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

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

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa912 ◽

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.

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AM Herculis - A unique X-ray binary as revealed through the optical light curve

The Astrophysical Journal ◽

10.1086/182387 ◽

1977 ◽

Vol 212 ◽

pp. L113 ◽

Cited By ~ 34

Author(s):

P. Szkody ◽

D. E. Brownlee

Keyword(s):

Light Curve ◽

X Ray ◽

Optical Light Curve

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Light Curve Models for SN 1987A and Diagnosis of Supernova Interior

International Astronomical Union Colloquium ◽

10.1017/s0252921100094070 ◽

1988 ◽

Vol 108 ◽

pp. 319-334

Author(s):

Ken’ichi Nomoto ◽

Toshikazu Shigeyama ◽

Masa-aki Hashimoto

Keyword(s):

Light Curve ◽

Reasonable Agreement ◽

Light Curves ◽

Shock Propagation ◽

Helium Abundance ◽

X Ray ◽

Sn 1987A ◽

Shock Heating ◽

Helium Stars ◽

Optical Light Curve

AbstractPresupernova evolution of the progenitor of SN 1987A, hydrodynamics of explosion (shock propagation, explosive nucleosynthesis), optical light curve due to shock heating and 56Co decay, and X-ray and γ-ray light curves are calculated and compared with the observations of SN 1987A. Constraints on the mass of the hydrogen-rich envelope Menv (i.e., mass loss history) and the helium abundance in the envelope are obtained from the progenitor’s blue-red-blue evolution as well as from the light curve. The explosion energy E and the mass and distribution of 56Ni are inferred from the light curves. Models and observations are in reasonable agreement for E/Menv = 1.5 ± 0.5 × 1050 erg/M⊙, Menv = 5 - 10 M⊙, and MNi ∼ 0.07 M⊙. Mixing of 56Ni into the envelope is indicated.Light curves of exploding bare helium stars are also calculated to see whether the observed Type Ib supernova light curves can be accounted for.

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GRB 161017A, the circumburst environment is an intermediate regime between the homogeneous interstellar medium and wind-type medium

International Journal of Modern Physics D ◽

10.1142/s0218271820500431 ◽

2020 ◽

Vol 29 (06) ◽

pp. 2050043 ◽

Cited By ~ 1

Author(s):

Qi-Qi Zhou ◽

Shuang-Xi Yi ◽

Xiao-Li Huang ◽

Shu-Qing Zhong ◽

Yuan-Chuan Zou ◽

...

Keyword(s):

Interstellar Medium ◽

Light Curve ◽

Density Profile ◽

Early Time ◽

Intermediate Regime ◽

X Ray ◽

Central Engine ◽

Forward Shock ◽

Optical Light Curve ◽

Long Acting

We investigate the multi-band properties of the GRB 161017A with [Formula: see text], which was detected by Swift and Fermi satellites, and other instruments. The optical and X-ray afterglows were all detected at early times after the prompt emission. The optical light curve shows a very bright onset peak at about 100 s for 13 mag of [Formula: see text]-band, while the X-ray light curve occurs several flares at the beginning. We investigate the origin of X-ray and optical afterglows by analyzing the optical and X-ray data. Considering the smooth onset bump in the early time of the optical band and the erratic pulses for the X-ray lightcurve, we suppose that the early optical afterglow may be produced by the external shock, while the early time of X-ray light curve is dominated by flares. Therefore, GRB optical afterglows with smooth onset bump features at early time are possibly produced by external — forward shock (FS). According to the fireball external-model, the temporal slopes of the onset bumps are determined by both the medium density profile and the electron spectral index. Therefore, the afterglow onset bumps would be an ideal probe to study the properties of the fireball and the circumburst medium. The density profile has a slope of [Formula: see text], which suggests that the circumburst environment of the GRB 161017A would be an intermediate regime that are between the homogeneous interstellar medium (ISM) and wind-type medium. In addition, the optical light curve of the GRB 161017A exhibits a plateau feature and rebrightening after the onset bump, which may be related to the long-acting central engine of GRBs.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3561 ◽

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.

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Evidence for rapid disc formation and reprocessing in the X-ray bright tidal disruption event candidate AT 2018fyk

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1976 ◽

2019 ◽

Vol 488 (4) ◽

pp. 4816-4830 ◽

Cited By ~ 30

Author(s):

T Wevers ◽

D R Pasham ◽

S van Velzen ◽

G Leloudas ◽

S Schulze ◽

...

Keyword(s):

Light Curve ◽

Optical Spectra ◽

Emission Lines ◽

Tidal Disruption ◽

X Ray ◽

Physical Conditions ◽

High Ionization ◽

Optical Light Curve ◽

Narrow Emission ◽

Disruption Event

ABSTRACT We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray and UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN–18ul discovered by ASAS–SN. The Swift light curve is atypical for a TDE, entering a plateau after ∼40 d of decline from peak. After 80 d the UV/optical light curve breaks again to decline further, while the X-ray emission becomes brighter and harder. In addition to broad H, He, and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high-ionization (O iii) and low-ionization (Fe ii) lines, which are visible for ∼45 d. We similarly identify Fe ii lines in optical spectra of ASASSN–15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. The spectral similarity between AT 2018fyk, narrow-line Seyfert 1 galaxies, and some extreme coronal line emitters suggests that TDEs are capable of creating similar physical conditions in the nuclei of galaxies. The Fe ii lines can be associated with the formation of a compact accretion disc, as the emergence of low-ionization emission lines requires optically thick, high-density gas. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths. Such a two-component light curve is very similar to that seen in the TDE candidate ASASSN–15lh, and is a natural consequence of a relativistic orbital pericentre.

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Broad-line type Ic SN 2020bvc

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038152 ◽

2020 ◽

Vol 639 ◽

pp. L11 ◽

Cited By ~ 1

Author(s):

L. Izzo ◽

K. Auchettl ◽

J. Hjorth ◽

F. De Colle ◽

C. Gall ◽

...

Keyword(s):

Gamma Ray ◽

Optical Spectra ◽

Gamma Ray Bursts ◽

Archival Data ◽

Broad Line ◽

X Ray ◽

Long Duration ◽

Gamma Ray Emission ◽

Very High ◽

Line Type

Long-duration gamma-ray bursts (GRBs) are almost unequivocally associated with very energetic, broad-line supernovae of Type Ic-BL. While the gamma-ray emission is emitted in narrow jets, the SN emits radiation isotropically. Therefore, it has been hypothesized that some SN Ic-BL not associated with GRBs arise from events with inner engines such as off-axis GRBs or choked jets. Here we present observations of the nearby (d = 120 Mpc) SN 2020bvc (ASAS-SN 20bs) that support this scenario. Swift-UVOT observations reveal an early decline (up to two days after explosion), while optical spectra classify it as a SN Ic-BL with very high expansion velocities (≈70 000 km s−1), similar to that found for the jet-cocoon emission in SN 2017iuk associated with GRB 171205A. Moreover, the Swift X-Ray Telescope and CXO X-ray Observatory detected X-ray emission only three days after the SN and decaying onward, which can be ascribed to an afterglow component. Cocoon and X-ray emission are both signatures of jet-powered GRBs. In the case of SN 2020bvc, we find that the jet is off axis (by ≈23 degrees), as also indicated by the lack of early (≈1 day) X-ray emission, which explains why no coincident GRB was detected promptly or in archival data. These observations suggest that SN 2020bvc is the first orphan GRB detected through its associated SN emission.

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