ABSTRACT
Superluminous supernovae (SLSNe) and long gamma-ray bursts (LGRBs) have been proposed as progenitors of repeating fast radio bursts (FRBs). In this scenario, bursts originate from the ...interaction between a young magnetar and its surrounding supernova remnant (SNR). Such a model could explain the repeating, apparently non-Poissonian nature of FRB121102, which appears to display quiescent and active phases. This bursting behaviour is better explained with a Weibull distribution, which includes parametrization for clustering. We observed 10 SLSNe/LGRBs for 63 h, looking for repeating FRBs with the Effelsberg 100-m radio telescope, but have not detected any bursts. We scale the burst rate of FRB121102 to an FRB121102-like source inhabiting each of our observed targets, and compare this rate to our upper burst rate limit on a source by source basis. By adopting a fiducial beaming fraction of 0.6, we obtain 99.99 per cent and 83.4 per cent probabilities that at least one, and at least half of our observed sources are beamed towards us, respectively. One of our SLSN targets, PTF10hgi, is coincident with a persistent radio source, making it a possible analogue to FRB121102. We performed further observations on this source using the Effelsberg 100-m and Parkes 64-m radio telescopes. Assuming that PTF10hgi contains an FRB121102-like source, the probabilities of not detecting any bursts from a Weibull distribution during our observations are 14 per cent and 16 per cent for Effelsberg and Parkes, respectively. We conclude by showing that a survey of many short observations increases burst detection probability for a source with Weibull distributed bursting activity.
Abstract The reciprocity approach is a powerful method to determine the expected signal power of axion haloscopes in a model-independent way. Especially for open and broadband setups like the MADMAX ...dielectric haloscope the sensitivity to the axion field is difficult to calibrate since they do not allow discrete eigenmode analysis and are optically too large to fully simulate. The central idea of the reciprocity approach is to measure a reflection-induced test field in the setup instead of trying to simulate the axion-induced field. In this article, the reciprocity approach is used to determine the expected signal power of a dish antenna and a minimal dielectric haloscope directly from measurements. The results match expectations from simulation but also include important systematic effects that are too difficult to simulate. In particular, the effect of antenna standing waves and higher order mode perturbations can be quantified for the first time in a dielectric haloscope.
We present 3D calculations for dielectric haloscopes such as the currently envisioned MADMAX experiment. For ideal systems with perfectly flat, parallel and isotropic dielectric disks of finite ...diameter, we find that a geometrical form factor reduces the emitted power by up to 30 % compared to earlier 1D calculations. We derive the emitted beam shape, which is important for antenna design. We show that realistic dark matter axion velocities of 10-3 c and inhomogeneities of the external magnetic field at the scale of 10 % have negligible impact on the sensitivity of MADMAX. We investigate design requirements for which the emitted power changes by less than 20 % for a benchmark boost factor with a bandwidth of 50 MHz at 22 GHz, corresponding to an axion mass of 90 μ eV. We find that the maximum allowed disk tilt is 100 μ m divided by the disk diameter, the required disk planarity is 20 μ m (min-to-max) or better, and the maximum allowed surface roughness is 100 μ m (min-to-max). We show how using tiled dielectric disks glued together from multiple smaller patches can affect the beam shape and antenna coupling.
Abstract The axion emerges in extensions of the Standard Model that explain the absence of CP violation in the strong interactions. Simultaneously, it can provide naturally the cold dark matter in ...our universe. Several searches for axions and axion-like particles (ALPs) have constrained the corresponding parameter space over the last decades but no unambiguous hints of their existence have been found. The axion mass range below 1 meV remains highly attractive and a well motivated region for dark matter axions. In this White Paper we present a description of a new experiment based on the concept of a dielectric haloscope for the direct search of dark matter axions in the mass range of 40 to 400 $$\upmu \hbox {eV}$$ μeV . This MAgnetized Disk and Mirror Axion eXperiment (MADMAX) will consist of several parallel dielectric disks, which are placed in a strong magnetic field and with adjustable separations. This setting is expected to allow for an observable emission of axion induced electromagnetic waves at a frequency between 10 to 100 GHz corresponding to the axion mass.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Context. Sites of massive star formation have complex internal structures. Local heating by young stars and kinematic processes, such as outflows and stellar winds, generate large temperature and ...velocity gradients. Complex cloud structures lead to intricate emission line shapes. CO lines from high mass star forming regions are rarely Gaussian and show often multiple peaks. Furthermore, the line shapes vary significantly with the quantum number Jup, due to the different probed physical conditions and opacities. Aims. The goal of this paper is to show that the complex line shapes of 12CO and 13CO in NGC 2024 showing multiple emission and absorption features, which vary with rotational quantum number J can be explained consistently with a model, whose temperature and velocity structure are based on the well-established scenario of a PDR and the “Blister model”. Methods. We present velocity-resolved spectra of seven 12CO and 13CO lines ranging from $J_{\rm up}=3$ to $J _{\rm up}=13$. We combined these data with 12CO high-frequency data from the ISO satellite and analyzed the full set of CO lines using an escape probability code and a one-dimensional full radiative transfer code. Results. We find that the bulk of the molecular cloud associated with NGC 2024 consists of warm (75 K) and dense ($9\times 10^5$ cm-3) gas. An additional hot (~300 K) component, located at the interface of the HII region and the molecular cloud, is needed to explain the emission of the high-J CO lines. Deep absorption notches indicate that very cold material (~20 K) exists in front of the warm material, too. Conclusions. A temperature and column density structure consistent with those predicted by PDR models, combined with the velocity structure of a “Blister model”, appropriately describes the observed emission line profiles of this massive star forming region. This case study of NGC 2024 shows that, with physical insights into these complex regions and careful modeling, multi-line observations of 12CO and 13CO can be used to derive detailed physical conditions in massive star forming regions.
The axion emerges in extensions of the Standard Model that explain the absence of CP violation in the strong interactions. Simultaneously, it can provide naturally the cold dark matter in our ...universe. Several searches for axions and axion-like particles (ALPs) have constrained the corresponding parameter space over the last decades but no unambiguous hints of their existence have been found. The axion mass range below 1 meV remains highly attractive and a well motivated region for dark matter axions. In this White Paper we present a description of a new experiment based on the concept of a dielectric haloscope for the direct search of dark matter axions in the mass range of 40 to 400
μ
eV
. This MAgnetized Disk and Mirror Axion eXperiment (MADMAX) will consist of several parallel dielectric disks, which are placed in a strong magnetic field and with adjustable separations. This setting is expected to allow for an observable emission of axion induced electromagnetic waves at a frequency between 10 to 100 GHz corresponding to the axion mass.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The axion emerges in extensions of the Standard Model that explain the absence of CP violation in the strong interactions. Simultaneously, it can provide naturally the cold dark matter in our ...universe. Several searches for axions and axion-like particles (ALPs) have constrained the corresponding parameter space over the last decades but no unambiguous hints of their existence have been found. The axion mass range below 1 meV remains highly attractive and a well motivated region for dark matter axions. In this White Paper we present a description of a new experiment based on the concept of a dielectric haloscope for the direct search of dark matter axions in the mass range of 40 to 400 Formula omitted. This MAgnetized Disk and Mirror Axion eXperiment (MADMAX) will consist of several parallel dielectric disks, which are placed in a strong magnetic field and with adjustable separations. This setting is expected to allow for an observable emission of axion induced electromagnetic waves at a frequency between 10 to 100 GHz corresponding to the axion mass.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aims. We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT ...of the Arizona Radio Observatory (ARO). Methods. We installed VLBI equipment and measured the APEX station position to 1 cm accuracy (1σ). We then observed 3C 279 on 2012 May 7 in a 5 h 230 GHz VLBI track with baseline lengths of 2800 Mλ to 7200 Mλ and a finest fringe spacing of 28.6 μas. Results. Fringes were detected on all baselines with signal-to-noise ratios of 12 to 55 in 420 s. The correlated flux density on the longest baseline was ~0.3 Jy beam-1, out of a total flux density of 19.8 Jy. Visibility data suggest an emission region ≲ 38 μas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 1010 K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ~ 38 μas. Conclusions. With APEX the angular resolution of 230 GHz VLBI improves to 28.6 μas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40 μas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed.
Context.The THz atmospheric “windows”, centered at roughly 1.3 and 1.5 THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N II line at 205 μm, and ...the ground transition of para-H2D+. The CO lines are tracers of hot (several 100 K), dense gas; N II is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20 K), dense gas. Aims.As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. Methods.CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. Results.The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical $T_{\rm rec}=1600$ K and spectral Allan variance times of ~30 s. CONDOR's “first light” observations of CO 13-12 emission from the hot core Orion FIR 4 (= OMC1 South) revealed a narrow line with $T_{\rm MB}\approx 210$ K and $\Delta V\approx 5.4$ km s-1. A search for N II emission from the ionization front of the Orion Bar resulted in a non-detection. Conclusions.The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.
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