The intermediate-mass star-forming region Lynds 1340. An optical view

We have performed an optical spectroscopic and photometric search for young stellar objects associated with the molecular cloud Lynds 1340, and examined the structure of the cloud by constructing an extinction map, based on SDSS data. The new extinction map suggests a shallow, strongly fragmented cloud, having a mass of some 3700~Msun. Longslit spectroscopic observations of the brightest stars over the area of L1340 revealed that the most massive star associated with L1340 is a B4 type, about 5 solar mass star. The new spectroscopic and photometric data of the intermediate mass members led to a revised distance of 825 (+110 /-80) pc, and revealed seven members of the young stellar population with M > 2 solar masses. Our search for H alpha emission line stars, conducted with the Wide Field Grism Spectrograph 2 on the 2.2-meter telescope of the University of Hawaii and covering a 30 arcmin x 40 arcmin area, resulted in the detection of 75 candidate low-mass pre-main sequence stars, 58 of which are new. We constructed spectral energy distributions of our target stars, based on SDSS, 2MASS, Spitzer, and WISE photometric data, derived their spectral types, extinctions, and luminosities from BVRIJ fluxes, estimated masses by means of pre-main sequence evolutionary models, and examined the disk properties utilizing the 2-24 micron interval of the spectral energy distribution. We measured the equivalent width of the H alpha lines and derived accretion rates. The optically selected sample of pre-main sequence stars has a median effective temperature of 3970 K, stellar mass 0.7 Msun, and accretion rate of 7.6 10^{-9} Msun/yr.Comment: 47 pages, 15 figures, 10 tables; accepted for publication in ApJ, typos correcte

Iron oxyhydroxide aerogels and xerogels by controlled hydrolysis of FeCl3[middle dot]6H2O in organic solvents: stages of formation

Iron oxyhydroxide aerogels and xerogels were prepared by controlled hydrolysis of FeCl3[middle dot]6H2O in organic solvents by using a limited amount of water or consuming solely water molecules available from the crystals. Ethanol, ethylene glycol, dimethyl sulfoxide (DMSO) and dimethyl formamide (DMFA) solvents were used, the hydrolysis was promoted with epichlorohydrin proton scavanger. High surface area aerogels were prepared by supercritical CO2 extraction of solvents, surface area and pore distribution measurements were performed on them. Aerogel and xerogel samples were characterized by XRD, Mossbauer spectroscopy and HRTEM methods. The process of hydrolysis was followed by recording Mossbauer spectra of frozen reaction mixtures. Stepwise progress and appearance of transient components were detected in DMSO and DMFA solvents. Aerogel samples exhibit asymmetric spectra with low probability of Mossbauer effect in their as synthesized state. In contrast, frozen reaction mixtures, gels, dry xerogels and compressed aerogels display symmetric spectra with high probability of the Mossbauer resonance. XRD proves the dominant presence of 2-line ferrihydrite. HRTEM studies reveal 4-8 nm typical particle sizes with 0.21-1.0 nm characteristic lattice distances. Different types of coordination environments are distinguished for iron in the formed ferrihydrite nanoparticles due to structural features and imperfections

Association study of suicidal behavior and affective disorders with a genetic polymorphism in ABCG1, a positional candidate on chromosome 21q22.3

The gene that codes for the ABC transporter ABCG1 is located in a chromosomal susceptibility region (21q22.3) for affective disorders. Genetic variations in ABCG1 have been associated with affective disorders in Japanese males. In this study, we investigated the distribution of a G2457A polymorphism in patients with affective disorders, suicide attempters with various psychiatric diagnoses and healthy subjects, We initially found a trend towards a modest association with affective disorders in males (p = 0.046 for allele frequencies and p = 0.046 for AA versus GG). We conducted a replication study with independent patients and controls, There was no association with affective disorders, either in the replication or in the combined group, Furthermore, we found no association with suicidal behavior, These findings do not support the hypothesis that ABCG1 is a susceptibility gene for affective disorders or suicidal behavior. Copyright (C) 2000 S. Karger AG, Basel

Activity of 50 Long-Period Comets Beyond 5.2 AU

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by afrho values >3--4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.Comment: 21 pages, 4 figures, accepted for publication in A

WO3–EDA hybrid nanoplates and nanowires: synthesis, characterization, formation mechanism and thermal decomposition

Previously the WO3–EDA hybrid material was obtained only from solvothermal reactions.</p

Exploring the circumstellar environment of the young eruptive star V2492 Cyg

Context. V2492 Cyg is a young eruptive star that went into outburst in 2010. The near-infrared color changes observed since the outburst peak suggest that the source belongs to a newly defined sub-class of young eruptive stars, where time-dependent accretion and variable line-of-sight extinction play a combined role in the flux changes. Aims. In order to learn about the origin of the light variations and to explore the circumstellar and interstellar environment of V2492 Cyg, we monitored the source at ten different wavelengths, between 0.55 \mu m and 2.2 \mu m from the ground and between 3.6 \mu m and 160 \mu m from space. Methods. We analyze the light curves and study the color-color diagrams via comparison with the standard reddening path. We examine the structure of the molecular cloud hosting V2492 Cyg by computing temperature and optical depth maps from the far-infrared data. Results. We find that the shapes of the light curves at different wavelengths are strictly self-similar and that the observed variability is related to a single physical process, most likely variable extinction. We suggest that the central source is episodically occulted by a dense dust cloud in the inner disk, and, based on the invariability of the far-infrared fluxes, we propose that it is a long-lived rather than a transient structure. In some respects, V2492 Cyg can be regarded as a young, embedded analog of UX Orionis-type stars. Conclusions. The example of V2492 Cyg demonstrates that the light variations of young eruptive stars are not exclusively related to changing accretion. The variability provided information on an azimuthally asymmetric structural element in the inner disk. Such an asymmetric density distribution in the terrestrial zone may also have consequences for the initial conditions of planet formation.Comment: 9 pages, 7 figures, 2 online tables, accepted for publication in A&

Agrobacterium vitis strains lack tumorigenic ability on in vitro grown grapevine stem segments

Grapevine stem segments were cocultivated with three different Agrobacterium tumefaciens and three different A. vitis strains. A. tumefaciens strains induced tumors at variable frequencies, while A. vitis-infected stem segments never formed crown galls. The tumorous nature of tissues grown on hormone free medium was confirmed by opine assays. Bioinformatic and PCR analysis of the virulence regions of various A. tumefaciens and A. vitis Ti plasmids showed that virH2 and virK genes are common in A. tumefaciens but they are lacking from A. vitis. Thus virH2 and virK genes may be essential for grapevine stem segment transformation, but expression of certain T-DNA genes of A. vitis may also prevent the growth of transformed cells. Our data indicate that the tumorigenic ability of A. vitis is different on intact plant and on their explants, and that the specific host association of A. vitis on grapevine is probably determined by physiological and biochemical factors (e. g., better colonizing ability) rather than by its increased tumorigenic ability. Therefore it is not reasonable to develop „helper” plasmids for grapevine transformation from A. vitis pTis, unless their avirulence on in vitro explants is determined by T-DNA gene(s). Due to the inability of A. vitis to induce tumors on grapevine stem segments, the use of in vitro explant assays cannot be reliably used to select A. vitis resistant grapevine genotypes or transgenic lines

Multi-wavelength study of the low-luminosity outbursting young star HBC 722

HBC 722 (V2493 Cyg) is a young eruptive star in outburst since 2010. It is an FU Orionis-type object with an atypically low outburst luminosity. Because it was well characterized in the pre-outburst phase, HBC 722 is one of the few FUors where we can learn about the physical changes and processes associated with the eruption. We monitored the source in the BVRIJHKs bands from the ground, and at 3.6 and 4.5 $\mu$m from space with the Spitzer Space Telescope. We analyzed the light curves and the spectral energy distribution by fitting a series of steady accretion disk models at many epochs. We also analyzed the spectral properties of the source based on new optical and infrared spectra. We also mapped HBC 722 and its surroundings at millimeter wavelengths. From the light curve analysis we concluded that the first peak of the outburst in 2010 September was due to an abrupt increase of the accretion rate in the innermost part of the system. This was followed by a long term process, when the brightening was mainly due to a gradual increase of the accretion rate and the emitting area. Our new observations show that the source is currently in a constant plateau phase. We found that around the peak the continuum was bluer and the H$\alpha$ profile changed significantly between 2012 and 2013. The source was not detected in the millimeter continuum, but we discovered a flattened molecular gas structure with a diameter of 1700 au and mass of 0.3 M$_{\odot}$ centered on HBC 722. While the first brightness peak could be interpreted as a rapid fall of piled-up material from the inner disk onto the star, the later monotonic flux rise suggests the outward expansion of a hot component according to the theory of Bell & Lin (1994). Our study of HBC 722 demonstrated that accretion-related outbursts can occur in young stellar objects even with very low mass disks, in the late Class II phase.Comment: 11 pages, 7 figures, 3 online tables. Accepted for publication in the A&

New Candidate Eruptive Young Stars in Lynds 1340

We report on the discovery of three candidate eruptive young stars, found during our comprehensive multi-wavelength study of the young stellar population of the dark cloud L1340. These stars are as follows. (1) IRAS 02224+7227 (2MASS 02270555+7241167, HH 487S) exhibited FUor-like spectrum in our low-resolution optical spectra. The available photometric data restrict its luminosity to 23 L_☉ < L_(bol) < 59 L_☉. (2) 2MASS 02263797+7304575, identified as a classical T Tauri star during our Hα survey, exhibited an EXor-type brightening in 2005 November at the time of the Sloan Digital Sky Survey observations of the region. (3) 2MASS 02325605+7246055, a low-mass embedded young star, associated with a fan-shaped infrared nebula, underwent an outburst between the DSS 1 and DSS 2 surveys, leading to the appearance of a faint optical nebula. Our [S II] and Hα images, as well as the Spitzer Infrared Array Camera 4.5 μm images, revealed Herbig-Haro objects associated with this star. Our results suggest that amplitudes and timescales of outbursts do not necessarily correlate with the evolutionary stage of the stars

Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej

We present extensive optical ($UBVRI$, $g'r'i'z'$, and open CCD) and near-infrared ($ZYJH$) photometry for the very nearby Type IIP SN ~2013ej extending from +1 to +461 days after shock breakout, estimated to be MJD $56496.9\pm0.3$. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive $UBVRIJHK$ bolometric calibrations from $UBVRI$ and unfiltered measurements that potentially reach 2\% precision with a $B-V$ color-dependent correction. We observe moderately strong Si II $\lambda6355$ as early as +8 days. The photospheric velocity ($v_{\rm ph}$) is determined by modeling the spectra in the vicinity of Fe II $\lambda5169$ whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives $v_{\rm ph} = 4500\pm500$ km s$^{-1}$ at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10--12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be $9.0_{-0.6}^{+0.4}$ Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be $94\pm7$ days long, yields an explosion energy of $0.9\pm0.3\times10^{51}$ ergs, a final pre-explosion progenitor mass of $15.2\pm4.2$~M$_\odot$ and a radius of $250\pm70$~R$_\odot$. We observe a broken exponential profile beyond +120 days, with a break point at +$183\pm16$ days. Measurements beyond this break time yield a $^{56}$Ni mass of $0.013\pm0.001$~M$_\odot$.Comment: 29 pages, 23 figures, 15 tables, Published in The Astrophisical Journa