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New Short-Period δ Scuti Stars in OGLE-IV Fields toward the Galactic Bulge

Pietrukowicz P., Ratajczak M., Soszyński I., Udalski A., Szymański M. K., Ulaczyk K., Poleski R., Kozłowski S., Skowron J., Skowron D. M., Mróz P., Rybicki K., Iwanek P., Wrona M., Gromadzki M.

Acta Astronomica

2022

Vol. 72, No. 3

161--170

We report the classification of 24 puzzling short-period variable stars located in OGLE-IV Galactic bulge fields. The stars are low-amplitude (<0.05 mag) multi-periodic objects with dominant periods between 22 min and 54 min whose type could not have been unambiguously established based on photometry only. A low-resolution spectroscopic follow-up observations have shown that all the objects are main sequence A/F-type stars. Thus, all the variables are δ Sct-type pulsators. We have added them to the OGLE-IV Collection of Variable Stars.

Over 10 000 δ Scuti Stars toward the Galactic Bulge from OGLE-IV

Pietrukowicz P., Soszyński I., Netzel H., Wrona M., Udalski A., Szymański M. K., Poleski R., Kozłowski S., Skowron J., Ulaczyk K., Skowron D. M., Mróz P., Rybicki P., Iwanek P., Gromadzki M.

Acta Astronomica

2020

Vol. 70, No. 4

241--263

We present a collection of 10 111 genuine δ Sct-type pulsating variable stars detected in the OGLE-IV Galactic bulge fields. In this sample, 9835 variables are new discoveries. For most of the stars photometric data cover the whole decade 2010-2019. We illustrate a huge variety of light curve shapes of δ Sct variables. Long-term observations have allowed us to spot objects with evident period, amplitude, and mean brightness variations. Our analysis indicates that about 28% of the stars are single-mode pulsators. Fourteen δ Sct stars show additional eclipsing or ellipsoidal binary modulation. We report significant attenuation or even disappearance of the pulsation signal in six sources. The whole set of variables is a mix of objects representing various Milky Way's populations, with the majority of stars from the Galactic bulge. There are also representatives of the Sagittarius Dwarf Spheroidal Galaxy. Some of the newly detected variables could be SX Phe-type stars residing in globular clusters. The collection, including full V- and I-band time-series data, is available to the astronomical community from the OGLE On-line Data Archive.

HAT Discovery of 76 Bright Periodic Variable Stars Toward the Galactic Bulge

Nataf D. M., Stanek K. Z., Bakos G. Á.

Acta Astronomica

2010

Vol. 60, No. 3

261--282

We report on photometric I-band observations of 147 bright periodic variable stars toward the Galactic bulge including 76 new discoveries. We used one of the HATnet telescopes to obtain 151 exposures spanning 88 nights in 2005 of an 8.4°×8.4° field of view (FOV) approximately centered on (l,b)=(1.73,-4.68). We observed the Galactic bulge in 2005 as part of a microlensing feasibility study, and here we discuss the periodic variable stars we found in our data. Among our discoveries we count 52 new eclipsing binaries and 24 other periodic variable stars.