Astrophysical Journal Letters 970, L21 (2024) The Tarantula Nebula in the Large Magellanic Cloud is known for its high star
formation activity. At its center lies the young massive star cluster R136,
...providing a significant amount of the energy that makes the nebula shine so
brightly at many wavelengths. Recently, young massive star clusters have been
suggested to also efficiently produce high-energy cosmic rays, potentially
beyond PeV energies. Here, we report the detection of very-high-energy
$\gamma$-ray emission from the direction of R136 with the High Energy
Stereoscopic System, achieved through a multicomponent, likelihood-based
modeling of the data. This supports the hypothesis that R136 is indeed a very
powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide
an updated measurement of the $\gamma$-ray emission from 30 Dor C, the only
superbubble detected at TeV energies presently. The $\gamma$-ray luminosity
above $0.5\,\mathrm{TeV}$ of both sources is $(2-3)\times
10^{35}\,\mathrm{erg}\,\mathrm{s}^{-1}$. This exceeds by more than a factor of
2 the luminosity of HESS J1646$-$458, which is associated with the most massive
young star cluster in the Milky Way, Westerlund 1. Furthermore, the
$\gamma$-ray emission from each source is extended with a significance of
$>3\sigma$ and a Gaussian width of about $30\,\mathrm{pc}$. For 30 Dor C, a
connection between the $\gamma$-ray emission and the nonthermal X-ray emission
appears likely. Different interpretations of the $\gamma$-ray signal from R136
are discussed.
PSR B1259-63 is a gamma-ray binary system that hosts a pulsar in an eccentric orbit, with a 3.4 year period, around an O9.5Ve star. At orbital phases close to periastron passages, the system radiates ...bright and variable non-thermal emission. We report on an extensive VHE observation campaign conducted with the High Energy Stereoscopic System, comprised of ~100 hours of data taken from \(t_p-24\) days to \(t_p+127\) days around the system's 2021 periastron passage. We also present the timing and spectral analyses of the source. The VHE light curve in 2021 is consistent with the stacked light curve of all previous observations. Within the light curve, we report a VHE maximum at times coincident with the third X-ray peak first detected in the 2021 X-ray light curve. In the light curve -- although sparsely sampled in this time period -- we see no VHE enhancement during the second disc crossing. In addition, we see no correspondence to the 2021 GeV flare in the VHE light curve. The VHE spectrum obtained from the analysis of the 2021 dataset is best described by a power law of spectral index \(\Gamma = 2.65 \pm 0.04_{\text{stat}}\) \(\pm 0.04_{\text{sys}}\), a value consistent with the previous H.E.S.S. observations of the source. We report spectral variability with a difference of \(\Delta \Gamma = 0.56 ~\pm~ 0.18_{\text{stat}}\) \(~\pm~0.10_{\text{sys}}\) at 95% c.l., between sub-periods of the 2021 dataset. We also find a linear correlation between contemporaneous flux values of X-ray and TeV datasets, detected mainly after \(t_p+25\) days, suggesting a change in the available energy for non-thermal radiation processes. We detect no significant correlation between GeV and TeV flux points, within the uncertainties of the measurements, from \(\sim t_p-23\) days to \(\sim t_p+126\) days. This suggests that the GeV and TeV emission originate from different electron populations.
The radio galaxy M87 is a variable very-high energy (VHE) gamma-ray source, exhibiting three major flares reported in 2005, 2008, and 2010. Despite extensive studies, the origin of the VHE gamma-ray ...emission is yet to be understood. In this study, we investigate the VHE gamma-ray spectrum of M87 during states of high gamma-ray activity, utilizing 20.2\(\,\) hours the H.E.S.S. observations. Our findings indicate a preference for a curved spectrum, characterized by a log-parabola model with extra-galactic background light (EBL) model above 0.3\(\,\)TeV at the 4\(\sigma\) level, compared to a power-law spectrum with EBL. We investigate the degeneracy between the absorption feature and the EBL normalization and derive upper limits on EBL models mainly sensitive in the wavelength range 12.4$\,$$\mu\(m - 40\)\,$$\mu$m.
Most $\gamma$-ray detected active galactic nuclei are blazars with one of
their relativistic jets pointing towards the Earth. Only a few objects belong
to the class of radio galaxies or misaligned ...blazars. Here, we investigate the
nature of the object PKS 0625-354, its $\gamma$-ray flux and spectral
variability and its broad-band spectral emission with observations from
H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S.
light curve above 200 GeV shows an outburst in the first night of observations
followed by a declining flux with a halving time scale of 5.9h. The
$\gamma\gamma$-opacity constrains the upper limit of the angle between the jet
and the line of sight to $\sim10^\circ$. The broad-band spectral energy
distribution shows two humps and can be well fitted with a single-zone
synchrotron self Compton emission model. We conclude that PKS 0625-354, as an
object showing clear features of both blazars and radio galaxies, can be
classified as an intermediate active galactic nuclei. Multi-wavelength studies
of such intermediate objects exhibiting features of both blazars and radio
galaxies are sparse but crucial for the understanding of the broad-band
emission of $\gamma$-ray detected active galactic nuclei in general.
In July 2021, PKS 1510-089 exhibited a significant flux drop in the high-energy gamma-ray (by a factor 10) and optical (by a factor 5) bands and remained in this low state throughout 2022. Similarly, ...the optical polarization in the source vanished, resulting in the optical spectrum being fully explained through the steady flux of the accretion disk and the broad-line region. Unlike the aforementioned bands, the very-high-energy gamma-ray and X-ray fluxes did not exhibit a significant flux drop from year to year. This suggests that the steady-state very-high-energy gamma-ray and X-ray fluxes originate from a different emission region than the vanished parts of the high-energy gamma-ray and optical jet fluxes. The latter component has disappeared through either a swing of the jet away from the line-of-sight or a significant drop in the photon production efficiency of the jet close to the black hole. Either change could become visible in high-resolution radio images.
Magnetic fields in galaxies and galaxy clusters are believed to be the result of the amplification of intergalactic seed fields during the formation of large-scale structures in the universe. ...However, the origin, strength, and morphology of this intergalactic magnetic field (IGMF) remain unknown. Lower limits on (or indirect detection of) the IGMF can be obtained from observations of high-energy gamma rays from distant blazars. Gamma rays interact with the extragalactic background light to produce electron-positron pairs, which can subsequently initiate electromagnetic cascades. The \(\gamma\)-ray signature of the cascade depends on the IGMF since it deflects the pairs. Here we report on a new search for this cascade emission using a combined data set from the Fermi Large Area Telescope and the High Energy Stereoscopic System. Using state-of-the-art Monte Carlo predictions for the cascade signal, our results place a lower limit on the IGMF of \(B > 7.1\times10^{-16}\) G for a coherence length of 1 Mpc even when blazar duty cycles as short as 10 yr are assumed. This improves on previous lower limits by a factor of 2. For longer duty cycles of \(10^4\) (\(10^7\)) yr, IGMF strengths below \(1.8\times10^{-14}\) G (\(3.9\times10^{-14}\) G) are excluded, which rules out specific models for IGMF generation in the early universe.
The Tarantula Nebula in the Large Magellanic Cloud is known for its high star formation activity. At its center lies the young massive star cluster R136, providing a significant amount of the energy ...that makes the nebula shine so brightly at many wavelengths. Recently, young massive star clusters have been suggested to also efficiently produce high-energy cosmic rays, potentially beyond PeV energies. Here, we report the detection of very-high-energy \(\gamma\)-ray emission from the direction of R136 with the High Energy Stereoscopic System, achieved through a multicomponent, likelihood-based modeling of the data. This supports the hypothesis that R136 is indeed a very powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide an updated measurement of the \(\gamma\)-ray emission from 30 Dor C, the only superbubble detected at TeV energies presently. The \(\gamma\)-ray luminosity above \(0.5\,\mathrm{TeV}\) of both sources is \((2-3)\times 10^{35}\,\mathrm{erg}\,\mathrm{s}^{-1}\). This exceeds by more than a factor of 2 the luminosity of HESS J1646\(-\)458, which is associated with the most massive young star cluster in the Milky Way, Westerlund 1. Furthermore, the \(\gamma\)-ray emission from each source is extended with a significance of \(>3\sigma\) and a Gaussian width of about \(30\,\mathrm{pc}\). For 30 Dor C, a connection between the \(\gamma\)-ray emission and the nonthermal X-ray emission appears likely. Different interpretations of the \(\gamma\)-ray signal from R136 are discussed.
Pancreatic heterotopia (PH) is a common, but typically small (<1 cm), incidental and asymptomatic finding; however, PH should be considered even for large and symptomatic upper gastrointestinal ...masses. A 27-year-old white woman presented with a 3-week history of burning epigastric pain, nausea, early satiety, and constipation. Physical examination revealed epigastric and right upper quadrant tenderness with normal laboratory workup, but imaging revealed a 5-cm, partly cystic mass arising from the gastric antrum with resulting pyloric stenosis and partial gastric outlet obstruction. Endoscopic ultrasound-guided fine needle aspiration revealed PH – an anomalous pancreatic tissue lying in a nonphysiological site. The patient ultimately underwent a resection and recovered uneventfully, with a complete pathologic examination revealing normal exocrine pancreatic tissue (PH type 2) without malignant transformation. We report a case of heterotopic pancreas manifesting as severe gastric outlet obstruction, in addition to a thorough diagnostic workup and surgical follow-up, in a young adult. Differential diagnoses and features that speak to benignity of a large, symptomatic mass lesion (PH in particular) are discussed.
CONTEXT Multislice computed tomography (MSCT) has recently evolved as a modality
for noninvasive coronary imaging. OBJECTIVE To assess the accuracy and robustness of MSCT vs the criterion standard
of ...invasive coronary angiography for detection of obstructive coronary artery
disease. DESIGN, SETTING, AND PATIENTS Prospective, single-center study conducted in a referral center setting
in Germany and enrolling 103 consecutive patients (mean age, 61.5 SD, 9.7
years) from November 2003–August 2004 who were undergoing both invasive
coronary angiography and MSCT using a scanner with 16 detector rows. MAIN OUTCOME MEASURES Blinded results for both modalities compared using the patient as the
primary unit of analysis, with supplementary segment- and vessel-based analyses. RESULTS One thousand three hundred eighty-four segments (≥1.5 mm diameter)
were identified by invasive coronary angiography; nondiagnostic image quality
of MSCT was identified for only 88 (6.4%) of these segments, mainly due to
faster heart rates. Compared with invasive coronary angiography for detection
of significant lesions (>50% stenosis), segment-based sensitivity, specificity,
and positive and negative predictive values of MSCT were 95%, 98%, 87%, and
99%, respectively. Quantitative comparison of MSCT and invasive coronary angiography
showed good correlation (r = 0.87, P<.001), with MSCT systematically measuring greater-percentage
stenoses (bias, +12%). In the patient-based analysis, the area under the receiver
operating characteristic curve was 0.97 (95% confidence interval, 0.90-1.00),
indicating high discriminative power to identify patients who might be candidates
for revascularization (>50% left main artery stenosis and/or >70% stenosis
in any other epicardial vessel). Threshold optimization allowed either detection
of these patients with 100% sensitivity at a reasonable false-positive rate
(specificity, 76.5%; MSCT stenosis, >66%) or optimization of both the sensitivity
and specificity (>90%; MSCT stenosis, >76%). CONCLUSIONS Multislice computed tomography provides high accuracy for noninvasive
detection of suspected obstructive coronary artery disease. This promising
technology has potential to complement diagnostic invasive coronary angiography
in routine clinical care.
PDF
