- ID:
- ivo://CDS.VizieR/J/MNRAS/353/705
- Title:
- OGLE Variables in Magellanic Clouds
- Short Name:
- J/MNRAS/353/705
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The data of 8852 and 2927 variable stars detected by the OGLE survey in the Large and Small Magellanic Clouds are presented. They are cross-identified with the SIRIUS JHK survey data, and their infrared properties are discussed. Variable red giants are well separated on the period-(J-K) plane, suggesting that it could be a good tool to distinguish their pulsation mode and type.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AcA/56/219
- Title:
- OGLE variable stars in NGC 6259
- Short Name:
- J/AcA/56/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for variable stars in the field of NGC6259. Altogether 85 variable stars have been discovered. 36 of them are eclipsing systems. This group contains 13 EA, 2 EB and 21 EW-type stars. Light curves of two variable stars resemble those of Miras. The remaining 47 variable stars detected in the field of this open cluster are most probably highly obscured red giants (OSARG, irregular). For all detected variable stars we provide their light curves, preliminary classification, discussion on the possible cluster membership, equatorial coordinates, finding charts and periods when possible.
- ID:
- ivo://CDS.VizieR/J/A+A/297/494
- Title:
- OH maser from semiregular variables
- Short Name:
- J/A+A/297/494
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a high sensivity (~0.15Jy) search in the OH main-lines for maser emission from a sample of 181 semiregular variables.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A136
- Title:
- OMC-2 FIR4 fits images
- Short Name:
- J/A+A/657/A136
- Date:
- 21 Mar 2022 09:38:35
- Publisher:
- CDS
- Description:
- Isotopic fractionation is an important tool for investigating the chemical history of our Solar System. In particular, the isotopic fraction of nitrogen (^14^N/^15^N) is lower in comets and other pristine Solar System bodies with respect to the value measured for the protosolar nebula, suggesting a local chemical enrichment of ^15^N during the formation of the Solar System. Therefore, interferometric studies of nitrogen fractionation in Solar System precursors are needed for us to obtain clues about our astrochemical origins. In this work we have investigated the variation in the ^14^N/^15^N ratio in one of the closest analogues of the environment in which the Solar System was born: the protocluster OMC-2 FIR4. We present the first comparison at high angular resolution between HCN and N_2_H^+^ using interferometric data. We analysed observations of the HCN isotopologues H^13^CN and HC^15^N in the OMC-2 FIR4 protocluster. Specifically, we observed the transitions H^13^CN (1-0) and HC^15^N (1-0) with the NOrthern Extended Millimeter Array (NOEMA) within the context of the IRAM Seeds Of Life In Space (SOLIS) Large Program. We combined our results with analysis of archival data obtained with the Atacama Large Millimeter Array (ALMA) of N_2_H^+^ and its ^15^N isotopologues. Our results show a small regional variation in the ^14^N/^15^N ratio for HCN, from ~250 to 500. The ratios in the central regions of FIR4, where the candidate protostars are located, are largely consistent with one another and within that range (~300). They also show little variation from the part of the protocluster known to harbour a high cosmic-ray ionisation rate to the portion with a lower rate. We also found a small variation in the ^14^N/^15^N ratio of N_2_H^+^ across different regions, from ~200 to ~400. These results suggest that local changes in the physical parameters occurring on the small linear scales probed by our observations in the protocluster do not seem to affect the ^14^N/^15^N ratio in either HCN or N_2_H^+^ and hence that this is independent of the molecule used. Moreover, the high level of irradiation due to cosmic rays does not affect the N fractionation either.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A120
- Title:
- omega Cen RR Lyrae and SX Phoenicis stars
- Short Name:
- J/A+A/604/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The globular cluster {omega} Centauri (NGC 5139) hosts hundreds of pulsating variable stars of different types, thus representing a treasure trove for studies of their corresponding period-luminosity (PL) relations. Our goal in this study is to obtain the PL relations for RR Lyrae and SX Phoenicis stars in the field of the cluster, based on high-quality, well-sampled light curves in the near-infrared (IR). Observations were carried out using the VISTA InfraRed CAMera (VIRCAM) mounted on the Visible and Infrared Survey Telescope for Astronomy (VISTA). A total of 42 epochs in J and 100 epochs in K_S_ were obtained, spanning 352 days. Point-spread function photometry was performed using DoPhot and DAOPHOT crowded-field photometry packages in the outer and inner regions of the cluster, respectively. Based on the comprehensive catalog of near-IR light curves thus secured, PL relations were obtained for the different types of pulsators in the cluster, both in the J and K_S_ bands. This includes the first PL relations in the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and periods of Type II Cepheids and RR Lyrae stars were used to derive an updated true distance modulus to the cluster, with a resulting value of (m-M)_0_=13.708+/-0.035+/-0.10mag, where the error bars correspond to the adopted statistical and systematic errors, respectively. Adding the errors in quadrature, this is equivalent to a heliocentric distance of 5.52+/-0.27kpc.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A95
- Title:
- omega Cen RR Lyrae and Type II Cepheids
- Short Name:
- J/A+A/644/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The separation between RR Lyrae (RRLs) and type II Cepheid (T2Cs) variables based on their period is debated. Both types of variable stars are distance indicators, and we aim to promote the use of T2Cs as distance indicators in synergy with RRLs. We adopted new and existing optical and Near-Infrared (NIR) photometry of omega Cen to investigate several diagnostics (colour-magnitude diagram, Bailey diagram, Fourier decomposition of the light curve, amplitude ratios) for the empirical separation between Type II Cepheids (T2Cs) and RR Lyrae (RRLs). We also derived NIR period-luminosity relations and found a distance modulus of 13.65+/-0.07 (err.)+/-0.01 (sigma) mag, in agreement with the recent literature. We also found that RRLs and T2Cs obey the same PL relations in the NIR.
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/4833
- Title:
- Oosterhoff dichotomy in Galactic bulge
- Short Name:
- J/MNRAS/484/4833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the Oosterhoff (Oo) dichotomy in the Galactic bulge using 8141 fundamental-mode RR Lyrae stars. We used public photometric data from the Optical Gravitational Lensing Experiment and the Vista Variables in the Via Lactea survey. We carefully selected fundamental-mode stars without modulation and without association with any globular cluster located towards the Galactic bulge. Subsequently, we identified and separated the Oosterhoff groups I and II on the basis of their period-amplitude distribution and using a relation fitted to the Oosterhoff I locus. Both Oosterhoff groups were then compared to observations of two bulge globular clusters and with models of stellar pulsation and evolution. We found that some of the variables classified as Oo II belong to a third Oo group. The Oosterhoff II variables are more metal-poor on average, more massive, and cooler than their Oosterhoff I counterparts. The analysis of their spatial distribution shows a systematic difference between foreground, central, and background regions in the occurrence of the Oosterhoff II group. The difference between the Oo I and II groups is also seen in their distance distributions with respect to the Galactic bar, but neither group is associated with the bar.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/114
- Title:
- Opacity-sampling models of Mira variables
- Short Name:
- J/MNRAS/418/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four model series of the CODEX dynamical opacity-sampling models of Mira variables with solar abundances, designed to have parameters similar to {omicron} Cet, R Leo and R Cas. We demonstrate that the CODEX models provide a clear physical basis for the molecular shell scenario used to explain interferometric observations of Mira variables. We show that these models generally provide a good match to photometry and interferometry at wavelengths between the near-infrared and the radio, and make the model outputs publicly available. These models also demonstrate that, in order to match visible and infrared observations, the Fe-poor silicate grains that form within 3 continuum radii must have small grain radii and therefore cannot drive the winds from O-rich Mira variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/L8
- Title:
- Optical and IR photometry of [KOS94] HA11
- Short Name:
- J/ApJ/733/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a long-term optical photometric and spectroscopic monitoring of the strongly variable, accreting young sun-like star [KOS94] HA11, associated with the dark cloud Lynds 1340 that exhibited large amplitude (5-6mag in the I_C_ band) brightness variations on 2-3 years timescales, flat spectral energy distribution (SED), and extremely strong (300<~EW/{AA}<~900) H{alpha} emission. In this Letter we describe the basic properties of the star, derived from our observations between 1999 and 2011, and put into context the observed phenomena. The observed variations in the emission spectra, near-infrared colors, and SED suggest that [KOS94] HA11 (spectral type: K7-M0) is an eruptive young star, possibly similar in nature to V1647 Ori: its large-scale photometric variations are governed by variable accretion rate, associated with variations in the inner disk structure. The star recently has undergone strong and rapid brightness variations, thus its further observations may offer a rare opportunity for studying structural and chemical rearrangements of the inner disk, induced by variable central luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/145/59
- Title:
- Optical and mid-IR photometry of PTF 10nvg
- Short Name:
- J/AJ/145/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report extensive new photometry and spectroscopy of the highly variable young stellar object PTF 10nvg (also known as IRAS 20496+4354 and V2492 Cyg), including optical and near-infrared time-series data as well as mid-infrared and millimeter data. Following the previously reported 2010 rise to R_PTF_<~13.5^m^ and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening, followed by several magnitude dimming events including prolonged faint states at R_PTF_>~20^m^. The observed high-amplitude variations are largely consistent with extinction changes ({Delta}A_V_ up to 30mag) having a ~220day quasi-periodic signal. However, photometry measured when the source was near maximum brightness in mid-2010 as well as in late-2012 does not phase well to this period. Spectral evolution includes not only changes in the spectral slope but also correlated variation in the prominence of TiO/VO/CO bands and atomic line emission, as well as anti-correlated variation in forbidden line emission which, along with H_2_, dominates optical and infrared spectra at faint epochs. Notably, night-to-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra were obtained in a variety of photometric states and reveal time-variable line profiles. Neutral and singly ionized atomic species are likely formed in an accretion flow and/or impact while the origin of zero-velocity atomic LiI{lambda}6707 in emission is unknown. Forbidden lines, including several rare species, exhibit blueshifted emission profiles and likely arise from an outflow/jet. Several of these lines are also seen spatially offset from the continuum source position, presumably in a shocked region of an extended jet. Blueshifted absorption components of the NaI D doublet, KI{lambda}{lambda}7665,7669 doublet, and the OI 7774 triplet, as well as blueshifted absorption components seen against the broad H{alpha} and CaII triplet emission lines, similarly are formed in the outflow. CARMA maps resolve on larger scales a spatially extended outflow in millimeter-wavelength CO. We attribute the recently observed photometric and spectroscopic behavior to rotating circumstellar disk material located at separation a~0.7(M_*_/M_{sun}_)^1/3^AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven (perhaps analogous to V1647 Ori) and extinction-driven (perhaps analogous to UX Ori or GM Cep) high-amplitude variability phenomena.
