Pre-main sequence stars with disks in the Eagle Nebula observed in scattered light

NGC6611 and its parental cloud, the Eagle Nebula (M16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. We identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0 micron. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared. We confirm the membership of these stars to M16 by a spectroscopic analysis. The physical properties of these stars with disks are studied by comparing their spectral energy distributions (SEDs) with the SEDs predicted by models of T-Tauri stars with disks and envelopes. We show that the age of these stars estimated from the V vs. V-I diagram is unreliable since their V-I colors are altered by the light scattered by the disk into the line of sight. Only in a few cases their SEDs are compatible with models with excesses in V band caused by optical veiling. Candidate members with disks and photospheric IRAC colors are selected by the used NIR disk diagnostic, which is sensitive to moderate excesses, such as those produced by disks with low masses. In 1/3 of these cases, scattering of stellar flux by the disks can also be invoked. The photospheric light scattered by the disk grains into the line of sight can affect the derivation of physical parameters of ClassII stars from photometric optical and NIR data. Besides, the disks diagnostic we defined are useful for selecting stars with disks, even those with moderate excesses or whose optical colors are altered by veiling or photospheric scattered light.Comment: Accepted for publication in A&

Correlation between the spatial distribution of circumstellar disks and massive stars in the young open cluster NGC 6611. II: Cluster members selected with Spitzer/IRAC

Context: the observations of the proplyds in the Orion Nebula Cluster, showing clear evidence of ongoing photoevaporation, have provided a clear proof about the role of the externally induced photoevaporation in the evolution of circumstellar disks. NGC 6611 is an open cluster suitable to study disk photoevaporation, thanks to its large population of massive members and of stars with disk. In a previous work, we obtained evidence of the influence of the strong UV field generated by the massive cluster members on the evolution of disks around low-mass Pre-Main Sequence members. That work was based on a multi-band BVIJHK and X-ray catalog purposely compiled to select the cluster members with and without disk. Aims: in this paper we complete the list of candidate cluster members, using data at longer wavelengths obtained with Spitzer/IRAC, and we revisit the issue of the effects of UV radiation on the evolution of disks in NGC 6611. Methods: we select the candidate members with disks of NGC 6611, in a field of view of 33'x34' centered on the cluster, using IRAC color-color diagrams and suitable reddening-free color indices. Besides, using the X-ray data to select Class III cluster members, we estimate the disks frequency vs. the intensity of the incident radiation emitted by massive members. Results: we identify 458 candidate members with circumstellar disks, among which 146 had not been revealed in our previous work. Comparing of the various color indices we used to select the cluster members with disk, we claim that they detect the excesses due to the emission of the same physical region of the disk: the inner rim at the dust sublimation radius. Our new results confirm that UV radiation from massive stars affects the evolution of nearby circumstellar disks.Comment: Accepted for publication at Astronomy & Astrophysic

The circumstellar disc around the Herbig AeBe star HD169142

We present 7 mm and 3.5 cm wavelength continuum observations toward the Herbig AeBe star HD169142 performed with the Very Large Array (VLA) with an angular resolution of ~1". We find that this object exhibits strong (~4.4 mJy), unresolved (~1") 7 mm continuum emission, being one of the brightest isolated Herbig AeBe stars ever detected with the VLA at this wavelength. No emission is detected at 3.5 cm continuum, with a 3 sigma upper limit of ~0.08 mJy. From these values, we obtain a spectral index of ~2.5 in the 3.5 cm to 7 mm wavelength range, indicating that the observed flux density at 7mm is most likely dominated by thermal dust emission coming from a circumstellar disc. We use available photometric data from the literature to model the spectral energy distribution (SED) of this object from radio to near-ultraviolet frequencies. The observed SED can be understood in terms of an irradiated accretion disc with low mass accretion rate, 10^{-8} solar masses per year, surrounding a star with an age of ~10 Myr. We infer that the mass of the disc is ~0.04 solar masses, and is populated by dust grains that have grown to a maximum size of 1 mm everywhere, consistent with the lack of silicate emission at 10 microns. These features, as well as indications of settling in the wall at the dust destruction radius, led us to speculate the disc of HD169142 is in an advanced stage of dust evolution, particularly in its inner regions.Comment: 13 pages, 2 figures. Accepted by MNRA

Vertical structure models of T Tauri and Herbig Ae/Be disks

In this paper we present detailed models of the vertical structure (temperature and density) of passive irradiated circumstellar disks around T Tauri and Herbig Ae/Be stars. In contrast to earlier work, we use full frequency- and angle-dependent radiative transfer instead of the usual moment equations. We find that this improvement of the radiative transfer has strong influence on the resulting vertical structure of the disk, with differences in temperature as large as 70 %. However, the spectral energy distribution (SED) is only mildly affected by this change. In fact, the SED compares reasonably well with that of improved versions of the Chiang & Goldreich (CG) model. This shows that the latter is a reasonable model for the SED, in spite of its simplicity. It also shows that from the SED alone, little can be learned about the vertical structure of a passive circumstellar disk. The molecular line emission from these disks is more sensitive to the vertical temperature and density structure, and we show as an example how the intensity and profiles of various CO lines depend on the adopted disk model. The models presented in this paper can also serve as the basis of theoretical studies of e.g. dust coagulation and settling in disks.Comment: 12 pages, 15 figures, accepted for publication in A&

Warm Molecular Layers in Protoplanetary Disks

We have investigated molecular distributions in protoplanetary disks, adopting a disk model with a temperature gradient in the vertical direction. The model produces sufficiently high abundances of gaseous CO and HCO+ to account for line observations of T Tauri stars using a sticking probability of unity and without assuming any non-thermal desorption. In regions of radius R > 10 AU, with which we are concerned, the temperature increases with increasing height from the midplane. In a warm intermediate layer, there are significant amounts of gaseous molecules owing to thermal desorption and efficient shielding of ultraviolet radiation by the flared disk. The column densities of HCN, CN, CS, H2CO, HNC and HCO+ obtained from our model are in good agreement with the observations of DM Tau, but are smaller than those of LkCa15. Molecular line profiles from our disk models are calculated using a 2-dimensional non-local-thermal-equilibrium (NLTE) molecular-line radiative transfer code for a direct comparison with observations. Deuterated species are included in our chemical model. The molecular D/H ratios in the model are in reasonable agreement with those observed in protoplanetary disks.Comment: 11 pages, Latex (aa.cls), to be published in Astronomy and Astrophysic

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

Canine parvovirus and pseudorabies virus coinfection as a cause of death in a wolf (Canis lupus) from southern Italy

Pseudorabies virus (PRV) or suid herpesvirus 1 (SHV-1) is the causative agent of Aujeszky's disease, a highly contagious viral infection which causes neurological fatal illness in mammals other than suids. Here we report a case of a young wolf (Canis lupus) of around 2 years found dead by a hunter in the province of Avellino, Campania Region. Necropsy showed pathological findings consistent with encephalitis and gastroenteritis. Organs were analysed by microbiological and molecular investigations following standard procedures to ascertain the possible cause of death. Real-time PCR revealed the presence of PRV in the brain and of canine parvovirus 2b in organs like intestine, liver, brain, kidney and pancreas. Death probably occurred very shortly after SHV-1 infection in an animal already weakened by parvovirosis

Testing Zimbardo’s Stanford Time Perspective Inventory (STPI)-Short Form: An Italian study

ABSTRACT. In the present study the psychometric properties of the Stanford Time Perspective Inventory (STPI – short version) are assessed in an Italian sample. Factorial analysis of STPI items was performed on 1507 respondents (965 women and 542 men). Results showed a clear correspondence between factorial components and a priori hypothesized dimensions by evidencing three factors (Future, Hedonistic Present, Fatalistic Present). Italian translation of the STPI indicates a fair degree of internal consistency and good metrological characteristics. The present results parallel those previously reported for an American sample. The present study, however, failed in evidencing the ‘Past’ as a factor in the factor structure. The results are discussed in terms of individual differences with respect to the relationships between demographic variables and temporal dimensions

Molecular Detection of Babesia spp. (Apicomplexa: Piroplasma) in Free-Ranging Canids and Mustelids From Southern Italy.

Babesiosis is an emerging tick-borne disease caused by apicomplexan parasites with widespread geographical distribution and various wildlife species as reservoir hosts. The aims of this study were to investigate the prevalence and assess the role of free-ranging canids and mustelids in the maintenance of Babesia spp. in southern Italy. PCR analysis of splenic samples targeting the 18S rRNA gene revealed the presence of Babesia spp. in 36 of 82 (43.9%) red foxes (Vulpes vulpes) including 29 (58%) from Campania region and seven (21.8%) from Calabria region, in seven of 13 (53.8%) Eurasian badgers (Meles meles), and in one of 13 (7.7%) gray wolves (Canis lupus). Samples from other host species including 9 Eurasian otters (Lutra lutra), 1 stone marten (Martes foina), 1 least weasel (Mustela nivalis), and 1 European polecat (Mustela putorius) tested Babesia spp. negative. Sequence analysis of the 18S rRNA gene demonstrated the presence of B. vulpes in the red fox and two sequence types of badger-associated Babesia spp. in the Eurasian badger. The Babesia sp. sequence detected in the gray wolf was identical to a badger-associated Babesia sp. This study shows that the number of Babesia spp. infecting free-ranging carnivores in Italy is higher than currently believed, and suggests that these hosts may play an important role in the maintenance of the sylvatic cycle of these parasites. It is the first report of badger-associated Babesia spp. in Italy and in a gray wolf