The visual binary AG Tri in β\beta Pictoris Association: can a debris disc cause very different rotation periods of its components?

We measure the photometric rotation periods of the components of multiple systems in young stellar associations to investigate the causes of the observed rotation period dispersion. We present the case of the wide binary AG Tri in the 23-Myr young beta Pictoris Association consisting of K4 + M1 dwarfs. Our multi-band, multi-season photometric monitoring allowed us to measure the rotation periods of both components P_A = 12.4d and P_B = 4.66d, to detect a prominent magnetic activity in the photosphere, likely responsible for the measured radial velocity variations, and for the first time, a flare event on the M1 component AG Tri B. We investigate either the possibility that the faster rotating component may have suffered an enhanced primordial disc dispersal, starting its PMS spin-up earlier than the slower rotating component, or the possibility that the formation of a debris disc may have prevented AG Tri A from gaining part of the angular momentum from the accreting disc.Comment: 28 pages, 7 figures, accepted for publication in Astrophysics and Space Science 2015, (ASTR-D-15-00445R2

Impact of winds on circumstellar dust in T Tauri stars

<p>The dynamical winds of Classical T Tauri stars (CTTS) are believed to originate from the MHD processes at the boundary between the inner disc and the stellar magnetosphere. We explore how the wind affects the circumstellar dusty environment. Long term spectroscopic and photometric monitoring of the CTTS RY Tau in 2013-2015 has revealed a tight correlation between the wind radial velocity and the circumstellar  extinction. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suggest that cyclic re-adjustments of the stellar magnetosphere and the subsequent magnetospheric mass ejections can have an impact on the dusty disk wind flows near the inner boundary of the circumstellar disk. A role of dusty winds in the  long-lasting dimming events in CTTS is discussed. </p

The dust storm in RW Aurigae

<p>The T Tauri star RW Aur A entered a very deep drop in brightness in 2013, and has since then remained at a level of about 3 magnitudes fainter in V than normal. We have carried out spectroscopic and photometric observations of the star with the aim to reveal the nature of this dimming.  The photospheric spectrum of RW Aur A and signatures of accretion have not changed indicating that the dimming is external and caused by a foreground obscuration by dust grains giving rise to a grey extinction. The forbidden [OI] and [SII] lines, formed in distant parts of the wind (jets), became strong relatively to the dimmed stellar spectrum meaning that only the star and its immediate surrounding were obscured, but not the distant wind.  NIR photometry in the JHKLM bands shows that when the star faded in V and JHK it became brighter in L and M. The K-L and L-M colours indicate excess radiation of a black-body at about 1000 K.  The most probable explanation is that the excess radiation in L and M comes from hot dust near the star, and that this dust is responsible for the dimming in the visual range. We propose that dust has been stirred up from the inner disk into the line-of-sight as the cause of this unusual phenomenon.</p

Oxyethylated Fluoresceine&mdash;(thia)calix[4]arene Conjugates: Synthesis and Visible-Light Photoredox Catalysis in Water&ndash;Organic Media

Fluorescent derivatives attract the attention of researchers for their use as sensors, photocatalysts and for the creation of functional materials. In order to create amphiphilic fluorescent derivatives of calixarenes, a fluorescein derivative containing oligoethylene glycol and propargyl groups was obtained. The resulting fluorescein derivative was introduced into three different (thia)calix[4]arene azide derivatives. For all synthesized compounds, the luminescence quantum yields have been established in different solvents. Using UV-visible spectroscopy, dynamic light scattering, as well as transmission and confocal microscopy, aggregation of macrocycles was studied. It was evaluated that calixarene derivatives with alkyl substituents form spherical aggregates, while symmetrical tetrafluorescein-containing thiacalix[4]arene forms extended worm-like aggregates. The macrocycle containing tetradecyl fragments was found to be the most efficient in photoredox ipso-oxidation of phenylboronic acid. In addition, it was shown that in a number of different electron donors (NEt3, DABCO and iPr2EtN), the photoredox ipso-oxidation proceeds best with triethylamine. It has been shown that a low molecular weight surfactant Triton-X100 can also improve the photocatalytic abilities of an oligoethylene glycol fluorescein derivative, thus showing the importance of a combination of micellar and photoredox catalysis

New Calix[4]arene—Fluoresceine Conjugate by Click Approach—Synthesis and Preparation of Photocatalytically Active Solid Lipid Nanoparticles

New fluorescent systems for photocatalysis, sensors, labeling, etc., are in great demand. Amphiphilic ones are of special interest since they can form functional colloidal systems that can be used in aqueous solutions. A new macrocycle platform for click chemistry and its adduct with o-propargylfluoresceine was synthesized and characterized using modern physical techniques. Nanosized solid lipid nanoparticles (SLNs) from the calixarene—fluoresceine adduct were synthesized through the solvent injection technique and well-characterized in the solution and in solid state using light-scattering and microscopy methods. The maximum fluorescence intensity of the SLNs was found to be in the pH range from 7 to 10. The Förster resonance energy transfer (FRET) efficiency from SLNs to rhodamine 6g was found to be 97.8%. Finally, pure SLNs and the FRET system SLNs—Rh6G were tested in model photocatalytic ipso oxidative hydroxylation of phenylboronic acid under blue LED light. The SLNs—Rh6G system was found to be the best, giving an almost qualitative phenol yield, which was shown by HPLC-UV analysis

New Calix[4]arene&mdash;Fluoresceine Conjugate by Click Approach&mdash;Synthesis and Preparation of Photocatalytically Active Solid Lipid Nanoparticles

New fluorescent systems for photocatalysis, sensors, labeling, etc., are in great demand. Amphiphilic ones are of special interest since they can form functional colloidal systems that can be used in aqueous solutions. A new macrocycle platform for click chemistry and its adduct with o-propargylfluoresceine was synthesized and characterized using modern physical techniques. Nanosized solid lipid nanoparticles (SLNs) from the calixarene&mdash;fluoresceine adduct were synthesized through the solvent injection technique and well-characterized in the solution and in solid state using light-scattering and microscopy methods. The maximum fluorescence intensity of the SLNs was found to be in the pH range from 7 to 10. The F&ouml;rster resonance energy transfer (FRET) efficiency from SLNs to rhodamine 6g was found to be 97.8%. Finally, pure SLNs and the FRET system SLNs&mdash;Rh6G were tested in model photocatalytic ipso oxidative hydroxylation of phenylboronic acid under blue LED light. The SLNs&mdash;Rh6G system was found to be the best, giving an almost qualitative phenol yield, which was shown by HPLC-UV analysis