I show that a flow structure where wide jets hit a slower expanding shell might be very efficient in channelling the kinetic energy of the jets to radiation, therefore accounting for, at a least a fraction of, intermediate luminosity optical transients (ILOTs) where the total radiation energy is much larger than what recombination energy of the outflow can supply. This type of flow might occur in the frame of the high-accretion-powered ILOT (HAPI) model, where there is a high mass accretion rate as a result of stellar merger or mass transfer in a binary system. I derive the condition on the jets half-opening angle for the jets not to penetrate through the slow shell, as well as the ratio of the photon diffusion time to expansion time. This ratio cannot be too large if a large fraction of the thermal energy is channelled to radiation. I apply the jet-powered radiation model to the Great Eruption of Eta Carinae, to V838~Mon, and to V4332~Sgr, and find a plausible set of parameters for these ILOTs. I expect the jet-powered radiation model to be more efficient in converting kinetic energy to radiation than ILOT models that are based on equatorial mass concentration. In many cases, thought, I expect both jets and equatorial mass concentration to occur in the same system.
We apply the jet-powered ILOT scenario to two recently studied intermediate luminosity optical transients (ILOTs), and find the relevant shell mass and jets' energy that might account for the outbursts of these ILOTs. In the jet-powered ILOT scenario accretion disk around one of the stars of a binary system launches jets. The interaction of the jets with a previously ejected slow shell converts kinetic energy to thermal energy, part of which is radiated away. We apply two models of the jet-powered ILOT scenario. In the spherical shell model the jets accelerate a spherical shell, while in the c…
I find that a 0.1-1Mo outflowing equatorial dusty disk (torus) that the binary system progenitor of an intermediate luminosity optical transient (ILOT) ejects several years to several months before and during the outburst can reduce the total emission to an equatorial observer by two orders of magnitude and shifts the emission to wavelengths of mainly >10mum. This is termed a type II ILOT (ILOT II). To reach this conclusion I use calculations of type II active galactic nuclei and apply them to the equatorial ejecta (disk/torus) of ILOTs II. This reduction in emission can last for tens of years…
We suggest and study the formation of intermediate luminosity optical transients (ILOTs) from the merger of two cool giant stars. For the two stars to merge when both are in their giant phases the stars must have close masses at their zero age main sequence, and the orbital separation must be in the right range. After the two giants merge, the two cores spiral-in toward each other within a common envelope. We study the energy sources of radiation in this process that include the ejection of mass that powers radiation by both recombination and by collision with previously ejected mass. This pro…
We propose that two recent intermediate luminosity optical transients (ILOTs), M31LRN 2015 and SN 2015bh (SNHunt 275; PTF 13efv) can be accounted for with a stellar binary model involving mass transfer that leads to the launching of jets. We inspect observations of the ILOT M31LRN 2015 and conclude that it cannot be explained by the onset of a common envelope evolution (CEE). Instead we conjecture that a $M \simeq 1 - 3 ~\rm{M_\odot}$ main sequence star accreted $\simeq 0.04 ~\rm{M_\odot}$ from the giant star, possibly during a periastron passage. The main sequence star accreted mass through a…
We propose a triple-star scenario where the merger of two pre-main sequence low mass stars, <0.5Mo, ejects a dusty equatorial outflow that obscures and temporarily causes the disappearance of a massive star, >8Mo. The merger of the low-mass inner binary powers a faint outburst, i.e., a faint intermediate luminosity optical transient (ILOT), but its main effect that can last for decades is to (almost) disappear the luminous massive star of the triple system. The typical orbital period of the triple system in about a year. The merger process proceeds as the more massive star of the two low-mass …
The low mass star ASASSN-13db experienced an EXor outburst in 2013, which identified it as a Young Stellar Object (YSO). Then, from 2014 to 2017 it had another outburst, longer and more luminous than the earlier. We analyze the observations of the second outburst, and compare it to eruptions of Intermediate Luminosity Optical Transients (ILOTs). We show that the decline of the light curve is almost identical to that of the V838 Mon, a prototype of a type of ILOT known as Luminous Red Nova (LRN). This similarity becomes conspicuous when oscillations that are associated with rotation are filtere…
We present optical spectroscopy, ultraviolet to infrared imaging and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d=1.86 Mpc) spanning from -6 to +6 years relative to the time of outburst in 2010. Based on the light curve and multi-epoch SEDs of SN 2010da, we conclude that the progenitor of SN 2010da is a ~10-12 Msol yellow supergiant possibly transitioning into a blue loop phase. During outburst, SN 2010da had a peak absolute magnitude of M<-10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer,…
A number of astrophyical transients originating from stellar explosions are powered by the collision of the ejected material with the circumstellar medium, which efficiently produces thermal radiation via shock dissipation. We investigate how such interaction-powered transients are distributed in the peak bolometric luminosity vs the rise time phase space. Taking the advantage of less time-consuming one-dimensional simulations with spherical symmetry, we calculated more than 500 models with different circumstellar mass and radius, ejecta mass and energy, and chemical compositions. The peak bol…
Millisecond magnetars can be formed via several channels: core-collapse of massive stars, accretion-induced collapse of white dwarfs (WDs), double WD mergers, double neutron star (NS) mergers, and WD-NS mergers. Because the mass of ejecta from these channels could be quite different, their light curves are also expected to be diverse. We evaluate the dynamic evolution of optical transients powered by millisecond magnetars. We find that the magnetar with short spin-down timescale converts its rotational energy mostly into the kinetic energy of the transient, while the energy of a magnetar with …
Shock interaction has been argued to play a role in powering a range of optical transients, including supernovae (particularly the superluminous class), classical novae, stellar mergers, tidal disruption events, and fast blue optical transients. These same shocks can accelerate relativistic ions, generating high-energy neutrino and gamma-ray emission via hadronic pion production. The recent discovery of time-correlated optical and gamma-ray emission in classical novae has revealed the important role of radiative shocks in powering these events, enabling an unprecedented view of the properties …
The groundbreaking discovery of the optical transient AT2017gfo associated with GW170817 opens a unique opportunity to study the physics of double neutron star (NS) mergers. We argue that the standard interpretation of AT2017gfo as being powered by radioactive decays of r-process elements faces the challenge of simultaneously accounting for the peak luminosity and peak time of the event, as it is not easy to achieve the required high mass, and especially the low opacity of the ejecta required to fit the data. A plausible solution would be to invoke an additional energy source, which is probabl…
Newly-born, rapidly-spinning magnetars have been invoked as the power sources of super-luminous transients, including the class of "fast-luminous optical transients" (FBOTs). The extensive multi-wavelength analysis of AT2018cow, the first FBOT discovered in real time, is consistent with the magnetar scenario and offers an unprecedented opportunity to comprehend the nature of these sources and assess their broader implications. Using AT2018cow as a prototype, we investigate high-energy neutrino and cosmic ray production from FBOTs and the more general class of superluminous supernovae (SLSNe). …
Electromagnetic precursors to black hole - neutron star gravitational wave events: Flares and reconnection-powered fast-radio transients from the late inspiral
Neutron star-neutron star mergers are known to be associated with short gamma-ray bursts. If the neutron star equation of state is sufficiently stiff, at least some of such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magnetic field (i.e., a magnetar). Such a magnetar signature may have been observed as the X-ray plateau following a good fraction (up to 50%) of short gamma-ray bursts, and it has been expected that one may observe short gamma-ray burst-less X-ray transients powered by double neutron star mergers. A fast X-ray transient …
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…
Transients powered by interaction with the circumstellar medium (CSM) are often observed in wavelengths other than optical, and multi-wavelength modelling can be important when inferring the properties of the explosion and CSM, or for distinguishing from other powering mechanisms. We develop a model calculating time dependent emission spectrum of interaction-powered transients. We solve energy equations of electron-proton plasma in the shocked SN ejecta and CSM and a radiation transfer equation out to the outer edge of the CSM, incorporating the collisional relaxation and the comptonization of…
From mass-loss histories to lightcurves: a generalised framework for interaction-powered transients
Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）；Astrophysical Big Bang Laboratory (ABBL), RIKEN Pioneering Research Institute (PRI)（理化学研究所先驱研究院天体物理大爆炸实验室）；School of Physics and Astronomy, Monash University（蒙纳士大学物理与天文学院）；OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery, Australia（澳大利亚ARC引力波发现卓越中心）
High energy neutrinos from pulsar-powered optical transients: LFBOTs as potential origin of the KM3NeT event KM3-230213A
Fermi National Accelerator Laboratory（费米国家加速器实验室）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙学物理研究所）；Frontier Research Institute for Interdisciplinary Sciences（东北大学理学研究科天文科学研究所前沿跨学科科学研究院）；Astronomical Institute, Graduate School of Science, Tohoku University
We present the public release of the Complete History of Interaction-Powered Supernovae (CHIPS) code, suited to model a variety of transients that arise from interaction with a dense circumstellar medium (CSM). Contrary to existing modellings which mostly attach the CSM by hand, CHIPS self-consistently simulates both the creation of the CSM from mass eruption of massive stars prior to core-collapse, and the subsequent supernova light curve. We demonstrate the performance of CHIPS by presenting examples of the density profiles of the CSM and the light curves. We show that the gross light curve …
Broad-lined type Ic supernovae (SNe Ic-BL) are a subclass of rare core collapse SNe whose energy source is debated in the literature. Recently a series of investigations on SNe Ic-BL with the magnetar (plus 56Ni) model were carried out. Evidence for magnetar formation was found for the well-observed SNe Ic-BL 1998bw and 2002ap. In this paper we systematically study a large sample of SNe Ic-BL not associated with gamma-ray bursts. We use photospheric velocity data determined in a homogeneous way. We find that the magnetar+56Ni model provides a good description of the light curves and velocity e…
In this paper we collect 19 hydrogen-deficient superluminous supernovae (SLSNe) and fit their light curves, temperature evolution, and velocity evolution based on the magnetar-powered model. To obtain the best-fitting parameters, we incorporate the Markov Chain Monte Carlo approach. We get rather good fits for 7 events ($χ^2$/d.o.f = $0.24-0.96$) and good fits for other 7 events ($χ^2$/d.o.f = $1.37-3.13$). We find that the initial periods ($P_{0}$) and magnetic strength ($B_{p}$) of the magnetars supposed to power these SLSNe are in the range of $\sim 1.2-8.3$ ms and $\sim (0.2-8.8)\times 10^…
Radio Emission from Fast Blue Optical Transients Powered by Trans-relativistic Shocks in Confined Circumstellar Material
Central China Normal University（华中师范大学）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）；Laboratory for Compact Object Astrophysics and Astronomical Technology, Central China Normal University（华中师范大学致密天体天文学与技术实验室）；Education Research and Application Center, National Astronomical Data Center（国家天文台教育研究与应用中心）
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…
It was proposed that a remnant stable magnetar could be formed in a binary neutron-star merger, leading to a fast X-ray transient (FXT) that can last for thousands of seconds. Recently, Xue et al. suggested that CDF-S XT2 was exactly such a kind of source. If confirmed, such emission can be used to search for electromagnetic counterparts to gravitational wave events from binary neutron-star mergers that have short gamma-ray bursts and the corresponding afterglows seen off-axis and thus too weak to be detected. Here we report the discovery of three new FXTs, XRT 170901, XRT 030511, and XRT 1109…
Magnetically powered outbursts from white dwarf mergers
一颗白矮星双星的合并产生了一个差异旋转的物体，预计会产生强大的磁场。储存在差速旋转的动能部分耗散在磁主导的日冕，形成一个热的可变流出与喷射速度相当于$10^9$厘米秒$^{-1}$。流出物应该会携带大量的质量和能量持续数小时到数天，形成一个具有以下特征的膨胀火球。(i)火球最初是不透明的，它的内能主要是由被捕获的热辐射。储存的热量部分地转换为流的动能（通过绝热冷却）并部分地辐射出去。(ii)内部冲击在火球中发展并增加其辐射输出。(iii)发射能量的很大一部分在光学波段。因此，从合并中可以预期亮度为$L\sim 10^{41}-10^{42}$ erg s $^{-1}$且特征峰持续时间相当于1天的明亮光学瞬变。与经典新星或超新星不同，瞬变不涉及核能。峰值后的衰减反映了合并残留物中的差异旋转的阻尼。这样的爆发可以在当前和即将到来的光学调查中在本地宇宙中检测到。
Short rise times of Fast Blue Optical Transients (FBOTs) require very light ejected envelopes, $M_{ej} \leq 10^{-1} M_\odot$, much smaller than of a typical supernova. Short peak times also mean that FBOTs should be hydrodynamically, not radioactively powered. The detection by Chandra of X-ray emission in AT2020mrf of $L_X \sim 10^{42} $ erg s$^{-1}$ after 328 days implies total, overall dominant, X-ray energetics at the Gamma Ray Bursts (GRBs) level of $\sim 6 \times 10^{49}$ erg. We further develop a model of Lyutikov & Toonen (2019), whereby FBOTs are the results of a late accretion induced…
EP251023a: A fast X-ray transient featuring a magnetar-powered optical internal plateau followed by a steep decay
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Altay Astronomical Observatory（阿勒泰天文台）；Department of Astronomy, School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院天文学系）；Department of Astronomy, Univer（大学天文学系）
A wind-driven model is a new framework to model observational properties of transients that are powered by continuous outflow from a central system. While it has been applied to Fast Blue Optical Transients (FBOTs), the applicability has been limited to post-peak behaviours due to the steady-state assumptions; non-steady-state physics, e.g., expanding outflow, is important to model the initial rising phase. In this paper, we construct a time-dependent wind-driven model, which can take into account the expanding outflow and the time evolution of the outflow rate. We apply the model to a sample …
Roaring to softly whispering: Persistent X-ray emission at the location of the Fast Blue Optical Transient AT2018cow $\sim$3.7 yrs after discovery and implications on accretion-powered scenarios
A Search for Fast Optical Transients in the Pan-STARRS1 Medium-Deep Survey: M Dwarf Flares, Asteroids, Limits on Extragalactic Rates, and Implications for LSST
The energy liberated by fallback accretion has been suggested as a possible engine to power hydrogen-poor superluminous supernovae. We systematically investigate this model using the Bayesian light-curve fitting code MOSFiT (Modular Open Source Fitter for Transients), fitting the light curves of 37 hydrogen-poor superluminous supernovae assuming a fallback accretion central engine. We find that this model can yield good fits to their light curves, with a fit quality that rivals the popular magnetar engine models. Examining our derived parameters for the fallback model, we find the total energy…
We discuss the electromagnetic radiation from newborn binary black holes (BBHs). As a consequence of the evolution of massive stellar binaries, a binary consisting of a primary black hole (BH) and a secondary Wolf-Rayet star is expected as a BBH progenitor system. We investigate optical transients from the birth of BBHs powered by the Bondi-Hoyle-Lyttleton accretion onto the primary BH, which occur $\sim1-10$ Gyr earlier than gravitational wave signals at the BH-BH merger. When the secondary massive star collapses into a BH, it may eject a fraction of its outer material and may form a disk aro…
A rapidly spinning magnetar in a young supernova (SN) can produce a superluminous transient by converting a fraction of its rotational energy into radiation. Here, we present the first three-dimensional hydrodynamical simulations ever performed of a magnetar-powered SN in the circumstellar medium formed by the ejection of the outer layers of the star prior to the blast. We find that hydrodynamical instabilities form on two scales in the ejecta, not just one as in ordinary core-collapse SNe: in the hot bubble energized by the magnetar and in the forward shock of the SN as it plows up ambient ga…
Modern wide-field high-cadence surveys have revealed the significant diversity of optical transient phenomena in their luminosity and timescale distributions, which led to the discovery of some mysterious fast optical transients (FOTs). These FOTs can usually rise and decline remarkably in a timescale of a few days to weeks, which are obviously much rapider than ordinary supernovae. SN 2019bkc/ATLAS19dqr is one of the fastest detected FOTs so far and, meanwhile, it was found to be un-associated with a host galaxy. These discoveries provide a good chance to explore the possible origins of FOTs.…
Luminous Red Novae as shock-powered transients I: Electron-scattering wings and deviations from Case B
Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）；Research Center for the Early Universe, Graduate School of Science, The University of Tokyo（东京大学理学研究科早期宇宙研究中心）；Astronomical Institute, Tohoku University（东北大学天文学研究所）
