Photometry of the eclipsing cataclysmic variable SDSS J152419.33+220920.0

Aims. We present new photometry of the faint and poorly studied cataclysmic variable SDSS J152419.33+220920.0, analyze its light curve and provide an accurate ephemeris for this system. Methods. Time-resolved CCD differential photometry was carried out using the 1.5m and 0.84m telescopes at the Observatorio Astronomico Nacional at San Pedro Martir. Results. From time-resolved photometry of the system obtained during six nights (covering more than twenty primary eclipse cycles in more than three years), we show that this binary presents a strong primary and a weak secondary modulation. Our light curve analysis shows that only two fundamental frequencies are present, corresponding to the orbital period and a modulation with twice this frequency. We determine the accurate ephemeris of the system to be HJD(eclipse)= 2454967.6750(1) + 0.06531866661(1) E. A double-hump orbital period modulation, a standing feature in several bounce-back systems at quiescence, is present at several epochs. However, we found no other evidence to support the hypothesis that this system belongs to the post-minimum orbital-period systems

A Radial Velocity Study of the Intermediate Polar EX Hydrae

A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to with the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated to the orbital modulation. Since our eclipse timings have been obtained almost 91,000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system mainly shows double-peaked H$\alpha$, H$\beta$ and HeI $\lambda$5876 \AA emission lines. From the profile of the H$\alpha$ line, we find two components; one with a steep rise and velocities not larger than $\sim$1000 km s$^{-1}$ and another broader component extending up to $\sim$2000 km s$^{-1}$, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to $K_1 = 58 \pm 5$ km s$^{-1}$ from H$\alpha$, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving $K_1$. This value is compatible with the values found in high-resolution both in the ultraviolet and X-ray. We find: $M_{1} = 0.78 \pm 0.03$ M$_{\odot}$, $M_{2} = 0.10 \pm 0.02$ M$_{\odot}$ and $a = 0.67 \pm 0.01$ R$_{\odot}$. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions. Our results indicate that EX Hya has a well formed disc and that the magnetosphere should extend only to about $3.75\,R_{\rm{WD}}$.Comment: 16 pages, 14 figures, accepted for publication in MNRA

Los sistemas fluviales cuaternarios de la Península Ibérica: conceptos y preguntas sin resolver

Los sistemas fluviales durante el Cuaternario adquieren especial relevancia porque registran tanto variaciones en el clima como en el nivel del mar o en la actividad tectónica para periodos en los que la actividad humana se ha desarrollado. La Península Ibérica es rica en su registro, si bien dadas las particularidades de la geología peninsular y las incertidumbres en la edad de los depósitos, el análisis de su registro es muy problemático. A pesar de ello, los diferentes grupos de investigadores consideran que la génesis de estas secuencias de depósitos se puede atribuir a los cambios climáticos que acontecieron durante este periodo y a los que se superpuso la actividad tectónica, modificando la disposición de las secuencias de terrazas e incluso su número. El efecto de las variaciones del nivel del mar sólo se ha invocado en el curso bajo del Tajo mientras que no se considera que haya afectado a las secuencias de terrazas del Guadalquivir.Departamento de Estratigrafía, Universidad Complutense de Madrid, EspañaDepartamento de Investigación en Recursos Geológicos, Instituto Geológico y Minero de España, Españ

Neutron transmission: A powerful technique for small accelerator-based neutron sources

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Sedimentación de plataforma durante el Carbonifero Inferior (Formación Terena) en el área de Santa Olalla del Cala (Huelva, España)

La Formación Terena (Carbonifero Inferior) representa un caso de sedimentación de plataforma en un contexto tectónicamenle activo. La sucesión general está constituida por una unidad basal carbonatada seguida de tres unidades terrígenas de caracter granodecreciente. La unidad basal representa depósitos de plataforma carbonatada estable mientras que las unidades siliciclásticas se interpretan en relación con corrientes de resaca densas y diluidas producidas por oleajes de tormenta. El depósito de la Fomación Terena registra un cambio en la naturaleza de la cuenca, que pasa de carbonatada a siliciclástica, con tres episodios de desestabilización relacionados genéticamente con pulsaciones tectónicas. [ABSTRACT] The Lower Carboniferous Terena Formation records deposition on a tectonically active shelf context. It is composed of a carbonate basal unit followed upwards by three fining upwards silicic1astic units. The basal unit represents sedimentation on a stable shelf. The siliciclastic units record sedimentation from dense and dilute storm surges on an unstable shelf. These deposits record a change in the nature of the basin, from carbonate to silieiclastic realms, with three episodes of reactivation genetically related to three tectonic pulses

El paleógeno del sector suroccidental de la Cuenca del Duero: nueva división estratigráfica y controles sobre su sedimentación

Como resultado de un detallado trabajo cartográfico, estratigráfico y sedimentológico, se propone la división del Paleógeno del sector suroccidental de la Cuenca del Duero en cuatro U.T.S. limitadas por discordancias. Estas D.T.S., que abarcan desde el tránsito Cretácico superior-Paleoceno hasta el Oligoceno, incluyen distintas unidades litoestratigráficas que sonreordenadas, modificando la sucesión estratigrática propuesta por los autores anteriores. Se asigna a la U.T.S. Me una edad Cretácico superior-Paleoceno. Se individualiza el Eoceno inferior (U.T.S. PI) en la zona de Salamanca. Se reinterpreta la relación existente entre los materiales del Eoceno mediosuperior y los del Eoceno superior-Oligoceno considerándolos en tránsito por lo que se asignan a una única U.T.S. (UT.S. P2, Eoceno medio Oligoceno inferior). Se incluyen en la U.T.S. P3 (Oligoceno superior) los sedimentos arcósicos anterionnente considerados como Vatlesienses. Así mismo, se considera que gran parte de los materiales asignados al mioceno inferior son sedimentos paleógenos afectados por un proceso de alteración de edad Miocena, lo que implica una variación en la extensión y límites de la cuenca neógena en su extremo SO. Se analiza la evolución de las distintas U.T.S. deduciendo un carácter tectónico para las megasecuencias propuestas relacionado con el progresivo levantamiento de las áreas fuente. El clima muestra un tránsito desde condiciones tropicales sin estaciones contrastadas (U,T.S. MC) hasta un clima mediterráneo árido (U.T.S. P3) con una estación seca muy marcada y una corta estación húmeda caracterizada por violentas avenidas. [ABSTRACT] A Paleogene four-fold stratigraphical division is proposed here as result fram the detailed studies carried out during the elaboration of 22 sheets of the Geological Map of Spain (E. 1 :50.000). This units (T.S.U.) are limited by regional discordances and they have a Upper Cretaceous to Oligocene ages. The previous stratigraphical schemes are rearranged due to the different stratigraphical relations observed between the lithostratigraphical units proposed by other workers (Jiménez, 1970; Corrochano, 1977; Alonso, 1981...). An Upper Cretaceous-Paleocene age is assumed to T.S.U. MC which is mainly composed by siliciclastic sediments strongly silicified forming a FU megasequence. It is intcrpretated as braided streams that flowed downslope filling paleovalleys erodcd onto Paleozoic materiaIs. Mineralogical features point to a tropical climate. Lower Eocene (T.S.U. P I ) is identified in the Salamanca area, where ir was considered as lacking. It is composed by arkosic sediments forming a CU megasequence. Fossil faunas of this T.S.U. record a subtropical clima te. It is observed a transition from high sinuosity streams to braided ones. T.S.U. P2 (Middle Eocene-Lower Oligocene) is composed of two lithostratigraphical units previously considered as bounded by a discordance (Alonso, 1981).It has a subarkosic to lithic nature and forms a CU megasequence. This unit records a subtropical climate with short arid periods and is interpretated as braided streams showing an increasing stability and enviromental energy to the topo T.S. U. P3 (Upper Oligocene) is composed by arkosic sediments previously considered of Vallesian (Middle to Upper Miocene) age. They form a CU megasequence that records braided streams prograding basinwardfrom higher arcas. Palinological associations and pedological features indicate an arid mediterranean climate with long arid periods and a short rainy season with strong floods. We consider that most of Lower Miocene sediments are of Paleogene age. They are afected by a widespread alteration profile developed along Lower Miocene that masked its more significative features. Sedimentological analysis of T.S.U. shows that its megasequentiality is related to the rates of tectonical uplift of source arcas whereas a distensive regime developed in the sedimentation basin

Mapping the spectral index of Cassiopeia A : evidence for flattening from radio to infrared

Funding: The work of VD is supported by a grant from the NWO graduate programme/GRAPPA-PhD programme. JVHS acknowledges support from the STFC grant ST/R000824/1.Synchrotron radiation from supernova remnants is caused by electrons accelerated through diffusive shock acceleration (DSA). The standard DSA theory predicts an electron spectral index of p = 2, corresponding to a radio spectral index of α = −0.5. An extension of DSA theory predicts that the accelerated particles change the shock structure, resulting in a spectrum that is steeper than p > 2 (α < −0.5) at low energies and flattens with energy. For Cassiopeia A, a synchrotron spectral flattening was previously reported for a small part of the remnant in the mid-infrared regime. Here, we present new measurements for spectral flattening using archival radio (4.72 GHz) and mid-infrared (3.6 μm) data, and we produce a complete spectral index map to investigate the spatial variations within the remnant. We compare this to measurements of the radio spectral index from L-band (1.285 GHz) and C-band (4.64 GHz) maps. Our result shows overall spectral flattening across the remnant (αR-IR ∼ −0.5 to −0.7), to be compared with the radio spectral index of αR = −0.77. The flattest values coincide with the locations of most recent particle acceleration. In addition to overall flattening, we detect a relatively steeper region in the south-east of the remnant (αR-IR ∼ −0.67). We explore whether these locally steeper spectra could be the result of synchrotron cooling, which provides constraints on the local magnetic field strengths and the age of the plasma, suggesting B ≲ 2 mG for an age of 100 yr, and even B ≲ 1 mG using the age of Cas A, in agreement with other estimates.Publisher PDFPeer reviewe

The very faint X-ray binary IGR J17062-6143: a truncated disc, no pulsations, and a possible outflow

We present a comprehensive X-ray study of the neutron star low-mass X-ray binary IGR J17062-6143, which has been accreting at low luminosities since its discovery in 2006. Analysing NuSTAR, XMM–Newton, and Swift observations, we investigate the very faint nature of this source through three approaches: modelling the relativistic reflection spectrum to constrain the accretion geometry, performing high-resolution X-ray spectroscopy to search for an outflow, and searching for the recently reported millisecond X-ray pulsations. We find a strongly truncated accretion disc at 77+22−18 gravitational radii (∼164 km) assuming a high inclination, although a low inclination and a disc extending to the neutron star cannot be excluded. The high-resolution spectroscopy reveals evidence for oxygen-rich circumbinary material, possibly resulting from a blueshifted, collisionally ionized outflow. Finally, we do not detect any pulsations. We discuss these results in the broader context of possible explanations for the persistent faint nature of weakly accreting neutron stars. The results are consistent with both an ultra-compact binary orbit and a magnetically truncated accretion flow, although both cannot be unambiguously inferred. We also discuss the nature of the donor star and conclude that it is likely a CO or O–Ne–Mg white dwarf, consistent with recent multiwavelength modelling