scholarly journals Optical, X-ray, and γ-ray observations of the candidate transitional millisecond pulsar 4FGL J0427.8-6704

2020 ◽  
Vol 494 (3) ◽  
pp. 3912-3926
Author(s):  
M R Kennedy ◽  
R P Breton ◽  
C J Clark ◽  
V S Dhillon ◽  
M Kerr ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Periodic Oscillation ◽  
Optical Data ◽  
Data Sets ◽  
Millisecond Pulsar ◽  
X Ray ◽  
State Classification ◽  
Optical Light Curve ◽  
Γ Ray

ABSTRACT We present an optical, X-ray, and γ-ray study of 1SXPS J042749.2-670434, an eclipsing X-ray binary that has an associated γ-ray counterpart, 4FGL J0427.8-6704. This association has led to the source being classified as a transitional millisecond pulsar (tMSP) in an accreting state. We analyse 10.5 yr of Fermi LAT data and detect a γ-ray eclipse at the same phase as optical and X-ray eclipses at the >5 σ level, a significant improvement on the 2.8 σ level of the previous detection. The confirmation of this eclipse solidifies the association between the X-ray source and the γ-ray source, strengthening the tMSP classification. However, analysis of several optical data sets and an X-ray observation do not reveal a change in the source’s median brightness over long time-scales or a bi-modality on short time-scales. Instead, the light curve is dominated by flickering, which has a correlation time of 2.6 min alongside a potential quasi-periodic oscillation at ∼21 min. The mass of the primary and secondary stars is constrained to be $M_1=1.43^{+0.33}_{-0.19}$ M⊙ and $M_2=0.3^{+0.17}_{-0.12}$ M⊙ through modelling of the optical light curve. While this is still consistent with a white dwarf primary, we favour the tMSP in a low accretion state classification due to the significance of the γ-ray eclipse detection.

scholarly journals The dual nature of blazar fast variability: Space and ground observations of S5 0716+714

2020 ◽  
Vol 501 (1) ◽  
pp. 1100-1115
Author(s):  
C M Raiteri ◽  
M Villata ◽  
D Carosati ◽  
E Benítez ◽  
S O Kurtanidze ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Light Curves ◽  
Spectral Variability ◽  
Short Term ◽  
Dual Nature ◽  
X Ray ◽  
Geometric Origin ◽  
Optical Light Curve ◽  
Doppler Factor

ABSTRACT Blazar S5 0716+714 is well-known for its short-term variability, down to intraday time-scales. We here present the 2-min cadence optical light curve obtained by the TESS space telescope in 2019 December–2020 January and analyse the object fast variability with unprecedented sampling. Supporting observations by the Whole Earth Blazar Telescope Collaboration in B, V, R, and I bands allow us to investigate the spectral variability during the TESS pointing. The spectral analysis is further extended in frequency to the UV and X-ray bands with data from the Neil Gehrels Swift Observatory. We develop a new method to unveil the shortest optical variability time-scales. This is based on progressive de-trending of the TESS light curve by means of cubic spline interpolations through the binned fluxes, with decreasing time bins. The de-trended light curves are then analysed with classical tools for time-series analysis (periodogram, autocorrelation, and structure functions). The results show that below 3 d there are significant characteristic variability time-scales of about 1.7, 0.5, and 0.2 d. Variability on time-scales $\lesssim 0.2$ d is strongly chromatic and must be ascribed to intrinsic energetic processes involving emitting regions, likely jet substructures, with dimension less than about 10−3 pc. In contrast, flux changes on time-scales $\gtrsim 0.5$ d are quasi-achromatic and are probably due to Doppler factor changes of geometric origin.

The Optical Light Curve of LMC X-4 and the 30-Day X-Ray Period

1981 ◽  
pp. 405-406
Author(s):  
C. Chevalier ◽  
S. A. Ilovaisky ◽  
C. Motch ◽  
M. Pakull ◽  
J. Lub ◽  
...  
Keyword(s):  
Light Curve ◽  
X Ray ◽  
Optical Light Curve

The optical light curve of LMC X-4 and the 30-day X-ray period

1981 ◽  
Vol 30 (1-4) ◽  
pp. 405-406 ◽  
Author(s):  
C. Chevalier ◽  
S. A. Ilovaisky ◽  
C. Motch ◽  
M. Pakull ◽  
J. Lub ◽  
...  
Keyword(s):  
Light Curve ◽  
X Ray ◽  
Optical Light Curve

scholarly journals A possible γ-ray quasi-periodic oscillation of ∼314 days in the blazar OJ 287

2020 ◽  
Vol 499 (1) ◽  
pp. 653-658
Author(s):  
Pankaj Kushwaha ◽  
Arkadipta Sarkar ◽  
Alok C Gupta ◽  
Ashutosh Tripathi ◽  
Paul J Wiita
Keyword(s):  
Light Curve ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Periodic Oscillation ◽  
Large Area ◽  
Quasi Periodic Oscillation ◽  
Bl Lacertae ◽  
Emission Models ◽  
Γ Ray ◽  
Blazar Oj 287

ABSTRACT We report the detection of a probable γ-ray quasi-periodic oscillation (QPO) of around 314 d in the monthly binned 0.1–300 GeV γ-ray Fermi-Large Area Telescope light curve of the well-known BL Lacertae blazar OJ 287. To identify and quantify the QPO nature of the γ-ray light curve of OJ 287, we used the Lomb–Scargle periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) analyses. We briefly discuss possible emission models for radio-loud active galactic nuclei that can explain a γ-ray QPO of such a period in a blazar.

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 Quest for the tertiary component in Cyg OB2 #5

2019 ◽  
Vol 627 ◽  
pp. A2
Author(s):  
Gregor Rauw ◽  
Yaël Nazé ◽  
Fran Campos
Keyword(s):  
Light Curve ◽  
High Energy ◽  
Optical Data ◽  
X Ray ◽  
Systemic Velocity ◽  
Short Period ◽  
Velocity Changes ◽  
The Times ◽  
High Energy Emission ◽  
First Time

Aims. The Cyg OB2 #5 system is thought to consist of a short-period (6.6 d) eclipsing massive binary orbited by an OB-star with a period of ~6.7 yr; these stars in turn are orbited by a distant early B-star with a period of thousands of years. However, while the inner binary has been studied many times, information is missing on the other stars, in particular the third star whose presence was indirectly postulated from recurrent modulations in the radio domain. Besides, to this date, the X-ray light curve could not be fully interpreted, for example in the framework of colliding-wind emission linked to one of the systems. Methods. We obtained new optical and X-ray observations of Cyg OB2 #5, which we combined to archival data. We performed a thorough and homogeneous investigation of all available data, notably revisiting the times of primary minimum in photometry. Results. In the X-ray domain, XMM-Newton provides scattered exposures over ~5000 d whilst Swift provides a nearly continuous monitoring for the last couple of years. Although the X-ray light curve reveals clear variability, no significant period can be found hence the high-energy emission cannot be explained solely in terms of colliding winds varying along either the short or intermediate orbits. The optical data reveal for the first time clear signs of reflex motion. The photometry indicates the presence of a 2366 d (i.e. 6.5 yr) period while the associated radial velocity changes are detected at the 3σ level in the systemic velocity of the He II λ 4686 emission line. With the revised period, the radio light curve is interpreted consistently in terms of a wind interaction between the inner binary and the tertiary star. From these optical and radio data, we derive constraints on the physical properties of the tertiary star and its orbit.

SN1993J: CHALLENGING NEW INSIGHTS FOR STELLAR STRUCTURE AND SUPERNOVA THEORIES

1995 ◽  
Vol 04 (04) ◽  
pp. 429-449
Author(s):  
RAMEN KUMAR PARUI
Keyword(s):  
Light Curve ◽  
Shell Structure ◽  
Stellar Structure ◽  
Present Review ◽  
Nearby Galaxy ◽  
X Ray ◽  
Gradual Development ◽  
Γ Ray ◽  
The Asymmetry

The appearance of supernova SN1993J in our nearby galaxy M81 is an important event in the modern study of supernovae. From the very beginning it created puzzles regarding its supernova type; then in its evolution further puzzles particularly in its spectra, light curve, nature of progenitor, X-ray and γ-ray emission, polarization, etc. Various puzzles have been solved with the help of both theoretical and observational investigations. Still many problems remain. In this present review we examine the gradual development of the various puzzles along with the evolution of SN1993J. We have also presented the unsolved problems as well as the important aspects which are to be measured. We particularly emphasize on the measurements of the shell structure of a radio supernova and of the asymmetry of the scattering envelope as a test to verify the prediction of shell structure in supernova theory i.e. supernova SN1993J will give us an opportunity to verify various aspects of supernova theory.

scholarly journals SN 2020bvc: A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart

2020 ◽  
Vol 902 (1) ◽  
pp. 86 ◽  
Author(s):  
Anna Y. Q. Ho ◽  
S. R. Kulkarni ◽  
Daniel A. Perley ◽  
S. Bradley Cenko ◽  
Alessandra Corsi ◽  
...  
Keyword(s):  
Light Curve ◽  
Broad Line ◽  
X Ray ◽  
Optical Light Curve ◽  
Line Type

scholarly journals Possible ~1 hour quasi-periodic oscillation in narrow-line Seyfert 1 galaxy MCG–06–30–15

2018 ◽  
Vol 616 ◽  
pp. L6 ◽  
Author(s):  
Alok C. Gupta ◽  
Ashutosh Tripathi ◽  
Paul J. Wiita ◽  
Minfeng Gu ◽  
Cosimo Bambi ◽  
...  
Keyword(s):  
Light Curve ◽  
Energy Range ◽  
Periodic Oscillation ◽  
Light Curves ◽  
Narrow Line ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
S Period

We found a possible ~1 h quasi-periodic oscillation (QPO) in a ~55 ks X-ray observation of the narrow-line Seyfert 1 galaxy MCG–06–30–15 made with the XMM-Newton EPIC/pn detector in the energy range 0.3–10 keV. We identify a total modulation of ~16% in the light curve and find a ≃3670 s quasi-period using Lomb-Scargle periodogram (LSP) and weighted wavelet Z-transform (WWZ) techniques. Our analyses of eight light curves of MCG–06–30–15, indicated the possible presence of an oscillation during one of them. The LSP indicates a statistically significant (≃3σ) QPO detection. A WWZ analysis shows that the signal at this possible roughly 3670 s period is present, and rather persistent, throughout the observation; however, a signal around 8735 s is more persistent. We briefly discuss models that can produce X-ray QPOs with such periods in narrow line Seyfert 1 galaxies, as both other claimed QPO detections in this class of AGN had very similar periods.

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