New Astronomy Reviews最新文献

For decades cataclysmic variables (CVs) were thought to be one of the few classes of accreting compact objects to not launch jets, and have consequently been used to constrain jet launching models. However, recent theoretical and observational advances indicate that CVs do in fact launch jets. Specifically, it was demonstrated that their accretion-outflow cycle is analogous to that of their higher mass cousins – the X-ray Binaries (XRBs). Subsequent observations of the CV SS Cygni confirmed this and have consistently shown radio flaring equivalent to that in the XRBs that marks a transient jet. Based on this finding and the emission properties, several studies have concluded that the radio emission is most likely from a transient jet. Observations of other CVs, while not conclusive, are consistent with this interpretation. However, the issue is not yet settled. Later observations have raised a number of questions about this model, as well as about potential alternative radio emission mechanisms. CVs are non-relativistic and many have well-determined distances; these properties would make them ideal candidates with which to address many of our outstanding questions about fundamental jet physics. Here we review the case for jets in CVs, discuss the outstanding questions and issues, and outline the future work necessary to conclusively answer the question of whether CVs launch jets.

INTEGRAL IBIS/ISGRI 18–60 keV observations of SS433 performed in 2003–2011 enabled for the first time the hard X-ray phase-resolved orbital and precessional light curves and spectra to be constructed. The spectra can be fitted by a power-law with photon index  ≃ 3.8 and remain almost constant while the X-ray flux varies by a factor of a few. This suggests that the hard X-ray emission in SS433 is produced not in relativistic jets but in an extended quasi-isothermal hot ‘corona’ surrounding central parts of a supercritical accretion disc. Regular variations of the hard X-ray flux in SS433 exhibit, on top of the orbital and precessional variability, a nutational variability with a period of  ~ 6.29 d. For the first time, a joint analysis of the broadband 18–60 keV orbital and precessional light curves was performed in the model that assumes a significant Roche lobe overfilling by the optical star, up to its filling the outer Lagrangian surface enabling mass loss through the outer Lagrangian L₂ point. From this modeling, the relativistic-to-optical component mass ratio $q=M_x/M_v\gtrsim 0.4÷0.8$ is estimated. An analysis of the observed long-term stability of the orbital period of SS433 with an account of the recent observations of SS433 by the VLTI GRAVITY interferometer enabled an independent mass ratio estimate q > 0.6. This estimate in combination with the radial velocity semi-amplitude for stationary He II emission, $K_x=168\pm 18{\mathrm{km}s}^{-1}$ (Hillwig et al., 2004) suggest the optical component mass in SS433 M_v > 12 M_⊙. Thus, the mass of the relativistic component in SS433 is M_x > 7 M_⊙, which is close to the mean mass of black holes in X-ray binaries ( ~ 8 M_⊙). The large binary mass ratio in SS433 allows us to understand why there is no common envelope in this binary at the secondary mass transfer evolutionary stage and the system remains semi-detached (van den Heuvel et al., 2017). We also discuss unsolved issues and outline prospects for further study of SS433.

In this chapter, we review some features of particle acceleration in astrophysical jets. We begin by describing four observational results relating to the topic, with particular emphasis on jets in active galactic nuclei and parallels between different sources. We then discuss the ways in which particles can be accelerated to high energies in magnetised plasmas, focusing mainly on shock acceleration, second-order Fermi and magnetic reconnection; in the process, we attempt to shed some light on the basic conditions that must be met by any mechanism for the various observational constraints to be satisfied. We describe the limiting factors for the maximum particle energy and briefly discuss multimessenger signals from neutrinos and ultrahigh energy cosmic rays, before describing the journey of jet plasma from jet launch to cocoon with reference to the different acceleration mechanisms. We conclude with some general comments on the future outlook.

The discovery of jets from tidal disruption events (TDEs) rejuvenated the old field of relativistic jets powered by accretion onto supermassive black holes. In this Chapter, we first review the extensive multi-wavelength observations of jetted TDEs. Then, we show that these events provide valuable information on many aspects of jet physics from a new prospective, including the on-and-off switch of jet launching, jet propagation through the ambient medium, γ/X-ray radiation mechanism, jet composition, and the multi-messenger picture. Finally, open questions and future prospects in this field are summarized.

We review current understanding of the population of radio galaxies and radio-loud quasars from an observational perspective, focusing on their large-scale structures and dynamics. We discuss the physical conditions in radio galaxies, their fuelling and accretion modes, host galaxies and large-scale environments, and the role(s) they play as engines of feedback in the process of galaxy evolution. Finally we briefly summarise other astrophysical uses of radio galaxy populations, including the study of cosmic magnetism and cosmological applications, and discuss future prospects for advancing our understanding of the physics and feedback behaviour of radio galaxies.

Seventeen years of hard X-ray observations with the instruments of the INTEGRAL observatory, with a focus on the Milky Way and in particular on the Galactic Centre region, have provided a unique database for exploration of the Galactic population of low-mass X-ray binaries (LMXBs). Our understanding of the diverse energetic phenomena associated with accretion of matter onto neutron stars and black holes has greatly improved. We review the large variety of INTEGRAL based results related to LMXBs. In particular, we discuss the spatial distribution of LMXBs over the Galaxy and their X-ray luminosity function as well as various physical phenomena associated with Atoll and Z sources, bursters, symbiotic X-ray binaries, ultracompact X-ray binaries and persistent black hole LMXBs. We also present an up-to-date catalogue of confirmed LMXBs detected by INTEGRAL, which comprises 166 objects. Last but not least, the long-term monitoring of the Galactic Centre with INTEGRAL has shed light on the activity of Sgr A* in the recent past, confirming previous indications that our supermassive black hole experienced a major accretion episode just  ~ 100 years ago. This exciting topic is covered in this review too.

In this paper we first review the results obtained by the INTEGRAL mission in the domain of Gamma-Ray Bursts (GRBs), thanks to the INTEGRAL Burst Alert System, which is able to deliver near real-time alerts for GRBs detected within the IBIS field of view. More than 120 GRBs have been detected to date and we summarize their properties here. In the second part of this review we focus on the polarimetric results obtained by IBIS and SPI on GRBs and Galactic compact objects.

I review new studies of type Ia supernovae (SNe Ia) from 2019, and use these to improve the comparison between the five binary SN Ia scenarios. New low polarisation measurements solidify the claim that most SN Ia explosions are globally spherically symmetric (clumps are possible). Explosions by dynamical processes, like explosions that take place during a merger process of two white dwarfs (WDs) in the double degenerate (DD) scenario, or during an accretion process in the double detonation (DDet) scenario and in the single degenerate (SD) scenario, lead to non-spherical explosions, in contradiction with observations of normal SNe Ia. I argue that these (DD, DDet, SD) scenarios account mainly for peculiar SNe Ia. The explosion of a Chandrasekhar mass (M_CH) WD (deflagration to detonation process) has a global spherical structure that is compatible with observations. To reach spherical explosions, SN Ia scenarios should allow for a time delay between the formation of an M_Ch-WD and its explosion. As such, I split the DD scenario to a channel without merger to explosion delay (MED) time (that forms mainly peculiar SNe Ia), and a channel with a MED, the DD-MED channel (scenario). I speculate that the main contributors to normal SNe Ia are the core degenerate (CD) scenario, the DD-MED scenario, both have M_CH spherical explosions, and the DD scenario that has sub-C_CH non-spherical explosions.

The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling. Detecting dual active galactic nuclei (AGN) – active SMBHs at projected separations larger than several parsecs – and binary AGN – probing the scale where SMBHs are bound in a Keplerian binary – is an observational challenge. The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics. The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web. This review describes the techniques used across the electromagnetic spectrum to detect dual and binary AGN candidates and proposes new avenues for their search. The current observational status is compared with the state-of-the-art numerical simulations and models for formation of dual and binary AGN. Binary SMBHs are among the loudest sources of gravitational waves (GWs) in the Universe. The search for a background of GWs at nHz frequencies from inspiralling SMBHs at low redshifts, and the direct detection of signals from their coalescence by the Laser Interferometer Space Antenna in the next decade, make this a theme of major interest for multi-messenger astrophysics. This review discusses the future facilities and observational strategies that are likely to significantly advance this fascinating field.

This review encompasses the current state of development of optical/IR energy-sensitive detectors with reference to both the earliest implementations of energy sensitive detector technology, and current development projects with a discussion of their future developmental potential. The review will focus mainly on detectors with reasonable detection efficiency in the optical (400–700 nm) and Near Infrared (700 nm - 5 μm) region of the electromagnetic spectrum, but will also discuss applications at longer wavelengths which may be useful for future optical-NIR sensitive sensors. The figures of merit for each of the different types of detector are presented with data current at the time of publication, these figures will be discussed with reference to the theoretical maximum performance which is expected with further development along with the timeframes during which these limits will be approached.