المؤلفون: Paraschos, G. F., Wielgus, M., Benke, P., Mpisketzis, V., Rösch, F., Dasyra, K., Ros, E., Kadler, M., Ojha, R., Edwards, P. G., Hyland, L., Quick, J. F. H., Weston, S.

المصدر: A&A 687, L6 (2024)

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena

الوصف: Radio galaxies harbouring jetted active galactic nuclei are a frequent target of very-long-baseline interferometry (VLBI) because they play an essential role in exploring how jets form and propagate. Hence, only few have not been detected with VLBI yet; Fornax A is one of the most famous examples. Here we present the first detection of the compact core region of Fornax A with VLBI. At 8.4 GHz the faint core is consistent with an unresolved point source. We constrained its flux density to be $S_0 = 47.5-62.3\,\textrm{mJy}$ and its diameter to be $D^\textrm{min}_0 \leq 70\,\mu\textrm{as}$. The high values of the measured brightness temperature ($T_\textrm{B} \gtrsim 10^{11}\,\textrm{K}$) imply that the observed radiation is of non-thermal origin, likely associated with the synchrotron emission from the active galactic nucleus. We also investigated the possibility of a second radio source being present within the field of view. Adding a second Gaussian component to the geometrical model-fit does not significantly improve the quality of the fit and we, therefore, conclude that our detection corresponds to the compact core of Fornax A. Analysis of the non-trivial closure phases provides evidence for the detection of more extended flux density, on the angular scale of $\sim4000\,\mu\textrm{as}$. Finally, the fractional circular polarisation of the core is consistent with zero, with a conservative upper limit being $m_\textrm{circ} \leq 4\%$.
Comment: 4 pages, 2 figures, accepted for publication in A&A

الوصول الحر: http://arxiv.org/abs/2406.02660Test

المؤلفون: Zuo, Wenwen, Guo, Hengxiao, Sun, Jingbo, Yuan, Qi, Lira, Paulina, Gu, Minfeng, Edwards, Philip G., Gupta, Alok C., Kishore, Shubham, Stevens, Jamie, An, Tao, Cai, Zhen-Yi, Feng, Haicheng, Ho, Luis C., Ilić, Dragana, Kovačević, Andjelka B., Li, ShaSha, Mezcua, Mar, Popović, Luka Č., Sun, Mouyuan, Tripathi, Tushar, U., Vivian, Vince, Oliver, Wang, Jianguo, Wang, Junxian, Wang, Shu, Wu, Xuebing, Zheng, Zhenya

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: To investigate the short-term variability and determine the size of the optical continuum emitting size of intermediate-mass black holes (IMBHs), we carried out high-cadence, multi-band photometric monitoring of a Seyfert 1 galaxy J0249-0815 across two nights, together with a one-night single-band preliminary test. The presence of the broad Ha component in our target was confirmed by recent Palomar/P200 spectroscopic observations, 23 years after Sloan Digital Sky Survey, ruling out the supernovae origin of the broad Ha line. The photometric experiment was primarily conducted utilizing four-channel imagers MuSCAT 3 & 4 mounted on 2-meter telescopes within the Las Cumbres Observatory Global Telescope Network. Despite the expectation of variability, we observed no significant variation (<1.4%) on timescales of 6-10 hours. This non-detection is likely due to substantial host galaxy light diluting the subtle AGN variability. Dual-band preliminary tests and tailored simulations may enhance the possibility of detecting variability and lag in future IMBH reverberation campaigns.
Comment: 14 pages, 6 figures, submitted to ApJ, comments welcome

الوصول الحر: http://arxiv.org/abs/2405.11750Test

المؤلفون: Eppel, F., Kadler, M., Heßdörfer, J., Benke, P., Debbrecht, L., Eich, J., Gokus, A., Hämmerich, S., Kirchner, D., Paraschos, G. F., Rösch, F., Schulga, W., Sinapius, J., Weber, P., Bach, U., Dorner, D., Edwards, P. G., Giroletti, M., Kraus, A., Hervet, O., Koyama, S., Krichbaum, T. P., Mannheim, K., Ros, E., Zacharias, M., Zensus, J. A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Aims. We introduce the TELAMON program which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, specifically TeV blazars and candidate neutrino-associated AGN. Here, we present and characterize our main sample of TeV-detected blazars. Methods. We analyze the data sample from the first ~2.5 years of observations between August 2020 and February 2023 in the range from 14 GHz to 45 GHz. During this pilot phase, we have observed all 59 TeV-detected blazars in the Northern Hemisphere (i.e., Dec. >0{\deg}) known at the time of observation. We discuss the basic data reduction and calibration procedures used for all TELAMON data and introduce a sub-band averaging method used to calculate average light curves for the sources in our sample. Results. The TeV-selected sources in our sample exhibit a median flux density of 0.12 Jy at 20 mm, 0.20 Jy at 14 mm and 0.60 Jy at 7 mm. The spectrum for most of the sources is consistent with a flat radio spectrum and we find a median spectral index ($S(\nu)\propto\nu^\alpha$) of $\alpha=-0.11$. Our results on flux density and spectral index are consistent with previous studies of TeV-selected blazars. Compared to the GeV-selected F-GAMMA sample, TELAMON sources are significantly fainter in the radio band. This is consistent with the double-humped spectrum of blazars being shifted towards higher frequencies for TeV-emitters (in particular for high-synchrotron peaked BL Lac type objects), which results in a lower radio flux density. The spectral index distribution of our TeV-selected blazar sample is not significantly different from the GeV-selected F-GAMMA sample. Moreover, we present a strategy to track the light curve evolution of sources in our sample for future variability and correlation analysis.
Comment: 16 pages, 11 figures, 4 tables, accepted for publication in A&A

الوصول الحر: http://arxiv.org/abs/2401.06296Test

المؤلفون: Briceño, Raúl A., Edwards, Robert G., Eaton, Miller, González-Arciniegas, Carlos, Pfister, Olivier, Siopsis, George

مصطلحات موضوعية: Quantum Physics, High Energy Physics - Lattice, High Energy Physics - Theory

الوصف: In recent years, applications of quantum simulation have been developed to study properties of strongly interacting theories. This has been driven by two factors: on the one hand, needs from theorists to have access to physical observables that are prohibitively difficult to study using classical computing; on the other hand, quantum hardware becoming increasingly reliable and scalable to larger systems. In this work, we discuss the feasibility of using quantum optical simulation for studying scattering observables that are presently inaccessible via lattice QCD and are at the core of the experimental program at Jefferson Lab, the future Electron-Ion Collider, and other accelerator facilities. We show that recent progress in measurement-based photonic quantum computing can be leveraged to provide deterministic generation of required exotic gates and implementation in a single photonic quantum processor.
Comment: 26 pages, 7 figures

الوصول الحر: http://arxiv.org/abs/2312.12613Test

المؤلفون: Timmermann, Viviane, Wall, Samuel T., Sundnes, Joakim, Lawen, Tarek, Baumeister, Peter A., Quinn, T. Alexander, McCulloch, Andrew D., Edwards, Andrew G.

مصطلحات موضوعية: Physics - Biological Physics

الوصف: Heterogeneous mechanical dyskinesis during acute myocardial ischaemia is thought to contribute to arrhythmogenic alterations to cardiac electrophysiology. Various forms of mechano-electric coupling (MEC) mechanisms have been suggested to contribute to these changes, with two primary mechanisms being: (1) myofilament-dependent calcium release events, and (2) the activation of stretch-activated currents (SACs). In this computational investigation, we assessed the collective impact of these processes on mechanically-induced alternans that create an arrhythmogenic substrate during acute ischaemia. To appraise the potential involvement of MEC in ischaemia-induced arrhythmias, we developed a coupled model of ventricular myocyte electrophysiology and contraction including SACs and stretch-dependent calcium buffering and release. The model, reflecting observed electrophysiological changes during ischaemia, was exposed to a series of stretch protocols that replicated both physiological and pathological mechanical conditions. Pathologically realistic myofiber stretch variations revealed calcium sensitivity changes dependent on myofilament, leading to alterations in cytosolic calcium concentrations. Under calcium overload conditions, these changes resulted in electrical alternans. The study implies that strain impacts cellular electrophysiology through myofilament calcium release and SAC opening in ventricular mechano-electrical models, parameterised to available data. This supports experimental evidence suggesting that both calcium-driven instability via MEC and SAC-induced effects contribute to electrical alternans in acute ischaemia.
Comment: 20 pages; 8 figures; original paper

الوصول الحر: http://arxiv.org/abs/2312.06535Test

المؤلفون: Lazarević, Sanja, Filipović, Miroslav D., Dai, Shi, Kothes, Roland, Ahmad, Adeel, Alsaberi, Rami Z. E., Balzan, Joel C. F., Barnes, Luke A., Cotton, William D., Edwards, Philip G., Gordon, Yjan A., Haberl, Frank, Hopkins, Andrew M., Koribalski, Bärbel S., Leahy, Denis, Maitra, Chandreyee, Mićić, Marko, Rowell, Gavin, Sasaki, Manami, Tothill, Nicholas F. H., Umana, Grazia, Velović, Velibor

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics

الوصف: We report the discovery of a bow-shock pulsar wind nebula (PWN), named Potoroo, and the detection of a young pulsar J1638-4713 that powers the nebula. We present a radio continuum study of the PWN based on 20-cm observations obtained from the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. PSR J1638-4713 was identified using Parkes radio telescope observations at frequencies above 3 GHz. The pulsar has the second-highest dispersion measure of all known radio pulsars (1553 pc/cm^3), a spin period of 65.74 ms and a spin-down luminosity of 6.1x10^36 erg/s. The PWN has a cometary morphology and one of the greatest projected lengths among all the observed pulsar radio tails, measuring over 21 pc for an assumed distance of 10 kpc. The remarkably long tail and atypically steep radio spectral index are attributed to the interplay of a supernova reverse shock and the PWN. The originating supernova remnant is not known so far. We estimated the pulsar kick velocity to be in the range of 1000-2000 km/s for ages between 23 and 10 kyr. The X-ray counterpart found in Chandra data, CXOU J163802.6-471358, shows the same tail morphology as the radio source but is shorter by a factor of 10. The peak of the X-ray emission is offset from the peak of the radio total intensity (Stokes I) emission by approximately 4.7", but coincides well with circularly polarised (Stokes V) emission. No infrared counterpart was found.
Comment: 16 pages, 8 figures, 4 tables; Accepted for publication in PASA on 18 Jan 2024

الوصول الحر: http://arxiv.org/abs/2312.06961Test

المؤلفون: Benke, Petra, Rösch, Florian, Ros, Eduardo, Kadler, Matthias, Ojha, Roopesh, Edwards, Philip G., Horiuchi, Shinji, Hyland, Lucas J., Phillips, Chris, Quick, Jonathan F. H., Stevens, Jamie, Tzioumis, Anastasios K., Weston, Stuart

المصدر: A&A 681, A69 (2024)

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: With the emergence of very high energy astronomy (VHE; E>100 GeV), new open questions were presented to astronomers studying the multi-wavelength emission from blazars. Answers to these open questions, such as the Doppler crisis, and finding the location of the high-energy activity have eluded us thus far. Recently, quasi-simultaneous multi-wavelength monitoring programs have shown considerable success in investigating blazar activity. After the launch of the Fermi Gamma-ray Space Telescope in 2008, such quasi-simultaneous observations across the electromagnetic spectrum became possible. In addition, with very long baseline interferometry (VLBI) observations we can resolve the central parsec region of active galactic nuclei (AGN) and compare morphological changes to the gamma-ray activity to study high-energy emitting blazars. To achieve our goals, we need sensitive, long-term VLBI monitoring of a complete sample of VHE detected AGN. We performed VLBI observations of TeV-detected AGN and high likelihood neutrino associations as of December of 2021 with the Long Baseline Array (LBA) and other southern hemisphere radio telescopes at 2.3 GHz. In this paper we present first light TANAMI S-band images, focusing on the TeV-detected sub-sample of the full TANAMI sample. Apart from these very high energy-detected sources, we also show images of the two flux density calibrators and two additional sources included in the observations. We study the redshift, 0.1-100 GeV photon flux and S-band core brightness temperature distributions of the TeV-detected objects, and find that flat spectrum radio quasars and low synchrotron peaked sources on average show higher brightness temperatures than high-synchrotron-peaked BL Lacs. Sources with bright GeV gamma-ray emission also show higher brightness temperature values than gamma-low sources.

الوصول الحر: http://arxiv.org/abs/2310.10206Test

المؤلفون: Rösch, F., Benke, P., Kadler, M., Ros, E., Ojha, R., Edwards, P. G., Eppel, F., Heßdörfer, J., Stevens, J.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The origin of high-energy cosmic neutrinos detected by the IceCube observatory is a hotly debated topic in astroparticle physics. There is growing evidence that some of these neutrinos can be associated with active galactic nuclei (AGN) and especially with blazars. Several recent studies have revealed a statistical correlation between radio-bright AGN samples and IceCube neutrino event catalogs. In addition, a growing number of individual high-energy neutrinos have been found to coincide with individual radio-flaring blazars. These observational results strongly call for high-quality, high angular-resolution radio observations of such neutrino-associated blazars to study their parsec-scale jet structures. TANAMI is the only large and long-term VLBI monitoring program focused on the Southern sky. Within TANAMI, we put an emphasis on Southern IceCube neutrino candidate blazars at 2.3 GHz and 8.4 GHz. Here we present first results of the first high-quality, high angular-resolution VLBI observations of nine Southern-Hemisphere blazars that were associated to IceCube neutrino hotspots in the Southern sky. In the near future, the rapidly growing KM3NeT will complement IceCube by being sensitive to high-energy neutrinos mainly from the Southern Hemisphere. This will increase the importance of Southern-Hemisphere radio monitoring programs of neutrino-associated blazars, like TANAMI.
Comment: 8 pages, 2 figures, 1 table, Proceedings of the 38th International Cosmic Ray Conference (ICRC2023)

الوصول الحر: http://arxiv.org/abs/2310.07468Test

المؤلفون: Heßdörfer, J., Kadler, M., Benke, P., Debbrecht, L., Eich, J., Eppel, F., Gokus, A., Hämmerich, S., Kirchner, D., Paraschos, G. F., Rösch, F., Schulga, W., Sinapius, J., Weber, P., Bach, U., Berge, D., Buson, S., Dorner, D., Edwards, P. G., Fromm, C. M., Giroletti, M., Hervet, O., Kappes, A., Koyama, S., Kraus, A., Krichbaum, T. P., Lindfors, E., Mannheim, K., Ojha, R., Pueschel, E., Ros, E., Schleicher, B., Sitarek, J., Wilms, J., Zacharias, M., Zensus, J. A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present recent results of the TELAMON program, which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN. Our sample includes all known Northern TeV-emitting blazars as well as blazars positionally coincident with IceCube neutrino alerts. Polarization can give additional insight into the source properties, as the polarized emission is often found to vary on different timescales and amplitudes than the total intensity emission. Here, we present an overview of the polarization properties of the TeV-emitting TELAMON sources at four frequencies in the 20 mm and 7 mm bands. While at 7 mm roughly $82\,\%$ of all observed sources are found to be significantly polarized, for 20 mm the percentage is $\sim58\,\%$. We find that most of the sources exhibit mean fractional polarizations of $<5\%$, matching the expectations of rather low polarization levels in these sources from previous studies at lower radio frequencies. Nevertheless, we demonstrate examples of how the polarized emission can provide additional information over the total intensity.
Comment: 9 pages, 2 figures, Proceedings of the 38th International Cosmic Ray Conference (ICRC2023)

الوصول الحر: http://arxiv.org/abs/2309.14794Test

المؤلفون: Wilson, David J., Thomas, Christopher E., Dudek, Jozef J., Edwards, Robert G.

مصطلحات موضوعية: High Energy Physics - Lattice, High Energy Physics - Phenomenology

الوصف: In order to explore the spectrum of hidden-charm scalar and tensor resonances, we study meson-meson scattering with $J^{PC}=0^{++}, 2^{++}$ in the charmonium energy region using lattice QCD. Employing a light-quark mass corresponding to $m_\pi \approx 391$ MeV, we determine coupled-channel scattering amplitudes up to around 4100 MeV considering all kinematically relevant channels consisting of a pair of open-charm mesons or a charmonium meson with a light meson. A single isolated scalar resonance near 4000 MeV is found with large couplings to $D\bar{D}$, $D_s \bar{D}_s$ and the kinematically closed $D^* \bar{D}^*$ channel. A single tensor resonance at a similar mass couples strongly to $D\bar{D}$, $D\bar{D}^*$ and $D^* \bar{D}^*$. We compare the extracted resonances to contemporary experimental candidate states, previous lattice results and theoretical modeling. In contrast to several other studies, we do not find any significant feature in the scalar amplitudes between the ground state $\chi_{c0}(1P)$ and the resonance found around 4000 MeV.
Comment: 55 pages, 36 figures

الوصول الحر: http://arxiv.org/abs/2309.14071Test