Abstract
Recently, the region surrounding eHWC J1842−035 has been studied extensively by γ-ray observatories due to its extended emission reaching up to a few hundred TeV and potential as a hadronic ...accelerator. In this work, we use 1910 days of cumulative data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a dedicated systematic source search of the eHWC J1842−035 region. During the search, we found three sources in the region, namely, HAWC J1844−034, HAWC J1843−032, and HAWC J1846−025. We have identified HAWC J1844−034 as the extended source that emits photons with energies up to 175 TeV. We compute the spectrum for HAWC J1844−034, and by comparing with the observational results from other experiments, we have identified HESS J1843−033, LHAASO J1843−0338, and TASG J1844−038 as very-high-energy γ-ray sources with a matching origin. Also, we present and use the multiwavelength data to fit the hadronic and leptonic particle spectra. We have identified four pulsar candidates in the nearby region in which PSR J1844−0346 is found to be the most likely candidate due to its proximity to HAWC J1844−034 and the computed energy budget. We have also found SNR G28.6−0.1 as a potential counterpart source of HAWC J1844−034 for which both leptonic and hadronic scenarios are feasible.
Treatment of the pure enantiomer 1 with methyllithium furnishes via cycloallene 2 its dimer 3 with high selectivity. In contrast, racemic 1 yielded only 5 % of 3 and 95 % of the cis isomer of 3. ...Thus, racemic 2 is an example of molecular recognition of remarkable selectivity.
d‐Lactate dehydrogenase (d‐LDH) is a membrane‐associated respiratory enzyme of Escherichia coli. The protein is composed of 571 amino acid residues with a flavin adenine dinucleotide (FAD) cofactor, ...has a molecular weight of approximately 65, 000, and requires lipids or detergents for full activity. We used NMR spectroscopy to investigate the structure of d‐LDH and its interaction with phospholipids. We incorporated 5‐fluorotryptophan (5F‐Trp) into the native enzyme, which contains five tryptophan residues, and into mutant enzymes, where a sixth tryptophan is substituted into a specific site by oligonucleotide‐directed mutagenesis, and studied the 5F‐Trp‐labeled enzymes using 19F‐NMR spectroscopy. In this way, information was obtained about the local environment at each native and substituted tryptophan site. Using a nitroxide spin‐labeled fatty acid, which broadens the resonance from any residue within 15 Å, we have established that the membrane‐binding area of the protein includes the region between Tyr 228 and Phe 369, but is not continuous within this region. This conclusion is strengthened by the results of 19F‐NMR spectroscopy of wild‐type enzyme labeled with fluorotyrosine or fluorophenylalanine in the presence and absence of a nitroxide spin‐labeled fatty acid. These experiments indicate that 9–10 Phe and 3–4 Tyr residues are located near the lipid phase.
3‐Bromo‐1‐methyl‐1,2,5,6‐tetrahydropyridine(N−B)borane (7) was prepared from 3‐bromopyridine by conversion to 3‐bromo‐1‐methylpyridinium iodide, hydrogenation of the latter with sodium ...tetrahydroborate and treatment of the resulting 3‐bromo‐1‐methyl‐1,2,5,6‐tetrahydropyridine (6) with borane−dimethyl sulfide. Whereas no trapping product of the possible intermediate 1‐methyl‐1‐azacyclohexa‐2,3‐diene (4) could be observed on treatment of 6 with potassium tert‐butoxide in the presence of furan, the subjection of 7 to the same conditions produced the hexahydroepoxyquinoline derivatives 8a−c. Treatment of 7, dissolved in styrene, with sodium bis(trimethylsilyl)amide furnished the hexahydrocyclobutapyridine derivatives 9a−c. The six‐membered cycloallene 1‐methyl‐1‐azacyclohexa‐2,3‐diene(N−B)borane (10) must be regarded as the key intermediate en route to 8 and 9.
Supernova remnants (SNRs) are believed to be capable of accelerating cosmic rays (CRs) to PeV energies. SNR G106.3+2.7 is a prime PeVatron candidate. It is formed by a head region, where the pulsar ...J2229+6114 and its boomerang-shaped pulsar wind nebula are located, and a tail region containing SN ejecta. The lack of observed gamma ray emission from the two regions of this SNR has made it difficult to assess which region would be responsible for the PeV CRs. We aim to characterize the very-high-energy (VHE, 0.1-100 TeV) gamma ray emission from SNR G106.3+2.7 by determining the morphology and spectral energy distribution of the region. This is accomplished using 2565 days of data and improved reconstruction algorithms from the HAWC Observatory. We also explore possible gamma ray production mechanisms for different energy ranges. Using a multi-source fitting procedure based on a maximum-likelihood estimation method, we evaluate the complex nature of this region. We determine the morphology, spectrum, and energy range for the source found in the region. Molecular cloud information is also used to create a template and evaluate the HAWC gamma ray spectral properties at ultra-high-energies (UHE, >56 TeV). This will help probe the hadronic nature of the highest-energy emission from the region. We resolve one extended source coincident with all other gamma ray observations of the region. The emission reaches above 100~TeV and its preferred log-parabola shape in the spectrum shows a flux peak in the TeV range. The molecular cloud template fit on the higher energy data reveals that the SNR's energy budget is fully capable of producing a purely hadronic source for UHE gamma rays.
HESS J1809-193 is an unidentified TeV source, first detected by the High Energy Stereoscopic System (H.E.S.S.) Collaboration. The emission originates in a source-rich region that includes several ...Supernova Remnants (SNR) and Pulsars (PSR) including SNR G11.1+0.1, SNR G11.0-0.0, and the young radio pulsar J1809-1917. Originally classified as a pulsar wind nebula (PWN) candidate, recent studies show the peak of the TeV region overlapping with a system of molecular clouds. This resulted in the revision of the original leptonic scenario to look for alternate hadronic scenarios. Marked as a potential PeVatron candidate, this region has been studied extensively by H.E.S.S. due to its emission extending up-to several tens of TeV. In this work, we use 2398 days of data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a systematic source search for the HESS J1809-193 region. We were able to resolve emission detected as an extended component (modelled as a Symmetric Gaussian with a 1 \(\sigma\) radius of 0.21 \(^\circ\)) with no clear cutoff at high energies and emitting photons up-to 210 TeV. We model the multi-wavelength observations for the region HESS J1809-193 using a time-dependent leptonic model and a lepto-hadronic model. Our model indicates that both scenarios could explain the observed data within the region of HESS J1809-193.
The first TeV gamma-ray source with no lower energy counterparts, TeV J2032+4130, was discovered by HEGRA. It appears in the third HAWC catalog as 3HWC J2031+415 and it is a bright TeV gamma-ray ...source whose emission has previously been resolved as 2 sources: HAWC J2031+415 and HAWC J2030+409. While HAWC J2030+409 has since been associated with the \emph{Fermi-LAT} Cygnus Cocoon, no such association for HAWC J2031+415 has yet been found. In this work, we investigate the spectrum and energy-dependent morphology of HAWC J2031+415. We associate HAWC J2031+415 with the pulsar PSR J2032+4127 and perform a combined multi-wavelength analysis using radio, X-ray, and \(\gamma\)-ray emission. We conclude that HAWC J2031+415 and, by extension, TeV J2032+4130 are most probably a pulsar wind nebula (PWN) powered by PSR J2032+4127.
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