More Like this

1. Zwicky Transient Facility and Globular Clusters: The Period–Luminosity and Period–Wesenheit Relations for Anomalous Cepheids Supplemented with Large Magellanic Cloud Sample

   https://doi.org/10.3847/1538-3881/ac8df2  

   Ngeow, Chow-Choong ; Bhardwaj, Anupam ; Graham, Matthew J. ; Groom, Steven L. ; Masci, Frank J. ; Riddle, Reed ( October 2022 , The Astronomical Journal)

   We present the firstgri-band period–luminosity (PL) and period–Wesenheit (PW) relations for the fundamental mode anomalous Cepheids. These PL and PW relations were derived from a combined sample of five anomalous Cepheids in globular cluster M92 and the Large Magellanic Cloud, both of which have distance accurate to ∼1% available from literature. Ourg-band PL relation is similar to theB-band PL relation as reported in previous study. We applied our PL and PW relations to anomalous Cepheids discovered in dwarf galaxy Crater II, and found a larger but consistent distance modulus than the recent measurements based on RR Lyrae. Our calibrations ofgri-band PL and PW relations, even though less precise due to small number of anomalous Cepheids, will be useful for distance measurements to dwarf galaxies.

    

   more » « less
2. Zwicky Transient Facility and Globular Clusters: The Period–Luminosity and Period–Wesenheit Relations for Type II Cepheids

   https://doi.org/10.3847/1538-3881/ac87a4  

   Ngeow, Chow-Choong ; Bhardwaj, Anupam ; Henderson, Jing-Yi ; Graham, Matthew J. ; Laher, Russ R. ; Medford, Michael S. ; Purdum, Josiah ; Rusholme, Ben ( September 2022 , The Astronomical Journal)

   Abstract We present the first gri -band period–luminosity (PL) and period–Wesenheit (PW) relations for 37 Type II Cepheids (TIICs) located in 18 globular clusters based on photometric data from the Zwicky Transient Facility. We also updated BVIJHK -band absolute magnitudes for 58 TIICs in 24 globular clusters using the latest homogeneous distances to the globular clusters. The slopes of g / r / i - and B / V / I -band PL relations are found to be statistically consistent when using the same sample of distance and reddening. We employed the calibration of ri -band PL/PW relations in globular clusters to estimate a distance to M31 based on a sample of ∼270 TIICs from the PAndromeda project. The distance modulus to M31, obtained using calibrated ri -band PW relation, agrees well with the recent determination based on classical Cepheids. However, distance moduli derived using the calibrated r - and i -band PL relations are systematically smaller by ∼0.2 mag, suggesting there are possible additional systematic errors on the PL relations. Finally, we also derive the period–color (PC) relations and for the first time the period–Q-index (PQ) relations, where the Q -index is reddening free, for our sample of TIICs. The PC relations based on ( r − i ) and near-infrared colors and the PQ relations are found to be relatively independent of the pulsation periods. 

   more » « less
3. Zwicky Transient Facility and Globular Clusters: The RR Lyrae gri-band Period–Luminosity–Metallicity and Period–Wesenheit–Metallicity Relations

   https://doi.org/10.3847/1538-3881/ac617e  

   Ngeow, Chow-Choong ; Bhardwaj, Anupam ; Dekany, Richard ; Duev, Dmitry A. ; Graham, Matthew J. ; Groom, Steven L. ; Mahabal, Ashish A. ; Masci, Frank J. ; Medford, Michael S. ; Riddle, Reed ( April 2022 , The Astronomical Journal)

   Based on time-series observations collected from the Zwicky Transient Facility (ZTF), we derived period–luminosity–metallicity (PLZ) and period–Wesenheit–metallicity (PWZ) relations for RR Lyrae located in globular clusters. We have applied various selection criteria to exclude RR Lyrae with problematic or spurious light curves. These selection criteria utilized information on the number of data points per light curve, amplitudes, colors, and residuals on the period–luminosity and/or period–Wesenheit relations. Due to blending, a number of RR Lyrae in globular clusters were found to be anomalously bright and have small amplitudes of their ZTF light curves. We used our final sample of ∼750 RR Lyrae in 46 globular clusters covering a wide metallicity range (−2.36 dex < [Fe/H] < −0.54 dex) to derive PLZ and PWZ relations in thegribands. In addition, we have also derived the period–color–metallicity and, for the first time, the period-Q-index-metallicity relations, where theQ-index is extinction-free by construction. We have compared our various relations to empirical and theoretical relations available in the literature and found a good agreement with most studies. Finally, we applied our derived PLZ relation to a dwarf galaxy, Crater II, and found that its true distance modulus should be larger than the most recent determination.

    

   more » « less
4. Zwicky Transient Facility and Globular Clusters: the Period-Luminosity and Period-Luminosity-Color Relations for Late-Type Contact Binaries

   Ngeow, Chow-Choong ; Liao, Szu-Han ; Bellm, Eric C ; Duev, Dmitry A ; Graham, Matthew J ; Mahabal, Ashish A ; Masci, Frank J ; Medford, Michael S ; Riddle, Reed ; Rusholme, Ben ( May 2021 , ArXivorg)

   In this work, we aimed to derive the gri-band period-luminosity (PL) and period-luminosity-color (PLC) relations for late-type contact binaries, for the first time, located in the globular clusters, using the homogeneous light curves collected by the Zwicky Transient Factory (ZTF). We started with 79 contact binaries in 15 globular clusters, and retained 30 contact binaries in 10 globular clusters that have adequate number of data points in the ZTF light curves and unaffected by blending. Magnitudes at mean and maximum light of these contact binaries were determined using a fourth-order Fourier expansion, while extinction corrections were done using the {\tt Bayerstar2019} 3D reddening map together with adopting the homogeneous distances to their host globular clusters. After removing early-type and "anomaly" contact binaries, our derived gri-band PL and period-Wesenheit (PW) relations exhibit a much larger dispersion with large errors on the fitted coefficients. Nevertheless, the gr-band PL and PW relations based on this small sample of contact binaries in globular clusters were consistent with those based on a larger sample of nearby contact binaries. Good agreements of the PL and PW relations suggested both samples of contact binaries in the local Solar neighborhood and in the distant globular clusters can be combined and used to derive and calibrate the PL, PW and PLC relations. The final derived gr-band PL, PW and PLC relations were much improved than those based on the limited sample of contact binaries in the globular clusters. 

   more » « less
5. RR Lyrae Mid-infrared Period–Luminosity–Metallicity and Period–Wesenheit–Metallicity Relations Based on Gaia DR3 Parallaxes

   https://doi.org/10.3847/1538-4357/acb20a  

   Mullen, Joseph P. ; Marengo, Massimo ; Martínez-Vázquez, Clara E. ; Chaboyer, Brian ; Bono, Giuseppe ; Braga, Vittorio F. ; Dall’Ora, Massimo ; D’Orazi, Valentina ; Fabrizio, Michele ; Monelli, Matteo ; et al ( March 2023 , The Astrophysical Journal)

   We present new empirical infrared period–luminosity–metallicity (PLZ) and period–Wesenheit–metallicity (PWZ) relations for RR Lyae based on the latest Gaia Early Data Release 3 (EDR3) parallaxes. The relations are provided in the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands, as well as in the W(W1,V− W1) and W(W2,V− W2) Wesenheit magnitudes. The relations are calibrated using a very large sample of Galactic halo field RR Lyrae stars with homogeneous spectroscopic [Fe/H] abundances (over 1000 stars in the W1 band), covering a broad range of metallicities (−2.5 ≲ [Fe/H] ≲ 0.0). We test the performance of our PLZ and PWZ relations by determining the distance moduli of both galactic and extragalactic stellar associations: the Sculptor dwarf spheroidal galaxy in the Local Group (finding${\overline{\mu }}_0=19.47\pm 0.06$), the Galactic globular clusters M4 (${\overline{\mu }}_0=11.16\pm 0.05$), and the Reticulum globular cluster in the Large Magellanic Cloud (${\overline{\mu }}_0=18.23\pm 0.06$). The distance moduli determined through all our relations are internally self-consistent (within ≲0.05 mag) but are systematically smaller (by ∼2–3σ) than previous literature measurements taken from a variety of methods/anchors. However, a comparison with similar recent RR Lyrae empirical relations anchored with EDR3 likewise shows, to varying extents, a systematically smaller distance modulus for PLZ/PWZ RR Lyrae relations.

    

   more » « less