REM near-IR and optical photometric monitoring of Pre-Main Sequence Stars in Orion

We performed an intensive photometric monitoring of the PMS stars falling in a field of about 10x10 arc-minutes in the vicinity of the Orion Nebula Cluster (ONC). Photometric data were collected between November 2006 and January 2007 with the REM telescope in the VRIJHK' bands. The largest number of observations is in the I band (about 2700 images) and in J and H bands (about 500 images in each filter). From the observed rotational modulation, induced by the presence of surface inhomogeneities, we derived the rotation periods for 16 stars and improved previous determinations for the other 13. The analysis of the spectral energy distributions and, for some stars, of high-resolution spectra provided us with the main stellar parameters (luminosity, effective temperature, mass, age, and vsini). We also report the serendipitous detection of two strong flares in two of these objects. In most cases, the light-curve amplitudes decrease progressively from the R to H band as expected for cool starspots, while in a few cases, they can only be modelled by the presence of hot spots, presumably ascribable to magnetospheric accretion. The application of our own spot model to the simultaneous light curves in different bands allowed us to deduce the spot parameters and particularly to disentangle the spot temperature and size effects on the observed light curves.Comment: 29 pages, 24 figure

Preliminary study on MC1R polymorphism in some cattle breeds raised in Italy

Ricerche preliminari sul polimorfismo del gene MC1R in alcune razze bovine allevate in Italia – Il gene MC1R è stato analizzato in 193 soggetti appartenenti a 8 razze bovine, tramite PCR, per la presenza di due mutazioni ad effetto fenotipico noto sulla pigmentazione del mantello: la delezione G310 e la sostituzione T296C, associate rispettivamente al fenotipo feomelanico (e) ed eumelanico nero (Ed). Sessanta soggetti di razza Limousine e Pezzata Rossa Italiana presentano genotipo e/e; 27 soggetti di razza Frisona Italiana mostrano genotipo Ed/Ed mentre 2 genotipo Ed/e. Gli 84 soggetti appartenenti alle razze Cabannina, Chianina, Marchigiana e Piemontese non presentano tali mutazioni, analogamente a 18 soggetti di razza Romagnola, nella quale però si sono anche osservati 2 soggetti portatori dell’allele e allo stato eterozigote

A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample

We present the first results of a ground-based programme conducted on 1-4m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical counterparts of RASS X-ray sources in the northern hemisphere. We concentrate on the 704 optically brightest (V_Ticho<=9.5 mag) candidates. We acquired high-res spectroscopy in the Halpha/Li spectral regions for 426 of such stars without relevant literature data. We describe the sample and the observations and we start to discuss its physical properties. We used a cross-correlation technique and other tools to derive accurate radial/rotational velocities and to perform a spectral classification for both single and SB2 stars. The spectral subtraction technique was used to derive chromospheric activity levels and Li abundances. We estimated the fraction of young single stars and multiple systems in stellar soft X-ray surveys and the contamination by more evolved systems, like RS CVn's. We classified stars on the basis of Li abundance and give a glimpse of their sky distribution. The sample appears to be a mixture of young Pleiades-/Hyades- like stars plus an older Li-poor population (~1-2 Gyr). 7 stars with Li abundance compatible with the age of IC 2602 (~30 Myr) or younger were detected as well, although 2 appear to be Li-rich giants. The discovery of a large number of Li-rich giants is another outcome of this survey. The contamination of soft X-ray surveys by old systems in which the activity level is enhanced by tidal synchronisation is not negligible, especially for K-type stars. 5 stars with Li content close to the primordial abundance are probably associated with known moving groups in the solar neighbourhood. Some of them are PTTS candidates according to their positions in the HR diagram.Comment: 16 pages, 12 figures, 6 tables; 2 figures and 2 tables in electronic form only. Paper accepted by Astronomy and Astrophysic

MC1R gene: comparison between different farm animal species

Il gene MC1R: confronto fra diverse specie animali di interesse zootecnico. Negli animali di interesse zootecnico, il polimorfismo del gene MC1R coinvolto nella pigmentazione \ue8 stato studiato a livello molecolare soltanto nell\u2019ultimo decennio. Si sono confrontate descrizioni fenotipiche e polimorfismi del gene MC1R in alcune razze bovine (Rendena, Bruna, Cabannina, Ottonese-Varzese e Pezzata Rossa) e nel cavallo (62 animali). Tutti gli animali feomelanici sono portatori delle mutazioni recessive allo stato omozigote indipendentemente dalla tonalit\ue0 del mantello. I cavalli neri sono portatori dell\u2019allele selvatico del gene MC1R e della mutazione recessiva del gene ASIP allo stato omozigote. Nei cavalli bai e nelle altre razze bovine studiate \ue8 presente, almeno allo stato eterozigote, l\u2019allele selvatico. Nella Bruna e nella Cabannina \ue8 presente anche l\u2019allele E1. Nel gene MC1R, sequenziato in capre di razza Bionda dell\u2019Adamello e Nera di Verzasca, si \ue8 evidenziata l\u2019unica mutazione descritta in letteratura. I risultati sono stati confrontati con le informazioni disponibili nella specie murina e umana.Coat colour genes in farm animals have only been studied at molecular level over the last ten years, starting with Klungland et al. in 1995. Among the genes involved in pigmentation, MC1R, previously known as Extension locus, revealed polymorphisms related to red and black coat colour in different farm animal species. More exactly, the MelanoCortin-1 Receptor (MC1R) gene, specifically expressed in melanocytes, encodes for the homonymous G-protein coupled receptor involved in the regulation of the type of melanin synthesized. Melanocytes produce in fact two different types of melanins: the black or brown eumelanin and the yellow or red pheomelanin. The hair distribution of eu- and pheomelanins depends on the activity of MC1R, which is normally modulated by response to the melanocortin hormone, antagonized by the action of Agouti protein encoded by the ASIP gene. We previously studied the MC1R polymorphisms in some cattle reared in Italy (Crepaldi et al., 2003) and we now present the data on MC1R in other Italian cattle breeds, horses and goats. The aim of this work is to compare the pigmentary phenotypes and causative MC1R mutations in different farm animals and model species, such as mouse and human, in order to highlight differences and similarities between phenotypes and MC1R polymorphisms. The relationship between phenotypes and Agouti locus is also discussed

Photometric/spectroscopic analyses and magnetic activity in young late-type stars

We present the work in progress of a study based on photometric and spectroscopic observations of young Weak-line T Tauri and Post T Tauri stars just attiving on the Zero Age Main Sequence. This study is part of a project based on high-resolution spectra obtained with FOCES@CAHA (Spain) and SARG@TNG (Spain) and contemporaneous photometry performed at Catania (Italy) and Ege (Turkey) observatories. The main aim is to investigate the topology of magnetic active regions at photospheric and chromospheric levels in young single stars. Since our targets are slow rotators (vsini < 25 km/s), corresponding to rotation periods larger than about 2 days, we are able to apply the spectroscopic technique based on line-depth ratio for the measure of the photospheric temperature modulation. These stars, possible members of Stellar Kinematic Groups, display emission cores in the CaII H&K and IRT lines, as well as a conspicuous filling-in of the Halpha core. Moreover, we detect absorption of the HeI-D3 line, coming from the upper chromospheric layers, derive the lithium abundance (age indicator), and measure the rotational and radial velocities. We find a clear rotational modulation, due to photospheric spots, both in the light and the temperature curves. The Halpha and the CaII-IRT emissions display a fair variation correlated with the rotation. Finally, we are developing a spot/plage model to reproduce the data and derive the spot parameters (namely, filling factor and temperature) and to recover information about the chromospheric inhomogeneities (flux contrast and filling factor). This study is very important to explore the correlations between global stellar parameters (e.g., surface gravity, effective temperature) and spot/plage characteristics in stars with different activity level and evolutionary stage.Comment: 4 pages, 4 figures, poster paper presented at the Cool Stars 15 (St. Andrews, Scotland), to be published in the Conference Proceedings Series of the American Institute of Physics (AIP

A Far-Ultraviolet Spectroscopic Survey of Luminous Cool Stars

FUSE ultraviolet spectra of 8 giant and supergiant stars reveal that high temperature (3 X 10^5 K) atmospheres are common in luminous cool stars and extend across the color-magnitude diagram from Alpha Car (F0 II) to the cool giant Alpha Tau (K5 III). Emission present in these spectra includes chromospheric H-Lyman Beta, Fe II, C I, and transition region lines of C III, O VI, Si III, Si IV. Emission lines of Fe XVIII and Fe XIX signaling temperatures of ~10^7 K and coronal material are found in the most active stars, Beta Cet and 31 Com. A short-term flux variation, perhaps a flare, was detected in Beta Cet during our observation. Stellar surface fluxes of the emission of C III and O VI are correlated and decrease rapidly towards the cooler stars, reminiscent of the decay of magnetically-heated atmospheres. Profiles of the C III (977A) lines suggest that mass outflow is underway at T~80,000 K, and the winds are warm. Indications of outflow at higher temperatures (3 X 10^5K) are revealed by O VI asymmetries and the line widths themselves. High temperature species are absent in the M-supergiant Alpha Ori. Narrow fluorescent lines of Fe II appear in the spectra of many giants and supergiants, apparently pumped by H Lyman Alpha, and formed in extended atmospheres. Instrumental characteristics that affect cool star spectra are discussed.Comment: Accept for publication in The Astrophysical Journal; 22 pages of text, 23 figures and 8 table

The young active star SAO 51891 (V383 Lac)

Our aim is investigating surface inhomogeneities of the young late-type star SAO51891, from photosphere to upper chromosphere, analyzing contemporaneous high-resolution spectra and broad-band photometry. The FOCES@CAHA spectral range is used to determine spectral classification and derive vsini and Vrad. The Li abundance is measured to estimate the age. The BVRIJHKs bands are used to construct the SED. The variations of our BV fluxes and Teff are used to infer the presence of photospheric spots and observe their behavior over time. The chromospheric activity is studied applying the spectral subtraction technique to Halpha, CaII H&K, Heps, and CaII IRT lines. We find SAO51891 to be a young K0-1V star with Li abundance close to the Pleiades upper envelope, confirming its youth (~100 Myr), also inferred from its kinematical membership to the Local Association. We detect no IR excess from SED analysis, and rotational modulation of luminosity, Teff, CaII, and Heps total fluxes. A spot model with two active regions, ~240 K cooler than the surrounding photosphere, fits our light/Teff curves, and reproduces the small-amplitude Vrad variations. The anti-correlation of light curves and chromospheric diagnostics indicates plages spatially associated with spots. The large amplitude observed in the Heps-flux curve suggests that this line is very sensitive to the plage presence. Finally, SAO51891 is a young active star, lacking significant amounts of circumstellar dust or any evidence for low mass companions. The spots turn out to be larger and warmer than those in less active MS stars. The Vrad variation produced by spots has an amplitude comparable with those induced by Jupiter-mass planets orbiting close to the star. SAO51891 is a good example of star where the detection of planets may be hampered by the high activity level.Comment: 16 pages, 12 figures, 7 tables, accepted by Astronomy and Astrophysics; abstract here was shortene

Crossing the Gould Belt in the Orion vicinity

We present a study of the large-scale spatial distribution of 6482 RASS X-ray sources in approximately 5000 deg^2 in the direction of Orion. We examine the astrophysical properties of a sub-sample of ~100 optical counterparts, using optical spectroscopy. This sub-sample is used to investigate the space density of the RASS young star candidates by comparing X-ray number counts with Galactic model predictions. We characterize the observed sub-sample in terms of spectral type, lithium content, radial and rotational velocities, as well as iron abundance. A population synthesis model is then applied to analyze the stellar content of the RASS in the studied area. We find that stars associated with the Orion star-forming region do show a high lithium content. A population of late-type stars with lithium equivalent widths larger than Pleiades stars of the same spectral type (hence younger than ~70-100 Myr) is found widely spread over the studied area. Two new young stellar aggregates, namely "X-ray Clump 0534+22" (age~2-10 Myr) and "X-ray Clump 0430-08" (age~2-20 Myr), are also identified. The spectroscopic follow-up and comparison with Galactic model predictions reveal that the X-ray selected stellar population in the direction of Orion is characterized by three distinct components, namely the clustered, the young dispersed, and the widespread field populations. The clustered population is mainly associated with regions of recent or ongoing star formation and correlates spatially with molecular clouds. The dispersed young population follows a broad lane apparently coinciding spatially with the Gould Belt, while the widespread population consists primarily of active field stars older than 100 Myr. We expect the "bi-dimensional" picture emerging from this study to grow in depth as soon as the distance and the kinematics of the studied sources will become available from the future Gaia mission.Comment: 17 pages, 13 figures, 4 tables. Accepted for publication in Astronomy and Astrophysics. Abstract shortene