scholarly journals X-Ray Observations of Classical and Recurrent Novae in Outburst

2004 ◽  
Vol 194 ◽  
pp. 182-186 ◽  
Author(s):  
M. Orio
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Circumstellar Matter ◽  
X Rays ◽  
Hydrogen Burning ◽  
X Ray ◽  
High Fraction ◽  
Emission Line Spectrum ◽  
Recurrent Nova ◽  
Red Giant

AbstractI review X-ray observations of classical and recurrent novae in outburst, some of them recently done with Chandra and XMM-Newton for 12 objects. Significant X-ray flux is emitted by the nova shell, with a peak luminosity up to Lx = 1035 erg s–1 in the 0.2-10 keV range. In recurrent nova systems, or in novae hosting a red giant, the source of X-rays may be previous circumstellar matter shocked by the nova wind. However, for most classical novae, X-rays originate inside the nebula ejected in the outburst. The data indicate a very high fraction of shocked material, and a non-smooth, varying wind outflow. A nebular emission line spectrum is also observed at late phases. In about half of the observed novae, the central white dwarf appears as a very luminous supersoft X-ray source for 1 to 9 years after the outburst. It is the best type of object to study the characteristics of shell hydrogen burning on white dwarfs in single degenerate systems. Still incomplete statistics indicate that the duration of the supersoft X-ray phase is peaked around ≃2 years. The correlation of the X-ray light curve with the nova properties is not quite clear. Recently, “template grating spectra” with high S/N have been obtained for V4743 Sgr. The X-ray light curve of this nova reveals a rich and complex power spectrum, with signatures of non-radial g-mode oscillations of the white dwarf. The oscillations and the spectra allow to determine the properties of the shell hydrogen burning white dwarf.

scholarly journals Supersoft X-ray phases of recurrent novae as an indicator of their white dwarf masses

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Mariko Kato ◽  
Izumi Hachisu
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Total Duration ◽  
Simple Relation ◽  
Light Curves ◽  
Curve Shape ◽  
Plateau Phase ◽  
Hydrogen Burning ◽  
X Ray ◽  
Recurrent Nova

Abstract We have examined the optical/X-ray light curves of seven well-observed recurrent novae, V745 Sco, M31N 2008-12a, LMC N 1968, U Sco, RS Oph, LMC N 2009a, T Pyx, and one recurrent nova candidate LMC N 2012a. Six novae out of the eight show a simple relation that the duration of supersoft X-ray source (SSS) phase is 0.70 times the total duration of the outburst (= X-ray turnoff time), i.e., tSSS = 0.70 toff, the total duration of which ranges from 10 to 260 d. These six recurrent novae show a broad rectangular X-ray light curve shape, the first half-period of which is highly variable in the X-ray count rate. The SSS phase also corresponds to an optical plateau phase that indicates a large accretion disk irradiated by a hydrogen-burning white dwarf (WD). The two other recurrent novae, T Pyx and V745 Sco, show a narrow triangular-shaped X-ray light curve without an optical plateau phase. Their relations between tSSS and toff are rather different from the above six recurrent novae. We also present theoretical SSS durations for recurrent novae with various WD masses and stellar metallicities (Z = 0.004, 0.01, 0.02, and 0.05) and compare them with the observed durations of these recurrent novae. We show that SSS duration is a good indicator of WD mass in recurrent novae with a broad rectangular X-ray light curve shape.

scholarly journals Possible X-Ray Flares in a Recurrent Nova

1990 ◽  
Vol 122 ◽  
pp. 427-428
Author(s):  
Izumi Hachisu ◽  
Hiroshi Itoh
Keyword(s):  
Dynamical Evolution ◽  
Spectral Shape ◽  
Spherically Symmetric ◽  
X Rays ◽  
X Ray ◽  
Wind Region ◽  
Recurrent Nova ◽  
Red Giant ◽  
Hydrodynamic Code

Abstract:The dynamical evolution and nonequilibrium X-ray emission of recurrent nova remnants have been investigated by using a spherically symmetric hydrodynamic code. We assume that the nova ejecta expand into a wind from a red-giant companion. The wind material is blast-shocked, and emits copious X-rays. The blast shock soon breaks out of the wind region and the X-ray emission declines drastically. The blast shock eventually catches up with the relatively slow ejecta of the previous outbursts. The X-ray emission may then be rejuvenated in both luminosity and spectral shape.

scholarly journals Thermal X-Rays due to Ejecta/CSM Interaction in SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 450-451
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
H. Itoh ◽  
K. Nomoto ◽  
T. Shigeyama
Keyword(s):  
Light Curve ◽  
Photon Energy ◽  
Thermal Emission ◽  
Circumstellar Matter ◽  
Expansion Velocity ◽  
X Rays ◽  
X Ray ◽  
Sn 1987A ◽  
Inner Radius

The X-ray spectrum observed by Ginga is characterized by a component below 10keV which decreases with increasing photon energy, and a component above 10keV which is nearly flat. This unusual X-ray spectrum may be understood as follows; X-rays below 10keV is likely to be due to thermal emission coming from the shock-heated ejecta, and X-rays above 10keV to be due to γ-ray degradation inside the ejecta. If thermal emission due to the collision of the ejecta with circumstellar matter (CSM) is responsible for X-rays below 10keV, the epoch of the collision can be estimated to be ∼ 0.2yr after the explosion if ∼ 0.5yr is the time when the X-ray flux at ∼ 10keV reaches its maximum. The X-ray light curve then requires the inner radius of CSM to be ∼ 1×1016cm for an expansion velocity, Vex ≃2×109cm s−1.

scholarly journals Optical Light Curve of Nova KT Eridani

2012 ◽  
Vol 8 (S290) ◽  
pp. 191-192
Author(s):  
W. P. Chen ◽  
L. W. Hung ◽  
Fred Walter
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Hot Spot ◽  
X Ray ◽  
Optical Emissions ◽  
Optical Light Curve ◽  
Recurrent Nova ◽  
Orbital Modulation ◽  
Type Giant

AbstractWe present the optical light curve of the very fast nova, KT Eridani, from its outburst in November 2009 to quiescence in 2012. Comparison of our data with the 24-hour monitoring by Swift on 2010 March 31 indicates a possible anticorrelation between the X-ray and optical emissions. A period of 57 d is found in the long-term optical light curve, which we interpret as the orbital modulation of the hot spot on the white dwarf disk accreting material from an early K-type giant. Our study lends support to the notation that KT Eri may be a recurrent nova.

scholarly journals The 2019 eruption of recurrent nova V3890 Sgr: observations by Swift, NICER, and SMARTS

2020 ◽  
Vol 499 (4) ◽  
pp. 4814-4831
Author(s):  
K L Page ◽  
N P M Kuin ◽  
A P Beardmore ◽  
F M Walter ◽  
J P Osborne ◽  
...  
Keyword(s):  
Light Curve ◽  
Periodic Oscillation ◽  
Uv Spectra ◽  
Continuum Emission ◽  
Modulation Amplitude ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
Show Evidence ◽  
Recurrent Nova ◽  
Red Giant

ABSTRACT V3890 Sgr is a recurrent nova that has been seen in outburst three times so far, with the most recent eruption occurring on 2019 August 27 ut. This latest outburst was followed in detail by the Neil Gehrels Swift Observatory, from less than a day after the eruption until the nova entered the Sun observing constraint, with a small number of additional observations after the constraint ended. The X-ray light curve shows initial hard shock emission, followed by an early start of the supersoft source phase around day 8.5, with the soft emission ceasing by day 26. Together with the peak blackbody temperature of the supersoft spectrum being ∼100 eV, these timings suggest the white dwarf mass to be high, $\sim 1.3\, {\rm M_{\odot }}$. The UV photometric light curve decays monotonically, with the decay rate changing a number of times, approximately simultaneously with variations in the X-ray emission. The UV grism spectra show both line and continuum emission, with emission lines of N, C, Mg, and O being notable. These UV spectra are best dereddened using a Small Magellanic Cloud extinction law. Optical spectra from SMARTS show evidence of interaction between the nova ejecta and wind from the donor star, as well as the extended atmosphere of the red giant being flash-ionized by the supersoft X-ray photons. Data from NICER reveal a transient 83 s quasi-periodic oscillation, with a modulation amplitude of 5 per cent, adding to the sample of novae that show such short variabilities during their supersoft phase.

scholarly journals X-ray spectra and light curves of cooling novae and a nova like

2020 ◽  
Vol 499 (2) ◽  
pp. 3006-3018
Author(s):  
Bangzheng Sun ◽  
Marina Orio ◽  
Andrej Dobrotka ◽  
Gerardo Juan Manuel Luna ◽  
Sergey Shugarov ◽  
...  
Keyword(s):  
Light Curve ◽  
Accretion Rate ◽  
High Energy ◽  
Gravitational Energy ◽  
Light Curves ◽  
Clear Correlation ◽  
X Rays ◽  
High State ◽  
X Ray ◽  
Low X

ABSTRACT We present X-ray observations of novae V2491 Cyg and KT Eri about 9 yr post-outburst of the dwarf nova and post-nova candidate EY Cyg, and of a VY Scl variable. The first three objects were observed with XMM–Newton, KT Eri also with the Chandra ACIS-S camera, V794 Aql with the Chandra ACIS-S camera and High Energy Transmission Gratings. The two recent novae, similar in outburst amplitude and light curve, appear very different at quiescence. Assuming half of the gravitational energy is irradiated in X-rays, V2491 Cyg is accreting at $\dot{m}=1.4\times 10^{-9}{\!-\!}10^{-8}\,{\rm M}_\odot \,{\rm yr}^{-1}$, while for KT Eri, $\dot{m}\lt 2\times 10^{-10}{\rm M}_\odot \,{\rm yr}$. V2491 Cyg shows signatures of a magnetized WD, specifically of an intermediate polar. A periodicity of  39 min, detected in outburst, was still measured and is likely due to WD rotation. EY Cyg is accreting at $\dot{m}\sim 1.8\times 10^{-11}{\rm M}_\odot \,{\rm yr}^{-1}$, one magnitude lower than KT Eri, consistently with its U Gem outburst behaviour and its quiescent UV flux. The X-rays are modulated with the orbital period, despite the system’s low inclination, probably due to the X-ray flux of the secondary. A period of  81 min is also detected, suggesting that it may also be an intermediate polar. V794 Aql had low X-ray luminosity during an optically high state, about the same level as in a recent optically low state. Thus, we find no clear correlation between optical and X-ray luminosity: the accretion rate seems unstable and variable. The very hard X-ray spectrum indicates a massive WD.

New insight into the origin of the GeV flare in the binary system PSR B1259-63/LS 2883 from the 2017 periastron passage

2020 ◽  
Vol 497 (1) ◽  
pp. 648-655
Author(s):  
M Chernyakova ◽  
D Malyshev ◽  
S Mc Keague ◽  
B van Soelen ◽  
J P Marais ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Energy Release ◽  
Broad Band ◽  
Strong Shock ◽  
Optical Observations ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton ◽  
Pulsar Wind

ABSTRACT PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around an O9.5Ve star, LS 2883, with a period of ∼3.4 yr. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broad-band emission in the radio, X-rays, GeV, and TeV domains. While the radio, X-ray, and TeV light curves show rather similar behaviour, the GeV light curve appears very different with a huge outburst about a month after a periastron. The energy release during this outburst seems to significantly exceed the spin-down luminosity of the pulsar and both the GeV light curve and the energy release vary from one orbit to the next. In this paper, we present for the first time the results of optical observations of the system in 2017, and also reanalyse the available X-ray and GeV data. We present a new model in which the GeV data are explained as a combination of the bremsstrahlung and inverse Compton emission from the unshocked and weakly shocked electrons of the pulsar wind. The X-ray and TeV emission is produced by synchrotron and inverse Compton emission of energetic electrons accelerated on a strong shock arising due to stellar/pulsar winds collision. The brightness of the GeV flare is explained in our model as a beaming effect of the energy released in a cone oriented, during the time of the flare, in the direction of the observer.

scholarly journals Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469

2020 ◽  
Vol 494 (3) ◽  
pp. 4057-4068
Author(s):  
Mayukh Pahari ◽  
I M McHardy ◽  
Federico Vincentelli ◽  
Edward Cackett ◽  
Bradley M Peterson ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Lag ◽  
Accretion Disc ◽  
Light Curves ◽  
X Rays ◽  
X Ray ◽  
Cross Correlation Analysis ◽  
Optical Continuum ◽  
Delay Prediction ◽  
Ngc 7469

ABSTRACT Using a month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220–1970 Å, we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469. Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Å by 3.49 ± 0.22 d, which is possibly caused by either propagating fluctuation or variable Comptonization. However, if variations slower than 5 d are removed from the X-ray light curve, the UV variations then lag behind the X-ray variations by 0.37 ± 0.14 d, consistent with reprocessing of the X-rays by a surrounding accretion disc. A very similar reverberation delay is observed between Swift/XRT X-ray and Swift/UVOT UVW2, U light curves. Continuum light curves extracted from the Swift/GRISM spectra show delays with respect to X-rays consistent with reverberation. Separating the UV continuum variations faster and slower than 5 d, the slow variations at 1825 Å lag those at 1315 Å by 0.29 ± 0.06 d, while the fast variations are coincident (0.04 ± 0.12 d). The UV/optical continuum reverberation lag from IUE, Swift, and other optical telescopes at different wavelengths are consistent with the relationship: τ ∝ λ4/3, predicted for the standard accretion disc theory while the best-fitting X-ray delay from RXTE and Swift/XRT shows a negative X-ray offset of ∼0.38 d from the standard disc delay prediction.

An Extremely Massive White Dwarf of the Symbiotic Classical Nova V407 Cyg as Suggested by the RS Oph and U SCO Models

2012 ◽  
Vol 21 (1-2) ◽  
Author(s):  
I. Hachisu ◽  
M. Kato
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Early Phase ◽  
Symbiotic Star ◽  
X Ray ◽  
Classical Nova ◽  
Optical Light Curve ◽  
Nova Outburst

AbstractWe have analyzed the optical light curve of the symbiotic star V407 Cyg that underwent a classical nova outburst in 2010 March. Being guided by a supersoft X-ray phase observed during days 20-40 after the nova outburst, we are able to reproduce the light curve during a very early phase of the nova outburst. Our model consists of an outbursting white dwarf and an extended equatorial disk. An extremely massive white dwarf of 1.35-1.37 M

scholarly journals An ASCA Observation of the Eclipsing Dwarf Nova HT Cas

1996 ◽  
Vol 158 ◽  
pp. 269-272
Author(s):  
K. Mukai ◽  
E. M. Schlegel ◽  
J. H. Swank ◽  
T. Naylor ◽  
Janet H. Wood
Keyword(s):  
Boundary Layer ◽  
White Dwarf ◽  
X Rays ◽  
X Ray ◽  
Dwarf Nova

AbstractWe report on a 1-day ASCA observation of the eclipsing dwarf nova HT Cas. We confirm the presence of an X-ray eclipse, which is narrow and deep. The data are consistent with the X-rays originating entirely from the immediate neighborhood of the white dwarf. We draw some preliminary conclusions on the boundary layer and other relevant issues.

Sign in / Sign up

Export Citation Format

Share Document