Calendar

Speaker: M. G. Dainotti (National Astronomical Observatory of Japan)
Title: The optical 2D and 3D correlation and their application as cosmological tool

Abstract: Gamma-ray bursts (GRBs) are fascinating events due to their
panchromatic nature. We study optical plateaus in GRB afterglows via
an extended search into archival data. We comprehensively analyze all
published GRBs with known redshifts and optical plateaus observed by
many ground-based telescopes (e.g., Subaru Telescope, RATIR) around
the world and several space-based observatories such as the Neil
Gehrels Swift Observatory. We fit 500 optical light curves, showing
the existence of the plateau in 179 cases. This sample is 75% larger
than the previous one, and it is the largest compilation so far of
optical plateaus. We discover the 3D fundamental plane relation at
optical wavelengths using this sample. This correlation is between the
rest-frame time at the end of the plateau emission, Topt * , its
optical luminosity, Lopt, and the peak in the optical prompt emission,
Lpeak,opt, thus resembling the three-dimensional (3D) X-ray
fundamental plane (the so-called 3D Dainotti relation). We correct our
sample for redshift evolution and selection effects, discovering that
this correlation is indeed intrinsic to GRB physics. We investigate
the rest-frame end-time distributions in X-rays and optical (Topt * ,
TX *), and conclude that the plateau is achromatic only when selection
biases are not considered. We also investigate 3D optical correlation
as a cosmological tool, finding that it is as efficacious as the X-ray
3D correlation.

Categories: Aula: Seminario

Jun

Thu

Progetto Academy of Distinction (rif. Miceli – Daricello)

Tickets

Jun 15 @ 9:00 – 13:00

18 studenti della classe astrofisica e 15 studenti della classe fisica

viaggio virtuale nell’universo con realtà aumentata

visita guidata del museo della specola

Categories: Aula: Seminario Museo

Jun

Thu

Seminario: Claudia Di Maio (UNIPA/INAF)

Tickets

Jun 22 @ 15:00 – 16:30

Speaker: Claudia Di Maio

Title: The mass determination challenge for exoplanetary science

Abstract:

The mass of an exoplanet is a key parameter for the characterisation of the internal structure of a planet, as well as the study of the formation and the evolution of the planet, and of its atmosphere.

The radial velocity technique allows measuring the planetary mass from the radial velocity variation of its parent star. However, limitations in the property determination of exoplanets, particularly in their masses, can arise from various sources especially from astrophysical noise due to stellar variability, caused by magnetic activity, which affects the detection and characterisation of exoplanets.

During my PhD, I aim to understand the impact of our knowledge of the planetary mass in the planetary atmospheric characterisation and to reduce the sources of uncertainty by a deep study of the stellar activity and by developing new techniques

for stellar variability filtering.

To this end, I analysed the impact of the planetary mass uncertainties of atmospheric retrievals of multiple targets from the mission reference sample of Ariel, the forthcoming ESA M4 mission aimed at studying planetary atmospheres.

I simulated different spectra as observed by Ariel, assuming primordial or secondary atmospheres of hot Jupiters, and sub-Neptunes or super-Earths, respectively, under different cloudy configurations. I estimated both the accuracy and precision necessary

for each analysed target, testing also the capability of retrieval in the case of incorrect mass estimation. I verified that one of the most crucial issues is the presence of high-altitude clouds, in particular in the secondary atmosphere cases.

For this reason, I tested the capability to retrieve the cloudy configuration or the presence of a secondary atmosphere during the first tier of the Ariel mission, to take an informed decision if including the planet in the Tier-2 sample.

I also developed SpotCCF, a photospheric stellar model, to optimise the radial velocity extraction in fast-rotating stars. This model, based on the cross-correlation function technique, takes into account the contribution of stellar activity by considering the presence of multiple spots on the stellar surface that caused deformation of the profile of the cross-correlation function.

Globally, I highlighted the importance of planetary mass characterization and the complexity of their determination due to the effects of stellar variability. In the context of the Ariel mission, it highlights the importance of a detailed and individual analysis of each target of the mission reference sample, to be able to accurately select the Tier-2 targets and characterise their planetary atmosphere, and represents a step forward towards the preparation of the ESA M4 Ariel mission. It also shows how this work cannot be disentangled from a detailed study of the stellar variability that is crucial in the determination of the planetary mass, both in its accuracy and precision.

Categories: Aula: Seminario

Jun

Wed

Seminario: M. Coniglio (INAF)

Tickets

Jun 28 @ 15:00 – 16:30

Speaker: Manuela Coniglio (INAF)
Titolo: L’affresco dimenticato: celebrazione di una scoperta
Abstract:
L’Osservatorio Astronomico di Palermo venne istituito alla fine del 1700, in piena età neoclassica, in un momento storico in cui i cantieri borbonici realizzavano opere monumentali di grande interesse artistico e architettonico. A partire da tali presupposti, sono stati condotti degli studi volti a rintracciare eventuali elementi decorativi dell’originaria Specola panormitana, oggi quasi del tutto assenti. Il viaggio tra carte e documenti ha portato alla consultazione di un variegato materiale archivistico, composto da lettere e note manoscritte ma anche disegni, incisioni e fotografie, conservati in diversi archivi. Dal loro studio è emerso qualcosa di inaspettato e del tutto dimenticato: un’imponente celebrazione artistica della scoperta di Cerere Ferdinandea, il primo asteroide individuato da Piazzi nella notte del 1° gennaio 1801, realizzata proprio nel Real Osservatorio di Palermo, da cui il pianetino venne osservato per la prima volta.

Categories: Aula: Seminario

Sep

Thu

Seminario: David Pascoe (University of St Andrews), Aula ore 15

Tickets

Sep 28 @ 15:00 – 16:30

Google meet: https://meet.google.com/sxz-cctp-tsc

Speaker: Dr David Pascoe (University of St Andrews)

Titolo: Modern Diagnostic Techniques for Stellar Atmospheres

Abstract:
The high spatial and temporal resolution provided by the Solar Dynamics Observatory inspired the development of advanced observational techniques to probe the solar atmosphere. For example, forward modelling of the EUV profile of coronal structures and the seismological analysis of magnetohydrodynamic waves provide powerful diagnostics to constrain properties such as the plasma density and magnetic field strength. We also increasingly employ Bayesian analysis to increase the robustness and accuracy of our modelling. These techniques are now also applied to study quasi-periodic pulsations associated with solar and stellar flares, and our models are being extended to take advantage of in situ measurements from Solar Orbiter and Parker Solar Probe.

Categories: Aula: Seminario

Oct

Wed

Seminario: presentazione della tesi di Marco Tarantino (UNIPA), Aula ore 12

Tickets

Oct 4 @ 12:00 – 13:30

Speaker: Marco Tarantino Studente Magistrale in Statistica e Data Science (LM-82), Universita’ degli Studi di Palermo

Titolo:
APPLICAZIONE DI TECNICHE STATISTICHE PER LA PREVISIONE DELLA
TEMPERATURA EFFETTIVA DI STELLE GIOVANI

Abstract:
Uno degli attuali argomenti di discussione riguarda la durata del processo di formazione di cluster stellari: vi sono modelli teorici che ipotizzano un unico evento dal quale si formano tutte le stelle appartenenti ad uno stesso cluster, considerando un processo di formazione rapido, altri modelli che, invece, suppongono piu’ eventi di formazione, tenendo conto di un processo di formazione lento. Uno dei metodi piu’ utilizzati per ricavare l’eta’ delle stelle si basa sul confronto della distribuzione delle stelle sul diagramma H-R con le isocrone teoriche. Una variabile fondamentale per applicare questo metodo e’ la temperatura efficace, la quale si puo’ ricavare in maniera accurata dalla spettroscopia. Tuttavia, nell’epoca delle grandi survey fotometriche, e’ necessario derivare la temperatura efficace basandosi sulla fotometria. L’obiettivo del lavoro consiste nel trovare un modello che permetta di ottenere buone previsioni della temperatura effettiva di stelle giovani, utilizzando variabili fotometriche di stelle ottenute da tre cataloghi differenti, ovvero Gaia, Gaia-ESO Survey, Pan-STARRS e 2MASS. I risultati previsivi evidenziano come il Random Forest rappresenti una buona soluzione per la previsione della temperatura effettiva. Durante questo seminario introdurro’ i cinque approcci statistici applicati nell’analisi svolta, evidenziando in particolare i risultati relativi al Random Forest, risultato il migliore dei cinque.

Categories: Aula: Seminario

May – October 2023 May – Oct 2023