- ID:
- ivo://CDS.VizieR/J/MNRAS/454/507
- Title:
- Short-period var. stars OmegaWhite survey
- Short Name:
- J/MNRAS/454/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the goals, strategy and first results of the OmegaWhite survey: a wide-field high-cadence g-band synoptic survey which aims to unveil the Galactic population of short-period variable stars (with periods <80min), including ultracompact binary star systems and stellar pulsators. The ultimate goal of OmegaWhite is to cover 400deg^2^ along the Galactic plane reaching a depth of g=21.5mag (10{sigma}), using OmegaCam on the VLT Survey Telescope (VST). The fields are selected to overlap with surveys such as the Galactic Bulge Survey and the VST Photometric H{alpha} Survey of the Southern Galactic Plane for multiband colour information. Each field is observed using 38 exposures of 39s each, with a median cadence of ~2.7min for a total duration of two hours. Within an initial 26deg^2^, we have extracted the light curves of 1.6 million stars, and have identified 613 variable candidates which satisfy our selection criteria. Furthermore, we present the light curves and statistical properties of 20 sources which have the highest likelihood of being variable stars. One of these candidates exhibits the colours and light-curve properties typically associated with ultracompact AM CVn binaries, although its spectrum exhibits weak Balmer absorption lines and is thus not likely to be such a binary system. We also present follow-up spectroscopy of five other variable candidates, which identifies them as likely low-amplitude {delta} Sct pulsating stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/562/A107
- Title:
- {sigma} Gem V-band differential light curve
- Short Name:
- J/A+A/562/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We model the photometry of RS CVn star sigma Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes.
- ID:
- ivo://CDS.VizieR/J/other/JAD/21.1
- Title:
- 1972-1974 sigma Sco ubvy light curves
- Short Name:
- J/other/JAD/21.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents and discusses information about the observations and data reductions of a time series of photometric measurements of sigma Sco that has been collected in 1972 and 1974. Nearly two thousand standardised uvby magnitude differences sigma Sco minus tau Sco, together with unpublished instrumental differential magnitudes, are herewith supplied. This extended dataset will enhance the applicability of these more than four decades old measurements when used in studies based on data obtained with modern-day techniques such as robotic and space telescopes.
- ID:
- ivo://CDS.VizieR/J/AJ/145/22
- Title:
- Simultaneous SiO and H2O maser observations
- Short Name:
- J/AJ/145/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of simultaneous observations of SiO v=1,2, ^29^SiO v=0, J=1-0, and H_2_O 6_16_-5_23_ maser lines toward 152 known stellar H_2_O maser sources using the Yonsei 21m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H_2_O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H_2_O maser detection was detected from 27 sources, while the H_2_O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H_2_O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H_2_O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H_2_O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.
- ID:
- ivo://CDS.VizieR/J/AJ/147/22
- Title:
- Simultaneous SiO and H2O maser observations. IV.
- Short Name:
- J/AJ/147/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the simultaneous observational results of SiO and H_2_O masers toward 401 evolved stars, we have performed statistical analyses. We find that the peak and integrated intensities of SiO masers are stronger than those of H_2_O masers in both Mira variables and OH/IR stars at most optical phases. However, the relative intensity ratios of H_2_O to SiO masers in OH/IR stars are larger than those in Mira variables. Moreover, the intensity ratios of H_2_O to SiO masers are found to be increased around the optical phases from 0-0.4. The H_2_O photon luminosities also tend to be more dependent on the optical phase compared with those of SiO masers. These facts suggest that H_2_O masers are more sensitive to expanding the motion of circumstellar envelopes and also shock waves arising from the pulsations of the central star compared with SiO masers. This result may also be related to the differences in the maser location and pumping mechanism between H_2_O and SiO masers. The full width at zero power of SiO masers in Mira variables shows similar values to those of OH/IR stars, while those of H_2_ O masers in OH/IR stars show larger values than those of Mira variables. These differences may originate from the different mass-loss rates and the different location of the two masers. The mean velocity shift of SiO and H_2_O masers with respect to the stellar velocity was investigated as a function of optical phase. The velocity shift of the H_2_O masers shows that the redshifted emission dominates during the phases from 0.3-0.6, while the blueshifted emission appears at phase 0.6 and coexists with the redshifted emission during other phases. These features show an associated pattern with the CO {Delta}V=3 radial velocity curve, which exhibits a typical pulsation motion. On the other hand, the velocity shift of the SiO v=2 maser shows slightly similar features to the H_2_O maser, while that of SiO v=1 does not show these similar features. Finally, the distributions of all 401 observed sources are investigated in the IRAS two-color diagram in relation to the late evolutionary processes of asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1425
- Title:
- Single-mode OGLE Cepheids additional modes
- Short Name:
- J/MNRAS/478/1425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed knowledge of the variability of classical Cepheids, in particular their modulations and mode composition, provides crucial insight into stellar structure and pulsation. However, tiny modulations of the dominant radial-mode pulsation were recently found to be very frequent, possibly ubiquitous in Cepheids, which makes secondary modes difficult to detect and analyse, since these modulations can easily mask the potentially weak secondary modes. The aim of this study is to re-investigate the secondary mode content in the sample of OGLE-III and OGLE-IV single-mode classical Cepheids using kernel regression with adaptive kernel width for pre-whitening, instead of using a constant-parameter model. This leads to a more precise removal of the modulated dominant pulsation, and enables a more complete survey of secondary modes with frequencies outside a narrow range around the primary. Our analysis reveals that significant secondary modes occur more frequently among first overtone Cepheids than previously thought. The mode composition appears significantly different in the Large and Small Magellanic Clouds, suggesting a possible dependence on chemical composition. In addition to the formerly identified non-radial mode at P_2_~=0.6...0.65P_1_ (0.62-mode), and a cluster of modes with near-primary frequency, we find two more candidate non-radial modes. One is a numerous group of secondary modes with P_2_~=1.25P_1_, which may represent the fundamental of the 0.62-mode, supposed to be the first harmonic of an l {in} {7, 8, 9} non-radial mode. The other new mode is at P_2_ ~=1.46P_1_, possibly analogous to a similar, rare mode recently discovered among first overtone RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A213
- Title:
- SiO maser emission in evolved stars
- Short Name:
- J/A+A/642/A213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to study the time evolution of the SiO maser lines in Mira-type and semi-regular variables at short timescales. We observed the SiO maser lines at 7mm and 3mm using the 40m Yebes antenna and the 30m IRAM telescope, respectively, with a minimum spacing of 1 day. We studied the semi-regular variables RX Boo and RT Vir and the Mira-type variables U Her, R LMi, R Leo, and chi Cyg.
- ID:
- ivo://CDS.VizieR/J/PASJ/64/4
- Title:
- SiO maser survey of nearby red variables
- Short Name:
- J/PASJ/64/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the streaming motions of miras in the Solar neighborhood, we newly surveyed 379 red variables in the SiO maser lines at 42.821 and 43.122GHz with the Nobeyama 45m radio telescope. Accurate radial velocities were obtained for 229 (220 new) detected stars. The sample was selected from optical variables found by new automated surveys: the Northern Sky Variability Survey and the All Sky Automated Survey. The new sample consists of "bluer" objects compared with those observed in the previous SiO surveys. The distances to the objects were estimated using the period-luminosity relation, and they are mostly less than 3kpc from the Sun. The longitude-velocity diagram reveals three prominent groups of stars deviant from circular galactic rotation with a flat rotation curve. In addition to the Hercules group of stars, which was studied before, we found two new deviant groups: one toward the Perseus arm and the other toward the Sagittarius arm. These two groups both exhibit anomalous motions toward the galactic center, which seem to be consistent with the noncircular motions of these spiral arms found in recent VLBI proper-motion measurements for maser gas clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A75
- Title:
- Six luminous red novae photometry
- Short Name:
- J/A+A/630/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present extensive datasets for a class of intermediate-luminosity optical transients known as "luminous red novae" (LRNe). They show doublepeaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC4490-2011OT1, M101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak show a blue continuum with superposed prominent narrow Balmer lines, with P Cygni profiles. Lines of FeII are also clearly observed, mostly in emission. During the second peak, the spectral continuum becomes much redder, H{alpha} is barely detected, and a forest of narrow metal lines is observed in absorption. Very late-time spectra (~6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (IR) domain. H{alpha} is detected in pure emission at such late phases, along with broad absorption bands due to molecular overtones (such as TiO, VO). We discuss a few alternative scenarios for LRNe. Although major instabilities of single massive stars cannot be definitely ruled out, we favour a common envelope ejection in a close binary system, with possibly a final coalescence of the two stars. The similarity between LRNe and the outburst observed a few months before the explosion of the Type IIn SN 2011ht is also discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/136/267
- Title:
- Six occultations of the exoplanet TrES-3
- Short Name:
- J/AJ/136/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry of the exoplanet host star TrES-3 spanning six occultations (secondary eclipses) of its giant planet. No flux decrements were detected, leading to 99%-confidence upper limits on the planet-to-star flux ratio of 2.4x10^-4^, 5.0x10^-4^, and 8.6x10^-4^ in the i-, z-, and R-bands respectively. The corresponding upper limits on the planet's geometric albedo are 0.30, 0.62, and 1.07. The upper limit in the i-band rules out the presence of highly reflective clouds, and is only a factor of 2-3 above the predicted level of thermal radiation from the planet.
