High-resolution X-ray spectroscopy of supergiant HMXB 4U 1700−37 during the compact object eclipse

We present an analysis of the first observation of the iconic high-mass X-ray binary 4U 1700−37 with the Chandra High-Energy Transmission Gratings (HETGs) during an X-ray eclipse. The goal of the observation was to study the structure/physical conditions in the clumpy stellar wind through high-resolution spectroscopy. We find the following: (a) Emission-line brightness from K-shell transitions, corresponding to near-neutral species, directly correlates with continuum illumination. However, these lines do not greatly diminish during eclipse. This is readily explained if fluorescence K α emission comes from the bulk of the wind. (b) The highly ionized Fe xxv and Fe xxvi Ly α diminish during eclipse. Thus, they must be produced in the vicinity of the compact object where log ξ > 3. (c) To describe the emission-line spectrum, the sum of two self-consistent photoionization models with low ionization (log ξ ∼ −1) and high ionization (log ξ ∼ 2.4) is required. From their emission measures, the clump-to-interclump density ratio can be estimated to be nc/ni ∼ 300. To fit the complex He-like Si xiii profile, the plasma requires a broadening with vbulk ∼ 840 km s−1. Reproducing the observed r ≈ f line fluxes requires the addition of a third collisionally ionized plasma. (d) Emission-line widths appear unresolved at the HETG resolution with the exception of silicon. There is no clear radial segregation between (quasi-)neutral and ionized species, consistent with cold wind clumps interspersed in a hot rarefied interclump medium.This research has been funded under the project ESP2017-85691-P. The research leading to these results has received funding from the European Union’s Horizon 2020 Programme under the Activities for the High-Energy Astrophysiscs Domain (AHEAD) project (grant agreement no. 654215). Victoria Grinberg (VG) was supported through the Margarete von Wrangell fellowship by the ESF and the Ministry of Science, Research and the Arts of Baden-Württemberg. Work at LLNL was performed under the auspices of the U.S. Department of Energy under contract no. DE-AC52-07NA27344 and supported through National Aeronautics and Space Administration (NASA) grants to Lawrence Livermore National Laboratory (LLNL). Lida M. Oskinova acknowledges Deutsches Zentrum für Luft und Raumfahrt (DLR) grant FKZ 50 OR 1508 and partial support by the Russian Government Program of Competitive Growth of Kazan Federal University

NuSTAR rules out a cyclotron line in the accreting magnetar candidate 4U2206+54

Based on our new NuSTAR X-ray telescope data, we rule out any cyclotron line up to 60 keV in the spectra of the high-mass X-ray binary 4U2206+54. In particular, we do not find any evidence of the previously claimed line around 30 keV, independently of the source flux, along the spin pulse. The spin period has increased significantly, since the last observation, up to 5750 ± 10 s, confirming the rapid spin-down rate ν˙=−1.8×10−14 Hz s−1. This behaviour might be explained by the presence of a strongly magnetized neutron star (Bs > several times 1013 G) accreting from the slow wind of its main-sequence O9.5 companion.This research has been supported by the grant ESP2017-85691-P. KP acknowledges support from the Russian Foundation for Basic Research grant 18-502-12025

Evidence of Compton cooling during an X-ray flare supports a neutron star nature of the compact object in 4U1700-37

Based on new Chandra X-ray telescope data, we present empirical evidence of plasma Compton cooling during a flare in the non pulsating massive X-ray binary 4U1700-37. This behaviour might be explained by quasispherical accretion onto a slowly rotating magnetised neutron star. In quiescence, the neutron star in 4U1700-37 is surrounded by a hot radiatively cooling shell. Its presence is supported by the detection of mHz quasi periodic oscillations likely produced by its convection cells. The high plasma temperature and the relatively low X-ray luminosity observed during the quiescence, point to a small emitting area about 1 km, compatible with a hot spot on a NS surface. The sudden transition from a radiative to a significantly more efficient Compton cooling regime triggers an episode of enhanced accretion resulting in a flare. During the flare, the plasma temperature drops quickly. The predicted luminosity for such transitions, Lx = 3 x 10^35 erg s-1, is very close to the luminosity of 4U1700-37 during quiescence. The transition may be caused by the accretion of a clump in the stellar wind of the donor star. Thus, a magnetised NS nature of the compact object is strongly favoured.Comment: Accepted for publication in MNRA

High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

Context. We present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. Aims. To examine the wind’s reaction to the flare, we performed both time-averaged and time-resolved analyses of the RGS spectrum and examined potential spectral changes. Methods. We focused on the high-resolution XMM-Newton RGS spectra and divided the observation into pre-flare, flare, and post-flare phases. We modeled the time-averaged and time-resolved spectra with phenomenological components and with the self-consistent photoionization models calculated via CLOUDY and XSTAR in the pre-flare phase, where strong emission lines due to resonant transitions of highly ionized ions are seen. Results. In the spectra, we find emission lines corresponding to K-shell transitions in highly charged ions of oxygen, neon, magnesium, and silicon as well as radiative recombination continua (RRC) of oxygen. Additionally, we observe potential absorption lines of magnesium at a lower ionization stage and features identified as iron L lines. The CLOUDY and XSTAR photoionization models provide contradictory results, either pointing towards uncertainties in theory or possibly a more complex multi-phase plasma, or both. Conclusions. We are able to demonstrate the existence of a plethora of variable narrow features, including the firm detection of oxygen lines and RRC that RGS enables to observe in this source for the first time. We show that Vela X-1 is an ideal source for future high-resolution missions, such as XRISM and Athena.V.G. is supported through the Margarete von Wrangell fellowship by the ESF and the Ministry of Science, Research and the Arts Baden-Württemberg. We acknowledge support from the ESTEC Faculty Visiting Scientist Programme to V.G. S.B. acknowledges financial support from the Italian Space Agency under grant ASI-INAF 2017-14-H.O. Work at LLNL was performed under the auspieces of the U.S. Department of Energy under contract No. DE-AC52-07NA27344. S.M.N. acknowledges funding by the Spanish Ministry MCIU under project RTI2018-096686-B-C21 (MCIU/AEI/FEDER, UE), co-funded by FEDER funds and by the Unidad de Excelencia María de Maeztu, ref. MDM-2017-0765

Evidence of Compton cooling during an X-ray flare supports a neutron star nature of the compact object in 4U1700−37

Based on new Chandra X-ray telescope data, we present empirical evidence of plasma Compton cooling during a flare in the non-pulsating massive X-ray binary 4U1700−37. This behaviour might be explained by quasi-spherical accretion on to a slowly rotating magnetized neutron star (NS). In quiescence, the NS in 4U1700−37 is surrounded by a hot radiatively cooling shell. Its presence is supported by the detection of mHz quasi-periodic oscillations likely produced by its convection cells. The high plasma temperature and the relatively low X-ray luminosity observed during the quiescence, point to a small emitting area ∼1 km, compatible with a hotspot on an NS surface. The sudden transition from a radiative to a significantly more efficient Compton cooling regime triggers an episode of enhanced accretion resulting in a flare. During the flare, the plasma temperature drops quickly. The predicted luminosity for such transitions, ∼3 × 1035 erg s−1, is very close to the luminosity of 4U1700−37 during quiescence. The transition may be caused by the accretion of a clump in the stellar wind of the donor star. Thus, a magnetized NS nature of the compact object is strongly favoured.This research has been supported by the grant ESP2014-53672-C3-3P. AB acknowledges support from STScI award 44A-1096046. JJRR acknowledges support from MECD fellowship PRX17/00114

Epidemiological characteristics and diagnostic approach in patients admitted to the emergency room for transient loos of consciousness: Group for Syncope Study in the Emergency Room (GESINUR) study

Aims: To assess the clinical presentation and acute management of patients with transient loss of consciousness (T-LOC) in the emergency department (ED). Methods and results: A multi-centre prospective observational study was carried out in 19 Spanish hospitals over 1 month. The patients included were 14 years old and were admitted to the ED because of an episode of T-LOC. Questionnaires and corresponding electrocardiograms (ECGs) were reviewed by a Steering Committee (SC) to unify diagnostic criteria, evaluate adherence to guidelines, and diagnose correctly the ECGs. We included 1419 patients (prevalence, 1.14%).ECG was performed in 1335 patients (94%) in the ED: 498 (37.3%) ECGs were classified as abnormal. The positive diagnostic yield ranged from 0% for the chest X-ray to 12% for the orthostatic test. In the ED, 1217 (86%) patients received a final diagnosis of syncope, whereas the remaining 202 (14%) were diagnosed of non-syncopal transient lossof consciousness (NST-LOC). After final review by the SC, 1080 patients (76%) were diagnosed of syncope, whereas 339 (24%) were diagnosed of NST-LOC (P , 0.001). Syncope was diagnosed correctly in 84% of patients. Only 25% of patients with T-LOC were admitted to hospitals. Conclusion Adherence to clinical guidelines for syncope management was low; many diagnostic tests were performed with low diagnostic yield. Important differences were observed between syncope diagnoses at the ED and by SC decision

Investigación docente para estudiar el razonamiento del alumnado en la resolución de problemas de física en titulaciones de ingeniería y arquitectura

En general, resulta demasiado habitual para el alumnado de grado en ingeniería o arquitectura utilizar las fórmulas matemáticas sin comprender adecuadamente su significado físico. El principal objetivo del trabajo es identificar si la evaluación objetiva del razonamiento estudiantil en la resolución de problemas contribuye a mejorar el aprendizaje de la física en el alumnado de forma significativa. Los resultados serán útiles para conocer cómo se adquieren las estrategias de resolución de problemas así como su interpretación de las leyes y conceptos de física. Como herramienta se ha empleado una rúbrica y se ha realizado un ejercicio demostrativo para el desarrollo de la experiencia. La novedad radica en que si no se explica la resolución del ejercicio paso a paso la máxima puntuación se reduce al 69% si se ha hecho correctamente. Se podrán detectar equívocos conceptuales aplicados y mejorar el proceso de enseñanza y aprendizaje de la física en el nivel universitario. Un cuestionario anónimo evaluará tanto la rúbrica como la experiencia educativa y la red evaluará la consistencia de la rúbrica

Unveiling the physics problem strategies of engineering and architecture students

It is very common for students of technical degrees to think that solving physics problems consists predominantly of applying a series of formulae and substituting data. In other words, they do not need to understand the physical meaning of an equation. Some experimental studies focusing on basic kinematics have revealed certain shortcomings in the resolution strategies related to this topic. The aim of this work is to extend the experience to other physics themes and to identify whether objective assessment of the engineering or architecture student’s reasoning significantly improves the learning of the matter in a dual teaching context. An illustrative example of how the evaluation rubric is applied to a problem proposed to students has been shown. To discourage copying or plagiarism in problem solving, learners have signed a declaration of honesty stating that they have not received any external help in doing the work. According to the students’ feedback, the learning initiative has been highly rated and improvements to the rubric have been suggested. The presence of several errors in the resolution submitted by the students has shown a dispersion of marks that makes it necessary to reconsider the rubric for the next academic year. In spite of this, the fewer mistakes, the lower deviation in the marks.The present work was supported by the Networks-I3CE Programme of Research in University Teaching of the Education Science Institute (ESI), University of Alicante (Calls 2019-20, Ref.: 4630 and 2020-21, Ref.: 5179)