Modeling of multimode radially pulsating High-Amplitude Delta Scuti stars from the OGLE Galactic bulge sample

Thanks to relatively firm mode identification, possible based on period ratios only, High Amplitude Delta Scuti Stars pulsating in at least three radial modes are promising targets for asteroseismic inference. In this study we used the most numerous sample of HADS from the OGLE inner bulge fields that likely pulsate in either three or four radial modes simultaneously. We have computed a grid of pulsation models along evolutionary tracks and determined the physical parameters of stars by matching their pulsation periods and period ratios. For 176 HADS we determined physical parameters, i.e. masses, luminosities, effective temperatures, metallicities and ages. We present the distribution of physical parameters and discuss their properties. We selected 16 candidates for SX Phoenicis stars.Comment: 13 pages, 14 figures, 2 tables, accepted for publication in MNRA

Frequency analysis of OGLE-IV photometry for classical Cepheids in Galactic fields: non-radial modes and modulations

We analyse photometry of $\sim$2000 Galactic Cepheids available in the OGLE Collection of Variable Stars. We analyse both Galactic disk and Galactic bulge fields; stars classified both as single- and multi-periodic. Our goal was to search for additional low-amplitude variability. We extend the sample of multi-mode radial pulsators by identifying ten new candidates for double-mode and six new candidates for triple-mode pulsation. In the first overtone OGLE sample, we found twelve Cepheids with additional periodicity having period ratio $P_{\rm x}/P_{\rm 1O}\in (0.60,\, 0.65)$. These periodicities do not correspond to any other radial mode. While such variables are abundant in the Magellanic Clouds, only one Cepheid of this class was known in the Galaxy before our analysis. Comparing our sample with the Magellanic Cloud Cepheids we note a systematic shift towards longer pulsation periods for more metal rich Galactic stars. Moreover in eleven stars we find one more type of additional variability, with characteristic frequencies close to half of that reported in the group with (0.60,\, 0.65) period ratios. Two out of the above inventory show simultaneous presence of both signals. Most likely, origin of these signals is connected to excitation of non-radial pulsation modes. We report three Cepheids with low-amplitude periodic modulation of pulsation: two stars are single-mode fundamental and first overtone Cepheids and one is a double-mode Cepheid pulsating simultaneously in fundamental and in first overtone modes. Only the former mode is modulated. It is a first detection of periodic modulation of pulsation in this type of double-mode Cepheids.Comment: 16 pages, 14 figures, Accepted in MNRA

Petersen Diagram Revolution

Over the recent years, the Petersen diagram for classical pulsators, Cepheids and RR Lyr stars, populated with a few hundreds of new multiperiodic variables. We review our analyses of the OGLE data, which resulted in the significant extension of the known, and in the discovery of a few new and distinct forms of multiperiodic pulsation. The showcase includes not only radial mode pulsators, but also radial-non-radial pulsators and stars with significant modulation observed on top of the beat pulsation. First theoretical models explaining the new forms of stellar variability are briefly discussed.Comment: 5 pages; to be published in the proceedings of the 22nd Los Alamos Stellar Pulsation Conference "Wide-field variability surveys: a 21st-century perspective", San Pedro de Atacama, Chile, Nov. 28 - Dec. 2, 201

The census of non-radial pulsation in first-overtone RRLyrae stars of the OGLE Galactic bulge collection

We analysed photometry for the up-to-date collection of the first-overtone RRLyrae stars (RRc; 11415 stars) and double-mode RRLyrae stars (RRd; 148 stars) towards the Galactic bulge from the Optical Gravitational Lensing Experiment (OGLE). We analysed frequency spectra of these stars in search for additional, low-amplitude signals, beyond the radial modes. We focused on stars from two groups: RR0.61 and RR0.68. In the first group, additional low-amplitude signals have periods shorter than the first-overtone period; period ratios fall in the 0.60-0.64 range. In the second group, additional low-amplitude signals have periods longer than the first-overtone period; period ratios tightly cluster around 0.68. Altogether we have detected 960 and 147 RRLyrae stars that belong to RR0.61 and RR0.68 groups, respectively, which yield the incidence rates of 8.3 and 1.3percent of the considered sample. We discuss statistical properties of RRLyrae stars with additional periodicities. For RR0.61 group we provide strong arguments that additional periodicities are connected to non-radial pulsation modes of degrees l=8 and l=9, as proposed by Dziembowski. We have also detected two double-periodic variables, with two close periodicities, similar to RRLyrae variable V37 in NGC6362. Properties of these peculiar variables, which may form a new group of double-mode pulsators, are discussed

Dual-locus DNA metabarcoding reveals southern hairy-nosed wombats (Lasiorhinus latifrons Owen) have a summer diet dominated by toxic invasive plants

Habitat degradation and summer droughts severely restrict feeding options for the endangered southern hairy-nosed wombat (SHNW; Lasiorhinus latifrons). We reconstructed SHNW summer diets by DNA metabarcoding from feces. We initially validated rbcL and ndhJ diet reconstructions using autopsied and captive animals. Subsequent diet reconstructions of wild wombats broadly reflected vegetative ground cover, implying local rather than long-range foraging. Diets were all dominated by alien invasives. Chemical analysis of alien food revealed Carrichtera annua contains high levels of glucosinolates. Clinical examination (7 animals) and autopsy (12 animals) revealed that the most degraded site also contained most individuals showing signs of glucosinolate poisoning. We infer that dietary poisoning through the ingestion of alien invasives may have contributed to the recent population crashes in the region. In floristically diverse sites, individuals appear to be able to manage glucosinolate intake by avoidance or episodic feeding but this strategy is less tractable in the most degraded sites. We conclude that recovery of the most affected populations may require effective Carrichtera management and interim supplementary feeding. More generally, we argue that protection against population decline by poisoning in territorial herbivores requires knowledge of their diet and of those food plants containing toxic principles