Search

WFIRST is NASA's first flagship mission with pre-defined core science programs to study dark energy and perform a statistical census of wide orbit exoplanets with a gravitational microlensing survey. Together, these programs are expected to use more than half of the prime mission observing time. Previously, only smaller, PI-led missions have had core programs that used such a large fraction of the observing time, and in many cases, the data from these PI-led missions was reserved for the PI's science team for a proprietary period that allowed the PI's team to make most of the major discoveries from the data. Such a procedure is not appropriate for a flagship mission, which should provide science opportunities to the entire astronomy community. For this reason, there will be no proprietary period for WFIRST data, but we argue that a larger effort to make WFIRST science accessible to the astronomy community is needed. We propose a plan to enhance community involvement in the WFIRST exoplanet microlensing survey in two different ways. First, we propose a set of high level data products that will enable astronomers without detailed microlensing expertise access to the statistical implications of the WFIRST exoplanet microlensing survey data. And second, we propose the formation of a WFIRST Exoplanet Microlensing Community Science Team that will open up participation in the development of the WFIRST exoplanet microlensing survey to the general astronomy community in collaboration for the NASA selected science team, which will have the responsibility to provide most of the high level data products. This community science team will be open to volunteers, but members should also have the opportunity to apply for funding., Astro2020 APC White Paper

The Wide Field Infrared Survey Telescope (WFIRST) is a NASA space observatory designed to address key questions about the Universe and the population of extrasolar planets in our Galaxy. WFIRST is planned for launch in the mid-2020s. One of the main WFIRST science program is a statistical census of exoplanets with a microlensing survey, using about one quarter of the overall observing time. Specifically, the microlensing campaign is expected to be sensitive to detect low-mass planets at orbital separation greater than about 1 AU and to free-floating planets down to the mass of Mars. I am going to introduce the science case of microlensing exoplanets and the WFIRST mission. I will describe the expected yield of the WFIRST microlensing survey and I will report on the main outcomes of some of the current observational programs preliminary to the WFIRST mission. Finally, I will outline the possible role of the VST during the WFIRST microlensing survey.&nbsp

The Wide Field Infrared Survey Telescope (WFIRST) was the top ranked large space mission in the 2010 New Worlds, New Horizons decadal survey, and it was formed by merging the science programs of 3 different mission concepts, including the Microlensing Planet Finder (MPF) concept (Bennett \etal\ 2010). The WFIRST science program (Spergel \etal\ 2015) consists of a general observer program, a wavefront controlled technology program, and two targeted science programs: a program to study dark energy, and a statistical census of exoplanets with a microlensing survey, which uses nearly one quarter of WFIRST's observing time in the current design reference mission. The New Worlds, New Horizons (decadal survey) midterm assessment summarizes the science case for the WFIRST exoplanet microlensing survey with this statement: "WFIRST's microlensing census of planets beyond 1 AU will perfectly complement Kepler's census of compact systems, and WFIRST will also be able to detect free-floating planets unbound from their parent stars\rlap.", Comment: White paper submitted to the National Academy Committee on an Exoplanet Science Strategy; 6 pages (typo fixed)

We report the discovery and initial characterization of Qatar-2b, a hot Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short period, P_b = 1.34 days. The mass and radius of Qatar-2b are M_P = 2.49 M_J and R_P = 1.14 R_J, respectively. Radial-velocity monitoring of Qatar-2 over a span of 153 days revealed the presence of a second companion in an outer orbit. The Systemic Console yielded plausible orbits for the outer companion, with periods on the order of a year and a companion mass of at least several M_J. Thus, Qatar-2 joins the short but growing list of systems with a transiting hot Jupiter and an outer companion with a much longer period. This system architecture is in sharp contrast to that found by Kepler for multi-transiting systems, which are dominated by objects smaller than Neptune, usually with tightly spaced orbits that must be nearly coplanar.

We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with perturbations near both peaks. We find that the event is produced by the passage of the source trajectory over the central perturbation regions associated with the individual components of a wide-separation binary. The event is special in the sense that the second perturbation, occurring $\sim 100$ days after the first, was predicted by the real-time analysis conducted after the first peak, demonstrating that real-time modeling can be routinely done for binary and planetary events. With the data obtained from follow-up observations covering the second peak, we are able to uniquely determine the physical parameters of the lens system. We find that the event occurred on a bulge clump giant and it was produced by a binary lens composed of a K and M-type main-sequence stars. The estimated masses of the binary components are $M_1=0.69 \pm 0.11\ M_\odot$ and $M_2=0.36\pm 0.06\ M_\odot$, respectively, and they are separated in projection by $r_\perp=10.9\pm 1.3\ {\rm AU}$. The measured distance to the lens is $D_{\rm L}=5.6 \pm 0.7\ {\rm kpc}$. We also detect the orbital motion of the lens system., 18 pages, 5 figures, 1 table

The Wide Field Infrared Survey Telescope (WFIRST) is a 2.4m space telescope with a 0.281 deg^2 field of view for near-IR imaging and slitless spectroscopy and a coronagraph designed for > 10^8 starlight suppresion. As background information for Astro2020 white papers, this article summarizes the current design and anticipated performance of WFIRST. While WFIRST does not have the UV imaging/spectroscopic capabilities of the Hubble Space Telescope, for wide field near-IR surveys WFIRST is hundreds of times more efficient. Some of the most ambitious multi-cycle HST Treasury programs could be executed as routine General Observer (GO) programs on WFIRST. The large area and time-domain surveys planned for the cosmology and exoplanet microlensing programs will produce extraordinarily rich data sets that enable an enormous range of Archival Research (AR) investigations. Requirements for the coronagraph are defined based on its status as a technology demonstration, but its expected performance will enable unprecedented observations of nearby giant exoplanets and circumstellar disks. WFIRST is currently in the Preliminary Design and Technology Completion phase (Phase B), on schedule for launch in 2025, with several of its critical components already in production., 14 pages, 3 figures, 2 tables

This thesis work is dedicated to the problem of the searchand the characterisation of dark matter. From an observationalpoint of view, on different lenght scale, from galatic to the entire Universe,it exists a disagreement between the dynamical and luminousestimation of the mass of astrophysical objects (as galaxies and clusterof galaxies). This is a sort of missing mass problem.This makes necessary, in the framwork of the standard cosmological model, the introduction of a dark componentof mass, dark meaning that it doesn't emit electromagnetic radiationand whose presence can be detected through its gravitational effects.Even if both theory and observation agree on the need ofsuch a component, a still unanswered question is the nature ofsuch mass component.We are going to address the problem of the dark matter component in galatic haloes, wherethe observational evidences in this sense (rotation curves)are very robust. To this end we use an original set of data(the MDM data) collected with the aim of studying the dark componenentin form of MACHOs (Massive Astrophysical Compact Halo Objects)in the halo of our and of the nearby galaxy of Andromeda (M31).This search is based on the gravitational microlensing effect,the deflection of light due to the presence of a massive body (the MACHO)along the line of sight between the observer and a luminous source.This effects shows as a temporal luminosity variation of the source.From this analysis it is possible to estimate the distributionof the mass in form of MACHO in the halo. This search has been caried out using the pixel lensing technique(proposed and developped by the AGAPE collaboration), that allows oneto detect luminosity variations of unresolved sources. In the first chapter we recall some basics points aboutthe cosmological model and on the problem of dark matter.We the review the microlensing effect and the pixel lensing tecnique. Chapter two is devoted to the description of the experimental setup,and to different points linked with the image analysis(calibration, composition). In chapter three we dealwith the tecniques used to analyse the signal with respect to the problem of the detectionof microlening event. The background noisebeing given here by variable stars, in particularwe study how we can characterize the achromaticitypropertie of the signal that interest us.We then discuss the results from two simulations:the first one aimed at the study of the selectioncriteria we use to detect interesting variations,the second a Monte Carlo simulaton of the experience.In chapter 4 we consider various aspects of the analysis.Dealing with the chromatic effects, we study somekind of variable sources. We carry out an extensionof known microlensing candidates detected by other collaborations.Eventually, we come to the discussion of the results of our selection,where we get five light curve compatible with a microlensing signal.Looking at the simulation, we then draw our conclusion on the problem.Our analysis tends to confirm that only a small fractionof the galactic haloes is in form of MACHO, and in particularto exclude as a major component substellar objects., Questo lavoro di tesi è dedicato al problema della ricerca edella caratterizzazione della \emph(materia oscura). A livelloosservativo, su diverse scale, da quelle galattiche (inparticolare nella Via Lattea) fino all'intero universo, esistedisaccordo tra le stime \emph(dinamiche) della massa di oggettiastrofisici (come galassie o ammassi di galassie) rispetto allastima della loro massa \emph(luminosa). Si tratta, in un certomodo, di un problema di massa \emph(mancante). Si rende cosìnecessaria, nell'ambito del quadro teorico del modellocosmologico standard, l'introduzione di una componente di materia``oscura'', nel senso che non emette radiazione elettromagnetica,la cui presenza può essere rilevata attraverso effettigravitazionali. Nonostante la convergenza di prove osservative edesigenze teoriche a sostegno dell'ipotesi della sua esistenza, uninterrogativo a cui non è ancora stata data una rispostabasata su solide evidenze sperimentali è quello della stessanatura di tale componente di massa.Affrontiamo in particolare il problema della materia oscura neglialoni galattici, dove le evidenze osservative (curve di rotazione)risultano più stringenti. Per questo analizziamo un insiemeoriginale di dati sperimentali (i dati ``MDM'', frutto di unaapposita campagna osservativa tuttora in corso di svolgimentopresso l'osservatorio Michigan-Dartmouth-MIT, USA) acquisiti perlo studio della componente oscura sotto forma di oggetti massivicompatti (MACHOs, \emph(Massive Astrophysical Compact HaloObjects)) nell'alone della Galassia (la nostra Via Lattea) edella galassia vicina di Andromeda, M31 (ovvero NGC224). Questaricerca si basa su di un effetto di natura gravitazionale, il\emph(microlensing), ovvero la deflessione della luce generata daun oggetto oscuro massivo in moto che attraversa la linea di vistatra l'osservatore e una sorgente luminosa che si manifesta con unincremento della luminosità della sorgente. Dallo studio diqueste variazioni di luminosità nel tempo è possibilerisalire, per via indiretta, alla distribuzione della materiasotto forma di MACHOs nell'alone. L'analisi è stata condottacon la tecnica detta del \emph(pixel lensing) (proposta eimplementata dalla collaborazione AGAPE, \emph(Andromeda GalaxyAmplified Pixel Experiment)), che permette il rilevamento divariazioni di luminosità di stelle \emph(non) risolte (inparticolare questo consente di considerare le possibili sorgentiin una galassia distante come M31).Nel capitolo 1, introdotti gli elementi del modello cosmologicostandard e quindi il problema della materia oscuranell'appropriato contesto cosmologico e astrofisico, delineamo iprincipi del \emph(microlensing) gravitazionale e il metodo del\emph(pixel lensing). Nel capitolo 2 descriviamo l'apparatosperimentale e l'acquisizione dei dati (a cui chi scrive ha avutomodo di partecipare direttamente). Quindi analizziamo indettaglio il trattamento preliminare delle immagini necessarioper rendere significativo il successivo studio dei segnaliastrofisici interessanti. In particolare vengono discussi alcuniaspetti quali la composizione di più immagini e le operazionidi ``normalizzazione'' del flusso. Nel capitolo 3 affrontiamo letematiche connesse all'analisi del segnale rispetto al problemadella selezione di eventi di \emph(microlensing). Il ``rumore''di fondo che ne contamina la ricerca è costituito da sorgentiintrensicamente variabili. Per questo consideriamo in dettaglioil modo di sfruttare la caratteristica \emph(acromaticità)del segnale che ci interessa. Basandoci su di una opportunasimulazione consideriamo inoltre il problema dell'efficacia deicriteri di selezione adottati. Discutiamo infine i risultatidelle simulazioni Monte Carlo dell'esperienza. Vengono quindiapprofonditi, nel capitolo 4, diversi aspetti legati all'analisieffettuata. Rivolgiamo particolare attenzione allo studio deglieffetti cromatici delle variazioni di luminosità rilevate ediscutiamo in questa prospettiva segnali di sorgenti variabili ein particolare alcuni attribuibili a delle \emph(novæ).Esponiamo quindi un primo risultato dell'analisi, lo studio delprolungamento sui nostri dati di candidati eventi\emph(microlensing) rilevati da altre collaborazioni. Infinediscutiamo i risultati della selezione, 5 \emph(curve di luce)(la variazione di flusso nel tempo in un elementodell'im\-ma\-gi\-ne) compatibili con un segnale di\emph(microlensing), e, alla luce delle simulazioni Monte Carlo,le conclusioni fisiche riguardo al problema posto.La nostra analisi tende a confermare (in accordo con i risultatidi analoghe esperienze svolte nell'ambito della Galassia) che solouna piccola frazione degli aloni galattici è costituita daMACHOs, e in particolare a escludere come componente importantequella di oggetti di massa substellare.