Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk

Using the Hubble Space Telescope, the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory, and the Spitzer Space Telescope, we have performed deep imaging from 0.8 to 8 um of the southern subcluster in the Chamaeleon I star-forming region. In these data, we have discovered an object, Cha 110913-773444, whose colors and magnitudes are indicative of a very low-mass brown dwarf with a circumstellar disk. In a near-infrared spectrum of this source obtained with the Gemini Near-Infrared Spectrograph, the presence of strong steam absorption confirms its late-type nature (>=M9.5) while the shapes of the H- and K-band continua and the strengths of the Na I and K I lines demonstrate that it is a young, pre-main-sequence object rather than a field dwarf. A comparison of the bolometric luminosity of Cha 110913-773444 to the luminosities predicted by the evolutionary models of Chabrier and Baraffe and Burrows and coworkers indicates a mass of 8+7/-3 M_Jup, placing it fully within the mass range observed for extrasolar planetary companions (M<=15 M_Jup). The spectral energy distribution of this object exhibits mid-infrared excess emission at >5 um, which we have successfully modeled in terms of an irradiated viscous accretion disk with M'<=10e-12 M_sun/year. Cha 110913-773444 is now the least massive brown dwarf observed to have a circumstellar disk, and indeed is one of the least massive free-floating objects found to date. These results demonstrate that the raw materials for planet formation exist around free-floating planetary-mass bodies.Comment: 5 pages, accepted to Astrophysical Journal Letter

Spitzer Spectroscopy of the Circumprimary Disk in the Binary Brown Dwarf 2MASS J04414489+2301513

Using the Spitzer Infrared Spectrograph, we have performed mid-infrared spectroscopy on the young binary brown dwarf 2MASS J04414489+2301513 (15 AU) in the Taurus star-forming region. The spectrum exhibits excess continuum emission that likely arises from a circumstellar disk around the primary. Silicate emission is not detected in these data, indicating the presence of significant grain growth. This is one of the few brown dwarf disks at such a young age (~1 Myr) that has been found to lack silicate emission. To quantitatively constrain the properties of the disk, we have compared the spectral energy distribution of 2MASS J04414489+2301513 to the predictions of our vertical structure codes for irradiated accretion disks. Our models suggest that the remaining atmospheric grains of moderately depleted layers may have grown to a size of ##IMG## [http://ej.iop.org/icons/Entities/gsim.gif] {gsim} 5 _m. In addition, our model fits indicate an outer radius of 0.2-0.3 AU for the disk. The small size of this circumprimary disk could be due to truncation by the secondary. The absence of an outer disk containing a reservoir of small, primordial grains, combined with a weak turbulent mechanism, may be responsible for the advanced grain growth in this disk.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90835/1/2041-8205_726_1_L3.pd

Risk factors for infections caused by carbapenem-resistant Enterobacterales: an international matched case-control-control study (EURECA)

Cases were patients with complicated urinary tract infection (cUTI), complicated intraabdominal (cIAI), pneumonia or bacteraemia from other sources (BSI-OS) due to CRE; control groups were patients with infection caused by carbapenem-susceptible Enterobacterales (CSE), and by non-infected patients, respectively. Matching criteria included type of infection for CSE group, ward and duration of hospital admission. Conditional logistic regression was used to identify risk factors. Findings Overall, 235 CRE case patients, 235 CSE controls and 705 non-infected controls were included. The CRE infections were cUTI (133, 56.7%), pneumonia (44, 18.7%), cIAI and BSI-OS (29, 12.3% each). Carbapenemase genes were found in 228 isolates: OXA-48/like, 112 (47.6%), KPC, 84 (35.7%), and metallo-beta-lactamases, 44 (18.7%); 13 produced two. The risk factors for CRE infection in both type of controls were (adjusted OR for CSE controls; 95% CI; p value) previous colonisation/infection by CRE (6.94; 2.74-15.53; <0.001), urinary catheter (1.78; 1.03-3.07; 0.038) and exposure to broad spectrum antibiotics, as categorical (2.20; 1.25-3.88; 0.006) and time-dependent (1.04 per day; 1.00-1.07; 0.014); chronic renal failure (2.81; 1.40-5.64; 0.004) and admission from home (0.44; 0.23-0.85; 0.014) were significant only for CSE controls. Subgroup analyses provided similar results. Interpretation The main risk factors for CRE infections in hospitals with high incidence included previous coloni-zation, urinary catheter and exposure to broad spectrum antibiotics

Feshbach-type resonances for two-particle scattering in graphene

Two-particle scattering in graphene is a multichannel problem, where the energies of the identical or opposite-helicity channels lie in disjoint energy segments. Due to the absence of Galilean invariance, these segments depend on the total momentum Q. The dispersion relations for the two opposite-helicity scattering channels are analogous to those of two one-dimensional tight-binding lattices with opposite dispersion relations, which are known to easily bind states at their edges. When an s-wave separable interaction potential is assumed, those bound states reveal themselves as three Feshbach resonances in the identical-helicity channel. In the limit Q -> 0, one of the resonances survives and the opposite-helicity scattering amplitudes vanish

A LAMOST Spectroscopic Study of T Tauri Stars in the Orion OB1a Subassociation

We present a spectroscopic analysis of T Tauri stars (TTSs) observed with the wide-field multifiber spectrograph LAMOST in the substellar associations Ori OB1a located in the Orion Star-forming Complex. Based on GAIA-DR3 data, we selected stars with proper motions and parallaxes expected for TTSs belonging to the young association. We perform a spectroscopic analysis to obtain the spectral types and measure the equivalent widths of Li i and H α to confirm the youth of the stars and estimate the accretion status. We also estimate extinctions, masses, and ages for the studied sample. Out of 342 TTSs with spectroscopic and kinematic properties indicating their membership of the subassociation, 2 are reported here for the first time. Finally, we detect four stellar kinematic groups located at different distances, two in the north fields and two in the south field. These groups also show different proper motions. This suggests that the star-forming scenario in this region is more complex than the traditional spatial-temporal scenario, in which a generation of stars triggers the formation of a new spatially differentiated generation of stars

Violencia de género desde un abordaje interdisciplinar

Este libro va dedicado a todas las mujeres que sufren o que han sufrido, en algún momento de sus vidas, cualquier tipo de violencia. Mujeres que afrontan una lucha interna para liberarse del trauma que se deriva del sometimiento vejatorio al que están o han estado expuestas, por causa de abusos de género de toda índole. Cuando una mujer logra salir del espinoso camino que la condujo a soportar la violencia de género, es cuando empieza a palpitar de nuevo, a vivir, a sentir que la vida le da otra oportunidad; que, esta vez sí, debe aprovechar y hacer frente al sufrimiento que le ha dejado ese oscuro pasado. Es cuando empieza, de nuevo, a quererse, a darse cuenta de que ella vale mucho más que lo que le han hecho creer, y es cuando, fruto de esta experiencia, decide, muchas veces, dar su apoyo a otras mujeres, inmersas en ese mismo calvario. Este libro recoge resultados de procesos investigativos relacionados con la violencia de género, fruto del análisis de diferentes profesionales que se han puesto en la tarea de explorar y tratar de comprender este grave problema de salud pública de ámbito mundial, y, a su vez, contribuir con sus trabajos a paliar el mayor de los flagelos con el que la mujer viene siendo ultrajada