Stellar Magnetism and starspots: the implications for exoplanets

Stellar variability induce by starspots can hamper the detection of exoplanets and bias planet property estimations. These features can also be used to study star-planet interactions as well as inferring properties from the underlying stellar dynamo. However, typical techniques, such as ZDI, are not possible for most host-stars. We present a robust method based on spot modelling to map the surface of active star allowing us to statistically study the effects and interactions of stellar magnetism with transiting exoplanets. The method is applied to the active Kepler-9 star where we find small evidence for a possible interaction between planet and stellar magnetosphere which leads to a 2:1 resonance between the spot rotation and orbital period.Comment: 4 pages, 1 figure, to be published in the proceedings of IAUS 302: Magnetic Fields Throughout Stellar Evolutio

Extinction techniques and impact on dust property determination

The near infrared extinction powerlaw index ($\beta$) and its uncertainty is derived from three different techniques based on star counts, colour excess and a combination of them. We have applied these methods to 2MASS data to determine maps of $\beta$ and near infrared extinction of the small cloud IC 1396 W. The combination of star counts and colour excess results in the most reliable method to determine $\beta$. It is found that the use of the correct $\beta$-map to transform colour excess values into extinction is fundamental for column density profile analysis of clouds. We describe how artificial photometric data, based on the model of stellar population synthesis of the Galaxy (Robin et al. 2003), can be used to estimate uncertainties and derive systematic effects of the extinction methods presented here. We find that all colour excess based extinction determination methods are subject to small but systematic offsets, which do not affect the star counting technique. These offsets occur since stars seen through a cloud do not represent the same population as stars in an extinction free control field.Comment: 10 pages, 9 figures, 1 table, accepted for publication in MNRA

Ahozkoaren lanketa irakaskuntzan: testuliburu baten azterketa

Ahozko mintzajarduna, espazio berean dauden mintzakideek elkarrekin eta elkarri eraginez burutzen duten ekintza dugu. Hau, banaka edo besteekin interlokuzioan egin daiteke. Ahozkoa eta idatzia bi modalitate ezberdin bezala irudikatu izan dira historian zehar, landugabetzat jo da lehena eta formalagotzat bigarrena. Adituek ikusi dutenez ordea, maila enuntziatibo eta linguistikoan, oso hurbil daude biak. Eta pentsatu izan denaren kontra, ahozkoak, idatzizkoak bezala, hainbat genero barnehartzen ditu. Kontu jakina da, luzaroan, irakaskuntzaren arloan, idatzia izan dela irakasgai garrantzitsuena eta ahozkoak alboratutako leku bat hartu izan duela. Ahozkoa landu den kasuetan gainera, ulermena landu da gehienetan eta ekoizpenaren lanketak bazterturik iraun du. Gaur egun, ahozkoa, zapaldu edo alboratutako bazter horretatik ateratzen saiatzeko hainbat aldarri egin dira, irakasle, aditu eta insitituzioen aldetik. Curriculum Dekretu berrian (Eusko Jaurlaritza, 2007), esaterako, hizkuntza irakasteko metodologia komunikazio-proiektu esanguratsuetan oinarriturik landu behar dela eta testu-genero ezberdinak komunikazio-unitate nagusi izango direla esan da. Gainera, irakaskuntza Sekuentzia Didaktikoetan antolatu behar dela ere aipatzen da bertan. Testuen gainean oinarritutako irakaskuntzaren aldeko aldarria, hauek komunikazio egoerekin duten loturagatik egin da. Testu-generoetan oinarritutako irakaskuntzan, generoen taldekatzeak lana aurrezteaz gain, erreferentziazko gizarte praktikak aintzat hartzea ahalbidetzen baita. Genevako Unibertsitateko adituek proposatzen dituzten Sekuentzia Didaktikoak eredutzat hartzeak hainbat onura dakarzkio irakaskuntzari, ahozkoaren lanketa osoago eta ebaluagarri bat egitea eskaintzen baitu. Lan honetan, aditu hauek proposatzen duten Sekuentzia Didaktiko hori zer den eta nola lantzen den deskribatuko da. Honez gain, ahozkoa lantzeko Sekuentzia Didaktiko baten adibidearen aurkezpena egingo da, teorian azaldutakoa hobeto ulertarazteko asmoz. Lan honen gaia testuratu ondoren eta ahozkoak gaur egun praktikan duen lekua ikuste aldera, Egizu 3 DBH Euskara eta Literatura liburuan ahozko testu-generoak nola lantzen diren aztertu da lanean. Ahozkoaren lanketa egungo ikastetxeetan nola lantzen den ikusteko. Azterketa horretarako ordea, liburuan aztertzen diren testu-genero guztien azterketa egiteko tarterik ez dudanez, eta ahozko testu-generoen bereizketarako erabiltzen den monologal/dialogal banaketa tradizionalari heldurik, liburuan ahozko genero monologalen lanketa nola egiten den aztertu dut: ahozko azalpena, ahoz zabalduriko ipuinak eta deklamazioa generoen lanketan arreta berezia jarriz. Genero hauek aipatu testuliburuan nola lantzen diren ikusteko, genero bakoitzaren definizioa egin ondotik, banan-banan liburuan ematen zaien lanketaren deskribapena egin da. Deskribapen honen bidez, liburuan hiru generoak lantzeko metodologia eta ariketen antzekotasuna ikusirik, genero bakar baten azterketa sakonagoa egin dut. Baten azterketak, beste bi generoen hutsune eta indarguneak argitara eramateko ere balioko zidala iruditu baitzait. Hiru generoen artean, ahozko azalpena aukeratu dut horretarako, gehien landutako generoa izanik, azterketa egokiagoa egitea ahalbidetu ziezadakeela deliberatu baitut. Ahozko azalpen generoa lantzeko dagozkion ariketak banaka azterturik, hainbat ondoriotara iritsi naiz, aztergai dudan liburuan ahozko generoaren lanketa egiteko saiakera badagoela ikusi dut, baita testu-generoetan oinarrituriko irakaskuntza proposamen saio bat ere. Hala ere, liburuan ez zaio ahozkoari idatzizkoak duen estatusa ematen eta azken honen menpe dagoela ikus daiteke, lanean zehar emango ditudan adibideek argi erakutsiko duten bezala

A large scale extinction map of the Galactic Anticenter from 2MASS

We present a 127deg x 63deg extinction map of the Anticenter of the Galaxy, based on and colour excess maps from 2MASS. This 8001 square degree map with a resolution of 4 arcminutes is provided as online material. The colour excess ratio / is used to determine the power law index of the reddening law (\beta) for individual regions contained in the area (e.g. Orion, Perseus, Taurus, Auriga, Monoceros, Camelopardalis, Cassiopeia). On average we find a dominant value of \beta=1.8+-0.2 for the individual clouds, in agreement with the canonical value for the interstellar medium. We also show that there is an internal scatter of \beta values in these regions, and that in some areas more than one dominant \beta value is present. This indicates large scale variations in the dust properties. The analysis of the A_V values within individual regions shows a change in the slope of the column density distribution with distance. This can either be attributed to a change in the governing physical processes in molecular clouds on spatial scales of about 1pc or an A_V dilution with distance in our map.Comment: 18 pages, 29 Figures, 1 Table, Accepted for publication by MNRAS, A version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

A detailed two-dimensional stellar population study of M32

We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region of M32 obtained with the 2D_FIS fibre spectrograph installed at the William Herschel Telescope. From these spectra line strength maps have been reconstructed for about 20 absorption lines, mostly belonging to the Lick system. We find good agreement with long-slit line strength profiles in the literature. In contrast with previous studies, indices were azimuthally averaged along continuum isophotes of M32. A remarkable result is that no gradients are presented in the spectral indices. So, we have fitted the mean values of each spectral index and central colours to the models of Vazdekis et al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and metallicity similar to solar (Z=0.02) are the best fitted values for the innermost region of M32.Comment: accepted in MNRA

PHASES: Opto-mechanical Solutions to Perform Absolute Spectrophotometry from Space

This work provides an update of the current status of PHASES, which is a project aimed at developing a space-borne telescope to perform absolute flux calibrated spectroscopy of bright stars. PHASES will make it possible to measure micromagnitude photometric variations due to, e.g., exo-planet/moon transits. It is designed to obtain 1% RMS flux calibrated low resolution spectra in the wavelength range 370–960 nm with signal-to-noise ratios \u3e100 for stars with V∼1 minute. The strategy to calibrate the system using A-type stars is outlined. PHASES will make possible a complete characterization of stars, some of them hosting planets. From the comparison of observed spectra with accurate model atmospheres stellar angular diameters will be determined with precisions of ∼0.5%. The light curves of transiting systems will be then used to extract the radius of the planet with similar precision. The demanding scientific requirements to be achieved under extreme observing conditions have shaped the optomechanical design. A computational model and a high-precision interferometric system have been developed to test the performance of the instrument