1. Gaia22dkvLb : a microlensing planet potentially accessible to radial-velocity characterizationZexuan Wu, Subo Dong, Tuan Yi, Zhuokai Liu, Kareem El-Badry, Andrew Gould, Łukasz Wyrzykowski, K. A. Rybicki, Mateusz Bronikowski, 2024, izvirni znanstveni članek Opis: We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with M_p = 0.59 (+0.15, -0.05) M_J at a projected orbital separation r_perpendicular = 1.4 (+0.8, -0.3) au, and the host is a ∼1.1 M⊙ turnoff star at ∼1.3 kpc. At r' ~= 14, the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the "inner–outer correlation" inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius θ_E but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system. Ključne besede: gravitational microlensing exoplanet detection, planetary astrophysics, astrophysics of galaxies, instrumentation astrophysics, methods for astrophysics, solar astrophysics, stellar astrophysics Objavljeno v RUNG: 23.08.2024; Ogledov: 664; Prenosov: 8 Celotno besedilo (5,11 MB) Gradivo ima več datotek! Več... |
2. Lens parameters for Gaia18cbf – a long gravitational microlensing event in the Galactic planeK. Kruszyńska, Ł. Wyrzykowski, K. A. Rybicki, M. Maskoliūnas, E. Bachelet, N. Rattenbury, P. Mróz, P. Zieliński, K. Howil, Z. Kaczmarek, S. T. Hodgkin, N. Ihanec, I. Gezer, M. Gromadzki, P. Mikołajczyk, A. Stankevičiūtė, V. Čepas, E. Pakštienė, K. Šiškauskaitė, J. Zdanavičius, V. Bozza, M. Dominik, R. Figuera Jaimes, A. Fukui, M. Hundertmark, N. Narita, R. Street, Y. Tsapras, Mateusz Bronikowski, M. Jabłońska, A. Jabłonowska, O. Ziółkowska, 2022, izvirni znanstveni članek Opis: Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes.
Aims. Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model.
Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star.
Results. This event is one of the longest ever detected, with the Einstein timescale of tE = 491.41−84.94+128.31 days for the best solution and tE = 453.74−105.74+178.69 days for the second best. Assuming Galaxy priors, this translates to the most probable lens masses of ML = 2.65−1.48+5.09 M⊙ and ML = 1.71−1.06+3.78 M⊙, respectively. The limits on the blended light suggest that this event was most likely not caused by a MS star, but rather by a dark remnant of stellar evolution. Ključne besede: gravitational lensing: micro, Galaxy: stellar content, stars: black holes, stars: neutron, Astrophysics - Solar and Stellar Astrophysics Objavljeno v RUNG: 13.11.2023; Ogledov: 1570; Prenosov: 5 Celotno besedilo (9,87 MB) Gradivo ima več datotek! Več... |
3. Flares from the centers of galaxies with Gaia and OGLE surveysNada Ihanec, 2018, magistrsko delo Opis: Modern wide-field-of-view and all-sky satellites (e.g. Gaia) and ground based surveys (e.g. OGLE) repeatedly cover a large part of the sky and are detecting new, transient astrophysical sources on daily basis.
In this thesis I analyzed the data from Gaia and OGLE transient surveys, with special focus on transients located near the centres of galaxies to detect possible Tidal Disruption Events. These occur when a star gets too close to a Super-Massive Black Hole, which lurks in the centres of most galaxies, and gets disrupted due to the black hole's gravitational tidal forces.
The goal of my research was to detect possible Tidal Disruption Events and eliminate false candidates, such as supernovae. The work involved daily inspection of new alerts, identified with Gaia and OGLE Transient Detection System. I searched for potential transients in galactic nuclei and in case there was such a transient detected, follow-up spectroscopic observations were initiated in order to help classify the object.
During the course of my work I analyzed spectra obtained with the largest telescopes in the world (SALT, VLT) and performed the spectral template matching, recognition of spectral features related to known classes of transients, determination of redshift etc. Ključne besede: Flares, transients, Gaia, OGLE, supernovae, tidal disruption events, nuclear transients Objavljeno v RUNG: 14.05.2019; Ogledov: 5119; Prenosov: 138 Celotno besedilo (8,11 MB) |