Search

We have performed a molecular line search towards the flaring 6.7-GHz masers G 24.33+0.13, and G 359.6−0.24 using the Australia Telescope Compact Array. We present spectra of the 6.7-GHz class II methanol and 22.2-GHz water masers towards these sources and provide a comparison with other recent flaring events these sources have experienced. We also detect the fourth example of a 23.4-GHz class I methanol maser and the 11th example of a 4.8-GHz formaldehyde maser towards G 24.33+0.13. Alongside these results, we also observe the previously detected ammonia (3,3) emission and report upper limits on the presence of various other cm-wavelength methanol, ammonia, and OH transitions. Our results are consistent with the flaring of G 24.33+0.13 being driven by a variable accretion rate in the host high mass young stellar object.

In this work one-stage, no presence of acidic catalyst hydrothermal extraction of pectin from sugar beet pulp (SBP) as a batch process was investigated, leading to increasing the value of this by-product of sugar beet industry. The comprehensive study of the effect of the extraction temperature and the extraction time on the yield and composition of the pectin-enriched products, the water soluble product fractions and the water insoluble product fractions, were used that are feasible for industrial upscaling. It was shown that the highest yield of satisfactory purity of pectin extract (136.3 g kg−1) was obtained at a temperature of 120 °C and a holding time of 20 min. Both further increase of the extraction temperature and extending extraction time favor the occurrence of partial hydrothermolysis of pectin and hemicellulose contained in the SBP, leading to the production of uronic acids, monosaccharides, carboxylic acids and furfurals. In the applied extraction conditions, other components of the SBP: cellulose, lignin and protein did not undergo depolymerization and were still present in the solid post-extraction residue. This work provides an important method for the recovery of pectin from SBP using environmentally friendly technique and should help to facilitate further studies to develop a new process for the hydrothermal production of pectin from waste biomass.

—Powerful flares in Galactic kilomasers are closely associated with regions of intense star formation. They contribute to the elucidation of physical processes occurring in these structures. We have recorded a superpowerful flare in the high-velocity −81 km s−1 line in the Galactic maser source W49N. As a result of our monitoring at the RT-22 (Simeiz), RT-32 (Torun), RT-100 (Effelsberg), and RT-32 (Medicina) radio telescopes in the period from September 2017 to November 2018, we have obtained the shape of the spectral flux density variations in the source with time. At the peak the flux density reached P ≈ 5 × 10^4 Jy. The flare has a double pattern and different durations of its components. The pattern of spectral flux density variations for the first flare with a considerably shorter duration is apparently related to a sharp increase in the density of the medium and the photon flux and to a significant rise in the temperature to hundreds of kelvins. We propose a mechanism of primary energy release related to the existence of close massive multiple systems in star-forming regions. A powerful gravitational perturbation at the system’s periastron can lead to a partial ejection of the envelope of the central massive star in a direction close to the major axis of the ellipse of the companion’s orbit. This explains the significant asymmetry of high-velocity lines in W49N. The ejected envelope is an energy source more significant than the stellar wind and can explain the giant flares in the object. Further comprehensive studies in this direction, including monitoring VLBI studies, are needed to confirm this assumption.

Discovery of periodic maser emission was an unexpected result from monitoring observations of methanol transitions in high-mass young stellar objects. We report on the detection of five new periodic sources from a monitoring program with the Torun 32 m telescope. Variability with a period of 149 to 540 d and different patterns from sinusoidal-like to intermittent was displayed. Three-dimensional structure of G59.633−0.192 determined from the time delays of burst peaks of the spectral features and high angular resolution map implies that the emission traces a disc. For this source the 6.7 GHz light curve followed the infrared variability supporting a radiative scheme of pumping. An unusual time delay of ∼80 d occurred in G30.400−0.296 could not be explained by the light travel time and may suggest a strong differentiation of physical conditions and excitation in this deeply embedded source. Our observations suggest the intermittent variability may present a simple response of maser medium to the underlying variability induced by the accretion luminosity while other variability patterns may reflect more complex changes in the physical conditions.

The results of long-term monitoring of the Galactic maser source IRAS 18316-0602 (G25.65+1.05) in the water-vapor line at frequency f = 22.235 GHz (6_16-5_23 transitioin) carried out on the 22-m Simeiz, 26-m HartRAO, and 26-m Torun radio telescopes are reported. The source has been episodically observed on the Simeiz telescope since 2000, with more regular observations beginning in 2017. A double flare was observed beginning in September 2017 and continuing to February 2018, which was the most powerful flare registered over the entire history of observations of this object. Most of the monitoring of the flare was carried out in a daily regime. Detailed analysis of the variations of the flux density, which reached a maximum value P ≈ 1.3 × 10^5 Jy, have led to important scientific conclusions about possible mechanisms for the emission in this water line. The exponential growth in the flux density in this double flare testifies that it was associated with a maser that was unsaturated right up to the maximum flux densities observed. An additional argument suggesting the maser was unsaturated is the relatively moderate degree of linear polarization (≈30%), nearly half the value displayed by the Galactic kilomasers in Orion KL. The accurate distance estimate for IRAS 18316-0602 (12.5 kpc) and the flux density at the flare maximum (≈1.3 × 10^5 Jy) makes this the most powerful Galactic kilomaser known. The double form of the flare with exponential rises in flux density rules out the possibility that the flare is the effect of directivity of a radiation beam relative to the observer. The physical nature of the flare is most likely related to internal parameters of the medium in which the maser clumps radiating in the water line are located. A rapid, exponential growth in the flux density of a kilomaser and associated exponential decays requires the presence of an explosive increase in the density of the medium and the photon flux, leading to an increase in the temperature by 10-40 K above the initial base level. A mechanism for the primary energy release in IRAS 18316-0602 is proposed, which is associated with a multiple massive star system located in a stage of evolution preceding its entry onto the main sequence. A flare in this object could initiate gravitational interaction between the central star and a massive companion at its periastron. The resulting powerful gravitational perturbation could lead to the ejection of the envelope of the central supermassive star, which gives rise to an explosive increase in the density and temperature of the associate gas-dust medium when it reaches the disk, where the maser clumps are located.

The hydrolysis of high methyl ester citrus-apple pectin as a model substance for plant biomass waste rich in pectin fraction resulting in an uronic acids was performed in a batch reactor using subcritical water. The effects of the reaction temperature and time on the composition of the products contained in the separated liquid fractions were studied. The optimal experimental design methodology was used for modelling and optimizing the yield of uronic acids. In good agreement with experimental results (R2 = 0.986), the model predicts an optimal yield of uronic acids (approx. 77.3 g kg-1 ± 0.7 g kg-1) at a temperature and a time of about 155°C and 36 min. Uronic acids were isolated from reaction mixture using the ion exchange method. Higher temperature and longer holding time resulted in a greater degree of thermal degradation of uronic acids and simultaneously higher yield of losses and gas fractions

Context. Class II methanol masers at 6.7 and 12.2 GHz occur close to high-mass young stellar objects (HMYSOs). When they are observed simultaneously, such studies may contribute to refining the characterisation of local physical conditions. Aims. We aim to search for the 12.2 GHz methanol emission in 6.7 GHz methanol masers that might have gone undetected in previous surveys of northern sky HMYSOs, mainly due to their variability. Contemporaneous observations of both transitions are used to refine the flux density ratio and examine the physical parameters. Methods. We observed a sample of 153 sites of 6.7 GHz methanol maser emission in the 12.2 GHz methanol line with the Torun 32 m radio telescope, using the newly built X-band receiver. Results. The 12.2 GHz methanol maser emission was detected in 36 HMYSOs, with 4 of them detected for the first time. The 6.7 GHz to 12.2 GHz flux density ratio for spectral features of the contemporaneously observed sources has a median value of 5.1, which is in agreement with earlier reports. The ratio differs significantly among the sources and for the periodic source G107.298+5.639 specifically, the ratio is weakly recurrent from cycle to cycle, but it generally reaches a minimum around the flare peak. This is consistent with the stochastic maser process, where small variations in the physical parameters along the maser path can significantly affect the ratio. A comparison of our data with historical results (from about ten years ago) implies significant (> 50%) variability for about 47% and 14% at 12.2 GHz and 6.7 GHz, respectively. This difference can be explained via the standard model of methanol masers., 14 pages, 7 figures, accepted to A&A

The largest Key Science Program of the RadioAstron space VLBI mission is a survey of active galactic nuclei (AGN). The main goal of the survey is to measure and study the brightness of AGN cores in order to better understand the physics of their emission while taking interstellar scattering into consideration. In this paper we present detection statistics for observations on ground-space baselines of a complete sample of radio-strong AGN at the wavelengths of 18, 6, and 1.3 cm. Two-thirds of them are indeed detected by RadioAstron and are found to contain extremely compact, tens to hundreds of $\mu$as structures within their cores., Comment: Accepted to the Advances in Space Research special issue "High-resolution Space-Borne Radio Astronomy"

Periodic flares of maser emission are thought to be induced either by variations of the seed photon flux in young binary systems or the pump rate regulated by stellar and accretion luminosities. We seek to study the variability of four maser transitions of three different species in G107.298+5.639 to constrain the dominant mechanism of periodic flares. Light curves of the 6.7 GHz methanol and 22.2 GHz water vapour maser were obtained with the Torun 32m radio telescope over 39 and 34 cycles, respectively. The target was also monitored at the 1.6 GHz hydroxyl transitions with the Nan\c{c}ay radio telescope over 13 cycles. All these maser lines were imaged using VLBI arrays. The study confirms alternating flares of the methanol and water masers with a period of 34.4d and reveals the synchronised behaviour of the methanol and hydroxyl masers in this source. The observed spatial distribution of the methanol maser cloudlets and the measured time delays of the flares of individual features imply a ring-like structure of radius 240au and thickness 30au. Internal proper motions indicate that the velocity of methanol cloudlets is dominated by a disc-wind component of about 5km/s. The methanol emission detected during only one VLBI observation is located in a region about 550au from a central star, which also exhibits OH maser flares. The erratic appearance of methanol features can be related to a powering object of relatively low luminosity which, during some variability cycles, can excite molecules only in the nearest part of the disc. A careful analysis of the maser and infrared light curves reveal a strong correlation between the 6.7 GHz line and the infrared flux densities supporting a radiative pumping of the maser. The synchronised behaviour of the hydroxyl and methanol transitions indicates a common pumping mechanism for the periodic flares of G107.298+5.639., Comment: 20 pages, 15 figures

Ring-like distributions of the 6.7 GHz methanol maser spots at milliarcsecond scales represent a family of molecular structures of unknown origin associated with high-mass young stellar objects (HMYSOs). We aim to study G23.657-00.127, which has a nearly circular ring of the 6.7 GHz methanol masers, and is the most suitable target to test hypotheses on the origin of the maser rings. The European Very Long Baseline Interferometry Network (EVN) was used at three epochs spanning 10.3 yr to derive the spatio-kinematical structure of the 6.7 GHz methanol maser emission in the target. The maser cloudlets, lying in a nearly symmetric ring, expand mainly in the radial direction with a mean velocity of 3.2 km s$^{-1}$. There is an indication that the radial component of the velocity increases with cloudlet's distance from the ring centre. The tangential component does not show any clear evidence for rotation of the cloudlets or any relationship with distance from the ring centre. The blue-shifted masers may hint at an anticlockwise rotation of cloudlets in the southern part of the ring. The nearly circular structure of the ring clearly persisted for more than 10 yr. Interferometric data demonstrated that about one quarter of cloudlets show significant variability in their brightness, although the overall spectrum was non-variable in single-dish studies. Taking into account the three-dimensional motion of the maser cloudlets and their spatial distribution along a small ring, we speculate about two possible scenarios where the methanol masers trace either a spherical outflow arising from an (almost) edge-on disc, or a wide angle wind at the base of a protostellar jet. The latter is associated with near- and mid-infrared emission detected towards the ring. High angular resolution images of complementary (thermal) tracers are needed to interpret the environment of methanol masers., accepted for publication in A\&A, 15 pages including on-line material

The high brightness temperatures, $T_\mathrm{b}\gtrsim 10^{13}$ K, detected in several active galactic nuclei by RadioAstron space VLBI observations challenge theoretical limits. Refractive scattering by the interstellar medium may affect such measurements. We quantify the scattering properties and the sub-mas scale source parameters for the quasar B0529+483. Using RadioAstron correlated flux density measurements at 1.7, 4.8, and 22 GHz on projected baselines up to 240,000 km we find two characteristic angular scales in the quasar core, about 100 $\mu$as and 10 $\mu$as. Some indications of scattering substructure are found. Very high brightness temperatures, $T_\mathrm{b}\geq 10^{13}$ K, are estimated at 4.8 GHz and 22 GHz even taking into account the refractive scattering. Our findings suggest a clear dominance of the particle energy density over the magnetic field energy density in the core of this quasar., Comment: 14 pages, 9 figures

Mitigation of radio frequency interferences (RFI) is crucial for improving the quality of collected radio observations. For the instruments working in the decimeter and meter ranges – LOFAR (LOw Frequency ARray) is a good example – RFI is particularly vexing thus the widest possible knowledge of man-made emissions in the vicinity of radio telescopes is highly desirable. The results of the measurements of RFI performed at the LOFAR PL612 station in Baldy as well as the Radio Astronomical Observatory in Piwnice and the Astronomical Observatory and Astronomical Education Centre in Bialkow are shown and a comparative analysis has been carried out. Owing to this, solutions either to suppress RFI sources or to filter out undesirable signals in the spectra have been proposed. The results will be particularly important for the development of the LOFAR system and the extension of its usable waveband to the 10–30 MHz range. The presented measurement results also suggest the necessity to introduce a continuous RFI monitoring at LOFAR sites.

High-mass young stellar objects (HMYSO) displaying methanol maser flux variability probably trace a variety of phenomena such as accretion events, magnetospheric activity, stellar flares and stellar wind interactions in binary systems. A long-term monitoring of the 6.7 GHz methanol line in a large sample of HMYSOs has been undertaken to characterize the variability patterns and examine their origins. The majority of the masers show significant variability on time-scales between a week and a few years. High amplitude short flares of individual features occurred in several HMYSOs. The maser features with low luminosity tend to be more variable than those with high luminosity. The variability of the maser features increases when the bolometric luminosity the powering star decreases. Statistical analysis of basic properties of exciting objects and the variability measures supports an idea that burst activity of methanol masers is driven mainly by changes in the infrared pumping rate.

We present new evidence for superradiance in the methanol 6.7 GHz spectral line for three different star-forming regions: S255IR-NIRS3, G24.329+0.144, and Cepheus A. Our analysis shows that some of the intensity flares exhibiting fast flux rise times and asymmetric light curves reported in these sources can naturally be explained within the context of superradiance. When a threshold for the inverted population column density is exceeded in a maser-hosting region, the radiation mode switches from one regulated by stimulated emission (maser) to superradiance. Superradiance, as a more efficient energy release mechanism, manifests itself through strong bursts of radiation emanating from spatially compact regions. Elevated inverted population densities and the triggering of superradiance can be due to a change in radiative pumping. Here, we show that an increase in the pump rate and the inverted population density of only a factor of a few results in a significant increase in radiation. While the changes in the pump rate can take place over a few hundred days, the rise in radiation flux density when superradiance is initiated is drastic and happens over a much shorter time-scale., Comment: 9 pages, 6 figures, Accepted in Monthly Notices of the Royal Astronomical Society, Jan 2019

We propose a one-stage hydrothermal extraction of sugar beet pulp leading to effective co-production of pectin and neutral monosaccharides with a relatively high yield and satisfactory purity without the presence of an acidic catalyst. The optimal experimental design methodology was used for modelling and optimizing the yield of pectin and neutral monosaccharides. In good agreement with experimental results (R2 = 0.955), the model predicts an optimal yield of pectin (approx. 121.1 g kg&minus, 1 &plusmn, 0.47 g kg&minus, 1) at a temperature and time of about 118.1 &deg, C and 21.5 min, respectively. The highest yield of the sum of neutral monosaccharides (approx. 82.6 g kg&minus, 0.72 g kg&minus, 1) was obtained at about 116.2 &deg, C and 26.4 min (R2 = 0.976). The obtained results are suitable for industrial upscaling and may provide an incentive to implement a new, environmentally friendly, simple, and effective method for treating waste product from the sugar refining industry, which has proved onerous until now.

Aims.We present our monitoring observations and analysis of water masers associated with W49N taken in 2017 and 2018. A significant flare occurred during these observations.Methods.We used ground-based radio telescopes in Simeiz (RT-22), Torun (RT-32), Medicina (RT-32), Effelsberg (RT-100) with broadband spectrometers. Observational data were collected and processed automatically.Results.We report a powerful flare of thev= +6 km s−1water maser feature; it increased in over ten months toS1.3 cm= 84 kJy in 2017 December, then decayed to the pre-flare quiescent value ofS1.3 cm= 8.7 kJy in 2018 August. We infer that this flaring feature is unsaturated based on the relationship between line width and flux density.

The excited states of OH masers detected in the environment of high-mass young stellar objects (HMYSOs) are important for improving our understanding of the physical conditions of these objects and also provide information about their magnetic fields. We aim to search for excited-state OH 6035 MHz maser emission in HMYSOs which might have escaped detection in previous surveys or were never searched for. A sample of HMYSOs derived from untargeted surveys of the 6668 MHz methanol maser line was observed at 6035 MHz OH transition with the Torun 32 m radio telescope. The 6035 MHz detections were observed in the OH 6031 MHz line. Two-thirds of the detections were observed at least three times over a two-year period. Out of 445 targets, 37 were detected at 6035 MHz, including seven new discoveries. The 6031 MHz line was detected towards ten 6035 MHz sources, one of which was not previously reported. All the newly detected sources are faint with the peak flux density lower than 4 Jy and show significant or high variability on timescales of 4 to 20 months. Zeeman pair candidates identified in three new sources imply a magnetic field intensity of 2 to 11 mG. Comparison of our spectra with those obtained $\sim$10 yr ago indicates different degrees of variability but there is a general increase in the variability index on an $\sim$25 yr timescale, usually accompanied by significant changes in the profile shape., Comment: 8 pages, 6 figures

Context: High-mass young stellar objects (HMYSOs) can undergo accretion episodes that strongly affect the star evolution, the dynamics of the disk, and its chemical evolution. Recently reported extraordinary bursts in the methanol maser emission may be the observational signature of accretion events in deeply embedded HMYSOs. Aims: We analyze the light curve of 6.7 GHz methanol masers in S255IR-NIRS3 during the 2015-2016 burst. Methods: 8.5-year monitoring data with an average sampling interval of 5 days were obtained with the Torun 32 m radio telescope. Archival data were added, extending the time series to ~27 years. Results: The maser emission showed moderate (25-30%) variability on timescales of months to years over ~23 years since its discovery. The main burst was preceded by a one-year increase of the total flux density by a factor of 2.5, then it grew by a factor of 10 over ~0.4 years and declined by a factor of 8 during the consecutive 2.4 years. The peak maser luminosity was a factor of 24.5 higher than the pre-burst quiescent value. The light curves of individual features showed considerable diversity but indicated a general trend of suppression of the maser emission at blueshifted (5.8 km s$^{-1}$. This new emission provided a contribution of about 80% to the maser luminosity around the peak of the burst. Conclusions: The onset of the maser burst exactly coincides with that of the infrared burst estimated from the motion of the light echo. This strongly supports the radiative pumping scheme of the maser transition. The growth of the maser luminosity is the result of an increasing volume of gas where the maser inversion is achieved., 9 pages, 9 figures

Studies of molecular emission amplified in the natural maser process are essential to explore various astrophysical phenomena. The natural maser emission is so strong that it can be observed in several astrophysical environments using medium-sized telescopes. Here we report an overview of equipments of the 32m radio telescope suitable for spectral observations. A summary of the main results of the Galaxy plane survey in the 6.7 GHz methanol maser line is given and the latest finding of the periodic and alternate flares of the methanol and water vapor masers in a high-mass protostar is highlighted.

Thermal emission of atmospheric water vapor has a great influence on the calibration of radio astronomical observations at millimeter wavelengths. The phenomenon of an atmospheric water vapor emits noise signal and attenuates astronomical emission. At 22 GHz, integrated water vapor (IWV) obtained from global navigation satellite systems (GNSS) is strictly related to atmospheric opacity ( $$\tau_{0}$$ ), which is a crucial parameter for data calibration. Therefore, providing highly precise and accurate IWV from GNSS measurements may be an alternative for microwave radiometers. Whereas it is not possible to estimate IWV directly from GNSS measurements, its value is strictly correlated with the zenith wet delay (ZWD) that is estimated together with the coordinates during the GNSS positioning. In this study, differential and Precise Point Positioning methods for ZWD estimation are tested using two different tropospheric mapping functions: Vienna mapping function (VMF) and global mapping function (GMF). After positioning, the IWV conversion is performed using meteorological parameters derived from a meteorological station located near a GNSS site. Analyses for a 3-month period from June 1 to August 30, 2016, were conducted. Based on these, we obtained a very high correlation between IWV and $$\tau_{0}$$ as measured by the Torun 32 m radio telescope, which amounts about 0.95, for both PPP and differential solutions. Thus, techniques can be successfully used to estimate IWV and calculate $$\tau_{0}$$ . However, the linear regression coefficients depend on the used positioning method.

We report results of 6.7 GHz methanol maser monitoring of 139 star-forming sites with theTorun 32 m radio telescope from June 2009 to February 2013. The targets were observedat least once a month, with higher cadences of 2-4 measurements per week for circumpolarobjects. Nearly 80 per cent of the sources display variability greater than 10 per cent on atime-scale between a week and a few years but about three quarters of the sample have only1-3 spectral features which vary significantly. Irregular intensity fluctuation is the dominanttype of variability and only nine objects show evidence for cyclic variations with periodsof 120 to 416 d. Synchronised and anti-correlated variations of maser features are detectedin four sources with a disc-like morphology. Rapid and high amplitude bursts of individualfeatures are seen on 3-5 occasions in five sources. Long (>50 d to 20 months) lasting burstsare observed mostly for individual or groups of features in 19 sources and only one sourceexperienced a remarkable global flare. A few flaring features display a strong anti-correlationbetween intensity and line-width that is expected for unsaturated amplification. There is aweak anti-correlation between the maser feature luminosity and variability measure, i.e. maserfeatures with low luminosity tend to be more variable than those with high luminosity. Theanalysis of the spectral energy distribution and continuum radio emission reveals that thevariability of the maser features increases when the bolometric luminosity and Lyman fluxof the exciting object decreases. Our results support the concept of a major role for infraredpumping photons in triggering outburst activity of maser emission.

In September 2016, the microquasar Cygnus X-3 underwent a giant radio flare, which was monitored for 6 days with the Medicina Radio Astronomical Station and the Sardinia Radio Telescope. Long observations were performed in order to follow the evolution of the flare on a hourly scale, covering six frequency ranges from 1.5 GHz to 25.6 GHz. The radio emission reached a maximum of 13.2 +/- 0.7 Jy at 7.2 GHz and 10 +/- 1 Jy at 18.6 GHz. Rapid flux variations were observed at high radio frequencies at the peak of the flare, together with rapid evolution of the spectral index: alpha steepened from 0.3 to 0.6 within 5 hours. This is the first time that such fast variations are observed, giving support to the evolution from optically thick to optically thin plasmons in expansion moving outward from the core. Based on the Italian network (Noto, Medicina and SRT) and extended to the European antennas (Torun, Yebes, Onsala), VLBI observations were triggered at 22 GHz on five different occasions, four times prior to the giant flare, and once during its decay phase. Flux variations of 2-hour duration were recorded during the first session. They correspond to a mini-flare that occurred close to the core ten days before the onset of the giant flare. From the latest VLBI observation we infer that four days after the flare peak the jet emission was extended over 30 mas., Comment: 13 pages, 9 figures. Accepted for publication in MNRAS

We have investigated the hydrothermolysis of rapeseed cake, which is a residual biomass with high protein and fat content. The effects of the process parameters, reaction temperature and holding time, on the composition of the products (amino acids and fatty acids) contained in the separated liquid fractions (water and ether, respectively) were studied. To model the hydrothermal process the experimental design methodology was used. Based on this, optimized operational parameters were determined yielding highest amounts of amino acids and high conversion of triacylglycerols to fatty acids. A maximum estimated yield of amino acids of 135.9 g kg-1 of rapeseed cake was obtained at 215 °C after 36 min. A further increase of both reaction temperature and holding time would lead to the Maillard reaction and the decomposition (deamination and decarboxylation) of the amino acids. Maximum conversion of triacylglycerols to fatty acids of 0.91 was predited at 246 °C during 65 min. In this case, a further increase of both reaction parameters would lead to enhanced cis–trans isomerization of the unsaturated fatty acids produced.

We have investigated the three-step hydrothermal decomposition of rapeseed straw, rich in lignocellulosic components, as a batch process. The effects of the reaction temperature and holding time on the composition of the reaction products were studied. After the first step of the treatment there prevailed products of the hydrolytic depolymerization of hemicellulose. The highest yield of xylose (5.87% (w/w)) was obtained at a temperature of 210 °C and a holding time of 10 min. In the second step of the process as a result of depolymerization of cellulose, glucose was obtained, with the largest yield (17.4% (w/w)) at a temperature of 270 °C after 5 min. Unreacted lignin was used in the third step of the treatment. Its decomposition was performed at a temperature of 330 °C. The highest yield of guaiacol (11.56% (w/w) and catechol (5.61% (w/w)), was obtained after a holding time of 0 min and 60 min, respectively, whereas the highest yields of phenol (4.11% (w/w)), m , p -cresol (4.09% (w/w)) and o -cresol (2.71% (w/w)), were obtained after 150 min. The solid residue obtained in the third step of the process consisted mainly of phenolic biochar.

The hydrothermolysis of rapeseed meal components, i.e. the protein and the lignocellulosic fractions, was carried out in a batch reactor in subcritical water. The optimal experiment design methodology was used for modelling and optimizing the yields of amino acids and saccharides: xylose and glucose. In good agreement with experimental results, the model predicts an optimal yield of amino acids (approx. 32.8% in relation to the content of the total protein fraction in the rapeseed meal) at a temperature and a time of about 205 °C and 51 min. The optimal yields of xylose (49.5% in relation to the content of hemicellulose in the rapeseed meal) and of glucose (19.4% in relation to the cellulose content in rapeseed meal) require higher temperatures but shorter reaction times. The further increase in reaction temperature and time would lead to secondary undesirable reactions of amino acids and saccharides.

Methanol and water vapour masers are signposts of early stages of high-mass star formation but it is generally thought that due to different excitation processes they probe distinct parts of stellar environments. Here we present observations of the intermediate-mass young stellar object G107.298+5.639, revealing for the first time that 34.4 d flares of the 6.7 GHz methanol maser emission alternate with flares of individual features of the 22 GHz water maser. High angular resolution data reveal that a few components of both maser species showing periodic behaviour coincide in position and velocity and all the periodic water maser components appear in the methanol maser region of size of 360 au. The maser flares could be caused by variations in the infrared radiation field induced by cyclic accretion instabilities in a circumstellar or protobinary disc. The observations do not support either the stellar pulsations or the seed photon flux variations as the underlying mechanisms of the periodicity in the source., 6 pages, 4 figures, 1 table, accepted for publication in MNRAS Letters

We report the observations of 289 methanol maser sources at 6.7 GHz obtained over a two month period with the Torun 32 m telescope. The data form a catalogue of all objects north of δ = –22° brighter than 7.5 Jy in the peak emission. The positions of sub-arcsecond accuracy are updated for 76 % of the objects. We find that about one third of the sources show changes in the peak fluxes by a factor of two or more on time scales of 8.5–9.5 years (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Alkali lignin as an example of waste plant biomass was subjected in a batch reactor to decomposition in sub- and supercritical water. Hydrothermolysis of alkali lignin with relatively highmolecular-weight led to the production of phenolic compounds such as guaiacol and catechol, as well as phenol, m -cresol, p -cresols and o -cresol. Both an increase growth in conversion time and an increase in reaction temperature promoted secondary reactions: degradation of alkali lignin decomposition products, leading to, their repolymerization and carbonization. The components of the liquid fractions of products were examined by GC–MS and HPLC, whereas the solid charred post-reaction residues were analyzed by elemental analysis and FTIR.

A recent polarimetric survey of OH masers in a large sample of AGB and post-AGB stars revealed widespread occurrence of polarized features. We made a statistical analysis of the polarization properties of this large data set. We discuss the alignment of polarization position angles between the extreme blue- and red-shifted parts of the 1612 MHz spectrum. The average polarization angle of OH masers from the opposite sides of the envelope agrees within 20° for 80% of the sources in the sample. For two objects monitored over ~6 years the polarization position angle at 1612 MHz is constant within measurement uncertainties: this suggests a stable and a very regular structure of the circumstellar magnetic fields. Alternatively, this could indicate a galactic origin of the field which may be amplified by the stellar wind in the outermost parts of the envelopes.

A strong outburst of 6.7 GHz methanol maser occurred in the high-mass young stellar object (HMYSO) G24.33+0.14 between November 2010 and January 2013. The target was observed with the Torun 32 m radio telescope as a part of a long-term monitoring programme. Almost all twelve spectral features from 108 to 120 km s−1 varied synchronously with time delays between the flux minima of about two weeks. This may indicate that the variability is driven by global changes in the pump rate. The flare peaks of the two features with the highest relative amplitude of 40-60 are delayed by about 2.5 months while their profiles undergo essential transformation with a velocity drift of 0.23 km s−1yr−1. This may suggest that the variability is caused by a rapid increase of the pump rate and excitation of a large portion of the HMYSO environment by an accretion event.

We summarize a long-term monitoring of 11 periodic 6.7 GHz methanol masers and a search for new periodic sources. Observations were carried out with the Torun 32 m telescope. Periods of observed sources range from 29 to 658 days and the data consist of more than 10 observed cycles for most of the masers. Inspection of archival data resulted in identification of 3 new periodic sources while 2 new periodic objects were found in observations started in 2014.

OH 1612 and 1667 MHz masers from the well known object OH127.8+0.0 were mon- itored in full-polarization mode over a period of 6.5 years and mapped with MERLIN at one epoch. The OH variability pattern of the star is typical of extremely long- period AGB stars. The distance determined from the 1612 MHz light curve and a new measurement of the angular radius is 3.87 (0.28) kpc. At both frequencies, the flux of polarized emission tightly follows the total flux variations while, the degrees of circu- lar and linear polarization are constant within measurement accuracy.. There is net polarization at both lines. The magnetic field strength estimated from a likely Zeeman pair is -0.6 mG at the distance of 5400 au from the star.At the near and far sides of the envelope, the polarization vectors are well aligned implying a regular structure of the magnetic field. The polarization characteristics of the OH maser emission suggest a radial magnetic field which is frozen in the stellar wind., 12 pages, 9 figures

We report the discovery of periodic flares of 6.7GHz methanol maser in the young massive stellar object G22.357+0.066. The target was monitored in the methanol maser line over 20 months with the Torun 32m telescope. The emission was also mapped at two epochs using the EVN. The 6.7GHz methanol maser shows periodic variations with a period of 179 days. The periodic behavior is stable for the last three densely sampled cycles and has even been stable over ~12 years, as the archival data suggest. The maser structure mapped with the EVN remains unchanged at two epochs just at the putative flare maxima separated by two years. The time delays of up to ~16 days seen between maser features are combined with the map of spots to construct the 3-dimensional structure of the maser region. The emission originating in a single ~100 AU layer can be modulated by periodic changes in the infrared pumping radiation or in the free-free background emission from an HII region., Comment: 6 pages, 5 figures; Accepted for publication in Astronomy and Astrophysics Letters

Context: Ground-state OH maser emission from late-type stars is usually polarized and remains a powerful probe of the magnetic field structure in the outer regions of circumstellar envelopes if observed with high angular and spectral resolutions. Observations in all four Stokes parameters are quite sparse and this is the most thorough, systematic study published to date. Aims: We aim to determine polarization properties of OH masers in an extensive sample of stars that show copious mass loss and search for candidate objects that are well-suited for high angular resolution studies. Methods: Full-polarization observations of the OH 1612 and 1667 MHz maser transitions were carried out for a sample of 117 AGB and post-AGB stars. Several targets were also observed in the 1665 MHz line. Results: Polarized features occur in more than 75% of the sources in the complete sample and there is no intrinsic difference in the occurrence of polarized emission between the three classes of objects of different infrared characteristics. The highest fractional polarization occurs for the post-AGB+PN and the Mira+SR classes at 1612 and 1667 MHz, respectively. Differences in the fractional polarization between the sources at different evolutionary stages appear to be related to depolarization caused by blending. The alignment of the polarization angles at the extreme sides of the shell implies a regular structure of the magnetic field of a strength of 0.3-2.3 mG. Conclusions: Polarized OH maser features are widespread in AGB and post-AGB stars. The relationship between the circular and linear fractional polarizations for a representative sample are consistent with the standard models of polarization for the Zeeman splitting higher than the Doppler line width, whereas the polarized features are the sigma components., Comment: Accepted for publication in Astronomy and Astrophysics. A version with appendices (Tab. A.1 and Fig. B.1) can be downloaded from http://paulo.astro.uni.torun.pl/~pw/arXiv_1

We present OH 1612 MHz maser observations towards the pre-planetary nebula OH17.7–2.0 taken with the Nançay radio telescope in 2002–2007. A bursting feature at 73 kms−1 grew by a factor of 11 in 740 days in left-hand circular polarization intensity, reaching a maximum in mid-2005. The OH flux density of features at neighbouring velocities exhibited a rise by a factor of 5–7. During the burst, the degree of circular polarization increased from 7 to 83%. The blue-shifted emission showed weak variations of 7–10% in amplitude with the exception of the bluest feature for which the OH flux decreased with the rate of ~4.4 Jy year−1. Very unusual OH outbursts of individual features and remarkable changes in the shape of the maser profile appear to be linked with recent evolutionary changes in the detached shell.

Context. OH masers from the envelopes of M-type supergiants show a significant degree of polarization, implying magnetic fields of a few mG. Nothing is known about the temporal characteristics of the magnetic fields or how such changes may affect stellar mass loss. Aims. We therefore observed two supergiant stars in order to quantify the long-term polarization behaviour of the maser emission. Methods. Full-polarization spectra at 1612 and 1667 MHz were obtained with the Nancay radio telescope at intervals over periods of 4 and 6 years for S Per and VX Sgr, respectively. Results. Time series of OH maser full polarization spectra are presented. Semiregular variations of the integrated flux densities generally follow the visual light curves as expected for radiative pumping cycles. For both sources the variability indices of individual features are higher at 1667 MHz than at 1612 MHz and their extreme values occur for the blue-shifted emission. The degrees of polarization at 1667 MHz show diverse behaviours usually uncorrelated with the total flux, whereas those at 1612 MHz are commonly stable on time scales of 4-6 yr. Several outbursts of the 1667 MHz emission on time scales of 0.5-2 yr were found in both targets. The bursting features are highly polarized and show drifts in velocity. Small changes of the degrees of polarization and smooth variations of position angle of linear polarization during the bursts were observed in S Per but they are more dramatic in VX Sgr. Conclusions. The OH outbursts do not seem to have any direct link to stellar events, but seem to be localized in the wind.

In recent years a small group of methanol maser sources showing periodic variability have been identified. There is ongoing discussion on causes of this type of behavior, but none of the explanations are satisfactory. Discovery of source G107.298+5.639 showing alternating and periodic flares of 6.7GHz methanol and 22GHz water vapor masers can give us a clue to processes leading to observed periodicity. Recently we confirmed OH maser periodicity in this object. Result of multiepoch EVN observations of methanol emission in G107.298 will be presented.