arXiv subjects

J. -J. Zhang

Publications and source records attributed to J. -J. Zhang.

13 recordsLinked to original sources

arXiv2026

SN 2019vxm: A luminous and long-lived Type IIn supernova with early flash-ionisation features

We present the photometric and spectroscopic analysis of the luminous and long-lasting Type IIn supernova (SN) 2019vxm. The SN reaches a peak V-band absolute magnitude of MV = -20.01 +/- 0.13 mag in 35.0 days, and displays slow evolution in both the light curves and spectra, resembling that of long-lived SNe IIn. A mid-infrared (MIR) excess is detected starting from seven months after maximum brightness, suggesting a few 10^-3 solar masses of dust are newly formed at >= 210 days (and up to 0.01 solar masses at +4.5 yr). The spectra are dominated by a blue continuum at early stages, with narrow, symmetric Balmer lines and flash-ionisation emission lines of C III, N III, and He II. Comparing our flash-ionised spectrum with early interacting SN spectral models, we estimate a lower limit for the mass-loss rate of the progenitor of >= 0.01 solar masses per year. A weak P Cygni absorption feature is detected in the H-beta profile of the high-resolution Echelle spectrum at +19.7 d, suggesting the presence of slow-moving (60 +/- 10 km/s), unshocked circumstellar material (CSM) arising from the pre-SN wind of the progenitor. The H-alpha and H-beta profiles gradually evolve and become broader and asymmetric, showing a progressively increasing blueshift, with a clear flux deficit in the red wings of the broad velocity component after +102 days. Our observed bolometric light curve before about 100 days can be well fitted by a power-law function (L(t) = 2 x 10^44 (t/day)^-0.49 erg/s), which is very similar to SN 2010jl.

astro-ph.SR↗

arXiv2026

The transitional Type Ibn/IIn SN 2022pda, with pre-explosion outbursts and a double-peaked light curve

We report the results of a photometric and spectroscopic follow-up campaign of the unusual interacting supernova (SN) 2022pda. Precursor variability lasting $\sim 100$ days is observed before the explosion. The SN light curve has a double peak shape. It reached a first maximum of $M_{\rm{r}} = -19.6 \pm 0.2$\,mag, followed by an initial two-month decline and a second, broad peak lasting about six months. The early spectra show a blue continuum with dominant H and He emission lines. A high-resolution pre-maximum spectrum shows that the profile of the \Hei~$λ$5876 line consists of a moderately narrow ($\sim 1900$ \kms) P~Cygni absorption superposed on a broader ($\sim 3300$ \kms) component. In the blue region, several spectral features are identified, including C {\sc iii}/N {\sc iii}/O {\sc ii} blends. Two broad bumps at 4600--5200 Å, 6400--6800~Å regions reveal a complex profile, which are likely due to blends of H, He, and other emission lines. Late-time spectra are still dominated by prominent and broad H and He lines in emission. Shock-driven model fits to the bolometric light curve suggest that the SN is powered by interaction with a massive CSM with enhanced mass loss rates $\sim 5$ \msun yr$^{-1}$, expelled during two events occurred $\sim 1$ and $\sim 0.2$ years before the explosion. The overall SN evolution indicates that SN\,2022pda is a transitional event between a H-rich SN IIn (SN\,2009ip-like) and a He-rich SN Ibn. Our findings suggest that the progenitor was likely a Luminous Blue Variable transitioning towards a Wolf--Rayet stage.

astro-ph.HE↗

arXiv2026

SN 2017ati: A luminous type IIb explosion from a massive progenitor

We present optical photometric and spectroscopic observations of the Type~IIb supernova (SN)~2017ati. It reached the maximum light at about 27~d after the explosion and the light curve shows a broad, luminous peak with an absolute $r$-band magnitude of $M_{r} = -18.48 \pm 0.16$~mag. At about 50~d after maximum light, SN~2017ati exhibits a decline rate close to that expected from the $^{56}$Co $\rightarrow$ $^{56}$Fe radioactive decay, at 0.98 mag per 100 days, as usually observed in SNe IIb. However, it remains systematically brighter at late times by about 1--2~mag, exceeding the usual upper luminosity range of this class. As a result, modelling the light curve of SN~2017ati with a standard $^{56}$Ni decay scenario requires a large nickel mass of up to $\sim0.37\,M_{\odot}$ and still fails to reproduce the early-time light curve adequately. In contrast, incorporating additional energy input from a magnetar yields a significantly improved fit to the light curve of SN~2017ati, which would reduce the nickel mass to $\sim0.21\,M_{\odot}$, still close to the upper end of the range typically inferred for SNe~IIb. Comparing the fitted results of SN~2017ati with the known sample of SNe~IIb indicates that its luminosity evolution is best explained by a combination of neutron star spin-down energy and radioactive nickel deposition. From late-time nebular spectra of SN~2017ati, the luminosity of the [\Oi]~$λ\lambda6300,6364$ doublet implies an oxygen mass of $\sim1.82-3.34\,M_{\odot}$, and the combination of a [\Caii]/[\Oi] flux ratio of $\sim0.5$ with nebular spectral model comparisons favours a progenitor zero-age main-sequence mass of $\geq17\,M_{\odot}$.

astro-ph.SR↗

arXiv2026

Massive stars exploding in a He-rich circumstellar medium XII. SN 2024acyl: A fast, linearly declining Type Ibn supernova with early flash-ionisation features

We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at $(3.5\pm0.8) \times 10^{42}$ erg s$^{-1}$, with a total radiated energy of $(5.0\pm0.4) \times 10^{48}$ erg. The spectra are dominated by a blue continuum at early stages, with narrow P Cygni He I lines and flash-ionisation emission lines of C III, N III, and He II. The P Cygni He I features gradually evolve and become emission-dominated in late-time spectra. Our multi-band light-curve modelling yields estimates of the ejecta mass of $M_{\rm ej} = 0.49^{+0.11}_{-0.09}$ M$_\odot$ with a kinetic energy of $E_{\rm k} = 0.06^{+0.01}_{-0.01} \times 10^{51}$ erg, and a $^{56}$Ni mass of $M_{\rm Ni} = 0.018$ M$_\odot$. The inferred CSM properties are characterised by a mass of $M_{\rm CSM} = 0.51^{+0.05}_{-0.04}$ M$_\odot$, an inner radius of $R_0 = 17.8^{+3.6}_{-3.0}$ AU, and a density of $ρ_{\rm CSM} =(8.3_{-1.2}^{+2.7})\times10^{-12}$ g cm$^{-3}$. The multi-epoch spectra are well reproduced by the CMFGEN/he4p0 model, corresponding to a He-ZAMS mass of 4 M$_\odot$ (H-ZAMS mass 18.11 M$_\odot$, pre-SN mass 3.16 M$_\odot$). These findings are consistent with a scenario of an SN powered by ejecta-CSM interaction, originating from a low-mass helium star that evolved within an interacting binary system where the CSM with some residual hydrogen may originate from the mass-transfer process. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet star with H, or an Ofpe/WN9 star with fallback accretion, cannot be entirely ruled out.

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arXiv2025

SN2017ckj: A linearly declining Type IIb supernova with a relatively massive hydrogen envelope

We present optical observations of the Type IIb supernova (SN) 2017ckj, covering approximately 180 days after the explosion. Its early-time multi-band light curves display no clear evidence of a shock-cooling tail, resembling the behavior of SN2008ax. The $V$-band light curve exhibits a short rise time of about 5 days and reaches an absolute fitted peak magnitude of $M_{\rm V}=-18.49\pm0.18\mathrm{mag}$. The late-time multi-band light curves reveal a linear decline. We modelled the bolometric light curve of SN2017ckj to constrain the progenitor and the explosion parameters. We estimated a total mass of $\rm ^{56}Ni$ synthesized by SN2017ckj of $M_{\rm Ni} = 0.21^{+0.05}_{-0.03}\ M_\odot$, with a massive H-rich envelope of $M_{\rm env} = 0.4^{+0.1}_{-0.1}\ M_\odot$. Both the $\rm ^{56}Ni$ mass and the envelope mass of SN2017ckj are higher than those of typical SNe IIb, in agreement with its peculiar light curve evolution. The early-time spectra of SN2017ckj are dominated by a blue continuum, accompanied by narrow $\rm H_α$ and \Heii emission lines. The earliest spectrum exhibits flash ionization features, from which we estimated a progenitor mass-loss rate of $\sim 3\times10^{-4}M_\odot \mathrm{yr}^{-1}$. At later epochs, the spectra develop broad P-Cygni profiles and become increasingly similar to those of SNe IIb, especially SN2018gk. The late-time spectrum at around 139 days does not show a distinct decline in the strength of $\rm H_α$ emission profile, also indicating a relatively massive envelope of its progenitor. Aside from the $\rm H_α$ feature, the nebular spectrum exhibits prominent emission lines of \Oi, \Caii, [\Caii], and \Mgi], which are consistent with the prototypical SN1993J.

astro-ph.SR↗

arXiv2025

Massive stars exploding in a He-rich circumstellar medium. XI. Diverse evolution of five Ibn SNe 2020nxt, 2020taz, 2021bbv, 2023utc and 2024aej

We present the photometric and spectroscopic analysis of five Type Ibn supernovae (SNe): SN 2020nxt, SN 2020taz, SN 2021bbv, SN 2023utc, and SN 2024aej. These events share key observational features and belong to a family of objects similar to the prototypical Type Ibn SN 2006jc. The SNe exhibit rise times of approximately 10 days and peak absolute magnitudes ranging from $-$16.5 to $-$19 mag. Notably, SN 2023utc is the faintest Type Ibn supernova discovered to date, with an exceptionally low r-band absolute magnitude of $-16.4$ mag. The pseudo-bolometric light curves peak at $(1-10) \times 10^{42}$ erg s$^{-1}$, with total radiated energies on the order of $(1-10) \times 10^{48}$ erg. Spectroscopically, these SNe display relatively slow spectral evolution; the early spectra are characterised by a hot blue continuum and prominent He I emission lines. Early spectra show blackbody temperatures exceeding $10000~\mathrm{K}$, with a subsequent decline in temperature during later phases. Narrow He I lines, indicative of unshocked circumstellar material (CSM), show velocities of approximately $1000~\mathrm{km~s^{-1}}$. The spectra suggest that the progenitors of these SNe underwent significant mass loss prior to the explosion, resulting in a He-rich CSM. Light curve modelling yields estimates for the ejecta mass ($M_{\rm ej}$) in the range $1-3~M_{\odot}$, with kinetic energies ($E_{\rm Kin}$) of $(0.1-1) \times 10^{50}$ erg. The inferred CSM mass ranges from $0.2$ to $1~M_{\odot}$. These findings are consistent with expectations for core-collapse events arising from relatively massive, envelope-stripped progenitors.

astro-ph.HE↗

arXiv2024

Massive stars exploding in a He-rich circumstellar medium $-$ X. Flash spectral features in the Type Ibn SN 2019cj and observations of SN 2018jmt

We present optical and near-infrared observations of two Type Ibn supernovae (SNe), SN 2018jmt and SN 2019cj. Their light curves have rise times of about 10 days, reaching an absolute peak magnitude of $M_g$(SN 2018jmt) = $-$19.07 $\pm$ 0.37 and $M_V$(SN 2019cj) = $-$18.94 $\pm$ 0.19 mag, respectively. The early-time spectra of SN 2018jmt are dominated by a blue continuum, accompanied by narrow (600$-$1000 km~s$^{-1}$) He I lines with P-Cygni profile. At later epochs, the spectra become more similar to those of the prototypical SN Ibn 2006jc. At early phases, the spectra of SN 2019cj show flash ionisation emission lines of C III, N III and He II superposed on a blue continuum. These features disappear after a few days, and then the spectra of SN 2019cj evolve similarly to those of SN 2018jmt. The spectra indicate that the two SNe exploded within a He-rich circumstellar medium (CSM) lost by the progenitors a short time before the explosion. We model the light curves of the two SNe Ibn to constrain the progenitor and the explosion parameters. The ejecta masses are consistent with either that expected for a canonical SN Ib ($\sim$ 2 M$_{\odot}$) or those from a massive WR star ($>$ $\sim$ 4 M$_{\odot}$), with the kinetic energy on the order of $10^{51}$ erg. The lower limit on the ejecta mass ($>$ $\sim$ 2 M$_{\odot}$) argues against a scenario involving a relatively low-mass progenitor (e.g., $M_{ZAMS}$ $\sim$ 10 M$_{\odot}$). We set a conservative upper limit of $\sim$0.1 M$_{\odot}$ for the $^{56}$Ni masses in both SNe. From the light curve modelling, we determine a two-zone CSM distribution, with an inner, flat CSM component, and an outer CSM with a steeper density profile. The physical properties of SN 2018jmt and SN 2019cj are consistent with those expected from the core collapse of relatively massive, stripped-envelope (SE) stars.

astro-ph.HE↗

arXiv2022

Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631

We present an observational study of the luminous red nova (LRN) AT\,2021biy in the nearby galaxy NGC\,4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from $\sim 231$\,days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT\,2021biy shows a short-duration blue peak, with a bolometric luminosity of $\sim 1.6 \times 10^{41}$\,erg\,s$^{-1}$, followed by the longest plateau among LRNe to date, with a duration of 210\,days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT\,2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum ($T_{\mathrm{BB}} \approx 2050$ K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT\,2021biy has local dust properties similar to those of V838\,Mon in the Milky Way Galaxy. Inspection of archival {\it Hubble Space Telescope} data taken on 2003 August 3 reveals a $\sim 20$\,\msun\ progenitor candidate with log\,$(L/{\rm L}_{\odot}) = 5.0$\,dex and $T_{\rm{eff}} = 5900$\,K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17--24\,\msun\ primary component.

astro-ph.SR↗

arXiv2018

The first 48: Discovery and progenitor constraints on the Type Ia supernova 2013gy

We present an early-phase $g$-band light curve and visual-wavelength spectra of the normal Type Ia supernova (SN) 2013gy. The light curve is constructed by determining the appropriate S-corrections to transform KAIT natural-system $B$- and $V$-band photometry and Carnegie Supernova Project natural-system $g$-band photometry to the Pan-STARRS1 $g$-band natural photometric system. A Markov Chain Monte Carlo calculation provides a best-fit single power-law function to the first ten epochs of photometry described by an exponent of $2.16^{+0.06}_{-0.06}$ and a time of first light of MJD 56629.4$^{+0.1}_{-0.1}$, which is $1.93^{+0.12}_{-0.13}$ days (i.e., $<48$~hr) before the discovery date (2013 December 4.84 UT) and $-19.10^{+0.12}_{-0.13}$ days before the time of $B$-band maximum (MJD 56648.5$\pm0.1$). The estimate of the time of first light is consistent with the explosion time inferred from the evolution of the Si II $λ$6355 Doppler velocity. Furthermore, discovery photometry and previous nondetection limits enable us to constrain the companion radius down to $R_c \leq 4\,R_{\odot}$. In addition to our early-time constraints, we use a deep +235 day nebular-phase spectrum from Magellan/IMACS to place a stripped H-mass limit of $< 0.018\,M_{\odot}$. Combined, these limits effectively rule out H-rich nondegenerate companions.

astro-ph.HE↗

arXiv2018

SN 2016coi/ASASSN-16fp: An example of residual helium in a type Ic supernova?

The optical observations of Ic-4 supernova (SN) 2016coi/ASASSN-16fp, from $\sim 2$ to $\sim450$ days after explosion, are presented along with analysis of its physical properties. The SN shows the broad lines associated with SNe Ic-3/4 but with a key difference. The early spectra display a strong absorption feature at $\sim 5400$ Å which is not seen in other SNe~Ic-3/4 at this epoch. This feature has been attributed to He I in the literature. Spectral modelling of the SN in the early photospheric phase suggests the presence of residual He in a C/O dominated shell. However, the behaviour of the He I lines are unusual when compared with He-rich SNe, showing relatively low velocities and weakening rather than strengthening over time. The SN is found to rise to peak $\sim 16$ d after core-collapse reaching a bolometric luminosity of Lp $\sim 3\times10^{42}$ \ergs. Spectral models, including the nebular epoch, show that the SN ejected $2.5-4$ \msun\ of material, with $\sim 1.5$ \msun\ below 5000 \kms, and with a kinetic energy of $(4.5-7)\times10^{51}$ erg. The explosion synthesised $\sim 0.14$ \msun\ of 56Ni. There are significant uncertainties in E(B-V)host and the distance however, which will affect Lp and MNi. SN 2016coi exploded in a host similar to the Large Magellanic Cloud (LMC) and away from star-forming regions. The properties of the SN and the host-galaxy suggest that the progenitor had $M_\mathrm{ZAMS}$ of $23-28$ \msun\ and was stripped almost entirely down to its C/O core at explosion.

astro-ph.HE↗

arXiv2018

SN 2016X: A Type II-P Supernova with A Signature of Shock Breakout from Explosion of A Massive Red Supergiant

We present extensive ultraviolet (UV) and optical photometry, as well as dense optical spectroscopy for type II Plateau (IIP) supernova SN 2016X that exploded in the nearby ($\sim$ 15 Mpc) spiral galaxy UGC 08041. The observations span the period from 2 to 180 days after the explosion; in particular, the Swift UV data probably captured the signature of shock breakout associated with the explosion of SN 2016X. It shows very strong UV emission during the first week after explosion, with contribution of $\sim$ 20 -- 30% to the bolometric luminosity (versus $\lesssim$ 15% for normal SNe IIP). Moreover, we found that this supernova has an unusually long rise time of about 12.6 $\pm$ 0.5 days in the $R$ band (versus $\sim$ 7.0 days for typical SNe IIP). The optical light curves and spectral evolution are quite similar to the fast-declining type IIP object SN 2013ej, except that SN 2016X has a relatively brighter tail. Based on the evolution of photospheric temperature as inferred from the $Swift$ data in the early phase, we derive that the progenitor of SN 2016X has a radius of about 930 $\pm$ 70 R$_{\odot}$. This large-size star is expected to be a red supergiant star with an initial mass of $\gtrsim$ 19 -- 20 M$_{\odot}$ based on the mass $--$ radius relation of the Galactic red supergiants, and it represents one of the most largest and massive progenitors found for SNe IIP.

astro-ph.HE↗

arXiv2016

Cylindrically confined assembly of diblock copolymer under oscillatory shear flow

Manipulating the self-assembly nanostructures with combined different control measures is emerging as a promising route for numerous applications to generate templates and scaffolds for nanostructured materials. Here, the two different control measures are a cylindrical confinement and an oscillatory shear flow. We study the phase behavior of diblock copolymer confined in nanopore under oscillatory shear by considering different $D/L_0$ ($D$ is the diameter of the cylindrical nanopore, $L_0$ is the domain spacing) and different shears via Cell Dynamics Simulation. Under different $D/L_0$, in the system occurs different morphology evolution and phase transition with the changing of amplitude and frequency. Meanwhile, it forms a series of novel morphologies. For each $D/L_0$, we construct a phase diagram of different forms and analyze the reason why the phase transition occurs. We find that although the morphologies are different under different $D/L_0$, the reason of the phase transition with the changing of amplitude and frequency is roughly the same, all caused by the interplay of the field effect and confinement effect. These results can guide an experimentalist to an easy method of creating the ordered, defect-free nanostructured materials using a combination of the cylindrical confinement and oscillatory shear flow.

cond-mat.soft↗

arXiv2015

Massive stars exploding in a He-rich circumstellar medium - IX. SN 2014av, and characterization of Type Ibn SNe

We present spectroscopic and photometric data of the Type Ibn supernova (SN) 2014av, discovered by the Xingming Observatory Sky Survey. Stringent pre-discovery detection limits indicate that the object was detected for the first time about 4 days after the explosion. A prompt follow-up campaign arranged by amateur astronomers allowed us to monitor the rising phase (lasting 10.6 days) and to accurately estimate the epoch of the maximum light, on 2014 April 23 (JD = 2456771.1 +/- 1.2). The absolute magnitude of the SN at the maximum light is M(R) = -19.76 +/- 0.16. The post-peak light curve shows an initial fast decline lasting about 3 weeks, and is followed by a slower decline in all bands until the end of the monitoring campaign. The spectra are initially characterized by a hot continuum. Later on, the temperature declines and a number of lines become prominent mostly in emission. In particular, later spectra are dominated by strong and narrow emission features of He I typical of Type Ibn supernovae (SNe), although there is a clear signature of lines from heavier elements (in particular O I, Mg II and Ca II). A forest of relatively narrow Fe II lines is also detected showing P-Cygni profiles, with the absorption component blue-shifted by about 1200 km/s. Another spectral feature often observed in interacting SNe, a strong blue pseudo-continuum, is seen in our latest spectra of SN 2014av. We discuss in this paper the physical parameters of SN 2014av in the context of the Type Ibn supernova variety.

astro-ph.SR↗