A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled ...dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.
ABSTRACT We present optical and ultraviolet (UV) photometry and spectra of the very nearby and highly reddened supernova (SN) 2014J in M82 obtained with the Swift Ultra-Violet/Optical Telescope ...(UVOT). Comparison of the UVOT grism spectra of SN 2014J with Hubble Space Telescope observations of SN2011fe or UVOT grism spectra of SN 2012fr are consistent with an extinction law with a low value of RV ∼1.4. The high reddening causes the detected photon distribution in the broadband UV filters to have a much longer effective wavelength than for an unreddened SN. The light curve evolution is consistent with this shift and does not show a flattening due to photons being scattered back into the line of sight (LOS). The light curve shapes and color evolution are inconsistent with a contribution scattered into the LOS by circumstellar dust. We conclude that most or all of the high reddening must come from interstellar dust. We show that even for a single dust composition, there is not a unique reddening law caused by circumstellar scattering. Rather, when considering scattering from a time-variable source, we confirm earlier studies that the reddening law is a function of the dust geometry, column density, and epoch. We also show how an assumed geometry of dust as a foreground sheet in mixed stellar/dust systems will lead to a higher inferred RV. Rather than assuming the dust around SNe is peculiar, SNe may be useful probes of the interstellar reddening laws in other galaxies.
Abstract
AMEGO-X, the All-sky Medium Energy Gamma-ray Observatory eXplorer, is a proposed instrument designed to bridge the so-called “MeV gap” by surveying the sky with unprecedented sensitivity ...from ∼100 keV to about 1 GeV. This energy band is of key importance for multimessenger and multiwavelength studies but it is nevertheless currently underexplored. AMEGO-X addresses this situation by proposing a design capable of detecting and imaging gamma rays via both Compton interactions and pair production processes. However, some of the objects that AMEGO-X will study, such as gamma-ray bursts and magnetars, extend to energies below ∼100 keV where the dominant interaction becomes photoelectric absorption. These events deposit their energy in a single pixel of the detector. In this work we show how the ∼3500 cm
2
effective area of the AMEGO-X tracker to events between ∼25 and ∼100 keV will be utilized to significantly improve its sensitivity and expand the energy range for transient phenomena. Although imaging is not possible for single-site events, we show how we will localize a transient source in the sky using their aggregate signal to within a few degrees. This technique will more than double the number of cosmological gamma-ray bursts seen by AMEGO-X, allow us to detect and resolve the pulsating tails of extragalactic magnetar giant flares, and increase the number of detected less-energetic magnetar bursts—some possibly associated with fast radio bursts. Overall, single-site events will increase the sensitive energy range, expand the science program, and promptly alert the community of fainter transient events.
A multi-messenger story Hartmann, Dieter H.
Nature,
07/2011, Volume:
475, Issue:
7356
Journal Article
Peer reviewed
Open access
GRBs have been proposed4,5 as a powerful accelerator of CRs. Because CRs are deflected by magnetic fields, a direct connection between CRs and GRBs is almost impossible to establish.
The particle-in-cell (PIC) method was developed to investigate microscopic phenomena, and with the advances in computing power, newly developed codes have been used for several fields, such as ...astrophysical, magnetospheric, and solar plasmas. PIC applications have grown extensively, with large computing powers available on supercomputers such as Pleiades and Blue Waters in the US. For astrophysical plasma research, PIC methods have been utilized for several topics, such as reconnection, pulsar dynamics, non-relativistic shocks, relativistic shocks, and relativistic jets. PIC simulations of relativistic jets have been reviewed with emphasis placed on the physics involved in the simulations. This review summarizes PIC simulations, starting with the Weibel instability in slab models of jets, and then focuses on global jet evolution in helical magnetic field geometry. In particular, we address kinetic Kelvin-Helmholtz instabilities and mushroom instabilities.
We constrain energy spectra of supernova neutrinos through the avoidance of an overproduction of the 11B abundance during Galactic chemical evolution. In supernova nucleosynthesis calculations with a ...parametrized neutrino spectrum as a function of temperature of nu(mu,tau) and nu(mu,tau) and total neutrino energy, we find a strong neutrino temperature dependence of the 11B yield. When the yield is combined with observed abundances, the acceptable range of the nu(mu,tau) and nu(mu,tau) temperature is found to be 4.8 to 6.6 MeV. Nonzero neutrino chemical potentials would reduce this temperature range by about 10% for a degeneracy parameter eta(nu) = mu(nu)/kT(nu) smaller than 3.
MAXI J1621-501 is the first Swift/XRT Deep Galactic Plane Survey transient that was followed up with a multitude of space missions (NuSTAR, Swift, Chandra, NICER, INTEGRAL, and MAXI) and ground-based ...observatories (Gemini, IRSF, and ATCA). The source was discovered with MAXI on 2017 October 19 as a new, unidentified transient. Further observations with NuSTAR revealed two Type I X-ray bursts, identifying MAXI J1621-501 as a low mass x-ray binary with a neutron star primary. Overall, 24 Type I bursts were detected from the source during a 15 month period. At energies below 10 keV, the source spectrum was best fit with three components: an absorbed blackbody with kT = 2.3 keV, a cutoff power law with index Γ = 0.7, and an emission line centered on 6.3 keV. Timing analysis of the X-ray persistent emission and burst data has not revealed coherent pulsations from the source or an orbital period. We identified, however, a super-orbital period ∼78 days in the source X-ray light curve. This period agrees very well with the theoretically predicted radiative precession period of ∼82 days. Thus, MAXI J1621-501 joins a small group of sources characterized with super-orbital periods.
PDF
