To make progress on the open questions on CME/CIR propagation, their interactions and the role and nature of the ambient solar wind, we need spatially resolved coverage of the inner heliosphere -- both in-situ and (critically) imaging -- at temporal scales matching the evolutionary timescales of these phenomena (tens of minutes to hours), and from multiple vantage points. The polar vantage is uniquely beneficial because of the wide coverage and unique perspective it provides. The ultimate goal is to achieve full $4π$ coverage of the solar surface and atmosphere by 2050.
The Heliospheric Imagers (HI) on board the two spacecraft of the Solar Terrestrial Relations Observatory (STEREO) provided white-light images of transients in the solar wind from dual perspectives from 2007 to 2014. In this paper, we develop a new method to identify and locate the transients automatically from simultaneous images from the two inner telescopes, known as HI-1, based on a correlation analysis. Correlation coefficient (cc) maps along the Sun-Earth line are constructed for the period from 1 Jan 2010 to 28 Feb 2011. From the maps, transients propagating along the Sun-Earth line are …
The solar wind transients propagating out in the inner heliosphere can be observed in white-light images from Heliospheric Imager-1 (HI1), an instrument of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on board the Solar Terrestrial Relations Observatory (STEREO), from two perspectives. The spatial velocity distribution inside solar wind transients is key to understanding their dynamic evolution processes. We generated a velocity map of transients in 3D space based on 2D white-light images and used it to estimate the expansion rate as well as some kinematic propertie…
We discuss the detection and evolution of a complex series of transient and quasi-static solar wind structures in the days following the well-known comet 2P / Encke tail disconnection event in April 2007. The evolution of transient solar wind structures ranging in size from < 105 km to > 106 km was characterized using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCA Tter (EISCA T) radar system. Simultaneously, the global structure and evolution of these features was characterized by the Heliospheric Imagers (HI) on the Solar TE…
We consider the situation where the luminosity from a transient event is reprocessed by an optically thick wind. Potential applications are the tidal disruption of stars by black holes, engine-powered supernovae, and unique fast transients found by current and future wide-field surveys. We derive relations between the injected and observed luminosity for steady and time dependent winds, and discuss how the temperature is set for scattering-dominated radiative transport. We apply this framework to specific examples of tidal disruption events and the formation of a black hole by a massive star, …
The 2008 optical transient in NGC 300 is one of a growing class of intermediate-luminosity transients that brighten several orders of magnitude from a previously optically obscured state. The origin of their eruptions is not understood. Our multi-wavelength photometry and spectroscopy from maximum light to more than a year later provide a record of its post-eruption behavior. We describe its changing spectral-energy distribution, the evolution of its absorption- and emission line-spectrum, the development ofa bipolar outflow, and the rapid transition from a dense wind to an optically thin ioni…
The cold-dense plasma is occasionally detected in the solar wind with in situ data, but the source of the cold-dense plasma remains illusive. Interchange reconnections (IRs) between closed fields and nearby open fields are well known to contribute to the formation of solar winds. We present a confined filament eruption associated with a puff-like coronal mass ejection (CME) on 2014 December 24. The filament underwent successive activations and finally erupted, due to continuous magnetic flux cancellations and emergences. The confined erupting filament showed a clear untwist motion, and most of…
We use recent observations of the He I $\lambda10830 Å$ absorption line and 3D hydrodynamical numerical simulations of the winds collision, to strengthen the case for an orientation of the semimajor axis of the massive binary system Eta Carinae where the secondary star is toward us at periastron passage. Those observations show that the fast blue absorption component exists for only several weeks prior to the periastron passage. We show that the transient nature of the fast blue absorption component supports a geometry where the fast secondary wind, both pre and post-shock material, passes in …
We propose a wind-driven model for peculiar transients, and apply the model to AT2018cow and iPTF14hls. In the wind-driven model, we assume that a continuous outflow like a stellar wind is injected from a central system. While these transients have different observational properties, this model can explain their photometric properties which are not reproduced by a supernova-like instantaneous explosion. Furthermore, the model predicts characteristic spectral features and evolution, which are well in line with those of AT2018cow and iPTF14hls. Despite the different observational properties, the…
We present the first direct evidence for dense clumps of matter in the companion wind in a Supergiant Fast X-ray Transient (SFXT) binary. This is seen as a brief period of enhanced absorption during one of the bright, fast flares that distinguish these systems. The object under study was IGR J17544-2619, and a total of 236 ks of data were accumulated with the Japanese satellite Suzaku. The activity in this period spans a dynamic range of almost 10000 in luminosity and gives a detailed look at SFXT behavior.
The black hole transient MAXI J1820+070 displayed optical P-Cyg profiles and other wind-related emission line features during the hard state of its discovery outburst. We present near-infrared (nIR) spectroscopy covering the different accretion states of the system during this event. Our 8-epoch data set (VLT/X-shooter) reveals strong variability in the properties of the nIR emission lines. This includes the presence of absorption troughs and extended emission line wings with kinetic properties that are remarkably similar to those inferred from the wind signatures observed in optical emission …
Motivated by recent theoretical work on tidal disruption events and other peculiar transients, we present moving-mesh radiation-hydrodynamic simulations of radiative luminosity emitted by a central source being reprocessed by a wind-like outflow. We couple the moving-mesh hydrodynamic code JET with our newly-developed radiation module based on mixed-frame grey flux-limited diffusion with implicit timestep update. This allows us to study the self-consistent multi-dimensional radiation-hydrodynamic evolution over more than ten orders of magnitude in both space and time in a single run. We simula…
We present the discovery of an optical accretion disk wind in the X-ray transient Swift J1858.6-0814. Our 90-spectrum data set, taken with the 10.4m GTC telescope over 8 different epochs and across five months, reveals the presence of conspicuous P-Cyg profiles in He I at 5876 Angs and Halpha. These features are detected throughout the entire campaign, albeit their intensity and main observational properties are observed to vary on time-scales as short as five minutes. In particular, we observe significant variations in the wind velocity, between a few hundreds and ~ 2400 km/s. In agreement wi…
SN2008S and the 2008 NGC300-OT were explosive transients of stars self-obscured by very dense, dusty stellar winds. An explosive transient with an un-observed shock break-out luminosity of order 10^10 Lsun is required to render the transients little obscured and visible in the optical at their peaks. Such a large break-out luminosity then implies that the progenitor stars were cool, red supergiants, most probably ~9 Msun extreme AGB (EAGB) stars. As the shocks generated by the explosions propagate outward through the dense wind, they produce a shock luminosity in soft X-rays that powers the lo…
Reconstructing solar wind inhomogeneous structures from stereoscopic observations in white-light: Solar wind transients in 3D
CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China（中国科学院空间环境重点实验室，地球与行星科学学院，中国科学技术大学）；CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China（中国科学院比较行星学卓越创新中心，中国科学技术大学）；Mengcheng National Geophysical Observatory, University of Science and Technology of China（蒙城国家地球物理观测台，中国科学技术大学）；SIGMA Weather Group, State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences（SIGMA天气研究组，空间天气国家重点实验室，空间科学应用研究中心，中国科学院）；Solar Physics and Space Plasma Research Center, School of Mathematics and Statistics, University of Sheffield（太阳物理与空间等离子体研究中心，数学与统计学院，谢菲尔德大学）
We present an optical spectroscopic study of the black hole X-ray transient V4641 Sgr (=SAX J1819.3-2525) covering the 1999, 2002 and 2004 outbursts. The spectra were taken over 22 different epochs during the low luminosity phases that follow the sharp and bright outburst peaks displayed by the system. The data reveal the frequent presence of wind-related features in H (Balmer) and He I emission lines in the form of P-Cygni profiles and strong emission lines with broad wings. The terminal velocity of the wind, as measured in the blue-shifted absorption (P-Cygni) components, is in the range of …
This analysis offers evidence of characteristic scale sizes in solar wind charge state data measured in-situ for thirteen quiet-sun Carrington rotations in 2008. Using a previously established novel methodology, we analyze the wavelet power spectrum of the charge state ratio C$^{6+}$/C$^{4+}$ measured in-situ by ACE/SWICS for 2-hour and 12-minute cadence. We construct a statistical significance level in the wavelet power spectrum to quantify the interference effects arising from filling missing data in the time series (Edmondson et al. 2013), allowing extraction of significant power from the m…
Massive star winds are complex radiation-hydrodynamic (sometimes magnetohydrodynamic) outflows that are propelled by their enormously strong luminosities. The winds are often found to be structured and variable, but can also display periodic or quasi-periodic behavior in a variety of wind diagnostics. The regular variations observed in putatively single stars, especially in UV wind lines, have often been attributed to corotating interaction regions (CIRs) like those seen in the solar wind. We present light curves for variable polarization from winds with CIR structures. We develop a model for …
The recent launches of Parker Solar Probe (PSP), Solar Orbiter (SO) and BepiColombo, along with several older spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously. We take advantage of this unique spacecraft constellation, along with low solar activity across two solar rotations between May and July 2020, to investigate how the solar wind structure, including the Heliospheric Current Sheet (HCS), varies with latitude. We visualise the sector structure of the inner heliosphere by ballistically mapping the polarity and …
Supergiant fast X-ray transient (SFXT) is a new class of the high mass X-ray binary that shows short X-ray flares. The physical mechanism of SFXT short flares is still open for discussion. The accretion process of dense clumps in stellar wind onto neutron star (NS) has been proposed as the origin of such short flares. In order to examine the applicability of the clumpy wind scenario, we focus on the accretion mode that depends on orbital parameters. Our goal is to impose restrictions on the orbital parameters of SFXT. Assuming a simple analytic model of clumpy wind, we investigate the conditio…
Radiation-ionization hydrodynamic simulations of AGN line-driven winds lead to transient shielding and BAL/UFO signatures
School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学院）；Eureka Scientific Inc.（尤里卡科学公司）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，天体物理学与行星学研究所）；Space Telescope Science Institute（太空望远镜科学研究所）；Department of Physics, Astrophysics, University of Oxford（牛津大学物理与天体物理系）；School of Mathematics and Physics, Queen’s University Belfast（贝尔法斯特女王大学数学与物理学院）
Interplanetary space is characteristically structured mainly by high-speed solar wind streams emanating from coronal holes and transient disturbances such as coronal mass ejections (CMEs). While high-speed solar wind streams pose a continuous outflow, CMEs abruptly disrupt the rather steady structure causing large deviations from the quiet solar wind conditions. For the first time, we give a quantification of the duration of disturbed conditions (preconditioning) for interplanetary space caused by CMEs. To this aim, we investigate the plasma speed component of the solar wind and the impact of …
Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black hole transients show outflows whose properties are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disc encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient black hole transient V404 Cyg, and interpreted as disrupted mass flow into the inner regions of its large accretion disc. Here, we report o…
Super-Chandrasekhar remnants of double white dwarf mergers could sometimes collapse into a rapidly rotating neutron star (NS), accompanying with a mass ejection of a few times $0.01M_{\odot}$. Bright optical transient emission can be produced by the ejecta due to heating by radioactivities and particularly by energy injection from the NS. Since the merger remnants before collapse resemble a star evolving from the asymptotic giant branch phase to the planetary nebula phase, an intense dusty wind is considered to be driven about several thousand years ago before the collapse and surround the rem…
Classical Supergiant X-ray Binaries (SGXBs) and Supergiant Fast X-ray Transients (SFXTs) are two types of High-mass X-ray Binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors' stellar wind can provide the required information to accomplish an adequate test of these theories. However, such…
A fraction of high-mass X-ray binaries are supergiant fast X-ray transients. These systems have on average low X-ray luminosities, but display short flares during which their X-ray luminosity rises by a few orders of magnitude. The leading model for the physics governing this X-ray behaviour suggests that the winds of the donor OB supergiants are magnetized. In agreement with this model, the first spectropolarimetric observations of the SFXT IGR J11215-5952 using the FORS2 instrument at the Very Large Telescope indicate the presence of a kG longitudinal magnetic field. Based on these results, …
The origin of the slow solar wind is still a topic of much debate. The continual emergence of small transient structures from helmet streamers is thought to constitute one of the main sources of the slow wind. Determining the height at which these transients are released is an important factor in determining the conditions under which the slow solar wind forms. To this end, we have carried out a multipoint analysis of small transient structures released from a north-south tilted helmet streamer into the slow solar wind over a broad range of position angles during Carrington Rotation 2137. Comb…
Current sheets are ubiquitous in the solar wind.They are a major source of the solar wind MHD turbulence intermittency. They may result from non-linear interactions of the solar wind MHD turbulence or are the boundaries of flux tubes that originate from the solar surface. Some current sheets appear in pairs and are the boundaries of transient structures such as magnetic holes and reconnection exhausts, or the edges of pulsed Alfvén waves. For an individual current sheet, discerning whether it is a flux tube boundary or due to non-linear interactions, or the boundary of a transient structure is…
All disc-accreting astrophysical objects produce powerful outflows. In binaries containing neutron stars (NS) or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated "soft states". By contrast,optical wind-formed lines have recently been detected in "hard states", when a hot corona dominates the luminosity. The relationship between these signatures is unknown, and no erupting system has revealed wind-formed lines between the X-ray and optic…
Evidence for a luminosity-class dichotomy in the supergiant donors of persistent high-mass X-ray binaries and supergiant fast X-ray transients
INAF-IASF Milano, Istituto di Astrofisica Spaziale e Fisica Cosmica（意大利国家天体物理研究所米兰空间天体物理学与宇宙物理学研究所）；INAF-OAS, Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所太空天体物理学与空间科学观测站）
We present a comprehensive nucleosynthesis study of the neutrino-driven wind in the aftermath of a binary neutron star merger. Our focus is the initial remnant phase when a massive central neutron star is present. Using tracers from a recent hydrodynamical simulation, we determine total masses and integrated abundances to characterize the composition of unbound matter. We find that the nucleosynthetic yields depend sensitively on both the life time of the massive neutron star and the polar angle. Matter in excess of up to $9 \cdot 10^{-3} M_\odot$ becomes unbound until $\sim 200~{\rm ms}$. Due…
We present results from a circular polarimetric survey of candidate detached magnetic white dwarf - M dwarf binaries obtained using the Nordic Optical Telescope, La Palma. We obtained phase resolved spectropolarimetry and imaging polarimetry of seven systems, five of which show clearly variable circular polarisation. The data indicate that these targets have white dwarfs with magnetic field strengths > 80 MG. Our study reveals that cyclotron emission can dominate the optical luminosity at wavelengths corresponding to the cyclotron emission harmonics, even in systems where the white dwarfs are …
We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray studies suggest X-2 is a Supergiant Fast X-ray Transient: a large-amplitude (factor of $\sim$ 100), short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R- and g-band light curves of X-2 from the intermediate Palomar Transient Factory taken between 2013 July 15 and 2017 Feb 14 show high-amplitude ($\gtrsim$ 1 mag), short-duration ($\lesssim8$ d) flares and dips ($\gtrsim$ 0.5 mag). Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I…
Supergiant Fast X-ray Transients are a class of Galactic High Mass X-ray Binaries with supergiant companions. Their extreme transient X-ray flaring activity was unveiled thanks to INTEGRAL/IBIS observations. The SFXTs dynamic range, with X-ray luminosities from 1E32 erg/s to 1E37 erg/s, and long time intervals of low X-ray emission, are puzzling, given that both their donor star properties and their orbital and spin periodicities seem very similar to those displayed by massive binaries with persistent X-ray emission. Clumpy supergiant winds, accretion barriers, orbital geometries and wind anis…
