Spatial distribution of the X-ray-emitting plasma of SS Cygni in quiescence and outburst

Abstract We present our analysis of the Suzaku data of SS Cygni (SS Cyg) from 2005 both in quiescence and outburst. A fluorescent iron Kα line bears significant information about the geometry of an X-ray-emitting hot plasma and a cold reflector, such as the surfaces of the white dwarf (WD) and the accretion disk (AD). Our reflection simulation has revealed that the X-ray-emitting hot plasma is located either very close to the WD surface in the boundary layer (BL), with an upper limit radial position of <1.004 times the white dwarf radius (RWD), or near the entrance of the BL where the optically thick AD is truncated at a distance of 1.14–1.27 RWD for the assumed WD mass of 1.19 M⊙ in quiescence. In the latter configuration, the plasma torus is located just above the inner edge of the AD. The result suggests that the accreting matter is heated up close to the maximum temperature immediately after the matter enters the BL. The matter probably expands precipitously at the entrance of the BL and leaves the disk plane to reach a height comparable to the radial distance of the plasma torus from the center of the WD. In outburst, on the other hand, our spectral analysis favors the picture that the optically thick disk reaches the WD surface. In addition, the plasma distributes above the disk like coronae, as suggested by a previous study, and the 90% upper limit of the coronae radial position is 1.2 RWD.

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Spatial distribution of the X-ray-emitting plasma of U Geminorum in quiescence and outburst

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa111 ◽

2020 ◽

Author(s):

Mai Takeo ◽

Takayuki Hayashi ◽

Manabu Ishida ◽

Nozomi Nakaniwa ◽

Yoshitomo Maeda

Keyword(s):

Boundary Layer ◽

White Dwarf ◽

Flow Model ◽

Accretion Rate ◽

Maximum Temperature ◽

Significant Information ◽

X Ray ◽

Cooling Flow ◽

Hot Plasma ◽

Data Coverage

Abstract We present our analysis of the Suzaku data of U Geminorum (U Gem) from 2012 both in quiescence and outburst. Unlike SS Cygni (SS Cyg), the hard X-ray flux of U Gem is known to increase at times of optical outburst. A sophisticated spectral model and reliable distance estimate now reveal that this can be attributed to the fact that the mass accretion rate onto the white dwarf (WD) does not exceed the critical rate that causes the optically thin to thick transition of the boundary layer. From comparison of the X-ray and optical light curves, the X-ray outburst peak seems to be retarded by 2.1 ± 0.5 d, although there remains uncertainty in the X-ray peak identification, due to short data coverage. The larger delay than SS Cyg (0.9–1.4 d) also supports the lower accretion rate in U Gem. A fluorescent iron 6.4 keV emission line bears significant information about the geometry of the X-ray-emitting hot plasma and the accretion disk (AD) that reflects the hard X-ray emission. Our reflection simulation has shown that the optically thick AD is truncated at a distance of 1.20–1.25 times the white dwarf radius (RWD) in quiescence, and the accreting matter in the disk turns into the optically thin hard-X-ray-emitting plasma at this radius. In outburst, on the other hand, our spectral analysis favors the picture that the optically thick disk reaches the WD surface, although disk truncation can take place in the region of <1.012 RWD. From the profile of the 6.4 keV line, we have also discovered that the accreting matter is heated up close to the maximum temperature immediately after the matter enters the boundary layer at the disk truncation radius. This is consistent with the fact that the hard X-ray spectra of dwarf novae, in general, can be well represented with the cooling flow model.

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High-Resolution X-Ray Spectroscopy of Galactic Supernova Remnants

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2014.01.0200 ◽

2014 ◽

Vol 1 (1) ◽

pp. 200-204

Author(s):

Satoru Katsuda ◽

Hiroshi Tsunemi

Keyword(s):

High Resolution ◽

Supernova Remnants ◽

Line Emission ◽

Collisionless Shock ◽

Reverse Shock ◽

X Ray ◽

Upper Limit ◽

Hot Plasma ◽

Forward Shock ◽

Intensity Ratios

High-resolution X-ray spectroscopy of Galactic supernova remnants (SNRs), based on grating spectrometers onboard XMM-Newton and Chandra, has been revealing a variety of new astrophysical phenomena. Broadened oxygen lines for a northwestern compact knot in SN 1006 clearly show a high oxygen temperature of ~300 keV. The high temperature together with a lower electron temperature (kTe ~ 1 keV) can be reasonably interpreted as temperature non-equilibration between electrons and oxygen behind a collisionless shock. An ejecta knot in the Puppis A SNR shows blueshifted line emission by ~ 1500kms-1. The line widths are fairly narrow in contrast to the SN 1006's knot; an upper limit of 0.9 eV is obtained for O VIII Lyα, which translates to an oxygen temperature of kTO < 30 keV. The low temperature suggests that the knot was heated by a reverse shock whose velocity is 4 times slower than that of a forward shock. Anomalous intensity ratios in O VII Heα lines, i.e., a stronger forbidden line than a resonance line, is found in a cloud-shock interaction region in Puppis A. The line ratio can be best explained by the charge-exchange emission that should arise at interfaces between the cold/warm clouds and the hot plasma. There are several other targets for which we plan to analyze high-quality grating data prior to the operation of the soft X-ray spectrometer onboard Astro-H.

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Exosat Observations of X-Rays from Classical Novae during Outburst Stage

International Astronomical Union Colloquium ◽

10.1017/s0252921100104981 ◽

1987 ◽

Vol 93 ◽

pp. 279-279

Author(s):

H. Ögelman ◽

J. Krautter ◽

K. Beuermann

Keyword(s):

White Dwarf ◽

Central Star ◽

Maximum Temperature ◽

Infrared Range ◽

First Year ◽

X Rays ◽

Core Mass ◽

X Ray ◽

Classical Novae ◽

Bolometric Luminosity

AbstractThe initial discovery of soft X-rays from Nova Muscae 1983 was followed by eight additional observations of the three brightest novae whose outburst stage coincided with the lifetime of EXOSAT satellite; namely three more observations of Nova Muscae 1983, three observations of Nova Vulpeculae 1984 # 1 (PW Vul), and two observations of Nova Vulpeculae 1984 # 2. Through these observations we sampled the soft X-ray light curve of classical novae from optical maximum to ~ 900 days after. The observations seem best explained by the constant bolometric luminosity model of a hot white dwarf remnant. Although the measurements suffer from limited statistics, very broad energy bandpass, and incomplete sampling of any single nova, their constraints on the theories of nova outburst are significant. One constraint is that the lifetime of the white dwarf remnant in Nova Muscae 1983 is ~ 2 to 3 years, which leads to the conclusion that the burned envelope mass Mburn should be of the order of . The second constraint is that the maximum temperature, of the white dwarf remnant should approximately be within 200 000 K to 400 000 K. We estimate that a white dwarf remnant evolving like the central star of a planetary nebula, with core mass of 0.8 to 0.9 M⊙, core luminosity of ~ 2 × 104L⊙, and envelope mass of 10−6M⊙, can explain the general characteristics of the X-ray measurements for Nova Muscae 1983. In order to have ≥ 1.1 M⊙ core mass, estimated from the early observations of bolometric luminosity in the UV to infrared range, a wind with Ṁ ≤ 5 × 10−7M⊙yr−1 appears to be necessary. The few observations of Nova Vulpeculae 1984 # 1 and Nova Vulpeculae 1984 # 2 , during the first year after outburst, give a risetime and intensity that is consistent with a constant bolometric luminosity model.

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Chandra and HST studies of six millisecond pulsars in the globular cluster M13

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab117 ◽

2021 ◽

Vol 502 (2) ◽

pp. 1596-1604

Author(s):

Jiaqi Zhao ◽

Yue Zhao ◽

Craig O Heinke

Keyword(s):

Globular Cluster ◽

White Dwarf ◽

Hubble Space Telescope ◽

X Rays ◽

Power Law Model ◽

Millisecond Pulsars ◽

X Ray ◽

V Band ◽

Upper Limit ◽

Single Power

ABSTRACT We analyse 55 ks of Chandra X-ray observations of the Galactic globular cluster (GC) M13. Using the latest radio timing positions of six known millisecond pulsars (MSPs) in M13 from Wang et al. (2020), we detect confident X-ray counterparts to five of the six MSPs at X-ray luminosities of LX(0.3–8 keV)∼3 × 1030–1031 erg s−1, including the newly discovered PSR J1641+3627F. There are limited X-ray counts at the position of PSR J1641+3627A, for which we obtain an upper limit LX < 1.3 × 1030 erg s−1. We analyse X-ray spectra of all six MSPs, which are well described by either a single blackbody (BB) or a single power-law model. We also incorporate optical/UV imaging observations from the Hubble Space Telescope (HST) and find optical counterparts to PSR J1641+3627D and J1641+3627F. Our colour–magnitude diagrams indicate the latter contains a white dwarf, consistent with the properties suggested by radio timing observations. The counterpart to J1641+3627D is only visible in the V band; however, we argue that the companion to J1641+3627D is also a white dwarf, since we see a BB-like X-ray spectrum, while MSPs with non-degenerate companions generally show non-thermal X-rays from shocks between the pulsar and companion winds. Our work increases the sample of known X-ray and optical counterparts of MSPs in GCs.

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Discovery of an X-Ray Off-State in the Supersoft Source CAL 83

International Astronomical Union Colloquium ◽

10.1017/s0252921100043670 ◽

1997 ◽

Vol 163 ◽

pp. 730-731

Author(s):

P. Kahabka

Keyword(s):

White Dwarf ◽

Accretion Rate ◽

X Rays ◽

X Ray ◽

Mass Accretion Rate ◽

Upper Limit ◽

Linear Decline

AbstractAn X-ray off state of CAL 83 has been observed in April 1996 with the ROSAT HRI three weeks after a normal on state. An upper limit for a linear decline time of the observed flux of ~20 days (and of an efolding decline time of ~6 days) is deduced. This decline may be due to the response of the white dwarf envelope to a temporary increased mass accretion rate giving rise to an envelope expansion. CAL 83 may resemble the recurrent supersoft LMC transient RX J0513.9–6951 with episodes of disappearance in X-rays.

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REMARKS ON THE X-RAY CONTINUUM SPECTRUM EMITTED BY A HOT PLASMA

Le Journal de Physique Colloques ◽

10.1051/jphyscol:1987968 ◽

1987 ◽

Vol 48 (C9) ◽

pp. C9-383-C9-386

Author(s):

C. MÖLLER ◽

R. Y. YIN ◽

M. LAMOUREUX

Keyword(s):

X Ray ◽

Continuum Spectrum ◽

Hot Plasma

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X-Ray Determination of the Black-Hole Mass in Cygnus X-1

Symposium - International Astronomical Union ◽

10.1017/s0074180900115669 ◽

1998 ◽

Vol 188 ◽

pp. 388-389

Author(s):

A. Kubota ◽

K. Makishima ◽

T. Dotani ◽

H. Inoue ◽

K. Mitsuda ◽

...

Keyword(s):

Black Hole ◽

Compact Object ◽

Optical Observations ◽

Black Hole Mass ◽

X Ray ◽

Upper Limit ◽

Supergiant Star ◽

X Ray Binaries ◽

Two Bodies

About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.

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Exploring the X-ray universe via timing: mass of the active galactic nucleus black hole XMMUJ134736.6+173403

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003312 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 348-350

Author(s):

Eva Šrámková ◽

K. Goluchová ◽

G. Török ◽

Marek A. Abramowicz ◽

Z. Stuchlík ◽

...

Keyword(s):

Black Hole ◽

Frequency Ratio ◽

Active Galactic Nucleus ◽

Periodic Modulation ◽

X Ray ◽

Upper Limit ◽

M 10 ◽

Frequency Ratios ◽

Quasiperiodic Oscillations ◽

Twin Peak

AbstractA strong quasi-periodic modulation has recently been revealed in the X-ray flux of the X-ray source XMMUJ134736.6+173403. The two observed twin-peak quasiperiodic oscillations (QPOs) exhibit a 3:1 frequency ratio and strongly support the evidence for the presence of an active galactic nucleus black hole (AGN BH). It has been suggested that detections of twin-peak QPOs with commensurable frequency ratios and scaling of their periods with BH mass could provide the basis for a method intended to determine the mass of BH sources, such as AGNs. Assuming the orbital origin of QPOs, we calculate the upper and lower limit on the AGN BH mass M, reaching M ≍ 107–109M⊙. Compared to mass estimates of other sources, XMMUJ134736.6+173403 appears to be the most massive source with commensurable QPO frequencies, and its mass represents the current observational upper limit on the AGN BH mass obtained from the QPO observations.

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White Dwarf Masses and Accretion Rates of Recurrent Novae: an X-ray Perspective

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312014962 ◽

2011 ◽

Vol 7 (S281) ◽

pp. 186-189

Author(s):

Koji Mukai ◽

Jennifer L. Sokoloski ◽

Thomas Nelson ◽

Gerardo J. M. Luna

Keyword(s):

White Dwarf ◽

Cataclysmic Variables ◽

The Other ◽

X Ray ◽

Other Hand ◽

Accretion Rates

AbstractWe present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RNe candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

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