Unidentified Sources Research Articles

Searching signals of dark matter from unidentified Fermi-LAT objects with H.E.S.S

Milky Way-sized galaxies harbor a population of unmerged dark matter subhalos, as shown from cosmological N-body simulations. These subhalos could shine in gamma-rays and be eventually detected as unidentified sources in gamma-ray surveys. From a thorough selection of unidentified Fermi-LAT Objects (UFOs), we observe four UFOs with H.E.S.S. and we search for very high-energy (VHE, E ≥ 100 GeV) gamma-ray emission. Considering dark matter masses above a few hundred GeV, the observed UFOs could be identified as dark matter subhalos, given their hard gamma-ray spectra in the few-ten-to-hundred GeV energy range. Since no significant very-high-energy gamma-ray emission is detected in any of the four UFOs dataset nor in the combined one, we derive constraints on the product of the velocity-weighted annihilation cross-section 〈συ〉 by the J-factor for the dark matter models. We derive 95% CL upper limits on 〈συ〉 J in W + W − and τ+τ− annihilation channels for the TeV dark matter particles. Considering thermal WIMPs, we derive constraints on the J-factors from the H.E.S.S. observations. Assuming model-dependent predictions from cosmological N-body simulations on the J-factor distribution for Milky Way-sized galaxies, the dark matter models with masses greater than 0.3 TeV for the UFO emissions can be ruled out at high confidence level.

Identifying γ-ray emitting blazars in the PASIPHAE era: polarimetry as a unique probe

AbstractThe Fermi γ-ray telescope has detected 6658 sources, with 1845 of them remaining unidentified. We show that polarimetry of γ-ray fields is a powerful asset in the hunt of active galactic nuclei (AGN) as potential optical counterparts for γ-ray sources. We have studied an unidentified Fermi field (3FGL J0221.2+2518) and found a previously-unknown highly-polarized extragalactic object as a potential optical counterpart within the 1-sigma error ellipse of the corresponding γ-ray source. Based on a collection of data, we find that it most probably is a composite object: a star-forming galaxy accompanied by AGN. PASIPHAE is a large polarimetric experiment which will measure the polarisation of sources away from the galactic plane. This will provide an excellent opportunity to study hundreds of unidentified γ-ray sources and unveil potential optical counterparts, using polarimetry.

A WISE perspective of the blazar hunt in the γ-ray sky

AbstractThanks to the data of the WISE all-sky survey we discovered that the non-thermal infrared emission of blazars, the largest population of associated γ-ray sources, has peculiar spectral properties. Here we provide a summary of all results achieved on the infrared–γ-ray connection. We also show results on the latest statistical analysis of the tight correlation between the mid-infrared colors and the γ-ray spectral index for Fermi blazars, a connection that links both emitted powers and spectral shapes of particles accelerated in blazar jets over ten decades in frequency of the electromagnetic spectrum. Finally, we outline all developments performed in the last decade achieved using the infrared– γ-ray connection to discover hundreds of new blazars within the sample of unidentified γ-ray sources thanks to optical spectroscopic observations.

A search for Planet 9 in the IRAS data

ABSTRACT I have carried out a search for Planet 9 in the IRAS data. At the distance range proposed for Planet 9, the signature would be a 60 $\mu$m unidentified IRAS point source with an associated nearby source from the IRAS reject file of sources which received only a single hours-confirmed (HCON) detection. The confirmed source should be detected on the first two HCON passes, but not on the third, while the single HCON should be detected only on the third HCON. I have examined the unidentified sources in three IRAS 60 $\mu$m catalogs: some can be identified with 2MASS galaxies, Galactic sources or as cirrus. The remaining unidentified sources have been examined with the IRSA Scanpi tool to check for the signature missing HCONs, and for association with IRAS reject file single HCONs. No matches of interest survive. For a lower mass planet (≤5ME) in the distance range 200–400 AU, we expect a pair or triplet of single HCONs with separations 2–35 arcmin. Several hundred candidate associations are found and have been examined with Scanpi. A single candidate for Planet 9 survives which satisfies the requirements for detected and non-detected HCON passes. A fitted orbit suggest a distance of 225 ± 15 AU and a mass of 3–5 ME. Dynamical simulations are needed to explore whether the candidate is consistent with existing planet ephemerides. If so, a search in an annulus of radius 2.5–4° centred on the 1983 position at visible and near-infrared wavelengths would be worthwhile.

Incorporating bioaccessibility and source apportionment into human health risk assessment of heavy metals in urban dust of Xiamen, China

Heavy metals in urban dust could pose noticeable human health risks, but there are few studies focusing on comprehensive human health risk assessment with the incorporation of both bioaccessibility and source apportionment in urban dust. Thus, fifty-eight urban dust samples were collected from kindergartens in Xiamen to analyze the bioaccessibility-based, source-specific health risk of heavy metals (V, Co, Ni, As, Mo, Cr, Mn, Cu, Zn, and Pb). Most heavy metals, except for V and Mn, were significantly enriched in urban dust based on their values of geoaccumulation index (Igeo) and may be influenced by human activities. The oral bioaccessibility values of heavy metals, which were estimated by the Solubility/Bioaccessibility Research Consortium (SBRC) in vitro model, ranged from 1.563% to 76.51%. The source apportionment determined by applying the absolute principal component analysis-multiple linear regression (APCS-MLR) model indicated five main potential sources, coal combustion, traffic and industrial, natural, construction and furniture sources, and unidentified sources, with contributions of 34.09%, 20.72%, 18.72%, 7.597% and 18.87%, respectively, to the accumulation of heavy metals in urban dust. After incorporating bioaccessibility adjustments, lower non-carcinogenic and carcinogenic risks of heavy metals were observed than those based on total metal content, with the mean hazard index (HI) values being less than the threshold value (1) and the mean total carcinogenic risk (TCR) values exceeding the precautionary criterion (10-6) for both adults and children. By combining bioaccessibility-based health risk assessment and source apportionment, traffic and industrial emissions and coal combustion dominated the noncarcinogenic and carcinogenic risks induced by heavy metals in urban dust, respectively. This study is expected to promote the systematic integration of source apportionment and bioaccessibility into health risk estimation for heavy metal contamination in urban dust, thus providing useful implications for better human health protection.

The Internal Structure of Placer Gold of the North-East of the Siberian Platform as a Reliable Search Sign of Primary Sources

Typomorphic features of placer gold are carriers of the most important information necessary for the reconstruction of the history of the formation of placer and ore occurrences of gold and can be used as mineralogical criteria in the search for primary sources of placers. The study of these features is relevant for placer areas with unidentified gold sources, which include the territory of the north-east of the Siberian Platform. The internal structure of native gold is one of the most informative typomorphic features is. We studied the internal gold structures of modern placers and conglomerates of the Early Permian age in the north-east of the Siberian Platform. The purpose of the work: to identify the features of the internal structure of placer gold, depending on the chemical composition and the degree of its transformations, as well as the possibility of their use as a prospecting indicator. Structural etching of native gold was performed using the reagent: HCl + HNO3 + FeCl3 × 6H2O + CrO3 + thiurea + water. As a result of the research, it was found that the well-rounded high-grade gold of modern placers has undergone repeated redeposition through intermediate sources. The discovery of slightly rounded gold with an internal structure without signs of exogenous transformation indicates that it entered the modern alluvium from a nearby primary source. This was a prerequisite for setting up ore gold exploration, resulting in identification of apocarbonate hydrothermal-metasomatic formations with disseminated gold-sulfide mineralization were identified. Thus, the features of the internal structures of placer gold in combination with other typomorphic features are additional indications of determining the sources of formation of gold-bearing placers.

Velocity dispersion and dynamical mass for 270 galaxy clusters in the Planck PSZ1 catalogue

We present the velocity dispersion and dynamical mass estimates for 270 galaxy clusters included in the first Planck Sunyaev-Zeldovich (SZ) source catalogue, the PSZ1. Part of the results presented here were achieved during a two-year observational program, the ITP, developed at the Roque de los Muchachos Observatory (La Palma, Spain). In the ITP we carried out a systematic optical follow-up campaign of all the 212 unidentified PSZ1 sources in the northern sky that have a declination above −15° and are without known counterparts at the time of the publication of the catalogue. We present for the first time the velocity dispersion and dynamical mass of 58 of these ITP PSZ1 clusters, plus 35 newly discovered clusters that are not associated with the PSZ1 catalogue. Using Sloan Digital Sky Survey archival data, we extend this sample, including 212 already confirmed PSZ1 clusters in the northern sky. Using a subset of 207 of these galaxy clusters, we constrained the MSZ–Mdyn scaling relation, finding a mass bias of (1 − B) = 0.83 ± 0.07(stat) ± 0.02(sys). We show that this value is consistent with other results in the literature that were obtained with different methods (X-ray, dynamical masses, or weak-lensing mass proxies). This result cannot dissolve the tension between primordial cosmic microwave background anisotropies and cluster number counts in the ΩM–σ8 plane.

Date of introduction and epidemiologic patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Mogadishu, Somalia: estimates from transmission modelling of satellite-based excess mortality data in 2020

Background: In countries with weak surveillance systems, confirmed coronavirus disease 2019 (COVID-19) deaths are likely to underestimate the pandemic’s death toll. Many countries also have incomplete vital registration systems, hampering excess mortality estimation. Here, we fitted a dynamic transmission model to satellite imagery data of cemeteries in Mogadishu, Somalia during 2020 to estimate the date of introduction and other epidemiologic parameters of the early spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this low-income, crisis-affected setting. Methods: We performed Markov chain Monte Carlo (MCMC) fitting with an age-structured compartmental COVID-19 model to provide median estimates and credible intervals for the date of introduction, the basic reproduction number ( R 0 ) and the effect of non-pharmaceutical interventions (NPIs) up to August 2020. Results: Under the assumption that excess deaths in Mogadishu March-August 2020 were attributable to SARS-CoV-2 infections, we arrived at median estimates of November-December 2019 for the date of introduction and low R 0 estimates (1.4-1.7) reflecting the slow and early rise and long plateau of excess deaths. The date of introduction, the amount of external seeding, the infection fatality rate (IFR) and the effectiveness of NPIs are correlated parameters and not separately identifiable in a narrow range from deaths data. Nevertheless, to obtain introduction dates no earlier than November 2019 a higher population-wide IFR (≥0.7%) had to be assumed than obtained by applying age-specific IFRs from high-income countries to Somalia’s age structure. Conclusions: Model fitting of excess mortality data across a range of plausible values of the IFR and the amount of external seeding suggests an early SARS-CoV-2 introduction event may have occurred in Somalia in November-December 2019. Transmissibility in the first epidemic wave was estimated to be lower than in European settings. Alternatively, there was another, unidentified source of sustained excess mortality in Mogadishu from March to August 2020.

Measurement of ambient vibration in empty buildings and relation to external noise

We measure and analyse the ambient vibration induced in residential buildings in urban settings. While most vibration studies focus on strong, well identified sources, our goal has been the ambient vibration of unidentified sources from the surrounding environment. To that end we have chosen buildings which are finished, ready to deliver, but otherwise empty and with all facilities turned off.Lacking any clue of the origin of the vibration, we have tried to relate it to three variables: the position of the accelerometer in the slab, the floor level and the color of the noise map in the façade of the building.We have measured the vibration in 80 different settings. We have checked the acceleration time histories to be stationary time series and have characterized them by the root mean square value of the series. We have been able to relate these values with the color of the noise map and the floor level.In addition, we have identified peak values of the vibration (those values over twice the r.m.s. value of the series) and have confirmed their random origin, but with different rates at different colors of the noise map.

Provocative mesenteric angiography for localizing ambiguous gastrointestinal hemorrhage

Objectives: Five percent of patients with recurrent gastrointestinal (GI) hemorrhage have indeterminate origin by radiological and endoscopic examinations. To improve diagnostic accuracy and therapeutic embolization, the technique of provocative mesenteric angiography (PMA) has been developed. It involves the addition of pharmacologic agents to standard angiographic protocols to induce bleeding. Material and Methods: This is an institutional review board-approved, retrospective study of 20 patients who underwent PMA between 2014 and 2019. All patients had clinical evidence of GI hemorrhage without a definite source. PMA consisted of anticoagulation with 5000 units of heparin and selective transcatheter injection of up to 600 μg of nitroglycerine, followed by slow infusion of up to 24 mg of tissue plasminogen activator into the arterial distribution of the highest suspicion mesenteric artery. Results: Among the 20 patients who underwent PMA, 11/20 (55%) resulted in angiographically visible extravasation. Of these 11 patients, nine patients underwent successful embolization with coil or glue and were discharged upon achieving hemodynamic stability. Two patients spontaneously stopped bleeding. In our series, PMA resulted in the successful treatment of 9/20 (45%) patients with recurrent hemorrhage. No procedure-associated complications were reported with these 20 patients during the procedure and their course of hospitalization. Conclusion: In our experience, PMA is an effective and safe approach in localizing and treating the source of GI bleeding in about half of patients with an otherwise unidentifiable source.

Date of introduction and epidemiologic patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Mogadishu, Somalia: estimates from transmission modelling of satellite-based excess mortality data in 2020.

Background: In countries with weak surveillance systems, confirmed coronavirus disease 2019 (COVID-19) deaths are likely to underestimate the pandemic's death toll. Many countries also have incomplete vital registration systems, hampering excess mortality estimation. Here, we fitted a dynamic transmission model to satellite imagery data of cemeteries in Mogadishu, Somalia during 2020 to estimate the date of introduction and other epidemiologic parameters of the early spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this low-income, crisis-affected setting. Methods: We performed Markov chain Monte Carlo (MCMC) fitting with an age-structured compartmental COVID-19 model to provide median estimates and credible intervals for the date of introduction, the basic reproduction number ( R 0 ) and the effect of non-pharmaceutical interventions (NPIs) up to August 2020. Results: Under the assumption that excess deaths in Mogadishu March-August 2020 were attributable to SARS-CoV-2 infections, we arrived at median estimates of November-December 2019 for the date of introduction and low R 0 estimates (1.4-1.7) reflecting the slow and early rise and long plateau of excess deaths. The date of introduction, the amount of external seeding, the infection fatality rate (IFR) and the effectiveness of NPIs are correlated parameters and not separately identifiable in a narrow range from deaths data. Nevertheless, to obtain introduction dates no earlier than November 2019 a higher population-wide IFR (≥0.7%) had to be assumed than obtained by applying age-specific IFRs from high-income countries to Somalia's age structure. Conclusions: Model fitting of excess mortality data across a range of plausible values of the IFR and the amount of external seeding suggests an early SARS-CoV-2 introduction event may have occurred in Somalia in November-December 2019. Transmissibility in the first epidemic wave was estimated to be lower than in European settings. Alternatively, there was another, unidentified source of sustained excess mortality in Mogadishu from March to August 2020.

A CASE OF POST-OBSTRUCTIVE NECROTIZING PNEUMONIA IN THE SETTING OF METASTATIC NON-SMALL CELL LUNG CANCER

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Necrotizing pneumonia (NP) is a rare condition that is characterized by pulmonary liquefaction and necrosis. Associated symptoms are fever, chills, shortness of breath and cough. Advanced sequelae include pulmonary gangrene, empyema, abscess and hemoptysis. Prognosis is poor with an overall mortality rate of 56% [1]. Here, we present an unusual case of metastatic pulmonary adenocarcinoma complicated by NP leading to the patient's demise. CASE PRESENTATION: A 70 year old male smoker with no known PMH presented with productive cough, unintentional weight loss and hemoptysis. CT chest showed narrowing of the left main bronchus and left main pulmonary artery due to a possible hilar mass (Figure 1,2). There was also an extensive left-sided consolidation with pleural effusion. The patient's significant leukocytosis was poorly responsive to antibiotic therapy. No infectious etiology could be identified on extensive testing. The patient developed acute respiratory distress requiring mechanical ventilation. Bronchoscopy showed severe bleeding from an unidentifiable source in the left lung. BAL showed possible lung carcinoma with post-obstructive PNA. CT abdomen showed right adrenal metastasis. IR-guided bronchial artery embolism was attempted twice to control bleeding; however, no source of bleeding could be identified. The chest tube drained a considerable amount of serosanguinous fluid. The patient underwent segmentectomy after worsening bleeding through the ETT and was found to have extensive metastatic disease in the chest. Lobectomy could not be performed due to the inability to access hilum and was deemed unsafe. Biopsy showed poorly differentiated adenocarcinoma with venous invasion and thrombosis and NP with scattered bacterial colonies. The patient received compassionate care given a high likelihood of imminent death. DISCUSSION: The purpose of this case report was to describe a rare case of post-obstructive NP secondary to poorly differentiated metastatic lung adenocarcinoma. Current management of NP involves the surgical removal of the necrotic tissue along with a long course of broad-spectrum antibiotics to treat the underlying polymicrobial infection [2,3]. Our patient's prognosis was very poor because of the extent of his NP and malignancy. An early approach to endobronchial stenting would have stabilized the airway which was being severely compromised by the tumor, whereas a pneumonectomy would have made it easier to control the patient's fatal hemorrhage. This is why we believe that an early and aggressive intervention would have improved the patient's outcome. CONCLUSIONS: NP in the setting of advanced pulmonary adenocarcinoma is a rare phenomenon that is poorly described in current literature. If a patient with advanced lung cancer develops NP, an early surgical intervention with palliative stenting should be considered to minimize complications. REFERENCE #1: Gillet Y, Vanhems P, Lina G, Bes M, Vandenesch F, Floret D, Etienne J. Factors predicting mortality in necrotizing community-acquired pneumonia caused by Staphylococcus aureus containing Panton-Valentine leukocidin. Clin Infect Dis. 2007 Aug 1;45(3):315-21. doi: 10.1086/519263. Epub 2007 Jun 15. PMID: 17599308. REFERENCE #2: Cengiz AB, Kanra G, Caĝlar M, Kara A, Güçer S, Ince T. Fatal necrotizing pneumonia caused by group A streptococcus. J Paediatr Child Health. 2004 Jan-Feb;40(1-2):69-71. doi: 10.1111/j.1440-1754.2004.00296.x. PMID: 14718011. REFERENCE #3: Kohno S, Koga H, Oka M, et al: The pattern of respiratory infection in patients with lung cancer. Tohoku J Exp Med 173:405-411, 1994. DISCLOSURES: No relevant relationships by Frantzcess Compas, source=Web Response No relevant relationships by Zarwa Idrees, source=Web Response No relevant relationships by Vikram Sumbly, source=Web Response No relevant relationships by Theo Trandafirescu, source=Web Response

S3648 Pyogenic Liver Abscess: Where Did It Come From, How Did It Grow?

Introduction: Liver abscesses are suppurative space occupying lesions resulting from the invasion of the liver tissue by insult/injury, intraabdominal infection disseminated from the portal venous circulation, or originate in the biliary system. Three different etiologies consist of pyogenic, amebic and fungal abscesses. The common cause of liver abscess in the United States is bacterial intraabdominal source. Additionally, the right lobe of liver is mostly an affected region as it’s predominately supplied by superior mesenteric vein. We describe an unusual case of right hepatic lobe abscess with unidentifiable source. Case Description/Methods: We present a 79-year-old woman with a medical history of diabetes and hypertension who presented with complaint of fatigue. She otherwise denied recent illness, travel, hospitalizations or intestinal infections. On presentation, she was hypotensive and admission labs significant for neutrophil predominant leukocytosis. The patient exhibited right upper quadrant tenderness. Blood cultures were obtained. Broad spectrum antibiotics were started. Pertinent imaging revealed a hepatic mass measuring 8.9 x 8.3 x 7.1 cm in the right lower lobe of liver. Interventional radiology performed a biopsy and aspiration of 60 mL purulent fluid. Blood cultures grew Bacteriodes fragilis. Surgical liver pathology was predominately fragments of necrotic hepatic tissue with acute inflammation. Liver abscess cultures speciated Escherichia coli, Klebsiella pneumonia, and Streptococcus intermedius. Antibiotics were tailored accordingly. This prompted an echocardiogram which was negative for valvular vegetations. The patient opted for outpatient colonoscopy for further evaluation. Repeat liver imaging showed enlarging abscess, therefore drain was placed. Patient was sent home on 6 week course of antibiotics. Discussion: While the incidence of liver abscess is low, it is essential to have a complete understanding of the disease activity and harm potential because the severity of these abscesses have a high mortality if left untreated. The physiology of disease is so delicate in these patients that an abscess located in the liver parenchyma close to the diaphragm can cause referred pain to the right shoulder or potentially a cough caused by diaphragmatic irritation. Although imaging was negative for etiology of the abscess, the workup is still in progress. This case highlights the importance of antibiotic therapy with drain placement to achieve source control and clinical and bacteriologic cure.Figure 1.: CT imaging demonstrating hepatic mass measuring 8.9 x 8.3 x 7.1 cm in the right lower lobe of liver.

S2345 A Rare Case of Bleeding Ulceration From the Excluded Stomach After Roux-en-Y Gastric Bypass Surgery

Introduction: Roux-en-Y gastric bypass (RYGB) is among the most common bariatric surgeries for treatment of morbid obesity, with >450,000 RYGB performed in the United States since 2011. Formation of an excluded stomach and duodenum that are difficult to access via conventional endoscopy can pose a unique challenge for diagnosis and treatment of gastrointestinal (GI) bleeding in post-RYGB patients. Case Description/Methods: A 60-year-old man with a history of morbid obesity and status post RYGB in 2017 presented in January 2021 with black tarry stools and a hemoglobin of 7.4 from a baseline of 13 g/dL without recent NSAID or tobacco use. He underwent upper endoscopy, colonoscopy, push enteroscopy and video capsule endoscopy without identification of a bleeding source. He was ultimately discharged home after stabilization and no further bleeding. Due to concern for an unidentified source of bleeding, further outpatient workup was pursued. CT enterography was unrevealing. Attempted endoscopic ultrasound (EUS)-guided gastrotomy to access the excluded stomach was unsuccessful due to inability to pass an Axios stent into the excluded stomach. Antegrade balloon enteroscopy failed to reach the jejuno-jejunal anastomosis. The patient was re-admitted in April 2021 for recurrent melena and a hemoglobin of 8.3 g/dL. Laparoscopic gastrotomy was performed with intraoperative transgastric endoscopy which revealed blood in the excluded stomach and duodenum. An ulcer in the excluded stomach was discovered and excised via subtotal gastrectomy. Pathology revealed focal transmural ulceration without dysplasia; H. pylori testing was negative. The patient was discharged home without recurrence of bleeding. Discussion: Alteration in GI anatomy after RYGB impedes access to excluded segments of the upper GI tract. Access to the excluded segments may be achieved by balloon enteroscopy depending on the length of the alimentary limb, EUS-assisted gastrotomy or laparoscopic formation of a temporary gastrotomy with transgastric endoscopy. A review of post-RYGB cases of excluded segment ulceration found that 93% of patients required surgery for definitive treatment. The most common interventions were remnant gastrectomy and oversewing of perforated ulcers with a 94% cure rate at short-term follow-up. Our case demonstrates that a high degree of suspicion for bleeding from the excluded gastric or small bowel segments should be maintained in patients with RYGB presenting with upper GI bleeding and initial negative GI tract evaluation.Figure 1.: Transmural ulceration in the remnant stomach status post subtotal gastrectomy

Timing observations of three Galactic millisecond pulsars

ABSTRACT We report observed and derived timing parameters for three millisecond pulsars (MSPs) from observations collected with the Parkes 64-m telescope, Murriyang. The pulsars were found during reprocessing of archival survey data by Mickaliger et al. One of the new pulsars (PSR J1546–5925) has a spin period P = 7.8 ms and is isolated. The other two (PSR J0921–5202 with P = 9.7 ms and PSR J1146–6610 with P = 3.7 ms) are in binary systems around low-mass (${\gt}0.2\, {\rm M}_{\odot }$) companions. Their respective orbital periods are 38.2 and 62.8 d. While PSR J0921–5202 has a low orbital eccentricity e = 1.3 × 10−5, in keeping with many other Galactic MSPs, PSR J1146–6610 has a significantly larger eccentricity, e = 7.4 × 10−3. This makes it a likely member of a group of eccentric MSP–helium white dwarf binary systems in the Galactic disc whose formation is poorly understood. Two of the pulsars are co-located with previously unidentified point sources discovered with the Fermi satellite’s Large Area Telescope, but no γ-ray pulsations have been detected, likely due to their low spin-down powers. We also show that, particularly in terms of orbital diversity, the current sample of MSPs is far from complete and is subject to a number of selection biases.

Evidence of 100 TeVγ-ray emission from HESS J1702-420: A new PeVatron candidate

Aims.The identification of PeVatrons, hadronic particle accelerators reaching the knee of the cosmic ray spectrum (few × 1015 eV), is crucial to understand the origin of cosmic rays in the Galaxy. We provide an update on the unidentified source HESS J1702-420, a promising PeVatron candidate.Methods.We present new observations of HESS J1702-420 made with the High Energy Stereoscopic System (H.E.S.S.), and processed using improved analysis techniques. The analysis configuration was optimized to enhance the collection area at the highest energies. We applied a three-dimensional likelihood analysis to model the source region and adjust non thermal radiative spectral models to theγ-ray data. We also analyzed archivalFermiLarge Area Telescope data to constrain the source spectrum atγ-ray energies > 10 GeV.Results.We report the detection ofγ-rays up to 100 TeV from a specific region of HESS J1702-420, which is well described by a new source component called HESS J1702-420A that was separated from the bulk of TeV emission at a 5.4σconfidence level. The power lawγ-ray spectrum of HESS J1702-420A extends with an index of Γ = 1.53 ± 0.19stat ± 0.20sysand without curvature up to the energy band 64−113 TeV, in which it was detected by H.E.S.S. at a 4.0σconfidence level. This makes HESS J1702-420A a compelling candidate site for the presence of extremely high energy cosmic rays. With a flux above 2 TeV of (2.08 ± 0.49stat ± 0.62sys) × 10−13 cm−2 s−1and a radius of (0.06 ± 0.02stat ± 0.03sys)°, HESS J1702-420A is outshone – below a few tens of TeV – by the companion HESS J1702-420B. The latter has a steep spectral index of Γ = 2.62 ± 0.10stat ± 0.20sysand an elongated shape, and it accounts for most of the low-energy HESS J1702-420 flux. Simple hadronic and leptonic emission models can be well adjusted to the spectra of both components. Remarkably, in a hadronic scenario, the cut-off energy of the particle distribution powering HESS J1702-420A is found to be higher than 0.5 PeV at a 95% confidence level.Conclusions.For the first time, H.E.S.S. resolved two components with significantly different morphologies and spectral indices, both detected at > 5σconfidence level, whose combined emissions result in the source HESS J1702-420. We detected HESS J1702-420A at a 4.0σconfidence level in the energy band 64−113 TeV, which brings evidence for the source emission up to 100 TeV. In a hadronic emission scenario, the hardγ-ray spectrum of HESS J1702-420A implies that the source likely harbors PeV protons, thus becoming one of the most solid PeVatron candidates detected so far in H.E.S.S. data. However, a leptonic origin of the observed TeV emission cannot be ruled out either.

Search for Dark Matter Annihilation Signals from Unidentified Fermi-LAT Objects with H.E.S.S.

Abstract Cosmological N-body simulations show that Milky Way–sized galaxies harbor a population of unmerged dark matter (DM) subhalos. These subhalos could shine in gamma-rays and eventually be detected in gamma-ray surveys as unidentified sources. We performed a thorough selection among unidentified Fermi-Large Area Telescope Objects (UFOs) to identify them as possible tera-electron-volt-scale DM subhalo candidates. We search for very-high-energy (E ≳ 100 GeV) gamma-ray emissions using H.E.S.S. observations toward four selected UFOs. Since no significant very-high-energy gamma-ray emission is detected in any data set of the four observed UFOs or in the combined UFO data set, strong constraints are derived on the product of the velocity-weighted annihilation cross section 〈σ v〉 by the J factor for the DM models. The 95% confidence level observed upper limits derived from combined H.E.S.S. observations reach 〈σ v〉J values of 3.7 × 10−5 and 8.1 × 10−6 GeV2 cm−2 s−1 in the W + W − and τ + τ − channels, respectively, for a 1 TeV DM mass. Focusing on thermal weakly interacting massive particles, the H.E.S.S. constraints restrict the J factors to lie in the range 6.1 × 1019–2.0 × 1021 GeV2 cm−5 and the masses to lie between 0.2 and 6 TeV in the W + W − channel. For the τ + τ − channel, the J factors lie in the range 7.0 × 1019–7.1 × 1020 GeV2 cm−5 and the masses lie between 0.2 and 0.5 TeV. Assuming model-dependent predictions from cosmological N-body simulations on the J-factor distribution for Milky Way–sized galaxies, the DM models with masses >0.3 TeV for the UFO emissions can be ruled out at high confidence level.

Classification of Fermi-LAT sources with deep learning using energy and time spectra

ABSTRACT Despite the growing number of gamma-ray sources detected by the Fermi-Large Area Telescope (LAT), about one-third of the sources in each survey remains of uncertain type. We present a new deep neural network approach for the classification of unidentified or unassociated gamma-ray sources in the last release of the Fermi-LAT catalogue (4FGL-DR2) obtained with 10 yr of data. In contrast to previous work, our method directly uses the measurements of the photon energy spectrum and time series as input for the classification, instead of specific, human-crafted features. Dense neural networks, and for the first time in the context of gamma-ray source classification recurrent neural networks, are studied in depth. We focus on the separation between extragalactic sources, i.e. active galactic nuclei, and Galactic pulsars, and on the further classification of pulsars into young and millisecond pulsars. Our neural network architectures provide powerful classifiers, with a performance that is comparable to previous analyses based on human-crafted features. Our benchmark neural network predicts that of the sources of uncertain type in the 4FGL-DR2 catalogue, 1050 are active galactic nuclei and 78 are Galactic pulsars, with both classes following the expected sky distribution and the clustering in the variability–curvature plane. We investigate the problem of sample selection bias by testing our architectures against a cross-match test data set using an older catalogue, and propose a feature selection algorithm using autoencoders. Our list of high-confidence candidate sources labelled by the neural networks provides a set of targets for further multiwavelength observations addressed to identify their nature. The deep neural network architectures we develop can be easily extended to include specific features, as well as multiwavelength data on the source photon energy and time spectra coming from different instruments.

Effects of contact with crude oil and its ingestion by the symbiotic polychaete Branchiosyllis living in sponges (Cinachyrella sp.) following the 2019 oil spill on the tropical coast of Brazil

In August 2019, thousands of tons of crude oil from an unidentified source began washing up on the Brazilian coast, causing the most severe environmental disaster that has ever impacted the South Atlantic Ocean. Paiva beach, which has some of the best-preserved tropical coral reefs on the Brazilian coast, was one of the coastal environments most severely affected by this oil. We report on the impact of the disaster on the local population of the symbiotic polychaete Branchiosyllis spp. associated with the sponge Cinachyrella sp. Following the oil spill sponges were found with oil stains on their surface and in their channels, and oil droplets were identified among the grains of the sediment accumulated within these channels. During this same period, the polychaetes in sponges had oil droplets on the surface of the body or in their pharynxes. Solubility tests using mineral oil and Raman spectra indicated that these oil droplets, found in both the sponges and the polychaetes, had similar chemical characteristics to those of the crude oil that washed up on the beach. Following the disaster, the abundance of Branchiosyllis declined sharply, although there was no significant shift in the mean size of individuals. By December 2019, the density of polychaetes was significantly lower than in the preceding months (107.9 ± 28.31 ind.10 mL−1 of sponge in August 2019 vs. 18.62 ± 35.48 ind.10 mL−1 of sponge in December 2019). This abrupt reduction in abundance with no change in the mean size of the individuals indicates that mortality affected all size (age) classes similarly, which is typical of anthropogenic impacts rather than natural mortality. It is thus clear that the contamination of polychaetes with crude oil increased mortality, causing a significant reduction in the Branchiosyllis populations of the coral reefs of Paiva beach following the 2019 oil spill.

Swift/UVOT follow-up of gravitational wave alerts in the O3 era

ABSTRACT In this paper, we report on the observational performance of the Swift Ultra-violet/Optical Telescope (UVOT) in response to the gravitational wave (GW) alerts announced by the Advanced Laser Interferometer Gravitational Wave Observatory and the Advanced Virgo detector during the O3 period. We provide the observational strategy for follow-up of GW alerts and provide an overview of the processing and analysis of candidate optical/UV sources. For the O3 period, we also provide a statistical overview and report on serendipitous sources discovered by Swift/UVOT. Swift followed 18 GW candidate alerts, with UVOT observing a total of 424 deg2. We found 27 sources that changed in magnitude at the 3σ level compared with archival u- or g-band catalogued values. Swift/UVOT also followed up a further 13 sources reported by other facilities during the O3 period. Using catalogue information, we divided these 40 sources into five initial classifications: 11 candidate active galactic nuclei (AGNs)/quasars, three cataclysmic variables (CVs), nine supernovae, 11 unidentified sources that had archival photometry, and six uncatalogued sources for which no archival photometry was available. We have no strong evidence to identify any of these transients as counterparts to the GW events. The 17 unclassified sources are likely a mix of AGN and a class of fast-evolving transient, and one source may be a CV.