scholarly journals ASCA Observations of 44I Bootis and VW Cephei

1998 ◽  
Vol 188 ◽  
pp. 226-227
Author(s):  
Chul-Sung Choi ◽  
Tadayasu Dotani
Keyword(s):  
Spectral Analysis ◽  
Light Curve ◽  
Plasma Model ◽  
X Ray ◽  
Long Duration ◽  
Orbital Phase ◽  
Different Temperatures ◽  
Archive Data ◽  
Peak Luminosity

We analyze X-ray archive data of the W UMa-type binaries 44i Boo and VW Cep, taken with ASCA on 1994 May 10 and 1993 November 5, respectively. By analyzing the light curve of VW Cep, we find a long-duration flare of ≈ 7.5 hrs with the peak luminosity of 1.2 × 1030 ergs s−1 (0.4-3.0 keV) for the assumed distance of 23.2 pc. We also find appreciable flux variations from the light curve of 44i Boo, and the variations are erratic and are not orbital phase dependent. From the spectral analysis of both data, we see that the spectra could be reproduced by the variable abundance plasma model with a combination of two different temperatures, kT = 0.64 – 0.65 keV and kT = 1.85 – 1.91 keV.

scholarly journals The 2016 January eruption of recurrent Nova LMC 1968

2019 ◽  
Vol 491 (1) ◽  
pp. 655-679 ◽  
Author(s):  
N P M Kuin ◽  
K L Page ◽  
P Mróz ◽  
M J Darnley ◽  
S N Shore ◽  
...  
Keyword(s):  
Light Curve ◽  
Large Magellanic Cloud ◽  
Recurrence Time ◽  
Uv Spectrum ◽  
Orbital Inclination ◽  
X Ray ◽  
Orbital Phase ◽  
Colour Changes ◽  
Recurrent Nova ◽  
Ir Photometry

ABSTRACT We present a comprehensive review of all observations of the eclipsing recurrent Nova LMC 1968 in the Large Magellanic Cloud which was previously observed in eruption in 1968, 1990, 2002, 2010, and most recently in 2016. We derive a probable recurrence time of 6.2 ± 1.2 yr and provide the ephemerides of the eclipse. In the ultraviolet–optical–IR photometry the light curve shows high variability right from the first observation around 2 d after eruption. Therefore no colour changes can be substantiated. Outburst spectra from 2016 and 1990 are very similar and are dominated by H and He lines longward of 2000 Å. Interstellar reddening is found to be E(B − V) = 0.07 ± 0.01. The super soft X-ray luminosity is lower than the Eddington luminosity and the X-ray spectra suggest the mass of the white dwarf (WD) is larger than 1.3 M⊙. Eclipses in the light curve suggest that the system is at high orbital inclination. On day 4 after the eruption a recombination wave was observed in Fe ii ultraviolet absorption lines. Narrow-line components are seen after day 6 and explained as being due to reionization of ejecta from a previous eruption. The UV spectrum varies with orbital phase, in particular a component of the He ii 1640 Å emission line, which leads us to propose that early-on the inner WD Roche lobe might be filled with a bound opaque medium prior to the re-formation of an accretion disc. Both this medium and the ejecta can cause the delay in the appearance of the soft X-ray source.

scholarly journals X-ray emission from the mixed-morphology supernova remnant HB 9

2020 ◽  
Vol 72 (4) ◽  
Author(s):  
Mariko Saito ◽  
Shigeo Yamauchi ◽  
Kumiko K Nobukawa ◽  
Aya Bamba ◽  
Thomas G Pannuti
Keyword(s):  
Spectral Analysis ◽  
Central Region ◽  
Supernova Remnant ◽  
Interstellar Matter ◽  
Plasma Model ◽  
Ionization Equilibrium ◽  
Equilibrium Plasma ◽  
X Ray ◽  
Collisional Ionization ◽  
Matter Component

Abstract We present the results of a spectral analysis of the central region of the mixed-morphology supernova remnant HB 9. A prior Ginga observation of this source detected a hard X-ray component above 4 keV, and the origin of this particular X-ray component is still unknown. Our results demonstrate that the extracted X-ray spectra are best represented by a model consisting of a collisional ionization equilibrium plasma with a temperature of ∼0.1–0.2 keV (interstellar matter component) and an ionizing plasma with a temperature of ∼0.6–0.7 keV and an ionization timescale of >1 × 1011 cm−3 s (ejecta component). No significant X-ray emission was found in the central region above 4 keV. The recombining plasma model reported by a previous work does not explain our spectra.

scholarly journals Systematic Spectral Lag Analysis of Swift Known-zGRBs

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Yuta Kawakubo ◽  
Takanori Sakamoto ◽  
Atsumasa Yoshida ◽  
Demos Kazanas
Keyword(s):  
Gamma Ray ◽  
Empirical Relationship ◽  
High Energy ◽  
X Ray ◽  
Long Duration ◽  
Spectral Lag ◽  
Break Time ◽  
The Difference ◽  
The Relationship ◽  
Peak Luminosity

The difference of photon arrival time, which is known as spectral lag, is well known characteristics of gamma-ray bursts (GRBs). In particular, long duration GRBs show a soft lag which means that high energy photons arrive earlier than soft photons. The lag-luminosity relation is the empirical relationship between the isotropic peak luminosity and the spectral lag. We calculated the spectral lags for 40 known redshift GRBs observed bySwiftaddition to the previous 31 GRB samples. We confirmed that most of our samples follow the lag-luminosity relation. However, we noticed that there are some GRBs which show a significant scatter from the relation. We also confirm that the relationship between the break time and the luminosity of the X-ray afterglow (so-called Dainotti relation) extends up to the lag-luminosity relation.

scholarly journals An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

2018 ◽  
Vol 612 ◽  
pp. A102 ◽  
Author(s):  
R. Terrier ◽  
M. Clavel ◽  
S. Soldi ◽  
A. Goldwurm ◽  
G. Ponti ◽  
...  
Keyword(s):  
Line Emission ◽  
Molecular Complexes ◽  
Massive Black Hole ◽  
X Ray ◽  
Open Questions ◽  
Long Duration ◽  
Sgr A ◽  
Thermal Diffuse ◽  
Archive Data ◽  
Do So

There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 yr or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Kα line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000–2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000–2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 yr) events.

scholarly journals Colliding winds in Wolf-Rayet binaries: further developments within a complicated story

1999 ◽  
Vol 193 ◽  
pp. 298-305 ◽  
Author(s):  
Rolf Walder ◽  
Doris Folini ◽  
Simin M. Motamen
Keyword(s):  
Heat Conduction ◽  
Magnetic Fields ◽  
Light Curve ◽  
Large Scale ◽  
Opening Angle ◽  
3D Simulations ◽  
X Ray ◽  
Orbital Phase ◽  
The Impact ◽  
Colliding Winds

We present large scale 3D simulations of colliding winds in the WR binary γ2 Velorum (WR 11). The O-star wind is confined by cold, high density shells and forms a spirally shaped region within the WR-wind. As a consequence of the elliptic orbit, the opening angle and the curvature of the spiral as well as the ratio of the volumes occupied by the WR- and the O-wind are functions of the orbital phase. Our model qualitatively reproduces the observed X-ray light-curve. The impact of magnetic fields and heat conduction on the physics of colliding winds is briefly discussed and some remarks on the important question of stability are made.

scholarly journals Multiwavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632 + 057 with NuSTAR, VERITAS, MDM, and Swift

2021 ◽  
Vol 923 (1) ◽  
pp. 17
Author(s):  
Y. M. Tokayer ◽  
H. An ◽  
J. P. Halpern ◽  
J. Kim ◽  
K. Mori ◽  
...  
Keyword(s):  
Light Curve ◽  
Binary Systems ◽  
Gamma Ray ◽  
Neutral Hydrogen ◽  
High Energy ◽  
Secondary Peak ◽  
Spectral Evolution ◽  
X Ray ◽  
Orbital Parameters ◽  
Orbital Phase

Abstract HESS J0632+057 belongs to a rare subclass of binary systems that emit gamma rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp “primary” peak and broader “secondary” peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between 2019 December and 2020 February, when the orbital phase (ϕ) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multiwavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from 2019 October to 2020 March, the MDM observatory did not detect significant variation in Hα and Hβ line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light-curve data with an intrabinary shock model constrained the orbital parameters, suggesting two orbital phases (at ϕ D = 0.13 and 0.37), where the pulsar crosses the Be-disk, as well as phases for the periastron (ϕ 0 = 0.30) and inferior conjunction (ϕ IFC = 0.75). The broadband X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases.

RSCVn Stars in the Southern Hemisphere

1979 ◽  
Vol 46 ◽  
pp. 371-384 ◽  
Author(s):  
J.B. Hearnshaw
Keyword(s):  
Light Curve ◽  
Southern Hemisphere ◽  
Orbital Period ◽  
Binary Stars ◽  
Small Amplitude ◽  
Light Variation ◽  
Orbital Phase

RSCVn stars are fully detached binary stars which show intrinsic small amplitude (up to 0.3 amplitude peak-to-peak) light variations, as well as, in most of the known cases, eclipses. The spectra are F to G, IV to V for the hotter component and usually KOIV for the cooler. They are also characterised by abnormally strong H and K emission from the cooler star, or, occasionally, from both components. The orbital and light curve periods are in the range 1 day to 2 weeks. An interesting feature is the migration of the light variations to earlier orbital phase, as the light variation period is shorter than the orbital period by a few parts in 10+4to a few parts in 10+3.

ASCAObservation of a Long‐Duration X‐Ray Flare from the W UMa–Type Binary VW Cephei

1998 ◽  
Vol 492 (2) ◽  
pp. 761-766 ◽  
Author(s):  
C. S. Choi ◽  
T. Dotani
Keyword(s):  
X Ray ◽  
Long Duration

scholarly journals X-ray and UV emission of the ultrashort-period, low-mass eclipsing binary system BX Trianguli

2018 ◽  
Vol 619 ◽  
pp. A138
Author(s):  
V. Perdelwitz ◽  
S. Czesla ◽  
J. Robrade ◽  
T. Pribulla ◽  
J. H. M. M. Schmitt
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Binary Systems ◽  
Uv Light ◽  
Close Binary ◽  
Eclipsing Binary ◽  
X Ray ◽  
Uv Emission ◽  
Low Mass ◽  
Orbital Modulation

Context.Close binary systems provide an excellent tool for determining stellar parameters such as radii and masses with a high degree of precision. Due to the high rotational velocities, most of these systems exhibit strong signs of magnetic activity, postulated to be the underlying reason for radius inflation in many of the components. Aims.We extend the sample of low-mass binary systems with well-known X-ray properties. Methods.We analyze data from a singular XMM-Newton pointing of the close, low-mass eclipsing binary system BX Tri. The UV light curve was modeled with the eclipsing binary modeling tool PHOEBE and data acquired with the EPIC cameras was analyzed to search for hints of orbital modulation. Results.We find clear evidence of orbital modulation in the UV light curve and show that PHOEBE is fully capable of modeling data within this wavelength range. Comparison to a theoretical flux prediction based on PHOENIX models shows that the majority of UV emission is of photospheric origin. While the X-ray light curve does exhibit strong variations, the signal-to-noise ratio of the observation is insufficient for a clear detection of signs of orbital modulation. There is evidence of a Neupert-like correlation between UV and X-ray data.

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