We present the most extensive and detailed reddening maps of the Magellanic Clouds (MCs) derived from the color properties of Red Clump (RC) stars. The analysis is based on the deep photometric maps ...from the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV), covering approximately 670 deg2 of the sky in the Magellanic System region. The resulting maps provide reddening information for 180 deg2 in the Large Magellanic Cloud (LMC) and 75 deg2 in the Small Magellanic Cloud (SMC), with a resolution of 1 7 × 1 7 in the central parts of the MCs, decreasing to approximately 27′ × 27′ in the outskirts. The mean reddening is E(V − I) = 0.100 0.043 mag in the LMC and E(V − I) = 0.047 0.025 mag in the SMC. We refine methods of calculating the RC color to obtain the highest possible accuracy of reddening maps based on RC stars. Using spectroscopy of red giants, we find the metallicity gradient in both MCs, which causes a slight decrease of the intrinsic RC color with distance from the galaxy center of ∼0.002 mag/deg in the LMC and between 0.003 and 0.009 mag/deg in the SMC. The central values of the intrinsic RC color are 0.886 and 0.877 mag in the LMC and SMC, respectively. The reddening map of the MCs is available both in downloadable form and as an interactive interface.
ABSTRACT
We have performed a frequency analysis of 10 092 δ Scuti-type stars detected in the fourth phase of the Optical Gravitational Lensing Experiment towards the Galactic bulge, which is the most ...numerous homogeneous sample of δ Scuti stars observed so far. The main goal was to search for stars pulsating in at least two radial modes simultaneously. We have found 3083 candidates for such stars, which is the largest set obtained to date. Among them, 2655 stars pulsate in two radial modes, 414 stars pulsate in three radial modes, and 14 stars pulsate in four radial modes at the same time. We report the identification of 221 δ Scuti stars pulsating in the fundamental mode, first overtone, and third overtone simultaneously. We show the most populated Petersen and Bailey diagrams and discuss statistical properties of the identified frequencies based on this numerous sample. Additionally, we present theoretical predictions of period ratios for δ Scuti stars pulsating in overtones from the fourth to the seventh.
Abstract
Long secondary periods (LSPs), observed in a third of pulsating red giant stars, are the only unexplained type of large-amplitude stellar variability known at this time. Here we show that ...this phenomenon is a manifestation of a substellar or stellar companion orbiting the red giant star. Our investigation is based on a sample of about 16,000 well-defined LSP variables detected in the long-term OGLE photometric database of the Milky Way and Magellanic Clouds, combined with the mid-infrared data extracted from the NEOWISE-R archive. From this collection, we selected about 700 objects with stable, large-amplitude, well-sampled infrared light curves and found that about half of them exhibit secondary eclipses, thus presenting an important piece of evidence that the physical mechanism responsible for LSPs is binarity. Namely, the LSP light changes are due to the presence of a dusty cloud orbiting the red giant together with the companion and obscuring the star once per orbit. The secondary eclipses, visible only in the infrared wavelength, occur when the cloud is hidden behind the giant. In this scenario, the low-mass companion is a former planet that has accreted a significant amount of mass from the envelope of its host star and grown into a brown dwarf.
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 pulsators). For all the newly identified RR Lyr stars, we publish time-series photometry obtained during the OGLE Galaxy Variability Survey. We present the spatial distribution of RR Lyr stars on the sky, provide a list of globular clusters hosting RR Lyr variables, and discuss the Petersen diagram for multimode pulsators. We find new RRd stars belonging to a compact group in the Petersen diagram (with period ratios P 1O/PF≈0.74 and fundamental-mode periods P F≈0.44$ d) and we show that their spatial distribution is roughly spherically symmetrical around the Milky Way center.
Abstract We report the discovery of the classical Cepheid OGLE-GD-CEP-1884 (= GDS_J1535467-555656) with the longest pulsation period known in our Galaxy. The period of 78.14 days is nearly 10 days ...longer than that of the previous record-holding Cepheid, S Vulpeculae, and thus, OGLE-GD-CEP-1884 can be categorized as the first ultra-long-period Cepheid in the Milky Way. This star is present in the ASAS-SN and Gaia DR3 catalogs of variable stars, but it has been classified as a long-period variable in those catalogs. Based on more than 10 yr of the photometric monitoring of this star carried out by the OGLE project in the I and V bands and a radial velocity curve from the Gaia Focused Product Release, we unequivocally demonstrate that this object is a fundamental-mode classical Cepheid. By employing the mid-infrared period–luminosity relation, we determine the distance to OGLE-GD-CEP-1884 (4.47 ± 0.34 kpc) and place it on the Milky Way map, along with about 2400 other classical Cepheids. We also discuss the potential of finding additional ultra-long-period Cepheids in our Galaxy.
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 doubles the number of known Galactic classical Cepheids. Due to the long-term monitoring and large number of epochs the selected sample is very pure, generally free from contaminating stars of other types often mimicking Cepheids. Its completeness is high at 90% level for classical Cepheids - tested using recent samples of Galactic Cepheids: ASAS-SN, ATLAS, Gaia DR2 and Wise catalog of variable stars. Our comparisons indicate that the completeness of the two latter datasets, Gaia DR2 and Wise catalog, is very low, at <10% level in the magnitude range of the OGLE GVS survey (10.8<I<19.5 mag). Both these samples are severely contaminated by non-Cepheids (the purity is 67% and 56%, respectively). We also present several interesting objects found in the new OGLE Collection - multi-mode pulsators, first Galactic candidates for eclipsing systems containing Cepheid, a binary Cepheid candidate. New OGLE Collection of Galactic Cepheids is available for the astronomical community from the OGLE Internet Archive in similar form as previous parts of the OGLE Collection of Variable Stars.
Context.
Eccentric ellipsoidal variables (also known as heartbeat stars) is a class of eccentric binaries in which proximity effects, and tidal distortion due to time-dependent tidal potential in ...particular, lead to measurable photometric variability close to the periastron passage. Varying tidal potential may also give rise to tidally excited oscillations (TEOs), which are forced eigenmodes with frequencies close to the integer multiples of the orbital frequency. TEOs may play an important role in the dynamical evolution of massive eccentric systems.
Aims.
Our study is aimed at detecting TEOs and characterising the long-term behaviour of their amplitudes and frequencies in the extreme-amplitude heartbeat star MACHO 80.7443.1718, consisting of a blue supergiant and a late O-type massive dwarf.
Methods.
We used two seasons of Transiting Exoplanet Survey Satellite (TESS) observations of the target to obtain new 30-min cadence photometry by means of the difference image analysis of TESS full-frame images. In order to extend the analysis to longer timescales, we supplemented the TESS data with 30-year long ground-based photometry of the target. Both TESS and ground-based photometry are carefully analysed by means of Fourier techniques in order to detect TEOs, examine the long-term stability of their amplitudes and frequencies, and characterise other types of variability in the system.
Results.
We confirm the detection of the known
n
= 23, 25, and 41 TEOs and announce the detection of two new TEOs, with
n
= 24 and 230, in the photometry of MACHO 80.7443.1718. Amplitudes of all TEOs were found to vary on a timescale of years or months. For
n
= 25, the TEO amplitude and frequency changes are related, which may indicate that the main cause of the amplitude drop in this TEO in TESS observations is the change in its frequency and increase in its detuning parameter. The light curve of the
n
= 230 TEO is strongly non-sinusoidal. Its high frequency may indicate that the oscillation is a strange mode. Stochastic variability observed in the target fits the behaviour observed in massive stars well and independently confirms that the primary is an evolved star. We also find that the orbital period of the system decreases at a rate of about 11 s (yr)
−1
. This can be explained by several phenomena: a significant mass loss, mass transfer between components, tidal dissipation, and the presence of a tertiary in the system. All of these phenomena may contribute to the observed changes.
Conclusions.
The discovery of variable amplitudes and frequencies of TEOs prompts for similar studies in other eccentric elliptical variables with TEOs. Long-term photometric monitoring of these targets is also desirable. The results we obtained pose a challenge for theory. In particular, it needs to be explained why
n
= 230 TEO is excited. In a general context, studies on the long-term behaviour of TEOs may help to explain the role of TEOs in the dynamical evolution of massive eccentric systems.
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Objectives The aim was to study the association between venous disorders and leg symptoms in the population based cross sectional Bonn Vein Study 1 (BVS1). Methods A total of 1,350 men and 1,722 ...women aged 18–79 years were enrolled into BVS1. Chronic venous insufficiency (CVI), varicose veins (VVs), and clinical classes (C-classes/CEAP Clinical, Etiological, Anatomical, and Pathophysiological) were determined by clinical and duplex investigation. Leg symptoms (heaviness, tightness, swelling, pain after standing or sitting, pain while walking, muscle cramps, itching, and restless legs) were assessed in a standardized interview. For 2,624 subjects (48.7% male) with complete information on venous disorders, relevant characteristics and information on at least one leg symptom, multivariate logistic regression analysis was performed. Results More women (929/63.0%) reported at least one leg symptom within the last 4 weeks than men (560/48.7%). Prevalence of reported symptoms increased with age (45.4% of the 18–29 year olds, 73.9% of the 70–79 year olds). Leg symptoms were more frequent in obese and underweight subjects. As confirmed by clinical and duplex examination 22.6% had VV and 15.8% had CVI. VV (OR: 1.4; CI: 1.1–1.7) and CVI (OR: 1.8; CI: 1.3–2.3) were significantly associated with reporting at least one leg symptom. In particular, there was a positive association of VV and CVI with itching, feeling of heaviness, tightness, swelling, and pain after standing or sitting. C2–C6 showed a statistically significant association with feeling of heaviness, tightness, swelling, and itching, while for pain on walking and muscle cramps this was shifted towards C classes C3–C6 and C3–C4, respectively. Conclusions Venous disorders show significant associations with several leg symptoms. Itching, feeling of heaviness, or tightness seem to be more closely related than other symptoms. The associations between C classes and symptoms seem to be restricted to classes C2 or higher.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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 Cepheids located in the area of about 3000 square degrees covering the disk and bulge of the Milky Way. We present the most interesting objects in our sample: an isolated group of long-period double-mode classical Cepheids pulsating in the fundamental mode and first overtone, the first known Galactic double-mode Cepheid with the second and third overtone excited, double-mode type II Cepheids, candidates for single-mode first-overtone BL Her stars, and Cepheids showing simultaneous eclipsing variability. We also discuss type II and anomalous Cepheids that are potential members of globular clusters.
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 are possible and close orbit is preferred. We run extensive simulations of the planet detection efficiency, robustly taking into account the finite-source effects. We find that the extrapolation of the previously measured rate of microlensing planets significantly under-predicts the number of wide-orbit planets. On average, every microlensing star hosts 1.4+0.9_-0.6 ice giant planets.
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