Search results for: P. Mróz

Items from 1 to 20 out of 109 results

article

Blue Large-Amplitude Pulsators and Other Short-Period Variable Stars in the OGLE-IV Galactic Disk Fields

J. Borowicz, P. Pietrukowicz, P. Mróz, I. Soszyński, more

Acta Astronomica > 2023 > Vol. 73, No. 1 > 1--19

Blue Large-Amplitude Pulsators (BLAPs) form a mysterious class of variable stars with typical periods of tens of minutes and amplitudes above 0.1 mag. In this work, we present results of a variability search focused on timescales shorter than 1 h, conducted in OGLE-IV Galactic disk fields containing about 1.1 billion stellar sources down to I≈20 mag. Twenty-five BLAPs have been detected, 20 of which...

article

The OGLE Collection of Variable Stars. Over 15 000 δ Scuti Stars in the Large Magellanic Cloud

I. Soszyński, P. Pietrukowicz, A. Udalski, J. Skowron, more

Acta Astronomica > 2023 > Vol. 73, No. 2 > 105--126

We present the OGLE collection of δ Scuti stars in the Large Magellanic Cloud and in its foreground. Our dataset encompasses a total of 15 256 objects, constituting the largest sample of extragalactic δ Sct stars published so far. In the case of 12 δ Sct pulsators, we detected additional eclipsing or ellipsoidal variations in their light curves. These are the first known candidates for binary systems...

article

Candidates for Transiting Planets in OGLE-IV Galactic Bulge Fields

M. Mróz, P. Pietrukowicz, R. Poleski, A. Udalski, more

Acta Astronomica > 2023 > Vol. 73, No. 2 > 127--158

We present results of a search for transiting exoplanets in 10-yr long photometry with thousands of epochs taken in the direction of the Galactic bulge. This photometry was collected in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV). Our search covered ≈222 000 stars brighter than I=15.5 mag. Selected transits were verified using a probabilistic method. The search resulted...

article

Search for Dormant Black Holes in the OGLE Data

M. Kapusta, P. Mróz

Acta Astronomica > 2023 > Vol. 73, No. 3 > 197--226

Light curves of ellipsoidal variables collected by the Optical Gravitational Lensing Experiment (OGLE) were analyzed, in order to search for dormant black hole candidates. After the preselection based on the amplitude of ellipsoidal modulation, each object was investigated by means of the spectral energy distribution fit, which allowed us to select objects that are in close agreement with the spectrum...

article

Proficiency development and smartphone usage in study abroad: Microgenetic longitudinal case studies of French learners

Aurore P. Mroz, Tricia Thrasher

Foreign Language Annals > 55 > 2 > 455 - 493

This longitudinal study explores how the language proficiency of eight (N = 8) US‐affiliated university students developed relative to their smartphone usage during study abroad (SA) in Paris. Phone usage was tracked daily with Space, proficiency weekly using NCSSFL‐ACTFL Can‐Do statements, and language use monthly via a Language Engagement Questionnaire. Adopting a Complex Dynamic Systems Theory...

article

The OGLE Collection of Variable Stars. Over 2600 δ Scuti Stars in the Small Magellanic Cloud

I. Soszyński, A. Udalski, J. Skowron, P. Pietrukowicz, more

Acta Astronomica > 2022 > Vol. 72, No. 4 > 245--256

We present the first-ever collection of δ Scuti stars found over the entire area of the Small Magellanic Cloud (SMC). The sample consists of 2810 variables of which over 2600 objects belong to the SMC while the remaining stars are most likely members of the Milky Way's halo. The sample has been divided into 2733 single mode and 77 multimode pulsators. We provide observational parameters (pulsation...

article

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

P. Pietrukowicz, M. Ratajczak, I. Soszyński, A. Udalski, more

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...

article

Measuring the Mass Function of Isolated Stellar Remnants with Gravitational Microlensing I. Revisiting the OGLE-III Dark Lens Candidates

P. Mróz, Ł. Wyrzykowski

Acta Astronomica > 2021 > Vol. 71, No. 2 > 89--102

Gravitational microlensing may detect dark stellar remnants - black holes or neutron stars - even if they are isolated. However, it is challenging to estimate masses of isolated dark stellar remnants using solely photometric data for microlensing events. A recent analysis of OGLE-III long-timescale microlensing events exhibiting the annual parallax effects claimed that a number of bright events were...

article

Wide-Orbit Exoplanets are Common. Analysis of Nearly 20 Years of OGLE Microlensing Survey Data

R. Poleski, J. Skowron, P. Mróz, A. Udalski, more

Acta Astronomica > 2021 > Vol. 71, No. 1 > 1--23

We use nearly 20 yr of photometry obtained by the OGLE survey to measure the occurrence rate of wide-orbit (or ice giant) microlensing planets, i.e., with separations from ≈5 a.u. to ≈15 a.u. and mass-ratios from 10^-4 to 0.033. In a sample of 3112 events we find six previously known wide-orbit planets and a new microlensing planet or brown dwarf OGLE-2017-BLG-0114Lb, for which close and wide orbits...

article

Over 24 000 δ Scuti Stars in the Galactic Bulge and Disk from the OGLE Survey

I. Soszyński, P. Pietrukowicz, J. Skowron, A. Udalski, more

Acta Astronomica > 2021 > Vol. 71, No. 3 > 189--204

We present the largest collection of δ Scuti-type stars in the Milky Way. Together with the recently published OGLE collection of δ Sct variables in the inner Galactic bulge, our sample consists of 24 488 objects distributed along the Milky Way plane, over galactic longitudes ranging from about -170° to +60°. The collection data include the I- and V-band time-series photometry collected since 1997...

article

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

P. Pietrukowicz, I. Soszyński, H. Netzel, M. Wrona, more

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,...

article

Identifying Microlensing Events Using Neural Networks

P. Mróz

Acta Astronomica > 2020 > Vol. 70, No. 3 > 169--180

Current gravitational microlensing surveys are observing hundreds of millions of stars in the Galactic bulge - which makes finding rare microlensing events a challenging tasks. In almost all previous works, microlensing events have been detected either by applying very strict selection cuts or manually inspecting tens of thousands of light curves. However, the number of microlensing events expected...

article

Additional Galactic Cepheids from the OGLE Survey

I. Soszyński, A. Udalski, M. K. Szymański, P. Pietrukowicz, more

Acta Astronomica > 2020 > Vol. 70, No. 2 > 101--119

We report on the results of a comprehensive search for Cepheid variable stars in the fields photometrically monitored by the OGLE Galaxy Variability Survey. We identify 742 Cepheids not included in the first release of the OGLE Collection of Galactic Cepheids and reclassify several dozen previously published variables. The upgraded collection comprises 1974 classical, 1625 type II, and 119 anomalous...

article

Properties of the Milky Way's Old Populations Based on Photometric Metallicities of the OGLE RR Lyrae Stars

P. Pietrukowicz, A. Udalski, I. Soszyński, D. M. Skowron, more

Acta Astronomica > 2020 > Vol. 70, No. 2 > 121--139

We have used photometric data on almost 91 000 fundamental-mode RR Lyr stars (type RRab) detected by the OGLE survey to investigate properties of old populations in the Milky Way. Based on their metallicity distributions, we demonstrate that the Galaxy is built from three distinct old components: halo, bulge, and disk. The distributions reach their maxima at approximately [Fe/H]_J95=-1.2 dex, -1.0...

article

Effect of cow age and stocking rate on milk output and milking duration

P. Wojcik, M. Meller, P. Mroz

Folia Pomeranae Universitatis Technologiae Stetinensis. Agricultura, Alimentaria,... > 2019 > 51 > 3(350)

article

Over 78 000 RR Lyrae Stars in the Galactic Bulge and Disk from the OGLE Survey

I. Soszyński, A. Udalski, M. Wrona, M. K. Szymański, more

Acta Astronomica > 2019 > Vol. 69, No. 4 > 321--337

We present an upgrade of the OGLE Collection of RR Lyrae stars in the Galactic bulge and disk. The size of our sample has been doubled and reached 78 350 RR Lyr variables, of which 56 508 are fundamental-mode pulsators (RRab stars), 21 321 pulsate solely in the first-overtone (RRc stars), 458 are classical double-mode pulsators (RRd stars), and 63 are anomalous RRd variables (including six triple-mode...

article

Mapping the Northern Galactic Disk Warp with Classical Cepheids

D. M. Skowron, J. Skowron, P. Mróz, A. Udalski, more

Acta Astronomica > 2019 > Vol. 69, No. 4 > 305--320

We present an updated three dimensional map of the Milky Way based on a sample of 2431 classical Cepheid variable stars, supplemented with about 200 newly detected classical Cepheids from the OGLE survey. The new objects were discovered as a result of a dedicated observing campaign of the ≈280 square degree extension of the OGLE footprint of the Galactic disk during 2018-2019 observing seasons. These...

article

Final Release of the OGLE Collection of Cepheids and RR Lyrae Stars in the Magellanic System. The Outer Regions

I. Soszyński, A. Udalski, M. K. Szymański, P. Pietrukowicz, more

Acta Astronomica > 2019 > Vol. 69, No. 2 > 87--99

We present the final release of the OGLE collection of classical pulsators (Cepheids and RR Lyr stars) in the Large and Small Magellanic Clouds. The sky coverage has been increased from 670 to 765 square degrees compared to the previous edition of our collection. We also add some Cepheids and RR Lyr stars found by the Gaia team and reclassify three Cepheids. Ultimately, our collection consists of...

article

OGLE Collection of Galactic Cepheids

A. Udalski, I. Soszyński, P. Pietrukowicz, M. K. Szymański, more

Acta Astronomica > 2018 > Vol. 68, No. 4 > 315--339

We present here a new major part of the OGLE Collection of Variable Stars - OGLE Collection of Galactic Cepheids. The new dataset was extracted from the Galaxy Variability Survey images - a dedicated large-scale survey of the Galactic disk and outer bulge conducted by the OGLE project since 2013. The OGLE collection contains 2721 Cepheids of all types - classical, type II and anomalous. It more than...

article

Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?

P. Iwanek, I. Soszyński, D. Skowron, J. Skowron, more

Acta Astronomica > 2018 > Vol. 68, No. 3 > 213--236

The nature of type II Cepheids and anomalous Cepheids is still not well known and their evolutionary channels leave many unanswered questions. We use complete collection of classical pulsating stars in the Magellanic Clouds discovered by the OGLE project, to compare their spatial distributions, which are one of the characteristic features directly related to the star formation history. In this analysis...

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Search results for: P. Mróz

Blue Large-Amplitude Pulsators and Other Short-Period Variable Stars in the OGLE-IV Galactic Disk Fields

The OGLE Collection of Variable Stars. Over 15 000 δ Scuti Stars in the Large Magellanic Cloud

Candidates for Transiting Planets in OGLE-IV Galactic Bulge Fields

Search for Dormant Black Holes in the OGLE Data

Proficiency development and smartphone usage in study abroad: Microgenetic longitudinal case studies of French learners

The OGLE Collection of Variable Stars. Over 2600 δ Scuti Stars in the Small Magellanic Cloud

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

Measuring the Mass Function of Isolated Stellar Remnants with Gravitational Microlensing I. Revisiting the OGLE-III Dark Lens Candidates

Wide-Orbit Exoplanets are Common. Analysis of Nearly 20 Years of OGLE Microlensing Survey Data

Over 24 000 δ Scuti Stars in the Galactic Bulge and Disk from the OGLE Survey

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

Identifying Microlensing Events Using Neural Networks

Additional Galactic Cepheids from the OGLE Survey

Properties of the Milky Way's Old Populations Based on Photometric Metallicities of the OGLE RR Lyrae Stars

Effect of cow age and stocking rate on milk output and milking duration

Over 78 000 RR Lyrae Stars in the Galactic Bulge and Disk from the OGLE Survey

Mapping the Northern Galactic Disk Warp with Classical Cepheids

Final Release of the OGLE Collection of Cepheids and RR Lyrae Stars in the Magellanic System. The Outer Regions

OGLE Collection of Galactic Cepheids

Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?

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