6 research outputs found
State-of-the-Art Collapsar Jet Simulations Imply Undetectable Subphotospheric Neutrinos
Mounting evidence suggests that the launching of collapsar jets is
magnetically driven. Recent general relativistic magneto-hydrodynamic
simulations of collapsars reveal that the jet is continuously loaded with
baryons, owing to strong mixing with the cocoon. This results in a high
photosphere at cm. Consequently, collisionless internal
shocks below the photosphere are disfavored, and the neutrino production in the
deepest jet regions is prevented, in contrast to what has been naively assumed
in the literature. We find that subphotospheric neutrino production could only
take place in the presence of collisionless sub-shocks or magnetic
reconnection. Efficient particle acceleration is not possible in the cocoon, at
the cocoon-counter cocoon shock interface, or at the shock driven by the cocoon
in the event of a jet halted in an extended envelope. These subphotospheric
neutrinos have energy GeV for initial jet magnetizations
-. More than one neutrino and antineutrino event is expected
to be observed in Hyper-Kamiokande and IceCube DeepCore for sources located at
only; considering the collapsar rate, this
implies that the detection chances are poor. Because of their energy, these
neutrinos do not contribute to the diffuse flux detected by the IceCube
Neutrino Observatory. Our findings have implications on neutrino searches
ranging from gamma-ray bursts to luminous fast blue optical transients.Comment: 28 pages, including 16 figures and 2 appendice
Probing gamma-ray bursts observed at very high energies through their afterglow
A growing number of gamma-ray burst (GRB) afterglows is observed at very-high
energies (VHE, GeV). Yet, our understanding of the mechanism
powering the VHE emission remains baffling. We make use of multi-wavelength
observations of the afterglow of GRB 180720B, GRB 190114C, and GRB 221009A to
investigate whether the bursts exhibiting VHE emission share common features,
assuming the standard afterglow model. By requiring that the blastwave should
be transparent to - pair production at the time of observation
of the VHE photons and relying on typical prompt emission efficiencies and data
in the radio, optical and X-ray bands, we infer for those bursts that the
initial energy of the blastwave is erg and the circumburst density is cm for a constant circumburst profile [or cm for a wind scenario]. Our findings
thus suggest that these VHE bursts might be hosted in low-density environments.
While these trends are based on a small number of bursts, the Cherenkov
Telescope Array has the potential to provide crucial insight in this context by
detecting a larger sample of VHE GRBs. In addition, due to the very poor
statistics, the non-observation of high-energy neutrinos cannot constrain the
properties of these bursts efficiently, unless additional VHE GRBs should be
detected at distances closer than Mpc when IceCube-Gen2 radio will be
operational.Comment: 13 pages, including 3 figures and 3 appendice
Transients stemming from collapsing massive stars: The missing pieces to advance joint observations of photons and high-energy neutrinos
Collapsing massive stars lead to a broad range of astrophysical transients,
whose multi-wavelength emission is powered by a variety of processes including
radioactive decay, activity of the central engine, and interaction of the
outflows with a dense circumstellar medium. These transients are also candidate
factories of neutrinos with energy up to hundreds of PeV. We review the energy
released by such astrophysical objects across the electromagnetic wavebands as
well as neutrinos, in order to outline a strategy to optimize multi-messenger
follow-up programs. We find that, while a significant fraction of the explosion
energy can be emitted in the infrared-optical-ultraviolet (UVOIR) band, the
optical signal alone is not optimal for neutrino searches. Rather, the neutrino
emission is strongly correlated with the one in the radio band, if a dense
circumstellar medium surrounds the transient, and with X-rays tracking the
activity of the central engine. Joint observations of transients in radio,
X-rays, and neutrinos will crucially complement those in the UVOIR band,
breaking degeneracies in the transient parameter space. Our findings call for
heightened surveys in the radio and X-ray bands to warrant multi-messenger
detections.Comment: 26 pages, including 7 figures and 2 appendice
Production of axion-like particles from photon conversions in large-scale solar magnetic fields
The Sun is a well-studied astrophysical source of axion-like particles
(ALPs), produced mainly through the Primakoff process. Moreover, in the Sun
there exist large-scale magnetic fields that catalyze an additional ALP
production via a coherent conversion of thermal photons. We study this
contribution to the solar ALP emissivity, typically neglected in previous
investigations. Furthermore, we discuss additional bounds on the ALP-photon
coupling from energy-loss arguments, and the detection perspectives of this new
ALP flux at future helioscope and dark matter experiments.Comment: v2: 15 pages, 7 pdf figures. Figures improved, typos removed. Matches
the version published on PR
Multi-messenger detection prospects of gamma-ray burst afterglows with optical jumps
Some afterglow light curves of gamma-ray bursts (GRBs) exhibit very complex
temporal and spectral features, such as a sudden intensity jump about one hour
after the prompt emission in the optical band. We assume that this feature is
due to the late collision of two relativistic shells and investigate the
corresponding high-energy neutrino emission within a multi-messenger framework,
while contrasting our findings with the ones from the classic afterglow model.
For a constant density circumburst medium, the total number of emitted
neutrinos can increase by about an order of magnitude when an optical jump
occurs with respect to the self-similar afterglow scenario. By exploring the
detection prospects with the IceCube Neutrino Observatory and future radio
arrays such as IceCube-Gen2 radio, RNO-G and GRAND200k, as well as the POEMMA
spacecraft, we conclude that the detection of neutrinos with IceCube-Gen2 radio
could enable us to constrain the fraction of GRB afterglows with a jump as well
as the properties of the circumburst medium. We also investigate the neutrino
signal expected for the afterglows of GRB 100621A and a GRB 130427A-like burst
with an optical jump. The detection of neutrinos from GRB afterglows could be
crucial to explore the yet-to-be unveiled mechanism powering the optical jumps.Comment: 44 pages, including 13 figures and 3 appendices. Discussion expanded,
conclusions unchanged. Matches version accepted for publication in JCA
Neutrino Emission from Luminous Fast Blue Optical Transients
Mounting evidence suggests that Luminous Fast Blue Optical Transients
(LFBOTs) are powered by a compact object, launching an asymmetric and fast
outflow responsible for the radiation observed in the ultraviolet, optical,
infrared, radio, and X-ray bands. Proposed scenarios aiming to explain the
electromagnetic emission include an inflated cocoon, surrounding a jet choked
in the extended stellar envelope. In alternative, the observed radiation may
arise from the disk formed by the delayed merger of a black hole with a
Wolf-Rayet star. We explore the neutrino production in these scenarios, i.e.
internal shocks in a choked jet and interaction between the outflow and the
circumstellar medium (CSM). If observed on-axis, the choked jet provides the
dominant contribution to the neutrino fluence. Intriguingly, the IceCube upper
limit on the neutrino emission inferred from the closest LFBOT, AT2018cow,
excludes a region of the parameter space otherwise allowed by electromagnetic
observations. After correcting for the Eddington bias on the observation of
cosmic neutrinos, we conclude that the emission from an on-axis choked jet and
CSM interaction is compatible with the detection of two track-like neutrino
events observed by the IceCube Neutrino Observatory in coincidence with
AT2018cow, and otherwise considered to be of atmospheric origin. While the
neutrino emission from LFBOTs does not constitute the bulk of the diffuse
background of neutrinos observed by IceCube, detection prospects of nearby
LFBOTs with IceCube and the upcoming IceCube-Gen2 are encouraging. Follow-up
neutrino searches will be crucial for unravelling the mechanism powering this
emergent transient class.Comment: 23 pages, including 9 figures and 1 appendix. Minor changes, matches
version accepted for publication in Ap