scholarly journals Defining Characteristics of Fast Novae

1979 ◽  
Vol 53 ◽  
pp. 532-532
Author(s):  
James W. Truran
Keyword(s):  
Light Curves ◽  
Theoretical Studies ◽  
Hydrogen Fuel ◽  
Core Mass ◽  
Infrared Observations ◽  
Bolometric Luminosity ◽  
Thermonuclear Burning ◽  
Residual Hydrogen ◽  
The Common ◽  
Nova Outburst

Scrutiny of the light curves of the common novae yields important clues concerning both the nature of the nova outburst and the characteristics of the underlying white dwarfs. Ultraviolet and infrared observations have served to make available essentially complete bolometric light curves for several recent novae. These data confirm our earlier prediction that, following maximum, both fast and slow novae experience an epoch (of varying duration) of substantially hydrostatic evolution defined by thermonuclear burning of the residual hydrogen fuel at constant bolometric luminosity. Theoretical studies reveal that the luminosity during this phase of a nova’s evolution is well represented by the Paczynski core mass-luminosity relation for such shell burning configurations involving degenerate stellar cores. This luminosity represents, as well, an increasingly significant fraction of the Eddington luminosity with increasing white dwarf mass.

scholarly journals W UMa Stars and Angular Momentum Loss

1980 ◽  
Vol 88 ◽  
pp. 491-494 ◽  
Author(s):  
Osmi Vilhu ◽  
Timo Rahunen
Keyword(s):  
Time Scale ◽  
Type Systems ◽  
Light Curves ◽  
Theoretical Studies ◽  
Mass Ratio ◽  
Subsequent Evolution ◽  
Convective Envelope ◽  
Angular Momentum Loss ◽  
Envelope Model ◽  
The Common

The structure and evolution of W UMa stars is still unsolved although considerable progress has been achieved in recent years. Most theoretical studies are based on the common convective envelope model by Lucy (1968a,b), which almost satisfactorily explains the nearly equal minima of the light curves. All A-type (Wilson, 1978) and some W-type systems (Whelan et al., 1979) may contain an evolved primary. In this case stable models exist (Hazlehurst, 1970; Moss and Whelan, 1970). Computations performed for the subsequent evolution (Moss, 1971; Hazlehurst and Meyer-Hofmeister, 1973; Rahunen and Vilhu, 1977) show nuclear time scale evolution towards more extreme mass ratio, supplemented by possible thermal time scale oscillations.

scholarly journals The Cause of the Nova Outburst

1976 ◽  
Vol 73 ◽  
pp. 155-172 ◽  
Author(s):  
S. Starrfield ◽  
W. M. Sparks ◽  
J. W. Truran
Keyword(s):  
White Dwarfs ◽  
Light Curves ◽  
Maximum Magnitude ◽  
Early Stages ◽  
The Common ◽  
Cno Abundances ◽  
The Relationship ◽  
Nova Outburst

We have evolved a large number of models of thermonuclear runaways in the hydrogen-rich envelopes of 1.00 M⊙ carbon-oxygen white dwarfs. Models characterized by enhanced CNO abundances satisfy the observations of the common nova outburst. They eject from 1027 to 1029 g moving with velocities of 200–2400 km s−1: kinetic energies of 1044 to 1045 erg. The theoretical light curves are similar to the observed light curves of common novae during the early stages of the outburst. As a consequence of our studies, we can present an explanation for the continuous ejection of mass which is observed for long times after the initial outburst and for the relationship between maximum magnitude and the decline to minimum. We are also now able to present an explanation for the constant luminosity phase of the outburst and the oval shapes of the ejected nebulae.We have extended our earlier work to models with extreme enhancements of 12C and to models which include the infalling material in the evolution. The extreme 12C studies result in outbursts which reach near supernova proportions while the accretion models result in light curves which resemble observed light curves quite closely. Finally, the accretion studies also demonstrate the need for enhanced abundances.

scholarly journals Light-curve properties of SN 2017fgc and HV SNe Ia

2021 ◽  
Vol 502 (3) ◽  
pp. 4112-4124
Author(s):  
Umut Burgaz ◽  
Keiichi Maeda ◽  
Belinda Kalomeni ◽  
Miho Kawabata ◽  
Masayuki Yamanaka ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Light Curves ◽  
Normal Velocity ◽  
External Effects ◽  
Band Maximum ◽  
Bolometric Luminosity ◽  
V Band ◽  
Photometric And Spectroscopic Observations ◽  
Type Ia

ABSTRACT Photometric and spectroscopic observations of Type Ia supernova (SN) 2017fgc, which cover the period from −12 to + 137 d since the B-band maximum are presented. SN 2017fgc is a photometrically normal SN Ia with the luminosity decline rate, Δm15(B)true  = 1.10 ± 0.10 mag. Spectroscopically, it belongs to the high-velocity (HV) SNe Ia group, with the Si ii λ6355 velocity near the B-band maximum estimated to be 15 200 ± 480 km s−1. At the epochs around the near-infrared secondary peak, the R and I bands show an excess of ∼0.2-mag level compared to the light curves of the normal velocity (NV) SNe Ia. Further inspection of the samples of HV and NV SNe Ia indicates that the excess is a generic feature among HV SNe Ia, different from NV SNe Ia. There is also a hint that the excess is seen in the V band, both in SN 2017fgc and other HV SNe Ia, which behaves like a less prominent shoulder in the light curve. The excess is not obvious in the B band (and unknown in the U band), and the colour is consistent with the fiducial SN colour. This might indicate that the excess is attributed to the bolometric luminosity, not in the colour. This excess is less likely caused by external effects, like an echo or change in reddening but could be due to an ionization effect, which reflects an intrinsic, either distinct or continuous, difference in the ejecta properties between HV and NV SNe Ia.

scholarly journals Relativistic accretion disc in tidal disruption events

2020 ◽  
Vol 496 (2) ◽  
pp. 1784-1802
Author(s):  
T Mageshwaran ◽  
Sudip Bhattacharyya
Keyword(s):  
Surface Density ◽  
Accretion Disc ◽  
Time Parameter ◽  
Light Curves ◽  
Initial Time ◽  
Late Time ◽  
Tidal Disruption ◽  
Bolometric Luminosity ◽  
Spectral Bands ◽  
Accretion Model

ABSTRACT We construct a time-dependent relativistic accretion model for tidal disruption events (TDEs) with an α-viscosity and the pressure dominated by gas pressure. We also include the mass fallback rate $\dot{M}_\mathrm{ f}$ for both full and partial disruption TDEs, and assume that the infalling debris forms a seed disc in time tc, which evolves due to the mass addition from the infalling debris and the mass-loss via accretion on to the black hole. Besides, we derive an explicit form for the disc height that depends on the angular momentum parameter in the disc. We show that the surface density of the disc increases at an initial time due to mass addition, and then decreases as the mass fallback rate decreases, which results in a decrease in the disc mass Md with a late-time evolution of Md ∝ t−1.05 and t−1.38 for full and partial disruption TDEs, respectively, where t is the time parameter. The bolometric luminosity L shows a rise and decline that follows a power law at late times given by L ∝ t−1.8 and t−2.3 for full and partial disruption TDEs, respectively. Our obtained luminosity declines faster than the luminosity inferred using $L \propto \dot{M}_\mathrm{ f}$. We also compute the light curves in various spectral bands.

scholarly journals The Youngest Star-Forming Regions in Galaxies: Giant Compact HII Regions and Protoglobular Clusters?

2001 ◽  
Vol 205 ◽  
pp. 224-227
Author(s):  
Jean L. Turner
Keyword(s):  
Dwarf Galaxy ◽  
Hii Regions ◽  
Starburst Galaxies ◽  
Mid Infrared ◽  
Infrared Observations ◽  
Star Forming ◽  
Bolometric Luminosity ◽  
Star Forming Regions ◽  
Young Clusters ◽  
Compact Hii Regions

Subarcsecond radio and infrared observations reveal a class of luminous, obscured, optically thick HII regions associated with extremely large young clusters in nearby starburst galaxies. VLA images show bright radio nebulae with ne ∼ 104 cm−3, densities characteristic of young Galactic compact HII regions. Excitation of the nebulae requires the presence of several thousand O stars within regions of 1-10 pc extent, corresponding to clusters containing 105–106 stars. The compact nebulae are also bright in the mid-infrared, and can for significant fractions of not only the total IR luminosity, but also the total bolometric luminosity, of the parent galaxies. The prototype for these “supernebulae” is the large, obscured cluster in the dwarf galaxy NGC 5253.

SN 1987a: A Progress Report

1987 ◽  
Vol 7 (2) ◽  
pp. 141-146 ◽  
Author(s):  
M. A. Dopita ◽  
N. Achilleos ◽  
J. A. Dawe ◽  
C. Flynn ◽  
S. J. Meatheringham ◽  
...  
Keyword(s):  
Light Curve ◽  
Thermal Energy ◽  
Radioactive Decay ◽  
Progress Report ◽  
Type Ii ◽  
Normal Type ◽  
Spectral Evolution ◽  
Core Mass ◽  
Sn 1987A ◽  
Residual Hydrogen

AbstractIt now appears almost certain that the precursor of SN 1987a was the brighter of the components of Sk-69 202, a blue supergiant, with a precursor mass of perhaps 12-16 solar masses. Prior to the explosion the precursor had a core mass of order six solar masses, and 0.1 to 0.2 solar masses of residual hydrogen envelope. The compact nature of this star can account for many of the odd features of the subsequent light curve and spectral evolution.An analysis of the light curve and colour evolution shows four distinct epochs, which probably relate to the initial expansion of the fireball and the escape of shock-deposited thermal energy, the hydrogen-rich layers becoming optically thin, the exposure of the helium core, and the increasing transparency of the helium core.The supernova appeared to be at its maximum on May 10, but is dimmer than a normal Type II because its light is apparently derived from recombinations and the radioactive decay of 56Ni to 56Co to 56Fe rather than by the thermal energy deposited by the passage of the shock.

scholarly journals Bolometric Light Curves of Symbiotic Novae

1992 ◽  
Vol 151 ◽  
pp. 435-438
Author(s):  
U. Mürset ◽  
H. Nussbaumer
Keyword(s):  
Total Energy ◽  
Energy Production ◽  
Light Curves ◽  
Classical Nova ◽  
Total Energies ◽  
Stellar Masses ◽  
Lower Limits ◽  
Nova Outburst

We determine bolometric light curves and total energies radiated away during the outburst of symbiotic novae. Time integrated lower limits to the total energy of 0.9×1046 <E[erg] < 7×1046 are found. Thus, the output is comparable to, or larger than the total energy production of a classical nova outburst. From the mass-luminosity relation we find the underlying stellar masses to be 0.5 < M/M⊙ < 1.1.

scholarly journals Theoretical Modes Fitting on Miras Light Curves

1993 ◽  
Vol 134 ◽  
pp. 139-140
Author(s):  
D. Barthés ◽  
Y. Tuchman ◽  
M. O. Mennessier ◽  
J. A. Mattei
Keyword(s):  
Power Spectrum ◽  
American Association ◽  
Variable Stars ◽  
Stellar Model ◽  
Light Curves ◽  
Long Period ◽  
Period Variable ◽  
The Common ◽  
Comparison Of The Results ◽  
Two Peaks

Visual observations of long period variable stars over 20 years were provided by the American Association of Variable Stars Observers, and were analysed as part of the preparation of the HIPPARCOS mission.A set of frequencies is extracted from the light curve by using Fourier transform, preliminary Van Cittert deconvolution and comparison of the results obtained through different kinds of spectral windows. The same procedure is applied to the residual obtained after nonlinear fit of the main frequency. After final comparison of both sets, a nonlinear fit of the common frequencies gives the ‘clean’ power spectrum.Different equilibrium stellar model (i) give theoretical linear nonadiabatic pulsation modes (vj) with their growth rates (ηj)i) (Tuchman 1978). The metallicity is taken between 0.005 and 0.02; the mixing length is λ = 1±0.2; the upper bound is r = 0.7. Assuming two peaks of the power spectrum to be the fundamental (vo) and first overtone (v1) modes, one looks for the corresponding models. The best one is selected by checking the other theoretical overtones they give. So are obtained the mass, the luminosity, the effective temperature and the effective radius of each star.

scholarly journals A Molecular Line Survey of the Carbon Star IRAS 15194-5115

1992 ◽  
Vol 150 ◽  
pp. 401-402
Author(s):  
L.-Å. Nyman ◽  
R. S. Booth ◽  
U. Carlström ◽  
L.E.B. Johansson ◽  
H. Olofsson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Carbon Star ◽  
Molecular Line ◽  
Infrared Observations ◽  
Bolometric Luminosity ◽  
The Third ◽  
Line Survey

IRAS 15194-5115 was discovered by IRAS and identified as a carbon star by Meadows et al. (1987). It is the third brightest carbon star at 12 μm, the brighter ones are IRC+10216 and CIT6. Its infrared properties are similar to those of IRC+10216. Le Bertre and Epchtein (1990) have monitored the star in the near-infrared and derived a period of 578 days. The distance to IRAS 15194-5115 is estimated to about 1 kpc from infrared observations, and also by comparing its bolometric luminosity with that of IRC+10216.

scholarly journals Intrinsic and observed dual AGN fractions from major mergers

2019 ◽  
Vol 624 ◽  
pp. A86 ◽  
Author(s):  
J. M. Solanes ◽  
J. D. Perea ◽  
G. Valentí–Rojas ◽  
A. del Olmo ◽  
I. Márquez ◽  
...  
Keyword(s):  
Observational Studies ◽  
Maximum Level ◽  
Theoretical Studies ◽  
Activity Levels ◽  
Nuclear Activity ◽  
Bolometric Luminosity ◽  
Global Properties ◽  
Relative Separation ◽  
Order Of Magnitude ◽  
Optical Wavelengths

A suite of 432 collisionless simulations of bound pairs of spiral galaxies with mass ratios 1:1 and 3:1, and global properties consistent with the ΛCDM paradigm, is used to test the conjecture that major mergers fuel the dual AGN (DAGN) of the local volume. Our analysis was based on the premise that the essential aspects of this scenario can be captured by replacing the physics of the central black holes with restrictions on their relative separation in phase space. We introduce several estimates of the DAGN fraction and infer predictions for the activity levels and resolution limits usually involved in surveys of these systems, assessing their dependence on the parameters controlling the length of both mergers and nuclear activity. Given a set of constraints, we find that the values adopted for some of the latter factors often condition the outcomes from individual experiments. Still, the results do not, in general, reveal very tight correlations, the clearest effect being the tendency of the frequencies normalized to the merger time to anticorrelate with the orbital circularity. In agreement with other theoretical studies, our simulations predict intrinsic DAGN abundances that range from ∼ a few to 15% depending on the maximum level of nuclear activity achieved, the higher the bolometric luminosity, the lower the fraction. At the same time, we show that these probabilities are reduced by about an order of magnitude when they are filtered with the typical constraints applied by observational studies of the DAGN fraction at low redshift. Seen as a whole, our results prove that consideration of the most common limitations involved in the detection of close active pairs at optical wavelengths is sufficient alone to reconcile the intrinsic frequencies envisaged in a hierarchical universe with the small fractions of double-peaked narrow-line systems which are often reported at kpc-scales.

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