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

Sumi, T. ; Wozniak, P. R. ; Eyer, L. ; Dobrzycki, A. ; Udalski, A. ; Szymanski, M. K. ; Kubiak, M. ; Pietrzynski, G. ; Soszynski, I. ; Zebrun, K. ; Szewczyk, O. ; Wyrzykowski, L.

In: Monthly Notices of the Royal Astronomical Society, 2005, vol. 356, no. 1, p. 331-335

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    Title
    • Variability-selected QSO candidates in OGLE-II Galactic bulge fields
    Author
    • Sumi, T.. Princeton University Observatory, Princeton, NJ 08544-1001, USA
    • Wozniak, P. R.. Los Alamos National Laboratory, MS-D436, Los Alamos, NM 87545, USA
    • Eyer, L.. Observatoire de Genève, CH 1290 Sauverny, Switzerland
    • Dobrzycki, A.. European Southern Observatory, D-85748 Garching bei München, Germany
    • Udalski, A.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Szymanski, M. K.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Kubiak, M.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Pietrzynski, G.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Soszynski, I.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Zebrun, K.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Szewczyk, O.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    • Wyrzykowski, L.. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:291041
    Summary
    We present 97 QSO candidates in 48 Galactic bulge fields of the Optical Gravitational Lensing Experiment II (OGLE-II) covering ∼11 deg2, 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 < I0 < 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