The first stars of the Rho Ophiuchi Dark Cloud. XMM-Newton view of Rho Oph and its neighbors

Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMM-Newton observation centered on the Rho Ophiuchi A+B binary system. Rho Ophiiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from Rho Ophiuchi as well as a group of surrounding X-ray sources. We detected 89 X-ray sources, 47 of them have at least one counterpart in 2MASS + All-WISE catalogs. Based on IR and X-ray properties, we can distinguish between young stellar objects (YSOs) belonging to the cloud and background objects. Among the cloud members, we detect 3 debris disk objects and 22 disk-less / Class III young stars. We show that these stars have ages in $5-10$ Myr, and are significantly older than the YSOs in L1688. We speculate that they are the result of an early burst of star formation in the cloud. An X-ray energy of $\ge5\times10^{44}$ ergs has been injected into the surrounding medium during the past $5$ Myr, we discuss the effects of such energy budget in relation to the cloud properties and dynamics.Comment: 17 pages, 9 figures, 7 tables. Accepted for publication to Astronomy & Astrophysic

Bis[μ-N-(diethyl­amino-κN)dimethyl­silylanilido-κ2 N:N]bis­[chlorido­cobalt(II)]

In the title binuclear CoII complex, [Co2(C12H21N2Si)2Cl2], an inversion center is located at the mid-point between the two Co atoms in the dimeric mol­ecule. The bidentate N-silylated anilide ligand coordinates the CoII atom in an N,N′-chelating mode and provides the anilide N atom as a bridge to link two CoII atoms. The two ends of the N—Si—N chelating unit exhibit different affinities for the metal atom. The Co—Nanilide bond is 2.031 (6) Å and Co—Namino bond is 2.214 (6) Å. The four-coordinate Co atom presents a distorted tetra­hedral geometry, while the dimeric aggregation exhibits a (CoN)2 rhombus core with 1.998 (6) Å as the shortest sides and shows a ladder structure composed of Co, N and Si atoms

Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties

Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean

Selective Calixarene Directed Synthesis of MXene Plates, Crumpled Sheets, Spheres and Scrolls

Fully exploiting the electronic and mechanical properties of 2D laminar materials not only requires efficient and effective means of their exfoliation into low dimensional layers, but also necessitates a means of changing their morphology so as to explore any enhancement that this may offer. MXenes are a rapidly emerging new class of such laminar materials with unique properties. However, access to other morphologies of MXenes has not yet been fully realised. To this end we have developed the synthesis of MXenes (Ti2C) as plates, crumpled sheets, spheres and scrolls, which involves selective intercalation of p-phosphonic calix[n]arenes, with control in morphology arising from the choice of the size of the macrocycle, n = 4, 5, 6 or 8. This opens up wider avenues of discovery/design for new morphologies from the wider family of MXenes beyond Ti2C, along with opportunities to exploit any new physico-chemical properties proffered

Holevo Cram\'er-Rao Bound for waveform estimation of gravitational waves

Detecting kilohertz gravitational waves from the post-merger remnants of binary neutron-star mergers could enhance our understanding of extreme matter. To enable this detection, a gravitational-wave interferometer can be detuned to increase its kilohertz sensitivity. The precision limits of detuned interferometers and other cavity--based quantum sensors, however, are not well understood. The sensitivity of the standard variational readout scheme does not reach the waveform-estimation Quantum Cram\'er-Rao Bound. We establish the fundamental precision limit, the waveform-estimation Holevo Cram\'er-Rao Bound, by identifying the incompatibility of the na\"ive estimates of the signal's cosine and sine phases. For an equal weighting between the phases, we prove that the standard scheme is indeed optimal. For unequal weights, however, we propose an experimental realisation of a new measurement scheme to significantly improve the sensitivity. This scheme could facilitate kilohertz gravitational-wave astronomy and has broader applications to detuned cavity--based quantum metrology.Comment: v2. Letter: 7 pages, 2 figures. Supplemental Material: 17 pages, 4 figures. Submitted on August 11 2023 to Physical Review Letter