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The brightest-of-all-time gamma-ray burst (GRB), GRB 221009A, is the first GRB observed to have emission line (up to 37 MeV) in its prompt emission spectra. It is naturally explained as |$e^-/e^+$|  annihilation line that was Doppler boosted in the relativistic jet of the GRB. In this work, we repeatedly apply the simple optical depth argument to different physical processes necessary to produce an observable |$e^-/e^+$|  annihilation line. This approach results in robust constraints on the physics of the line: We conclude that in GRB 221009A, the |$e^-/e^+$|  pairs were produced at a radius greater than |$4.3\times 10^{15}$|  cm from the central engine, and annihilated in a region between |$1.4\times 10^{16}$| and |$4.3\times 10^{16}$|  cm. From these constraints, we established a self-consistent picture of |$e^-/e^+$|  production, cooling, and annihilation. We also derived a criterion for pair production in the GRB prompt emission: |$E_{\rm {iso}} \gtrsim 3.3\times 10^{53} E_{\rm {peak},100} (1+z) R^2_{\rm {prod},16}~\text{erg}$|⁠. Using this criterion, we find tens of candidate GRBs that could have produced |$e^-/e^+$|  in prompt emissions to annihilate. GRB 221009A is with the highest likelihood according to this criterion. We also predict the presence of a thermal radiation, with a time-evolving blackbody temperature, sweeping through soft X-ray during the prompt emission phase. [ABSTRACT FROM AUTHOR]

In this paper, we studied the X-ray polarization of the jet in the Vela Pulsar Wind Nebula. After the background subtraction, we found a high degree of polarization in the helical jet region, close to the upper limit allowed by the synchrotron radiation mechanism. This result indicates the magnetic field is highly ordered, even though the jet's morphology is curved and varies rapidly, which suggests that the magnetic collimation process for the jet does not introduce significant turbulence. The polarization angle is perpendicular to the symmetry axis of the nebula, consistent with the results from the magnetohydrodynamic numerical simulations. This finding sheds light on the underlying mechanisms related to the dynamics and evolution of the jet structures. [ABSTRACT FROM AUTHOR]

Aims. Short gamma-ray bursts originate when relativistic jets emerge from the remnants of binary neutron star (BNS) mergers, as observed in the first multi-messenger event GW170817–GRB 170817A, which coincided with a gravitational wave signal. Both the jet and the remnant are believed to be magnetized, and the presence of magnetic fields is known to influence the jet propagation across the surrounding post-merger environment. In the magnetic interplay between the jet and the environment itself, effects due to a finite plasma conductivity may be important, especially in the first phases of jet propagation. We aim to investigate these effects, from jet launching to its final breakout from the post-merger environment. Methods. We used the PLUTO numerical code to perform 2D axisymmetric and full 3D resistive relativistic magnetohydrodynamic (MHD) simulations, employing spherical coordinates with spatial radial stretching. We considered and compared different models for physical resistivity, which must be small but still dominating over the intrinsic numerical dissipation (which yields unwanted smearing of structures in any ideal MHD code). Stiff terms in the current density are treated with IMplicit-EXplicit Runge Kutta algorithms for time-stepping. A Synge-like gas (Taub equation of state) is also considered. All simulations were performed using an axisymmetric analytical model for both the jet propagation environment and the jet injection; we leave the case of jet propagation in a realistic environment (i.e., imported from an actual BNS merger simulation) to a future study. Results. As expected, no qualitative differences are detected due to the effect of a finite conductivity, but significant quantitative differences in the jet structure and induced turbulence are clearly seen in 2D axisymmetric simulations, and we also compare different resistivity models. We see the formation of regions with a resistive electric field parallel to the magnetic field, and nonthermal particle acceleration may be enhanced there. The level of dissipated Ohmic power is also dependent on the various recipes for resistivity. Most of the differences arise before the breakout from the inner environment, whereas once the jet enters the external weakly magnetized environment region, these differences are preserved during further propagation despite the lower grid refinement. Finally, we show and discuss the 3D evolution of the jet within the same environment in order to highlight the emergence of nonaxisymmetric features. [ABSTRACT FROM AUTHOR]

Context. Due to the high visual extinction and lack of sensitive mid-infrared (MIR) telescopes, the origin and properties of outflows and jets from embedded Class 0 protostars are still poorly constrained. Aims. We aim to characterise the physical, kinematic, and dynamical properties of the HH 211 jet and outflow, one of the youngest protostellar flows. Methods. We used the James Webb Space Telescope (JWST) and its Mid-InfraRed Instrument (MIRI) in the 5–28 µm range to study the embedded HH 211 flow. We mapped a 0′.95 × 0′.22 region, covering the full extent of the blueshifted lobe, the central protostellar region, and a small portion of the redshifted lobe. We extracted spectra along the jet and outflow and constructed line and excitation maps of both atomic and molecular lines. Additional JWST NIRCam H2 narrow-band images (at 2.122 and 3.235 µm) provide a visualextinction map of the whole flow, and are used to deredden our data. Results. The jet-driving source is not detected even at the longest MIR wavelengths. The overall morphology of the flow consists of a highly collimated jet, which is mostly molecular (H2, HD) with an inner atomic ([Fe I], [Fe II], [S I], [Ni II]) structure. The jet shocks the ambient medium, producing several large bow shocks (BSs) that are rich in forbidden atomic ([Fe II], [S I], [Ni II], [Cl I], [Cl II], [Ar II], [Co II], [Ne II], [S III]) and molecular lines (H2, HD, CO, OH, H2O, CO2, HCO+), and is driving an H2 molecular outflow that is mostly traced by low- J, v = 0 transitions. Moreover, H2 0-0 S(1) uncollimated emission is also detected down to 2″-3″ (~650–1000 au) from the source, tracing a cold (T=200–400 K), less dense, and poorly collimated molecular wind. Two H2 components (warm, T =300–1000 K, and hot, T =1000–3500 K) are detected along the jet and outflow. The atomic jet ([Fe II] at 26 µm) is detected down to ~130 au from the source, whereas the lack of H2 emission (at 17 µm) close to the source is likely due to the large visual extinction (AV > 80 mag). Dust-continuum emission is detected at the terminal BSs and in the blue- and redshifted jet, and is likely attributable to dust lifted from the disc. Conclusions. The jet shows an onion-like structure, with layers of different size, velocity, temperature, and chemical composition. Moreover, moving from the inner jet to the outer BSs, different physical, kinematic, and excitation conditions for both molecular and atomic gas are observed. The mass-flux rate and momentum of the jet, as well as the momentum flux of the warm H2 component, are up to one order of magnitude higher than those inferred from the atomic jet component. Our findings indicate that the warm H2 red component is the main driver of the outflow, that is to say it is the most significant dynamical component of the jet, in contrast to jets from more evolved YSOs, where the atomic component is dominant. [ABSTRACT FROM AUTHOR]

Context. Characterising stellar jet asymmetries is key to setting robust constraints on jet launching models and improving our understanding of the underlying mechanisms behind jet launching. Aims. We aim to characterise the asymmetric properties of the bipolar jet coming from the Classical T Tauri Star Th 28. Methods. We combined data from integral field spectroscopy with VLT/MUSE and high-resolution spectra from VLT/X-shooter to map the optical emission line ratios in both jet lobes. We carried out a diagnostic analysis of these ratios to compare the density, electron temperature, and ionisation fraction within both lobes. The mass accretion rate was derived from the emission lines at the source and compared with the mass outflow rate derived for both lobes, using the estimated densities and measured [O I]λ6300 and [S II]λ6731 luminosities. Results. The blue-shifted jet exhibits a significantly higher electron temperature and moderately higher ionisation fraction than the red-shifted jet. In contrast to previous studies, we also estimated higher densities, denoted as nH , in the blue-shifted jet by a factor of ~2. These asymmetries are traced to within 1″ (160 au) of the source in the line ratio maps. We find Ṁacc = 2.4 × 10−7M⊙ yr−1, with an estimated obscuration factor of ~54 due to grey scattering around the star. Estimated values of Ṁout range between 0.66 and 13.7 × 10−9M⊙ yr−1 in the blue-shifted jet and 5–9 × 10−9M⊙ yr−1 in the red-shifted jet. Conclusions. The emission line maps and diagnostic results suggest that the jet asymmetries originate close to the source and are likely to be intrinsic to the jet. Furthermore, the combined dataset offers access to a broad array of accretion tracers. In turn, this enables a more accurate estimation of the mass accretion rate, revealing a value of Ṁacc that is higher by a factor >350 than would otherwise be determined. [ABSTRACT FROM AUTHOR]

Context. S26 is an extragalactic microquasar with the most powerful jets ever discovered. They have a kinetic luminosity of Lj ∼ 5 × 1040 erg s−1. This implies that the accretion power to the black hole should be super-Eddington, of the order of Lacc ∼ Lj. However, the observed X-ray flux of this system indicates an apparent very sub-Eddington accretion luminosity of LX ≈ 1037 erg s−1. Aims. We aim to characterize the nature of S26, explain the system emission, and study the feasibility of super-Eddington microquasars as potential PeVatron sources. Methods. We first analyze multi-epoch X-ray observations of S26 obtained with XMM-Newton and model the super-Eddington disk and its wind. We then develop a jet model and study the particle acceleration and radiative processes that occur in shocks generated near the base of the jet and in its terminal region. Results. We find that the discrepancy between the jet and the apparent disk luminosities in S26 is caused by the complete absorption of the disk radiation by the wind ejected from the super-Eddington disk. The nonthermal X-rays are produced near the base of the jet, and the thermal X-rays are emitted in the terminal regions. The radio emission observed with the Australia Telescope Compact Array can be explained as synchrotron radiation produced at the reverse shock in the lobes. We also find that S26 can accelerate protons to PeV energies in both the inner jet and the lobes. The ultra-high energy protons accelerated in the lobes of S26 are injected into the interstellar medium with a total power of ∼1036 erg s−1. Conclusions. We conclude that S26 is a super-Eddington microquasar with a dense disk-driven wind that obscures the X-ray emission from the inner disk, and that the supercritical nature of the system allows the acceleration of cosmic rays to PeV energies. [ABSTRACT FROM AUTHOR]

Supermassive black holes (SMBHs) at the centers of active galaxies are fed by accretion disks that radiate from the infrared or optical to the X-ray bands. Several types of objects can orbit SMBHs, including massive stars, neutron stars, clouds from the broad- and narrow-line regions, and X-ray binaries. Isolated black holes with a stellar origin (BHs of ∼10 M⊙) should also be present in large numbers within the central parsec of the galaxies. These BHs are expected to form a cluster around the SMBH as a result of the enhanced star formation rate in the inner galactic region and the BH migration caused by gravitational dynamical friction. However, except for occasional microlensing effects on background stars or gravitational waves from binary BH mergers, the presence of a BH population is hard to verify. In this paper, we explore the possibility of detecting electromagnetic signatures of a central cluster of BHs when the accretion rate onto the central SMBH is greater than the Eddington rate. In these supercritical systems, the accretion disk launches powerful winds that interact with the objects orbiting the SMBH. Isolated BHs can capture matter from this dense wind, leading to the formation of small accretion disks around them. If jets are produced in these single microquasars, they could be sites of particle acceleration to relativistic energies. These particles in turn are expected to cool by various radiative processes. Therefore, the wind of the SMBH might illuminate the BHs through the production of both thermal and nonthermal radiation. [ABSTRACT FROM AUTHOR]

Recent radio observations and coincident neutrino detections suggest that some tidal disruption events (TDEs) exhibit late-time activities, relative to the optical emission peak, and these may be due to delayed outflows launched from the central supermassive black hole. We investigate the possibility that jets launched with a time delay of days to months, interact with a debris that may expand outwards. We discuss the effects of the time delay and expansion velocity on the outcomes of jet breakout and collimation. We find that a jet with an isotropic-equivalent luminosity of |$\lesssim 5 \times 10^{45}\, {\rm erg\, s}^{-1}$| is likely to be choked for a delay time of |$\sim 3$| months. We also study the observational signatures of such delayed choked jets. The jet–debris interaction preceding the breakout would lead to particle acceleration and the resulting synchrotron emission can be detected by current and near-future radio, optical and X-ray telescopes, and the expanding jet-driven debris could explain late-time radio emission. We discuss high-energy neutrino production in delayed choked jets, and the time delay can significantly alleviate the difficulty of the hidden jet scenario in explaining neutrino coincidences. [ABSTRACT FROM AUTHOR]

We report two epochs of simultaneous near-infrared (IR) and X-ray observations of the low-mass X-ray binary black hole candidate Swift J1753.5–0127 with a subsecond time resolution during its long 2005–2016 outburst. Data were collected strictly simultaneously with VLT/ISAAC (KS band, 2.2 μm) and RXTE (2–15 keV) or XMM-Newton (0.7–10 keV). A clear correlation between the X-ray and the IR variable emission is found during both epochs but with very different properties. In the first epoch, the near-IR variability leads the X-ray by ∼130 ms, which is the opposite of what is usually observed in similar systems. The correlation is more complex in the second epoch, with both anti-correlation and correlations at negative and positive lags. Frequency-resolved Fourier analysis allows us to identify two main components in the complex structure of the phase lags: the first component, characterised by a near-IR lag of a few seconds at low frequencies, is consistent with a combination of disc reprocessing and a magnetised hot flow; the second component is identified at high frequencies by a near-IR lag of ≈0.7 s. Given the similarities of this second component with the well-known constant optical/near-IR jet lag observed in other black hole transients, we tentatively interpret this feature as a signature of a longer-than-usual jet lag. We discuss the possible implications of measuring such a long jet lag in a radio-quiet black hole transient. [ABSTRACT FROM AUTHOR]

Context. Over the past decade, choked jets have attracted particular attention as potential sources of high-energy cosmic neutrinos. It is challenging to test this hypothesis because of the missing gamma-ray counterpart. An identification of other electromagnetic signatures is therefore crucial. Extended H envelopes surrounding collapsing massive stars might choke launched jets. In addition, the same progenitors are expected to produce a shock-breakout signal in the ultraviolet (UV) and optical that lasts several days. Early UV radiation in particular carries important information about the presence and nature of choked jets. Aims. While UV observations of core-collapse supernovae have so far been limited, the full potential of observations in this spectral band will soon be transformed by the ULTRASAT satellite mission with its unprecedented field of view. We investigated the detection prospects of choked jet progenitors by ULTRASAT in relation to their visibility in the optical band by the currently operating telescope ZTF. In addition, as choked jets can produce neutrinos via hadronic and photohadronic interactions in choked jets, we also investigated how neutrino observations by existing Cherenkov high-energy neutrino telescopes (e.g. IceCube and KM3NeT) can be used in association with electromagnetic signals from shock-breakout events. Methods. By considering fiducial parameters of the source population and instrument performances, we estimated the maximum redshift up to which ULTRASAT and ZTF are able to detect ultraviolet and optical signals from these explosions, respectively. Furthermore, we discuss coordinated multi-messenger observations using ULTRASAT, ZTF, and high-energy neutrino telescopes. Results. We find that ULTRASAT will double the volume of the sky that is currently visible by ZTF for the same emitting sources. This will enlarge the sample of observed Type II supernovae by ∼60%. For optimised multi-messenger detections, the delay between neutrinos produced at the shock breakout (during the jet propagation inside the stellar envelope) and ULTRASAT observations should be of ∼4 (5) days, with subsequent follow-up by instruments such as ZTF about one week later. We estimate that fewer than 1% of the core-collapse supernovae from red supergiant stars that are detectable in UV with ULTRASAT might host a choked jet and release TeV neutrinos. Electromagnetic and neutrino detections, if accompanied by additional photometric and spectroscopic follow-up with compelling evidence for a relativistic jet launched by the central engine of the source, would suggest that core-collapse supernovae harbouring choked jets are the main contributors to the diffuse astrophysical high-energy neutrino flux. [ABSTRACT FROM AUTHOR]

The behaviour of a short gamma-ray burst (sGRB) afterglow light curve can reveal the angular structure of the relativistic jet and constrain the observer's viewing angle |$\theta _\textrm {obs}$|⁠. The observed deceleration time of the jet, and, therefore, the time of the afterglow peak, depends on the observer's viewing angle. A larger viewing angle leads to a later peak of the afterglow and a lower flux at peak. We utilize the earliest afterglow detections of 58 sGRBs detected with the Neil Gehrels Swift Observatory X-ray Telescope to constrain the ratio of the viewing angle |$\theta _\textrm {obs}$| to the jet's core |$\theta _\textrm {c}$|⁠. We adopt a power-law angular jet structure in both energy |$E(\theta)\propto \theta ^{-a}$| and Lorentz factor |$\Gamma (\theta)\propto \theta ^{-b}$| beyond the core. We find that either sGRBs are viewed within |$\theta _\textrm {obs}/\theta _\textrm {c}\lt 1$| or the initial Lorentz factor of material in their jet's core is extremely high (⁠|$\Gamma _0\gt 500$|⁠). If we consider tophat jets, we constrain 90 per cent of our sample to be viewed within |$\theta _\textrm {obs}/\theta _\textrm {c}\lt 1.06$| and 1.15 for our canonical and conservative afterglow scenarios. For a subset of events with measurements of the jet break, we can constrain |$\Gamma _0\theta _\textrm {c}\gtrsim 30$|⁠. This confirmation that cosmological sGRBs are viewed either on-axis or very close to their jet's core has significant implications for the nature of the prompt gamma-ray production mechanism and for the rate of future sGRB detections coincident with gravitational waves, implying that they are extremely rare. [ABSTRACT FROM AUTHOR]

We analytically and numerically study the hydrodynamic propagation of a precessing jet in the context of tidal disruption events (TDEs) where the star's angular momentum is misaligned with the black hole spin. We assume that a geometrically thick accretion disc undergoes Lense–Thirring precession around the black hole spin axis and that the jet is aligned with the instantaneous disc angular momentum. At large spin-orbit misalignment angles |$\theta _{\it LS}$|⁠ , the duty cycle along a given angle that the jet sweeps across is much smaller than unity. The faster jet and slower disc wind alternately fill a given angular region, which leads to strong shock interactions between the two. We show that precessing jets can only break out of the wind confinement if |$\theta _{\it LS}$| is less than a few times the jet opening angle |$\theta _{\rm j}$|⁠. The very small event rate of observed jetted TDEs is then explained by the condition of double alignment : both the stellar angular momentum and the observer's line of sight are nearly aligned with the black hole spin. In most TDEs with |$\theta _{\it LS}\gg \theta _{\rm j}$|⁠ , the jets are initially choked by the disc wind and may only break out later when the disc eventually aligns itself with the spin axis due to the viscous damping of the precession. Such late-time jets may produce delayed radio rebrightening as seen in many optically bright TDEs. Our model is also applicable to jets associated with (stellar mass) black hole-neutron star mergers where the black hole's spin is misaligned with the orbital angular momentum. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts (GRBs) are among the most powerful explosive events in the Universe. LHAASO recently observed the most luminous one: GRB 221009A, and unveiled its TeV light curve. The light curve exhibits a distinct jet break at around 670 s, enabling the derivation of the viewing angle based on the smoothness of the jet break. We constructed two models with or without considering the high-latitude radiation, where the viewing angle was treated as a free parameter, to fit the TeV light curve. The viewing angles obtained were 9.4 |$\times 10^{-4}$| and 5.9 |$\times 10^{-3}$| rad, respectively. These values closely resemble an on-axis scenario, given the opening angle is 1.4 |$\times 10^{-2}$| rad. [ABSTRACT FROM AUTHOR]

We conduct three-dimensional hydrodynamic simulations, and show that when a secondary star launches jets while interacting with a primary |$0.88~\mathrm{ M}_{\rm \odot }$| giant star in a close orbit, the system can avoid entering the common envelope evolution (CEE). Instead of a fast in-spiral, the companion slowly enters the envelope as the jets facilitate the unbinding of the giant star envelope outside the companion orbit, in what is termed the grazing envelope evolution (GEE). The assumptions are that the secondary main-sequence star accretes mass via an accretion disc, and that the accretion disc launches the jets. We perform two sets of simulations with and without jets for different companion masses at the range of 0.1–0.9 M |$_{\odot }$|⁠ , maintaining a constant jet power in the former case of |$1.5\times 10^{38}~{\rm ergs~s^{-1}}$|⁠. We examine which of the simulated systems undergo a GEE rather than a CEE and how efficiently the jets unbind the envelope. The results indicate that systems with companion masses at the range of 0.1–0.3 M |$_{\odot }$| are more likely to result in a phase of GEE lasting 1–3 yr. With the smallest companion, a 0.1 solar mass star, the jets unbind 65 per cent of the envelope mass, while almost none of the envelope is unbound if jets are not present. The results of the simulations show that the GEE can serve as an alternative to the CEE, in forming short-period binaries that have compact objects and an ejected envelope. [ABSTRACT FROM AUTHOR]

The recent detection of gamma-ray burst GRB 221009A has attracted attention due to its record brightness and first-ever detection of |$\gtrsim 10$| TeV gamma-rays from a GRB. Despite being the second-nearest GRB ever detected, at a redshift of |$z=0.151$|⁠ , the distance is large enough for severe attenuation of gamma-ray flux at these energies due to |$\gamma \gamma \rightarrow e^\pm$| pair production with the extragalactic background light (EBL). Here, we investigate whether the presence of cosmic voids along the line of sight can significantly impact the detectability of very high energy (VHE, |$\gt $| 100 GeV) gamma-rays from distant sources. Notably, we find that the gamma–gamma opacity for VHE gamma-rays can be reduced by approximately 10 per cent and up to 30 per cent at around 13 TeV, the highest-energy photon detected from GRB 221009A, for intervening cosmic voids along the line of sight with a combined radius of 110 Mpc, typically found from void catalogues, and 250 Mpc, respectively. This reduction is substantially higher for TeV photons compared to GeV photons, attributable to the broader target photon spectrum that TeV photons interact with. This finding implies that VHE photons are more susceptible to variations in the EBL spectrum, especially in regions dominated by cosmic voids. Our study sheds light on the detection of |$\gtrsim 10$| TeV gamma-rays from GRB 221009A in particular, and on the detection of extragalactic VHE sources in general. [ABSTRACT FROM AUTHOR]

Context. Young stars accrete matter from their surrounding protoplanetary disk and drive powerful outflows. These two processes shape the final system architecture, and studying how these processes interact is the goal of the ESO Large programme PENELLOPE. PENELLOPE complements the ULLYSES legacy programme on the Hubble Space Telescope (HST) by providing ground-based – Very Large Telescope (VLT) – optical and near-infrared spectroscopy of more than 80 low-mass young stars. Aims. The main goal of this study is to screen the PENELLOPE/UVES targets for outflow activity and find microjets. A spectro-astrometric analysis in the [OI]λ6300 line in the velocity components of the microjet can give insights into the origin of the line emission, that is, if they originate from a magneto-hydrodynamical (MHD) wind or a photoevaporative wind. Methods. In total, 34 T Tauri stars of the PENELLOPE survey have been observed with the high-resolution optical slit spectrograph UVES (R ~ 65 000, λ = 3300–6800 Å). We formulated four criteria to rank the targets according to their outflow activity. Most of the targets have been observed in three different slit positions rotated by 120° with UVES. Using spectro-astrometric techniques in the [OI]λ6300 and Hα emission lines in each slit position of each target, we searched for outflow signatures, that is, an offset emission with respect to the continuum contribution of the associated T Tauri star. We checked all spectra for the presence of other wind line emission of [SII]λ4068, [SII]λ4076, [OI]λ5577, [OI]λ6300, [OI]λ6363, [SII]λ6716, [SII]λ6731, [NII]λ6548, and [NII]λ6583. Line profiles of Hα were inspected for a P Cygni signature. All [OI]λ6300 line profiles were decomposed into their constituent high-velocity component (HVC) and low-velocity component (LVC). Results. Our spectro-astrometric analysis in the [OI]λ6300 wind line reveals two newly discovered microjets associated with Sz 103 and XX Cha. Both microjets have an extent of about 0″.04, that is, <10 au, and we confined their orientation by the three slit observations. We identified two other interesting targets for which all four outflow criteria are fulfilled: Sz 98 and Sz 99. These targets display peculiar wind lines in their spectra with multiple velocity components, however, with the lack of a spectro-astrometric outflow signature. Furthermore, we confirm the binary nature of VWCha and CVSO 109. We present (further) evidence that DK Tau B and CVSO 104 A are spectroscopic binaries. Sz 115 is tentatively a spectroscopic binary. We find that the P Cygni line profile in the Hα line is not a robust indicator for the presence of outflows. Conclusions. The utilised observing strategy (rotating the UVES slit in three different positions) is very powerful in detecting micro-jets in T Tauri stars. The three slit positions can confine the spatial extend of the forbidden emission line regions. The introduced metric to rank targets according to their outflow activity is useful for follow-up observations. The origin of the LVC, that is, MHD winds versus photoevaporative winds, of the Sz 103 and XX Cha microjets remains unclear. [ABSTRACT FROM AUTHOR]

Context. In recent years, some polarization measurements of gamma-ray bursts (GRBs) have been reported, and the polarization-angle (PA) rotation in the prompt emission phase has been found in several bursts. The physical mechanism of the PA evolution is still unclear. In this work, we studied the origin of the PA rotation in a toroidal magnetic field. Aims. We aim to provide an explanation for the PA rotation in GRBs and find the physical conditions that lead to the rotation by 90 degrees in the toroidal magnetic-field (MF) model. Moreover, we present some observable polarization properties in the MF model that can be tested in the future. Methods. We calculated the instantaneous polarization degree (PD) from a top-hat jet with different normalized viewing angles (q = θv/θj), jet opening angles (θj), and jet Lorentz factors (Γ) in three wavebands. When the PD changes between positive and negative values, it means that the PA flips by 90 degrees. On these grounds, we can summarize the range of parameters required for these PA flips. Considering these parameter conditions, we can further estimate the observed rate of the GRBs exhibiting such PA rotations. Results. We find that the PA rotation in the toroidal MF is primarily related to three critical factors: the viewing angle, the jet opening angle, and the jet Lorentz factor. Additionally, the PA can experience flips of 90 degrees twice. The conditions for the flips are q ≳ 0.5 (except for q ≃ 1) and yj = (Γθj)2 ≳ 4. However, the two flips in the PA might not be concurrently observable due to the constraint of flux. Taking these conditions into account and assuming a random orientation between the jet axis and the line of sight (LOS), we obtain a theoretical upper limit (without any constraints) for the observed rate of GRBs in the X-ray or γ-ray band displaying the flips in PA as Rch ≲ 80%. We further constrain the observed rate as Rch ∼ 16% according to the maximal post-flip polarized flux level, where the observed rate of single and double flips each account for ∼8%. It should be noted that the observed rates are different in various wavebands. The observed rate of the second PA flip in the optical bands should be higher than that in the X-ray or γ-ray band since the flux in the optical band declines much slower than that in the X-ray or γ-ray band. Moreover, when the LOS is close to the jet edge (q → 1), it is the easiest case in which to observe the 90-degree PA flip due to the relatively high post-flip polarized flux level. The first and second PA flips in a GRB pulse are most likely to occur at the observed times of tobs ∼ [2 − 3]tpeak and ∼[3 − 4]tpeak, respectively, where tpeak is the peak time of the pulse. It is also noted that the PA flip would not happen before the peak time. [ABSTRACT FROM AUTHOR]

The relativistic outflows that produce long gamma-ray bursts (LGRBs) can be described by a structured jet model where prompt |$\gamma$| -ray emission is restricted to a narrow region in the jet's core. Viewing the jet off-axis from the core, a population of afterglows without an associated GRB detection can be predicted. In this work, we conduct an archival search for these 'orphan' afterglows (OAs) with minute-cadence, deep (⁠|$g\sim 23$|⁠) data from the Dark Energy Camera (DECam) taken as part of the Deeper, Wider, Faster programme (DWF). We introduce a method to select fast-evolving OA candidates within DWF data that comprises a machine learning model, based on a realistic synthetic population of OAs. Using this classifier, we recover 51 OA candidates. Of these candidates, 42 are likely flare events from M-class stars. The remaining nine possess quiescent, coincident sources in archival data with angular profiles consistent with a star and are inconsistent with the expected population of LGRB host galaxies. We therefore conclude that these are likely Galactic events. We calculate an upper limit on the rate of OAs down to |$g\lt 22$| AB mag of 7.46 deg |$^{-2}$| yr |$^{-1}$| using our criteria and constrain possible jet structures. We also place an upper limit of the characteristic angle between the |$\gamma$| -ray-emitting region and the jet's half-opening angle. For a smooth power law and a power law with core jet model, respectively, these values are |$58.3^{\circ }$| and |$56.6^{\circ }$|⁠ , for a power-law index of 0.8 and |$75.3^{\circ }$| and |$76.8^{\circ }$| for a power-law index of 1.2. [ABSTRACT FROM AUTHOR]

One of the promising mechanisms to explain the stable jet speed of SS 433 is the magic speed, which is established by the balance between radiation pressure and radiation drag (and gravity). We examine the magic speed in the optically thick sub-relativistic flows for several typical situations, such as plane-parallel and spherical cases, and show that it is difficult to establish the magic speed in the simple optically thick flows in contrast to the optically thin ones. Instead, we propose the funnel jets as an improved model. That is, we consider the optically thick flows in the funnel, which is formed by the supercritical accretion disk, and mass and radiation energy are injected from the funnel wall. In this model the mass-accretion rate determines the configuration of the funnel, the increasing mass-loss rate of jets, the radiative environments, and then the sub-relativistic magic speed is naturally established. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "JOYS: Disentangling the warm and cold material in the high-mass IRAS 23385+6053 cluster." The article focuses on topics such as star formation, individual objects in the ISM (Interstellar Medium), stars with jets, and massive stars. The full text of the article is not available in HTML format. The authors of the article are listed as C. Gieser, H. Beuther, E. F. van Dishoeck, L. Francis, M. L. van Gelder, L. Tychoniec, P. J. Kavanagh, G. Perotti, A. Caratti o Garatti, T. P. Ray, P. Klaassen, K. Justtanont, H. Linnartz, W. R. M. Rocha, K. Slavicinska, L. Colina, M. Güdel, Th. Henning, P.-O. Lagage, G. Östlin, B. Vandenbussche, C. Waelkens, and G. Wright. [Extracted from the article]

Jets and outflows are the early signposts of stellar birth. Using the UKIRT Wide Field Infrared Survey for H2 (UWISH2) at 2.12  μ m, 127 outflows are identified in molecular cloud complexes Vulpecula OB1 and IRDC G53.2 covering 12 square degrees of the Galactic plane. Using multiwavelength data sets, from 1.2 to 70  μ m, 79 young stellar objects (YSOs) are proposed as potential driving sources, where ∼79  per cent are likely Class 0/I protostars, 17  per cent are Class II YSOs, and the remaining 4 per cent are Class III YSOs. The outflows are characterized in terms of their length, flux, luminosity, and knot-spacing. The identified outflows have a median lobe length of 0.22 and 0.17 pc for outflows in Vulpecula OB1 and IRDC G53.2, respectively. Our analysis, from the knot spacing, reveals a typical ejection frequency of ∼1.2 kyr suggesting an intermediate type between the FU-Ori and EX-Ori type of eruptions in both cloud complexes. Furthermore, the physical parameters of the driving sources are obtained by performing radiative transfer modelling to the observed spectral energy distributions, which suggest that the outflows are driven by intermediate mass stars. Various observed trends between the outflow properties and the corresponding driving sources, and various interesting outflows and star forming sites, including sites of triggered star formation and protocluster forming clump with clusters of jets, are discussed. The obtained results and the identified jet-bearing protostellar sample will pave the way to understand many aspects of outflows with future high-resolution observations. [ABSTRACT FROM AUTHOR]

In previous studies, the time evolution information is missed in deducing the time-integrated polarizations of gamma-ray burst prompt emission. Here, it is considered and the time-integrated polarizations is investigated through the summation of the time-resolved ones. The statistical properties of the distribution of the time-integrated polarization degree (Π) can be read from the q– Π curve, where q ≡ θ V /θ j . θ V and θ j are the observational and jet half-opening angles, respectively. Hence, only the q– Π curves are studied. In addition to a toroidal magnetic field in the radiation region, an aligned field is also discussed. We found the predicted time-integrated polarization degree is around |$(40\!-\!50)\,\, \mathrm{ per\,cent}$| for High-energy Polarimetry Detector (HPD) onboard POLAR-2 and is roughly |$(30\!-\!40)\,\, \mathrm{ per\,cent}$| for its Low-energy Polarimetry Detector (LPD). Therefore, Π value detected by the HPD will be larger than that of the LPD in statistics and the result of the former estimations will underestimate the value of Π in an ordered field. There are mainly two types of the q –Π curve profiles, corresponding to two ordered magnetic field configurations. [ABSTRACT FROM AUTHOR]

The production of heavy elements is one of the main by-products of the explosive end of massive stars. A long sought goal is finding differentiated patterns in the nucleosynthesis yields, which could permit identifying a number of properties of the explosive core. Among them, the traces of the magnetic field topology are particularly important for extreme supernova (SN) explosions, most likely hosted by magnetorotational effects. We investigate the nucleosynthesis of five state-of-the-art magnetohydrodynamic models with fast rotation that have been previously calculated in full 3D and that involve an accurate neutrino transport (M1). One of the models does not contain any magnetic field and synthesizes elements around the iron group, in agreement with other CC-SNe models in literature. All other models host a strong magnetic field of the same intensity, but with different topology. For the first time, we investigate the nucleosynthesis of MR-SNe models with a quadrupolar magnetic field and a 90° tilted dipole. We obtain a large variety of ejecta compositions reaching from iron nuclei to nuclei up to the third r -process peak. We assess the robustness of our results by considering the impact of different nuclear physics uncertainties such as different nuclear masses, β−-decays and β−-delayed neutron emission probabilities, neutrino reactions, fission, and a feedback of nuclear energy on the temperature. We find that the qualitative results do not change with different nuclear physics input. The properties of the explosion dynamics and the magnetic field configuration are the dominant factors determining the ejecta composition. [ABSTRACT FROM AUTHOR]

Very-high-energy (VHE) photons around TeV energies from a gamma-ray burst (GRB) jet will play an essential role in the multimessenger era, with a fair fraction of the events being observed off-axis to the jet. We show that different energy photons (MeV and TeV photons in particular) arrive from different emission zones for off-axis observers even if the emission radius is the same. The location of the emission region depends on the jet structure of the surface brightness, and the structures are generally different at different energies, mainly due to the attenuation of VHE photons by electron–positron pair creation. This off-axis zone-shift effect does not justify the usual assumption of the one emission zone at a certain radius and also produces a time delay of VHE photons comparable to the GRB duration, which is crucial for future VHE observations, such as by the Cherenkov Telescope Array. [ABSTRACT FROM AUTHOR]

We investigate the propagation of spherically symmetric shocks in relativistic homologously expanding media with density distributions following a power-law profile in their Lorentz factor. That is, |$\rho _{_{\rm {ej}}} \propto t^{-3}\gamma _{_{\rm {ej}}}(r,t)^{-\alpha }$|⁠ , where |$\rho _{_{\rm {ej}}}$| is the medium proper density, |$\gamma _{_{\rm {ej}}}$| is its Lorentz factor, α > 0 is constant, and t, r are the time and radius from the centre. We find that the shocks behaviour can be characterized by their proper velocity, |$U^{\prime }=\Gamma _s^{\prime }\beta _s^{\prime }$|⁠ , where |$\Gamma _s^{\prime }$| is the shock Lorentz factor as measured in the immediate upstream frame and |$\beta _s^{\prime }$| is the corresponding three velocity. While generally, we do not expect the shock evolution to be self-similar, for every α > 0 we find a critical value |$U^{\prime }_c$| for which a self-similar solution with constant U ′ exists. We then use numerical simulations to investigate the behaviour of general shocks. We find that shocks with |$U^{\prime }\gt U^{\prime }_c$| have a monotonously growing U ′, while those with |$U^{\prime }\lt U^{\prime }_c$| have a decreasing U ′ and will eventually die out. Finally, we present an analytic approximation, based on our numerical results, for the evolution of general shocks in the regime where U ′ is ultrarelativistic. [ABSTRACT FROM AUTHOR]

A population of binary stellar-mass black hole (BBH) mergers are believed to occur embedded in the accretion disc of active galactic nuclei (AGNs). In this Letter , we demonstrate that the jets from these BBH mergers can propagate collimatedly within the disc atmosphere along with a forward shock and a reverse shock forming at the jet head. Efficient proton acceleration by these shocks is usually expected before the breakout, leading to the production of TeV−PeV neutrinos through interactions between these protons and electron-radiating photons via photon–meson production. AGN BBH mergers occurring in the outer regions of the disc are more likely to produce more powerful neutrino bursts. Taking the host AGN properties of the potential GW190521 electromagnetic (EM) counterpart as an example, one expects ≳1 neutrino events detectable by IceCube if the jet is on-axis and the radial location of the merger is R ≳ 105 R g, where R g is the gravitational radius of the supermassive BH. Neutrino bursts from AGN BBH mergers could be detected by IceCube following the observation of gravitational waves (GWs), serving as precursor signals before the detection of EM breakout signals. AGN BBH mergers are potential target sources for future joint GW, neutrino, and EM multi-messenger observations. [ABSTRACT FROM AUTHOR]

The Mach number is the primary parameter in determining the intrinsic driving properties, and effect on the environment of a supersonic jet. In the most basic form, a jet is released when a wall of a large high-pressure gas reservoir is punctured. The resulting high-pressure jet contains a configuration of shocks that continue to disturb the environment after the initial bow shock has passed. Here, we perform numerical simulations to determine the properties attributable to pure adiabatic hydrodynamic effects, taking a uniform stream out of a circular nozzle. We take a range of Mach numbers that, along with the jet overpressure, determine the flow pattern and shock locations. We distinguish conditions that generate Mach shock discs rather than a diamond pattern of oblique regular reflections. Potential observational diagnostics explored include the disc size, the distance from the nozzle, and oscillations in shock positions. Rapid oscillations occur in the divergent–convergent pattern through a feedback/hysteresis effect promoted by the ambient medium. The underlying flow patterns are independent of relative jet density, but heavy jets display both lower amplitude and lower frequency oscillations. We also study the energy transferred into the environment. Overpressured jets may contribute to noise and sound wave generation through screeching. However, these oscillations in the near-field are not sufficiently significant to regulate star and galaxy formation. We expect that upcoming high dynamic range and resolution observations will increasingly detect the shock patterns as jet gas transits from protostellar and galactic cores. [ABSTRACT FROM AUTHOR]

This paper describes an overview of the FLASHING (Finest Legacy Acquisitions of SiO-/H2O-maser Ignitions by the Nobeyama Generation) project promoted using the 45 m telescope of Nobeyama Radio Observatory, which aims to intensively monitor H2O (at 22 GHz) and SiO (at 43 GHz) masers associated with so-called "water fountain" sources. Here we show scientific results based on the data taken in the first five seasons of FLASHING, from 2018 December to 2023 April. We show the evolution of the H2O maser spectra, discovering new spectral components that break the record of the jet's top speed and/or systematic velocity drifts in the spectrum indicating acceleration or deceleration of the maser gas clumps. For the 43 GHz SiO maser emission, we newly detect it in one source and find that it is no longer present in another source. This implies that the jets from these water fountains can be accelerated or decelerated, and show how circumstellar envelopes are destroyed. [ABSTRACT FROM AUTHOR]

Self-similar supersonic winds from an accretion disc around a central object are examined with/without radiation fields under the fully self-similar treatment of two-dimensional outflows. The thermal pressure and viscosity are ignored for simplicity. In the case without radiation fields, many solutions are not outflowing winds, but bound flows, except for limited cases which satisfy the escape condition with sufficiently large initial launch speed and rotational one. In the case with radiation fields, the radiation force acts as a driving force, and therefore, the winds blow easier. However, several solutions are unphysical, since the radiative energy density becomes negative. As a result, depending on the rotational motion and boundary conditions, the radiatively driven self-similar cold disc winds are divided into three types; bound solutions lacking launch speed or radiative acceleration, unphysical ones with a negative energy density, and escaping winds confined in the conical region or extending in the whole space as a special type. [ABSTRACT FROM AUTHOR]

We present Very Large Telescope/Multi-Unit Spectroscopic Explorer Narrow Field Mode observations of a pair of disc-bearing young stellar objects towards the Orion Bar: 203–504 and 203–506. Both of these discs are subject to external photoevaporation, where winds are launched from their outer regions due to environmental irradiation. Intriguingly, despite having projected separation from one another of only 1.65 arcsec(660 au at 400 pc), 203–504 has a classic teardrop shaped 'proplyd' morphology pointing towards θ2 Ori A (indicating irradiation by the EUV of that star, rather than |$\rm \theta ^1$| Ori C) but 203–506 has no ionization front, indicating it is not irradiated by stellar EUV at all. However, 203–506 does show [C  i ] 8727 Å and [O  i ] 6300 Å in emission, indicating irradiation by stellar FUV. This explicitly demonstrates the importance of FUV irradiation in driving mass loss from discs. We conclude that shielding of 203–506 from EUV is most likely due to its position on the observers side of an ionized layer lying in the foreground of the Huygens Region. We demonstrate that the outflow HH 519, previously thought to be emanating from 203–504 is actually an irradiated cloud edge and identify a new compact outflow from that object approximately along our line of sight with a velocity ∼130 km s−1. [ABSTRACT FROM AUTHOR]

Cygnus X-3 is a high-mass X-ray binary with a compact object accreting matter from a Wolf–Rayet donor star. Recently, it has been revealed by the Imaging X-ray Polarimetry Explorer (IXPE) as a hidden Galactic ultra-luminous X-ray (ULX) source with a luminosity above the Eddington limit, along the direction of a narrow (opening angle |$\lesssim 32^{\circ }$|⁠) funnel. In between the IXPE observations, we observed Cyg X-3 with the European very long baseline interferometry (VLBI) Network at 22 GHz and the NICER X-ray instrument. To probe possible relations between the X-ray funnel and the potential radio jet from the ULX, we analysed the simultaneous multiwavelength data. Our high-resolution VLBI image reveals an elongated structure with a position angle of −3.2 ± 0.4 °, accurately perpendicular to the direction of the linear X-ray polarization. Because Cyg X-3 was in the radio quiescent state on 2022 November 10, we identify the mas-scale structure as the innermost radio jet. The finding indicates that the radio jet propagates along and within the funnel. Moreover, the jet is marginally resolved in the transverse direction. This possibly results from the strong stellar winds and the rapid orbital motion of the binary system. [ABSTRACT FROM AUTHOR]

One of the intriguing puzzles concerning Swift J1644+57, the first jetted tidal disruption event (TDE) discovered, is the constant increase in its jet energy, as implied by radio observations. During the first two hundred days, the jet energy has increased by an order of magnitude. We suggest that the jet was viewed slightly off-axis. In this case, the apparent energy increase arises due to the slowing down of the jet and the corresponding broadening of its beaming cone. Using equipartition analysis, we infer an increasing jet energy as a larger region of the jet is observed. A simple off-axis model accounts nicely for the multi-wavelength radio observations, resolving this long-standing puzzle. The model allows us to self-consistently evolve the synchrotron signature from an off-axis jet as a function of time. It also allows us to estimate, for the first time, the beaming angle of the jet, θ0 ≈ 21°. Considering existing limits on the black hole mass, ≲107 M⊙, this angle implies that the prompt phase beaming corrected luminosity of Swift J1644+57, ∼1047 ergs sec−1, was super Eddington. We also present a closure relation between the spectral and temporal flux for off-axis jets, which can be used to test whether a given radio transient is off-axis or not. [ABSTRACT FROM AUTHOR]

GRB 170817A, the first short gamma-ray burst (sGRB) to be detected in coincidence with a gravitational wave signal, demonstrated that merging binary neutron star (BNS) systems can power collimated ultra-relativistic jets, and in turn, produce sGRBs. Moreover, it revealed that sGRB jets possess an intrinsic angular structure that is imprinted in the observable prompt and afterglow emission. Advanced numerical simulations represent the leading approach to investigate the physical processes underlying the evolution of sGRB jets breaking out of post-merger environments, and thus connect the final angular structure and energetics with specific jet launching conditions. In a previous paper, we carried out the first 3D special-relativistic hydrodynamic simulations of incipient (top-hat) sGRB jets propagating across the realistic environment resulting from a general-relativistic (GR) hydrodynamic BNS merger simulation. While the earlier work marked an important step toward a consistent end-to-end description of sGRB jets from BNS mergers, those simulations did not account for the presence of magnetic fields, which are expected to play a key role. Here, we overcome this limitation, reporting the first 3D special-relativistic magnetohydrodynamic (MHD) simulation of a magnetized (structured and rotating) sGRB jet piercing through a realistic magnetized post-merger environment, wherein the initial conditions of the latter are directly imported from the outcome of a previous GRMHD BNS merger simulation. [ABSTRACT FROM AUTHOR]

The Red Nova ZTF SLRN-2020 is the third transient event with properties that are compatible with the merger of a planet with a main-sequence (or close to) star on a dynamical time-scale. While the two first transient events occurred in young stellar objects, ZTF SLRN-2020 occurred in an old system. None the less, I show that the three star–planet intermediate luminosity optical transients (ILOTs, also termed Red Novae) occupy the same area in the energy–time diagram of ILOTs. Based on models for ILOTs that are power by stellar binary interaction, I suggest that the planet in ZTF SLRN-2020 launched jets at about its escape speed before it was engulfed by the star. Interestingly, the escape speed from the planet is similar to the orbital speed of the planet. This leads to an outflow with a very low terminal velocity, much below the escape velocity from the star, and in concentration around ≈45° to the equatorial plane. As well, the planet might have lost back some of the accreted mass just before engulfment, forming an accretion disc around the star. This disc might have launched jets during the main outburst of the event. The jets form a bipolar expanding nebula. [ABSTRACT FROM AUTHOR]

Exceptionally bright gamma-ray burst (GRB) afterglows can reveal the angular structure of their jets. GRB jets appear to have a narrow core (of half-opening angle θc), beyond which their kinetic energy drops as a power-law with angle θ from the jet's symmetry axis, |$E_{\mathrm{ k},\rm iso}(\theta)\propto [1+(\theta /\theta _\mathrm{ c})^2]^{-a/2}$|⁠. The power-law index a reflects the amount of mixing between the shocked jet and confining medium, which depends on the jet's initial magnetization. Weakly magnetized jets undergo significant mixing, leading to shallow (a ≲ 2) angular profiles. We use the exquisite multiwaveband afterglow observations of GRB 221009A to constrain the jet angular structure using a dynamical model that accounts for both the forward and reverse shocks, for a power-law external density profile, n ext ∝  R − k . Both the forward shock emission, that dominates the optical and X-ray flux, and the reverse shock emission, that produces the radio afterglow, require a jet with a narrow core (θc ≈ 0.021) and a shallow angular structure (a ≈ 0.8) expanding into a stellar wind (k ≈ 2). Moreover, these data appear to favour a small fraction (ξe ≈ 10−2) of shock heated electrons forming a power-law energy distribution in both shocks. [ABSTRACT FROM AUTHOR]

Transitional millisecond pulsars are an emerging class of sources that link low-mass X-ray binaries to millisecond radio pulsars in binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray to optical pulsations are observed only during the high mode. The root cause of this puzzling behaviour remains elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar prototype, PSR J1023+0038, covering from the radio to X-rays. The campaign was carried out over two nights in June 2021 and involved 12 different telescopes and instruments, including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA, and FAST. By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with ALMA at the high-to-low mode switch. The pulsar is subsequently re-enshrouded, completing our picture of the mode switches. [ABSTRACT FROM AUTHOR]

In MeerKAT observations pointed at a Galactic X-ray binary located on the Galactic plane, we serendipitously discovered a radio nebula with cometary-like morphology. The feature, which we named 'the Mini Mouse' based on its similarity with the previously discovered 'Mouse' nebula, points back towards the previously unidentified candidate supernova remnant G45.24+0.18. We observed the location of the Mini Mouse with MeerKAT in two different observations, and we localized with arcsecond precision the 138-ms radio pulsar PSR J1914+1054g, recently discovered by the FAST telescope, to a position consistent with the head of the nebula. We confirm a dispersion measure of about 418 pc cm−3 corresponding to a distance between 7.8 and 8.8 kpc based on models of the electron distribution. Using our accurate localization and two period measurements spaced 90 d apart, we calculate a period derivative of (2.7 ± 0.3) × 10 −14 s s−1. We derive a characteristic age of approximately 82 kyr and a spin-down luminosity of 4 × 1035 erg s−1. For a pulsar age comparable with the characteristic age, we find that the projected velocity of the neutron star is between 320 and 360 km s−1 if it was born at the location of the supernova remnant. The size of the proposed remnant appears small if compared with the pulsar characteristic age; however, the relatively high density of the environment near the Galactic plane could explain a suppressed expansion rate and thus a smaller remnant. [ABSTRACT FROM AUTHOR]

Tracking the motions of transient jets launched by low-mass X-ray binaries (LMXBs) is critical for determining the moment of jet ejection, and identifying any corresponding signatures in the accretion flow. However, these jets are often highly variable and can travel across the resolution element of an image within a single observation, violating a fundamental assumption of aperture synthesis. We present a novel approach in which we directly fit a single time-dependent model to the full set of interferometer visibilities, where we explicitly parametrize the motion and flux density variability of the emission components, to minimize the number of free parameters in the fit, while leveraging information from the full observation. This technique allows us to detect and characterize faint, fast-moving sources, for which the standard time binning technique is inadequate. We validate our technique with synthetic observations, before applying it to three Very Long Baseline Array (VLBA) observations of the black hole candidate LMXB MAXI J1803−298 during its 2021 outburst. We measured the proper motion of a discrete jet component to be 1.37 ± 0.14 mas h−1, and thus we infer an ejection date of MJD |$59348.08_{-0.06}^{+0.05}$|⁠ , which occurs just after the peak of a radio flare observed by the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/Sub-Millimeter Array (ALMA), while MAXI J1803−298 was in the intermediate state. Further development of these new VLBI analysis techniques will lead to more precise measurements of jet ejection dates, which, combined with dense, simultaneous multiwavelength monitoring, will allow for clearer identification of jet ejection signatures in the accretion flow. [ABSTRACT FROM AUTHOR]

We examine the binding energies of massive stripped-envelope core collapse supernova (SECCSN) progenitors with the stellar evolution code mesa , and find that the jittering jets explosion mechanism is preferred for explosions where carbon–oxygen cores with masses of |${\gtrsim} 20 \, \mathrm{M}_\odot$| collapse to leave a neutron star (NS) remnant. We calculate the binding energy at core collapse under the assumption that the remnant is an NS. Namely, stellar gas above mass coordinate of |${\simeq} 1.5\text{{--}}2.5 \, \mathrm{M}_\odot$| is ejected in the explosion. We find that the typical binding energy of the ejecta of stripped-envelope (SE) progenitors with carbon–oxygen core masses of |$M_{\rm CO} \gtrsim 20 \, \mathrm{M}_\odot$| is |$E_{\rm bind} \gtrsim 2 \times 10^{51} {~\rm erg}$|⁠. We claim that jets are most likely to explode such cores as jet-driven explosion mechanisms can supply high energies to the explosion. We apply our results to SN 2020qlb, which is an SECCSN with a claimed core mass of |${\simeq} 30\!-\!50 \, \mathrm{M}_\odot$|⁠ , and conclude that the jittering jets explosion mechanism best accounts for such an explosion that leaves an NS. [ABSTRACT FROM AUTHOR]

We conducted one-dimensional stellar evolutionary numerical simulations to build blue supergiant stellar models with a very low-envelope mass and a super-Eddington luminosity of 107 L ⊙ that mimic the last phase of a common envelope evolution (CEE) where a neutron star (NS) accretes mass from the envelope and launches jets that power the system. Common envelope jets supernovae (CEJSNe) are CEE transient events where an NS spirals-in inside the envelope and then the core of a red supergiant (RSG) star accretes mass and launches jets that power the transient event. In case the NS (or black hole) does not enter the core of the RSG, the event is a CEJSN-impostor. We propose that in some cases a CEJSN-impostor event might end with such a phase of a blue supergiant lasting for several years to few tens of years. The radius of the blue supergiant is about tens to few hundreds' solar radii. We use a simple prescription to deposit the jets' energy into the envelope. We find that the expected accretion rate of envelope mass onto the NS at the end of the CEE allows the power of the jets to be as we assume, 107 L ⊙. Such a low-mass envelope might be the end of the RSG envelope or a rebuilt envelope from mass fallback. Our study of a blue supergiant at the termination of a CEJSN-impostor event adds to the rich variety of transients that CEJSNe and CEJSN-impostors might form. [ABSTRACT FROM AUTHOR]

Protostellar jets are one of the primary signposts of star formation. A handful of protostellar objects exhibit radio emission from ionized jets, of which a few display negative spectral indices, indicating the presence of synchrotron emission. In this study, we characterize the radio spectra of HH80-81 jet with the help of a numerical model that we have developed earlier, which takes into account both thermal free–free and non-thermal synchrotron emission mechanisms. For modeling the HH80-81 jet, we consider jet emission towards the central region close to the driving source along with two Herbig-Haro objects, HH80 and HH81. We have obtained the best-fit parameters for each of these sources by fitting the model to radio observational data corresponding to two frequency windows taken across two epochs. Considering an electron number density in the range of 10 3 – 10 5 cm - 3 , we obtained the thickness of the jet edges and fraction of relativistic electrons that contribute to non-thermal emission in the range of 0. 01 ∘ – 0. 1 ∘ and 10 - 7 – 10 - 4 , respectively. For the best-fit parameter sets, the model spectral indices lie in the range of − 0.15 to + 0.11 within the observed frequency windows. [ABSTRACT FROM AUTHOR]

The ejection mechanism of transient relativistic jets from black hole binaries is studied. Based on observations of the limit-cycle behaviors of the superluminal jet source GRS 1915+105, we infer that transient jet ejections could happen just after the slim disk emerging from the standard disk at some distance runs over the standard disk and reaches the vicinity of the central black hole. The standard disk releases about half of the gravitational energy in the course of the accretion, but the released radiative energy could be absorbed by the optically thick slim disk covering the standard disk in this situation. Then, since the inward motion of the slim disk is much faster than that of the standard disk, a quantity of energy released by an amount of gas in the standard disk is received by the much smaller amount of gas in the slim disk. As a result, the energy per mass received by the slim disk is expected to be greatly amplified and is estimated to become highly relativistic. Since the energy is much larger than the gravitational energy, the height of the slim disk could increase significantly. Hence, the innermost part of the slim disk from which almost all the angular momentum has been transferred outward could have a much larger height than the black hole size, so they could collide with one another around the central axis of the disk, turning to an outward flow along the axis normal to the disk plane. The flow in this direction can be approximated to be that through the de Laval nozzle and could become supersonic near the distance where the flow has the smallest cross-section. [ABSTRACT FROM AUTHOR]

Astrophysical jets are relativistic outflows that remain collimated for remarkably many orders of magnitude. Despite decades of research, the origin of cosmic rays (CRs) remains unclear, but jets launched by both supermassive black holes in the centre of galaxies and stellar-mass black holes harboured in X-ray binaries (BHXBs) are among the candidate sources for CR acceleration. When CRs accelerate in astrophysical jets, they initiate particle cascades that form γ-rays and neutrinos. In the so-called hadronic scenario, the population of accelerated CRs requires a significant amount of energy to properly explain the spectral constraints, similarly to a purely leptonic scenario. The amount of energy required often exceeds the Eddington limit or even the total energy available within the jets. The exact energy source for the accelerated protons is unclear, but due to energy conservation along the jets, it is believed to come from the jet itself via transfer of energy from the magnetic fields or kinetic energy from the outflow. To address this hadronic energy issue and to self-consistently evolve the energy flux along the flows, we explore a novel treatment for including hadronic content, in which instabilities along the jet/wind border play a critical role. We discuss the impact of the different jet compositions on the jet dynamics for a pair dominated and an electron-proton jet and, consequently, the emitted spectrum, accounting for both leptonic and hadronic processes. Finally, we discuss the implications of this mass-loading scenario to address the proton energy issue. [ABSTRACT FROM AUTHOR]

The detection of a fast radio burst (FRB), FRB 200428, coincident with an X-ray burst (XRB) from the Galactic magnetar soft gamma repeater (SGR) SGR J1935+2154 suggests that magnetars can produce FRBs. Many XRBs have been detected from the source, but very few were found to be associated with bursty radio emission. Meanwhile, a number of weaker radio bursts have been detected from the source, which could in principle be slow radio bursts (SRBs): FRBs detected at viewing angles outside the FRB jet cone. In this paper, we use these X-ray and radio observations to constrain the geometric and relativistic beaming factors of FRBs under two hypotheses. First, we assume that all SRBs should be associated with XRBs like FRB 200428. We use the FRB–SRB closure relations to identify two SRBs and derive that FRB beaming must be geometrically narrow, θ j ≲ 10−2 rad and follow θ j Γ ∼ 2. Second, we assume a less stringent constraint for SRBs by not requiring that they are associated with XRBs. We identify a total of seven SRBs, five of which have Gaussian-like spectra, and derive that FRB beaming factors again follow θ j Γ ∼ 2. [ABSTRACT FROM AUTHOR]

Many stripped envelope supernovae (SNe) present a signature of high-velocity material responsible for broad absorption lines in the observed spectrum. These include SNe that are associated with long gamma-ray bursts (LGRBs) and low-luminosity GRBs (ll GRBs), and SNe that are not associated with GRBs. Recently it was suggested that this high-velocity material originates from a cocoon that is driven by a relativistic jet. In LGRBs, this jet breaks out successfully from the stellar envelope, while in ll GRBs and SNe that are not associated with GRBs the jet is choked. Here we use numerical simulations to explore the velocity distribution of an outflow that is driven by a choked jet, and its dependence on the jet and progenitor properties. We find that in all cases where the jet is not choked too deep within the star, the outflow carries a roughly constant amount of energy per logarithmic scale of proper velocity over a wide range of velocities, which depends mostly on the cocoon volume at the time of its breakout. This is a universal property of jets driven outflows, which does not exist in outflows of spherically symmetric explosions or when the jets are choked very deep within the star. We therefore conclude that jets that are choked (not too deep) provide a natural explanation to the fast material seen in the early spectra of stripped envelope SNe that are not associated with LGRBs, and that properties of this material could reveal information on the otherwise hidden jets. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts (GRBs) are produced during the propagation of ultra-relativistic jets. It is challenging to study the jet close to the central source, due to the high opacity of the medium. In this paper, we present numerical simulations of relativistic jets propagating through a massive, stripped envelope star associated to long GRBs, breaking out of the star and accelerating into the circumstellar medium. We compute the gravitational wave (GW) signal resulting from the propagation of the jet through the star and the circumstellar medium. We show that key parameters of the jet propagation can be directly determined by the GW signal. The signal presents a first peak corresponding to the jet duration and a second peak which corresponds to the break-out time for an observer located close to the jet axis (which in turn depends on the stellar size), or to much larger times (corresponding to the end of the acceleration phase) for off-axis observers. We also show that the slope of the GW signal before and around the first peak tracks the jet luminosity history and the structure of the progenitor star. The amplitude of the GW signal is h + D ∼ hundreds to several thousands cm. Although this signal, for extragalactic sources, is outside the range of detectability of current GW detectors, it can be detected by future instruments as BBO, DECIGO, and ALIA. Our results illustrate that future detections of GW associated to GRB jets may represent a revolution in our understanding of this phenomenon. [ABSTRACT FROM AUTHOR]

After the detection of GRB 170817A, the first unambiguous off-axis gamma-ray burst (GRB), several studies tried to understand the structure of GRB jets. The initial jet structure (directly produced by the central engine) can be partially preserved, or can be completely modified by the interaction with the environment. In this study, we perform three-dimensional, special relativistic hydrodynamics simulations of long GRB jets evolving through a massive progenitor star. Different jet scenarios were considered: Top-hat, Gaussian jets dominated by pressure or by kinetic energy, as well as a model of a supernova (SN) plus a jet both propagating through the progenitor. We found that, while propagating inside the progenitor star, jets with different initial structures are nearly indistinguishable. Kinetic-dominated jets are faster and more collimated than pressure-dominated jets. The dynamics of jets inside the progenitor star strongly depends on the presence of an associated SN, which can substantially decelerate the jet propagation. We show that the initial structure of GRB jets is preserved, or not, mainly depending on the jet collimation. The initial structure is preserved in uncollimated jets, i.e. jets which move through low-density environments. Meanwhile, jets which move through dense environments are shaped by the interaction with the medium and remain collimated. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the protostellar outflow activity in the massive star-forming region NGC 3324, as revealed by new Early Release Observations (EROs) from the James Webb Space Telescope (JWST). Emission from numerous outflows is revealed in narrow-band images of hydrogen Paschen α (Paα) and molecular hydrogen. In particular, we report the discovery of 24 previously unknown outflows based on their H2 emission. We find three candidate driving sources for these H2 flows in published catalogues of young stellar objects (YSOs), and we identify 15 infrared point sources in the new JWST images as potential driving protostars. We also identify several Herbig–Haro (HH) objects in Paα images from JWST ; most are confirmed as jets based on their proper motions measured in a comparison with previous Hubble Space Telescope (HST) Hα images. This confirmed all previous HST -identified HH jets and candidate jets, and revealed seven new HH objects. The unprecedented capabilities of JWST allow the direct comparison of atomic and molecular outflow components at comparable angular resolution. Future observations will allow quantitative analysis of the excitation, mass-loss rates, and velocities of these new flows. As a relatively modest region of massive star formation (larger than Orion but smaller than starburst clusters), NGC 3324 offers a preview of what star formation studies with JWST may provide. [ABSTRACT FROM AUTHOR]

We present a comprehensive analytic model of relativistic jet propagation in expanding homologous media (ejecta). This model covers the entire jet evolution as well as a range of configurations that are relevant to binary neutron star mergers. These include low- and high-luminosity jets, unmagnetized and mildly magnetized jets, time-dependent luminosity jets, and Newtonian and relativistic head velocities. We also extend the existing solution of jets in a static medium to power-law density media with index α < 5. Our model provides simple analytic formulae (calibrated by 3D simulations) for the jet head propagation and breakout times. We find that the system evolution has two main regimes: strong and weak jets. Strong jets start their propagation immediately within the ejecta. Weak jets are unable to penetrate the ejecta at first, and breach it only after the ejecta expands significantly, thus their evolution is independent of the delay between the onset of the ejecta and the jet launching. After enough time, both strong and weak jets approach a common asymptotic phase. We find that a necessary, but insufficient, criterion for the breakout of unmagnetized (weakly magnetized) jets is |$E_{j,{\rm iso,tot}} \gtrsim 3[0.4]\, {E_{ej,{\rm tot}}}\left({\, {\theta _{j,0}}}/{0.1{\rm ~rad}}\right)^2$|⁠ , where E j , iso, tot is the jet total isotropic equivalent energy, |$\, {\theta _{j,0}}$| is its opening angle, and |$\, {E_{ej,{\rm tot}}}$| is the ejecta energy. Applying our model to short gamma-ray bursts, we find that there is most likely a large diversity of ejecta mass, where mass ≲10−3 M⊙ (at least along the poles) is common. [ABSTRACT FROM AUTHOR]

We study ejection mechanisms for two kinds of steady jets: one observed from black hole binaries in the low/hard state and the other from SS 433. The specific energy of the ejected gas is required to be positive for the jets to get to infinity, while that of the accreted gas is naively considered to be negative at the outermost boundary of the accretion flow. To reconcile the opposite sign of the specific energies, we propose a situation where two layers exist in the accretion flow and one layer receives energy from the other sufficiently for the specific energy to be positive. For the steady jets in the low/hard state, the accretion ring at the outermost end of the accretion flow is considered to yield two-layer flow in which a geometrically thick advection-dominated accretion flow (ADAF) sandwiches a geometrically thin accretion disk and the thin disk is supposed to change to another ADAF on the inner side. The energy transfer is expected to occur through turbulent mixing between the two layers and the upper layer is discussed as having a positive specific energy large enough for the terminal velocity to be ∼0.1  c. For the steady jets from SS 433, it is argued that a slim disk separates into two stratified layers due to the photon diffusion in the direction perpendicular to the equatorial plane under the advection-dominated situation. In this case, the specific energy of the upper layer is expected to be positive such that the terminal velocity exceeds 0.2 c. The jet ejection process near the black hole is investigated commonly to both the two-layer cases and predicts that the jet opening angle becomes as small as 2°. [ABSTRACT FROM AUTHOR]