Real-time Discovery of AT2020xnd: A Fast, Luminous Ultraviolet Transient with Minimal Radioactive Ejecta
Daniel A. Perley, Anna Y. Q. Ho, Yuhan Yao, Christoffer Fremling, Joseph P. Anderson, Steve Schulze, Harsh Kumar, G. C. Anupama, Sudhanshu Barway, Eric C. Bellm… 展开作者
Daniel A. Perley, Anna Y. Q. Ho, Yuhan Yao, Christoffer Fremling, Joseph P. Anderson, Steve Schulze, Harsh Kumar, G. C. Anupama, Sudhanshu Barway, Eric C. Bellm, Varun Bhalerao, Ting-Wan Chen, Dmitry A. Duev, Lluís Galbany, Matthew J. Graham, Mariusz Gromadzki, Claudia P. Gutiérrez, Nada Ihanec, Cosimo Inserram, Mansi M. Kasliwal, Erik C. Kool, S. R. Kulkarni, Russ R. Laher, Frank J. Masci, James D. Neill, Matt Nicholl, Miika Pursiainen, Joannes van Roestel, Yashvi Sharma, Jesper Sollerman, Richard Walters, Philip Wiseman
The many unusual properties of the enigmatic AT2018cow suggested that at least some subset of the empirical class of fast blue optical transients (FBOTs) represents a genuinely new astrophysical phenomenon. Unfortunately, the intrinsic rarity and fleeting nature of these events have made it difficult to identify additional examples early enough to acquire the observations necessary to constrain theoretical models. We present here the Zwicky Transient Facility discovery of AT2020xnd (ZTF20acigmel, the "Camel") at z=0.243, the first unambiguous AT2018cow analog to be found and confirmed in real time. AT2018cow and AT2020xnd share all key observational properties: a fast optical rise, sustained high photospheric temperature, absence of a second peak attributable to ejection of a radioactively-heated stellar envelope, extremely luminous radio, millimetre, and X-ray emission, and a dwarf-galaxy host. This supports the argument that AT2018cow-like events represent a distinct phenomenon from slower-evolving radio-quiet supernovae, likely requiring a different progenitor or a different central engine. The sample properties of the four known members of this class to date disfavour tidal disruption models but are consistent with the alternative model of an accretion powered jet following the direct collapse of a massive star to a black hole. Contextual filtering of alert streams combined with rapid photometric verification using multi-band imaging provides an efficient way to identify future members of this class, even at high redshift.
The merger of two neutron stars produces an outflow of radioactive heavy nuclei. Within a second of merger, the central remnant is expected to also launch a relativistic jet, which shock-heats and disrupts a portion of the radioactive ejecta. Within a few hours, emission from the radioactive material gives rise to an ultraviolet, optical, and infrared transient (a kilonova). We use the endstates of a suite of 2D relativistic hydrodynamic simulations of jet-ejecta interaction as initial conditions for multi-dimensional Monte Carlo radiation transport simulations of the resulting viewing angle-d…
We study 31 luminous, rapidly evolving optical transients (REOTs), and use the magnetar model and the ejecta--circumstellar-matter (CSM) interaction (CSI) model to fit their multiband light curves. We find that 28 events can be fitted by the magnetar model. and the derived masses ($\sim0.05$--5.58\,M$_\odot$) are consistent with that of stripped and ultrastripped core-collapse supernovae (CCSNe). On the other hand, the CSI model can fit 25 events; the derived ejecta masses are $\sim 3$--30\,M$_\odot$, consistent with that of SNe~Ibn. The results, together with the fact that many luminous REOTs…
AAssociation of GW170817/GRB170817A/AT2017gfo provides the first direct evidence for neutron star mergers as significant sources of $r$-process nucleosynthesis. A gamma-ray transient (GRT) would be powered by the radioactive decay of the freshly-synthesized $r$-process elements. By analyzing the composition and gamma-ray opacity of the kilonova ejecta in details, we calculate the lightcurve and spectrum of the GRT for a range of spherically symmetric merger ejecta models with mass $M_{\rm ej}=0.001 \sim 0.05M_{\odot}$ and expansion velocity $v_{\rm ej}= 0.1\sim 0.4c$. It is found that the peak…
Plasma Instabilities Dominate Radioactive Transients Magnetic Fields: The self-confinement of leptons in Type Ia and Core-Collapse Supernovae, and Kilonovae
The process of unstable mass transfer in a stellar binary can result in either a complete merger of the stars or successful removal of the donor envelope leaving a surviving more compact binary. "Luminous red nova" (LRN) are the class of optical transients believed to accompany such merger/common envelope events. Past works typically model LRNe using analytic formulae for supernova light curves which make assumptions (e.g., radiation dominated ejecta, neglect of hydrogen recombination energy) not justified in stellar mergers due to the lower velocities and specific thermal energy of the ejecta…
The radioactively powered transient following a binary neutron star (BNS) merger, known as a kilonova (KN), is expected to enter the steady-state nebular phase a few days after merger. Steady-state holds until thermal reprocessing time-scales become long, at which point the temperature and ionisation states need to be evolved time-dependently. We study the onset and significance of time-dependent effects using the non-local thermodynamic equilibrium (NLTE) spectral synthesis code SUMO. We employ a simple single-zone model with an elemental composition of Te, Ce, Pt and Th, scaled to their resp…
A Long-Duration Luminous Type IIn Supernova KISS15s: Strong Recombination Lines from the Inhomogeneous Ejecta-CSM Interaction Region and Hot Dust Emission from Newly Formed Dust
我们报告了在木曾超新星巡天(KISS)过程中在一个红移z=0.038的低质量恒星形成星系中发现的一颗类SN 1988 Z IIn型超新星KISS 15 s。KISS 15 s显示出长时间的光学连续谱和发射线光变曲线,表明KISS 15 s是由膨胀的喷出物和致密的星周介质(CSM)之间的持续相互作用提供动力的。H $α$发射线轮廓可以分解为四个高斯的窄,中间,蓝移中间,和广泛的速度宽度分量,与半高全宽$\lesssim 100$,$\sim 2,000$,和$\sim 14,000$ km s ${}^{-1}$的窄,中间,和广泛的组件,分别。蓝移的中间分量的存在下,其中相对于系统速度的视线速度约为$-5,000$ km s ${}^{-1}$,表明喷出物-CSM相互作用区域具有不均匀的形态和各向异性的膨胀速度。我们发现,KISS 15 s显示出不断增加的红外连续辐射,这可以解释为热尘埃热发射的$T \sim 1,200$ K从新形成的尘埃在一个冷的,致密的壳层中的喷出物CSM相互作用区域。从热光度推断出的前身质量损失率是$\dot{M} \sim 0.4 M_{\odot} \text{yr}^{-1} (v_{w}/40 \text{km}~\text{s}^{-1})$,其中$v_{w}$是前身的恒星风速度。这意味着KISS 15 s的前身是一颗红超巨星或一颗发光的蓝色变星,在…
A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray Luminous Classical Nova to Date
最近发现,即使不是全部,也有一些经典新星在爆发时会发出GeV的伽马射线,但伽马射线产生的机制仍然没有得到很好的理解。我们在这里提出了一个全面的多波长数据集-从无线电到X射线-为迄今为止最伽马射线发光的经典新星,V1324 Sco。使用这个数据集,我们表明,V1324斯科是一个典型的尘埃Fe-II型新星,最大喷出物速度为2600公里秒$^{-1}$和喷出物质量的几个$\times 10^{-5}$ M $_{\odot}$。也有证据表明复杂的冲击相互作用,包括双峰射电光曲线,显示早期的高亮度温度。为了探索为什么V1324~Sco是如此的伽马射线发光,我们提出了一个具有强烈内部冲击的新星喷出物模型,并发现较高的伽马射线亮度来自较高的喷出物速度和/或质量损失率。V1324~Sco与其他γ射线探测到的新星的比较没有显示出任何一个明确的特征,我们得出结论,需要更大的样本,类似的良好观察的新星,以了解在新星的γ射线的起源和变化。
Several explosions of thermonuclear supernovae (SNe Ia) have been found to exhibit deviations from spherical symmetry upon closer inspection. Examples are the gamma-ray lines from SN 2014J as measured by INTEGRAL/SPI, and morphology information from radioactive isotopes in older remnants such as Tycho. A systematic study on the effects of parameters such as ignition geometry and burning morphology in SNe Ia is still missing. We use a 2D hydrodynamics code with post-processing nucleosynthesis and simulate the double detonations in a sub-Chandrasekhar mass carbon-oxygen white dwarf starting from…
The hydrogen-poor supernova PTF11rka (z = 0.0744), reported by the Palomar Transient Factory, was observed with various telescopes starting a few days after the estimated explosion time of 2011 Dec. 5 UT and up to 432 rest-frame days thereafter. The rising part of the light curve was monitored only in the R_PTF filter band, and maximum in this band was reached ~30 rest-frame days after the estimated explosion time. The light curve and spectra of PTF11rka are consistent with the core-collapse explosion of a ~10 Msun carbon-oxygen core evolved from a progenitor of main-sequence mass 25--40 Msun,…
Luminous fast blue optical transients (LFBOTs) such as AT2018cow form a rare class of engine-powered explosions of uncertain origin. A hallmark feature of these events is radio/millimeter synchrotron emission powered by the interaction of fast (v > 0.1 c) ejecta and dense circumstellar material (CSM) extending to large radii > 1e16 cm surrounding the progenitor. Assuming this CSM to be an outflow from the progenitor, we show that dust grains up to ~1 micron in size can form in the outflow in the years before the explosion. This dusty CSM would attenuate the transient's ultraviolet (UV) emissio…
Recently, FRB 190520B with the largest extragalactic dispersion measure (DM), was discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The DM excess over the intergalactic medium and Galactic contributions is estimated as $\sim 900$ pc cm$^{-3}$, which is nearly ten times higher than other fast radio bursts (FRBs) host galaxies. The DM decreases with the rate $\sim0.1$ pc cm$^{-3}$ per day. It is the second FRB associated with a compact persistent radio source (PRS). The rotation measure (RM) is found to be larger than $1.8 \times 10^{5} \mathrm{rad} ~\mathrm{m}^{-2}…
We present the discovery of the radio afterglow and near-infrared (NIR) counterpart of the Swift short GRB 200522A, located at a small projected offset of $\approx 1$ kpc from the center of a young, star-forming host galaxy at $z=0.5536$. The radio and X-ray luminosities of the afterglow are consistent with those of on-axis cosmological short GRBs. The NIR counterpart, revealed by our HST observations at a rest-frame time of $\approx2.3$ days, has a luminosity of $\approx (1.3-1.7) \times 10^{42}$ erg s$^{-1}$. This is substantially lower than on-axis short GRB afterglow detections, but is a f…
A statistical study of super-luminous supernovae in the magnetar engine model and implications for their connection with gamma-ray bursts and hypernovae
Ultraviolet Signatures of Jet-Ejecta Interaction in Early Kilonovae: Prediction from Realistic Atomic Opacities
Technische Universität Darmstadt(达姆施塔特工业大学);Tohoku University(东北大学);Max Planck Institute for Gravitational Physics (Albert Einstein Institute)(马克斯·普朗克引力物理研究所(爱因斯坦研究所));Yukawa Institute for Theoretical Physics, Kyoto University(京都大学汤川理论物理研究所)
Optical, near-infrared (NIR) photometric and spectroscopic studies, along with the optical imaging polarimetric results for SN 2012au, are presented in this article to constrain the nature of the progenitor and other properties. Well-calibrated multiband optical photometric data (from $-$0.2 to +413 d since $B$-band maximum) were used to compute the bolometric light curve and to perform semi-analytical light-curve modelling using the $\texttt{MINIM}$ code. A spin-down millisecond magnetar-powered model explains the observed photometric evolution of SN 2012au reasonably. Early-time imaging pola…