L. Wyrzykowski

Fast radio bursts: the observational case for a Galactic origin

There are by now ten published detections of fast radio bursts (FRBs), single bright GHz-band millisecond pulses of unknown origin. Proposed explanations cover a broad range from exotic processes at cosmological distances to atmospheric and terrestrial sources. Loeb et al. have previously suggested that FRB sources could be nearby flare stars, and pointed out the presence of a W-UMa-type contact binary within the beam of one out of three FRB fields that they examined. Using time-domain optical photometry and spectroscopy, we now find possible flare stars in additional FRB fields, with one to three such cases among eight FRB fields studied. We evaluate the chance probabilities of these possible associations to be in the range 0.1% to 9%, depending on the input assumptions. Further, we re-analyze the probability that two FRBs recently discovered 3 years apart within the same radio beam are unrelated. Contrary to other claims, we conclude with 99% confidence that the two events are from the same repeating source. The different dispersion measures between the two bursts then rule out a cosmological origin for the dispersion measure, but are consistent with the flare-star scenario with a varying plasma blanket between bursts. Finally, we review some theoretical objections that have been raised against a local flare-star FRB origin, and show that they are incorrect.

Variability-selected QSO candidates in OGLE-II Galactic bulge fields

We present 97 QSO candidates in 48 Galactic bulge fields of the Optical Gravitational Lensing Experiment II (OGLE-II) covering ∼11 deg 2 , which are selected via their variability. We extend light curves of variable objects which were detected in a 3-yr baseline in the OGLE-II variable star catalogue to fourth year. We search for objects that are faint (16 < I 0 < 18.5) and slowly variable over 4 yr in this catalogue by using the variogram/structure function. Finding the QSOs in such stellar-crowded and high extinction fields is challenging, but should be useful for the astrometric reference frame. Spectroscopic follow-up observations are required to confirm these QSO candidates. Follow-up observations are being prepared for four of these fields (BUL-SC1, 2, 32 and 45). Follow-up observations for other fields are strongly encouraged. The complete list and light curves of all 97 candidates are available in electronic format at http://www.astro.princeton.edu/ sumi/QSO-OGLEII/.

On the accuracy of mass measurement for microlensing black holes as seen by Gaia and OGLE

We investigate the impact of combining Gaia astrometry from space with precise, high cadence OGLE photometry from the ground. For the archival event OGLE3-ULENS-PAR-02, which is likely a black hole, we simulate a realistic astrometric time-series of Gaia measurements and combine it with the real photometric data collected by the OGLE project. We predict that at the end of the nominal 5 years of the Gaia mission, for the events brighter than

β Cephei and SPB stars in the Large Magellanic Cloud

G\approx15.5

The optical gravitational lensing experiment. Search for planetary and low-luminosity object transits in the galactic disk. Results of 2001 campaign

mag at the baseline, caused by objects heavier than 10

The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. I. Classical Cepheids in the Large Magellanic Cloud

M_{\odot}

The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. II. Type II Cepheids and Anomalous Cepheids in the Large Magellanic Cloud

, it will be possible to unambiguously derive masses of the lenses, with accuracy between a few to 15 per cent. We find that fainter events (

The Optical Gravitational Lensing Experiment. Catalog of RR Lyrae Stars in the Large Magellanic Cloud

G<17.5

The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational Campaigns

) can still have their lens masses determined, provided that they are heavier than 30

Over 38000 RR Lyrae Stars in the OGLE Galactic Bulge Fields

M_{\odot}