We present a homogeneous Hubble Space Telescope/Advanced Camera for Surveys F555W and F814W time-series census of variable stars in two M101 disk fields, using a uniform multiband reduction and reproducible variable-selection workflow for nearby supernova host galaxies. Supplementary archival F555W epochs are used only to refine selected long-period solutions. Candidates are selected with Lomb–Scargle period searches, Fourier light-curve modeling, two-band consistency statistics, artificial-star-test photometric corrections, and mode-aware Cepheid refinement. The final catalog contains 1417 variable-star candidates, including 1102 secure fundamental-mode and 78 secure first-overtone classical Cepheids. Of these secure Cepheids, 420 are newly identified relative to the B. J. Shappee & K. Z. Stanek catalog. The catalog also contains luminous candidates outside the classical Cepheid locus. We release the catalog and source-level two-band light curves for studies of Cepheid physics, stellar variability, and distance-scale applications.
{O2 stars define the hottest end of the normal O-star sequence, but their identification requires blue-optical nitrogen diagnostics absent from many surveys.} {We reassess three luminous Large Magellanic Cloud (LMC) sources with multi-epoch Sloan Digital Sky Survey V (SDSS-V) spectroscopy obtained with the Baryon Oscil...
A. Roman-Lopes, J. G. Fernández-Trincado, M. Kounkel et al.· 0 citations
We present results from the UKIRT M33 Monitoring Project, a near-infrared survey of variable red giants in the Local Group spiral galaxy M33. Combining four independent photometric datasets spanning UIST (2003), UFTI (2005), WFCAM (2005-2007), and a new UKIRT Hemisphere Survey epoch (2018), we construct a homogenised 1...
M. Alizadeh, F. Nikzat, A. Javadi et al.· 0 citations
We present a photometric analysis of the variable stars in the field of the globular cluster M22 (NGC 6656), using time-series photometry from the literature and from OGLE and Gaia-DR3 data. From a sample of 666 variable stars in the field, we identify 94 as cluster members, including 10 RRab, 17 RRc, 2 Type II Cepheid...
M. A. Yepez, B. Moreno-Amaro, M. Ornelas-Castañeda et al.· 0 citations
O2 stars define the hottest end of the normal O-star sequence, but their identification requires blue-optical nitrogen diagnostics, which are absent in many surveys.
We reassess three luminous Large Magellanic Cloud (LMC) sources with multi-epoch Sloan Digital Sky Survey V spectroscopy obtained with the Baryon Oscillat...
A. Roman-Lopes, J. G. Fernández-Trincado, M. Kounkel et al.· Astronomy & Astrophysics· 0 citations
Space-based photometry has enabled major advances in asteroseismology, particularly for intermediate-mass A-F type stars located at the intersection of the main sequence and the classical instability strip. These stars, including δ Scuti, γ Dor, and roAp variables, exhibit a wide range of pulsation regimes and excitati...
Carlos C. Camino Mesa, A. G. Hernández, J. Suárez et al.· Astronomy & Astrophysics· 0 citations
Blue horizontal-branch (BHB) stars are ideal tracers for mapping the structure of the Galactic stellar halo. However, traditional spectroscopic identification is limited by data quality and sample size, while broadband photometric methods often achieve only moderate completeness and purity. Building upon the color-spac...
Shuai Zhang, Xiao-Long Wang, Kai Xiao et al.· Astrophysical Journal Supple...· 0 citations
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