- ID:
- ivo://CDS.VizieR/J/A+A/578/A122
- Title:
- eta Carinae's 2014.6 spectroscopic event
- Short Name:
- J/A+A/578/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Every 5.5-years, {eta} Car's light curve and spectrum change remarkably across all observed wavelength bands. These so-called spectroscopic events are most likely caused by the close approach of a companion. We compare the recent spectroscopic event in mid-2014 to the events in 2003 and 2009 and investigate long-term trends. Eta Car was observed with HST STIS, VLT UVES, and CTIO 1.5m CHIRON for a period of more than two years in 2012-2015. Archival observations with these instruments cover three orbital cycles and the events of 2003.5, 2009.1, and 2014.6. The STIS spectra provide high spatial resolution and include epochs during the 2014 event when observations from most ground-based observatories were not feasible. The strategy for UVES observations allows for a multidimensional analysis, because each location in the reflection nebula is correlated with a different stellar latitude. Important spectroscopic diagnostics during {eta} Car's events show significant changes in 2014 compared to previous events. While the timing of the first HeII {lambda}4686 flash was remarkably similar to previous events, the HeII equivalent widths were slightly larger, and the line flux increased by a factor of ~7 compared to 2003. The second HeII peak occurred at about the same phase as in 2009, but was stronger. The HeI line flux grew by a factor of ~8 in 2009-2014 compared to 1998-2003. The NII emission lines also increased in strength. On the other hand, H{alpha} and FeII lines show the smallest emission strengths ever observed in {eta} Car. The optical continuum brightened by a factor of ~4 in the past 10-15 years. The polar spectrum shows fewer changes in the broad wind emission lines: the FeII emission strength decreased by a factor of ~2 (compared to a factor of ~4 in our direct line of sight). The HeII equivalent widths at FOS4 were larger in 2009 and 2014 than during the 2003 event.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PASP/132/K4202
- Title:
- Evryscope-South survey
- Short Name:
- J/PASP/132/K4202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using photometric data collected by Evryscope-South, we search for nearby young variable systems on the upper main sequence (UMS) and pre-main sequence (PMS). The Evryscopes are all-sky high-cadence telescope arrays operating in the Northern and Southern hemispheres. We base our search on a Gaia-selected catalog of young neighborhood upper- and pre-main sequence stars which were chosen through both astrometric and photometric criteria. We analyze 44971 Evryscope-South light curves in search of variability. We recover 615 variables, with 378 previously known, and 237 new discoveries including 84 young eclipsing binaries (EB) candidates. We discover a new highly eccentric binary system and recover a further four previously known systems, with periods ranging from 299 to 674hr. We find 158 long-period (>50hr) candidate EB systems, 9 from the PMS and 149 from the UMS, which will allow constraints on the mass/radius/age relation. These long-period EBs include a 179.3hr PMS system and a 867.8hr system from the UMS. For PMS variable candidates we estimate system ages, which range from 1 to 23Myr for non-EBs and from 2 to 17Myr for EBs. Other non-EB discoveries that show intrinsic variability will allow relationships between stellar rotation rates, ages, activity, and mass to be characterized.
- ID:
- ivo://CDS.VizieR/J/MNRAS/495/4924
- Title:
- Exoplanets in Southern open clusters
- Short Name:
- J/MNRAS/495/4924
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The scope of the project 'A PSF-based Approach to TESS High Quality data Of Stellar clusters' (PATHOS) is the extraction and analysis of high-precision light curves of stars in stellar clusters and young associations for the identification of candidate exoplanets and variable stars. The cutting-edge tools used in this project allow us to measure the real flux of stars in dense fields, minimizing the effects due to contamination by neighbour sources. We extracted about 200000 light curves of stars in 645 open clusters located in the Southern ecliptic hemisphere and observed by TESS during the first year of its mission. We searched for transiting signals and we found 33 objects of interest, 11 of which are strong candidate exoplanets. Because of the limited SNR, we did not find any Earth or super-Earth. We identified two Neptune-size planets orbiting stars with R*<1.5R_{sun}_, implying a frequency f*=1.3+/-0.95 per cent consistent with the frequency around field stars. The seven Jupiter candidates around stars with R*<1.5R_{sun}_ imply a frequency f*=0.19+/-0.07 per cent, which is smaller than in the field. more complete estimate of the survey completeness and false positive rate is needed to confirm these results. Light curves used in this work will be made available to the astronomical community on the Mikulski Archive for Space Telescope under the project PATHOS.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/16
- Title:
- Exoplanets in the Antarctic sky. I. AST3-II DR1
- Short Name:
- J/ApJS/240/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Located at Dome A, the highest point of the Antarctic plateau, the Chinese Kunlun station is considered to be one of the best ground-based photometric sites because of its extremely cold, dry, and stable atmosphere. A target can be monitored from there for over 40 days without diurnal interruption during a polar winter. This makes Kunlun station a perfect site to search for short- period transiting exoplanets. Since 2008, an observatory has existed at Kunlun station, and three telescopes are working there. Using these telescopes, the AST3 project has been carried out over the last 6yr with a search for transiting exoplanets as one of its key programs (CHinese Exoplanet Searching Program from Antarctica --CHESPA). In the austral winters of 2016 and 2017, a set of target fields in the southern continuous viewing zone (CVZ) of TESS were monitored by the AST3-II telescope. In this paper, we introduce the CHESPA and present the first data release containing photometry of 26,578 bright stars (m_i_<=15). The best photometric precision at the optimum magnitude for the survey is around 2 mmag. To demonstrate the data quality, we also present a catalog of 221 variables with a brightness variation greater than 5mmag from the 2016 data. Among these variables, 179 are newly identified periodic variables not listed in the AAVSO database (https://www.aavso.org/), and 67 are listed in the Candidate Target List. These variables will require careful attention to avoid false-positive signals when searching for transiting exoplanets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/3806
- Title:
- Exoplanets & variable stars in 47 Tuc field
- Short Name:
- J/MNRAS/490/3806
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The TESS mission will survey ~85 per cent of the sky, giving us the opportunity of extracting high-precision light curves of millions of stars, including stellar cluster members. In this work, we present our project 'A PSF-based Approach to TESS High quality data Of Stellar clusters' (PATHOS), aimed at searching and characterize candidate exoplanets and variable stars in stellar clusters using our innovative method for the extraction of high-precision light curves of stars located in crowded environments. Our technique of light-curve extraction involves the use of empirical point spread functions (PSFs), an input catalogue and neighbour-subtraction. The PSF-based approach allows us to minimize the dilution effects in crowded environments and to extract high-precision photometry for stars in the faint regime (G>13). For this pilot project, we extracted, corrected, and analysed the light curves of 16641 stars located in a dense region centred on the globular cluster 47 Tuc. We were able to reach the TESS magnitude T~16.5 with a photometric precision of ~1 per cent on the 6.5-h time-scale; in the bright regime we were able to detect transits with depth of ~34 parts per million. We searched for variables and candidate transiting exoplanets. Our pipeline detected one planetary candidate orbiting a main-sequence star in the Galactic field. We analysed the period-luminosity distribution for red-giant stars of 47 Tuc and the eclipsing binaries in the field. Light curves are uploaded on the Mikulski Archive for Space Telescopes under the project PATHOS.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/32
- Title:
- Extended Aperture Photometry of K2 RR Lyrae stars
- Short Name:
- J/ApJS/244/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler Space Telescope observed thousands of RR Lyrae stars in the K2 mission. In this paper, we present our photometric solutions using extended apertures in order to conserve the flux of the stars to the highest possible extent. With this method, we are able to avoid most of the problems that RR Lyrae light curves produced by other pipelines suffer from. For post-processing, we apply the K2SC pipeline to our light curves. We provide the EAP (Extended Aperture Photometry) of 432 RR Lyrae stars observed in campaigns 3, 4, 5, and 6. We also provide subclass classifications based on Fourier parameters. We investigated in particular the presence of the Blazhko effect in the stars and found it to be 44.7% among the RRab stars, in agreement with results from independent samples. We found that the amplitude and phase modulation in the Blazhko stars may behave rather differently, at least over the length of a K2 Campaign. We also identified four anomalous Cepheid candidates in the sample, one of which is potentially the first Blazhko-modulated member of its class.
- ID:
- ivo://CDS.VizieR/J/other/OEJV/87
- Title:
- Extended catalog of NSVS red AGB variable stars
- Short Name:
- J/other/OEJV/87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In this paper we present the catalog of new Mira-type and SR+L variable stars in the Northern Sky Variability Survey (NSVS) database, found after complementing the original NSVS object tables with a number of additional parameters. By extending the amount of criteria search queries can take advantage of and filtering known objects out, it became convenient to apply better constrained filters to search new variable star candidates. As an example of presented approach, the quest for red variables has resulted in 78 Mira-type and 717 SR+L stars found that have no identification in General Catalogue of Variable Stars, SIMBAD and VSX databases. Most likely the stars presented are new discoveries. The classification of these stars is based on the near-infrared colors from Two Micron All Sky Survey (2MASS) photometry, amplitude and period with the accuracy of the classification given ~90%, estimated basing on the current GCVS classification scheme.
- ID:
- ivo://CDS.VizieR/J/A+A/453/155
- Title:
- Extended envelopes around Galactic Cepheids II.
- Short Name:
- J/A+A/453/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of long-baseline interferometric observations of the classical Cepheids Polaris and delta Cep in the near infrared K' band (1.9-2.3 microns), using the FLUOR instrument of the CHARA Array. Following our previous detection of a circumstellar envelope (CSE) around L Car (Kervella et al., 2006A&A...448..623K), we report similar detections around Polaris and delta Cep. Owing to the large data set acquired on Polaris, in both the first and second lobes of visibility function, we have detected the presence of a circum-stellar envelope (CSE), located at 2.4+/-0.1 stellar radii, accounting for 1.5+/-0.4% of the stellar flux in the K' band. A similar model is applied to the delta Cep data, which shows improved agreement compared to a model without CSE. Finally, we find that the bias in estimating the angular diameter of delta Cep in the framework of the Baade-Wesselink method (Merand et al., 2005A&A...438L...9M) is of the order of 1% or less in the K' band. A complete study of the influence of the CSE is proposed in this context, showing that at the optimum baseline for angular diameter variation detection, the bias is of the order of the formal precision in the determination of the delta Cep pulsation amplitude (1.6%). Description: Individual interferometric squared visibility measurements. Data were acquired in the wide infrared K' band. We also provide informations about calibrator stars.
- ID:
- ivo://CDS.VizieR/J/other/IBVS/5296
- Title:
- Extrema of pulsating stars
- Short Name:
- J/other/IBVS/529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this 46th compilation of BAV results, photoelectric observations obtained in the years 2000 till 2002 are presented on 428 variable stars giving 843 minima and maxima. All moments of minima and maxima are heliocentric. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the lightcurves with evaluations can be obtained from the office of the BAV for inspection.
- ID:
- ivo://archive.stsci.edu/euve
- Title:
- Extreme Ultraviolet Explorer
- Short Name:
- EUVE
- Date:
- 22 Jul 2020 21:28:51
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- Launched in June, 1992, The Extreme Ultraviolet Explorer (EUVE) conducted the first extreme ultraviolet (70-760 Angstroms) survey of the sky and subsequently began a Guest Observer Program of pointed
