present results of the numerical simulations for the first 105 years of the development of spherically symmetric interstellar bubbles. We have assumed three phase interstellar medium (ISM) model and estimated the size of the interstellar bubbles (ISB). Our results are based on calculations including 106 virtual stellar wind particles. We discuss the result in the context of Asymptotic Giant Branch (AGB) star, Proto-Planetary Nebula (PPN) phase and Relativistic Wind (RW) star. The size of the ISB is found 0.14 pc to 9.03 pc in the case of AGB (Asymptotic Giant Branch) star. This size increases for the PPN and RW phase to 0.64 - 40.28 pc and 2.83 pc - 178.12 pc, respectively. It is found that the ISB can survive in the case of cold and warm interstellar medium. In the hot ISM, the ISB can not be formed due to the AGB wind. The bubble can survive in the case of PPN phase stellar wind for all kinds of the ISM. In addition, we found that the bubble can be formed in the case of RW when the ISM is hot. In the cold ISM, the ISB can not be formed due to the RW. In the warm ISM, bubble can be formed due to the relativistic (pulsar) wind if the mass loss rate is extremely high. In the warm ISM, the overall size of the bubble increases but do not exceed the recommended limit. Our result indicates that the hot ISM can not be considered as a good environment for the existence of the ISB. The size of the bubble exceeds the recommended limit (i.e., 1 to 5 kpc) in both the PPN and RW phase. However, suitable AGB wind can trigger the environment for a bubble in the hot ISM. The results of this work should be compared with the observations in the future. Key words: Interstellar medium; Stellar wind; Planetary nebula; Pulsar. DOI: 10.3126/sw.v6i6.2626 Scientific World, Vol. 6, No. 6, July 2008 8-15

scholarly journals On the asymptotic giant branch star origin of peculiar spinel grain OC2

2006 ◽  
Vol 461 (2) ◽  
pp. 657-664 ◽  
Author(s):  
M. Lugaro ◽  
A. I. Karakas ◽  
L. R. Nittler ◽  
C. M. O'D. Alexander ◽  
P. Hoppe ◽  
...  
Keyword(s):  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Star ◽  
Branch Star

scholarly journals AGB winds in interacting binary stars

2020 ◽  
Vol 493 (2) ◽  
pp. 2606-2617 ◽  
Author(s):  
Luis C Bermúdez-Bustamante ◽  
G García-Segura ◽  
W Steffen ◽  
L Sabin
Keyword(s):  
Radiation Pressure ◽  
Stellar Wind ◽  
Binary Stars ◽  
Massive Star ◽  
Density Ratio ◽  
Asymptotic Giant Branch ◽  
Surface Layers ◽  
Outflow Velocity ◽  
Analytical Formulae ◽  
Set Up

ABSTRACT We perform numerical simulations to investigate the stellar wind from interacting binary stars. Our aim is to find analytical formulae describing the outflow structure. In each binary system the more massive star is in the asymptotic giant branch (AGB) and its wind is driven by a combination of pulsations in the stellar surface layers and radiation pressure on dust, while the less massive star is in the main sequence. Time averages of density and outflow velocity of the stellar wind are calculated and plotted as profiles against distance from the centre of mass and colatitude angle. We find that mass is lost mainly through the outer Lagrangian point L2. The resultant outflow develops into a spiral at low distances from the binary. The outflowing spiral is quickly smoothed out by shocks and becomes an excretion disc at larger distances. This leads to the formation of an outflow structure with an equatorial density excess, which is greater in binaries with smaller orbital separation. The pole-to-equator density ratio reaches a maximum value of ∼105 at Roche lobe overflow state. We also find that the gas stream leaving L2 does not form a circumbinary ring for stellar mass ratios above 0.78, when radiation pressure on dust is taken into account. Analytical formulae are obtained by curve fitting the two-dimensional, azimuthally averaged density and outflow velocity profiles. The formulae can be used in future studies to set-up the initial outflow structure in hydrodynamic simulations of common-envelope evolution and formation of planetary nebulae.

scholarly journals Effect of ambient wind velocity on Planetary Nebula morphology

1997 ◽  
Vol 180 ◽  
pp. 224-224
Author(s):  
Vikram V. Dwarkadas ◽  
Roger A. Chevalier ◽  
John M. Blondin
Keyword(s):  
Wind Velocity ◽  
Ambient Medium ◽  
Asymptotic Giant Branch ◽  
Density Contrast ◽  
Expansion Velocity ◽  
Ambient Wind ◽  
Pn Velocity ◽  
Fast Wind ◽  
Self Similar ◽  
Slow Wind

Planetary Nebulae (PNe) are formed by the interaction of the fast wind from a post-Asymptotic Giant Branch Star with the slow ambient wind from a previous epoch. If the two interacting winds have constant properties, the velocity of the PN shell tends towards a constant with time and the shape becomes self-similar. Additionally, if the velocity of the fast wind is much higher than the expansion velocity of the shell, the interior of the hot shocked bubble becomes isobaric. Using semi-analytical methods, complemented by hydrodynamic simulations, we have calculated the shapes of PNe in the self-similar stage (Dwarkadas et al. 1996). We have investigated the contribution of the ambient wind velocity to PN morphology, which has hitherto not received much attention since the work of Kahn & West (1985). We find that the nebular morphology is a consequence of the density contrast between pole and equator in the ambient medium, the steepness of the density profile and the velocity of the ambient wind; classification of PNe purely on the basis of the first two factors may be misleading. In particular, the ratio of ambient wind velocity to PN velocity is important in determining whether the nebula shows a bulge or a cusp at the equator. A high density contrast coupled with a low velocity for the external medium gives rise to extremely bipolar nebulae. For large density contrasts and a significant value of the slow wind velocity, the surface density maximum of the shell shifts away from the equator, giving rise to peanut-shaped structures with pronounced equatorial bulges. As long as the external wind velocity is small compared to the expansion velocity of the nebula, the PNe tend to be more bipolar, even with a moderate density contrast. If the PN velocity is close to that of the external wind, the shape is relatively spherical. However, inclusion of an asymmetric velocity profile in the slow wind, with the velocity increasing towards the pole, can lead to a bipolar nebula if the equatorial velocity is sufficiently low. Preliminary results with a slow wind velocity increasing towards the equator (as is found in calculations of common envelope evolution) show that the nebulae tend to be more oblate, which is not often observed in nature. Representative results for shapes of PNe using various values of the relevant parameters are presented.

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