- ID:
- ivo://CDS.VizieR/IV/36
- Title:
- Gaia-IPHAS/KIS Value-Added Catalogues
- Short Name:
- IV/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sub-arcsecond cross-match of Gaia DR2 (Cat. I/345) against the INT Photometric H-alpha Survey of the Northern Galactic Plane Data Release 2 (IPHAS DR2, Cat. II/321) and the Kepler-INT Survey (KIS, Cat. J/AJ/144/24). The resulting value-added catalogues (VACs) provide additional precise photometry to the Gaia photometry (r, i and H-alpha for IPHAS, with additional U and g for KIS). In building the catalogue, proper motions given in Gaia DR2 are wound back to match the epochs of IPHAS DR2, thus ensuring high proper motion objects are appropriately cross-matched. The catalogues contain 7927224 and 791071 sources for IPHAS and KIS, respectively. The requirement of >5 sigma parallax detection for every included source means that distances out to 1-1.5kpc are well covered. We define two additional parameters for each catalogued object: (i) fc, a magnitude-dependent tracer of the quality of the Gaia astrometric fit; (ii) fFP, the false-positive rate for parallax measurements determined from astrometric fits of a given quality at a given magnitude. Selection cuts based on these parameters can be used to clean colour-magnitude and colour-colour diagrams in a controlled and justified manner. We provide both full and light versions of the VAC, with VAC-light containing only objects that represent our recommended trade-off between purity and completeness. Uses of the catalogues include the identification of new variable stars in the matched data sets, and more complete identification of H-alpha-excess emission objects thanks to separation of high-luminosity stars from the main sequence.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/606/A92
- Title:
- Gaia LMC eclipsing binary and multiple systems
- Short Name:
- J/A+A/606/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The advent of large scale multi-epoch surveys raises the need for automated light curve (LC) processing. This is particularly true for eclipsing binaries (EBs), which form one of the most populated types of variable objects. The Gaia mission, launched at the end of 2013, is expected to detect of the order of few million EBs over a 5-year mission. We present an automated procedure to characterize EBs based on the geometric morphology of their LCs with two aims: first to study an ensemble of EBs on a statistical ground without the need to model the binary system, and second to enable the automated identification of EBs that display atypical LCs. We model the folded LC geometry of EBs using up to two Gaussian functions for the eclipses and a cosine function for any ellipsoidal-like variability that may be present between the eclipses. The procedure is applied to the OGLE-III data set of EBs in the Large Magellanic Cloud (LMC) as a proof of concept. The bayesian information criterion is used to select the best model among models containing various combinations of those components, as well as to estimate the significance of the components. Based on the two-Gaussian models, EBs with atypical LC geometries are successfully identified in two diagrams, using the Abbe values of the original and residual folded LCs, and the reduced chi^2^. Cleaning the data set from the atypical cases and further filtering out LCs that contain non-significant eclipse candidates, the ensemble of EBs can be studied on a statistical ground using the two-Gaussian model parameters. For illustration purposes, we present the distribution of projected eccentricities as a function of orbital period for the OGLE-III set of EBs in the LMC, as well as the distribution of their primary versus secondary eclipse widths.
- ID:
- ivo://CDS.VizieR/J/MNRAS/481/307
- Title:
- Gaia Nuclear Transient (GNT) cand.
- Short Name:
- J/MNRAS/481/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high spatial resolution and precise astrometry and photometry of the Gaia mission should make it particularly apt at discovering and resolving transients occurring in, or near, the centres of galaxies. Indeed, some nuclear transients are reported by the Gaia Science Alerts (GSA) team, but not a single confirmed tidal disruption event (TDE) has been published. In order to explore the sensitivity of GSA, we performed an independent and systematic search for nuclear transients using Gaia observations. Our transient search is driven from an input galaxy catalogue (derived from the Sloan Digital Sky Survey Release 12). We present a candidate detection metric that is independent from the existing GSA methodology, to see if Gaia Alerts are biased against the discovery of nuclear transients, and in particular which steps may have an impact. Our technique does require significant manual vetting of candidates, making implementation in the GSA system impractical for daily operations, although it could be run weekly, which for month-to-year long transients would make a scientifically valuable addition. Our search yielded 480 nuclear transients, 5 of which were alerted and published by GSA. The list of (in some cases ongoing) transients includes candidates for events related to enhanced accretion on to a super-massive black hole and TDEs. An implementation of the detection methodology and criteria used in this paper as an extension of GSA could open up the possibility for Gaia to fulfil the role as a main tool to find transient nuclear activity as predicted in the literature.
- ID:
- ivo://CDS.VizieR/I/343
- Title:
- Gaia-PS1-SDSS (GPS1) proper motion catalog
- Short Name:
- I/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine Gaia DR1, PS1, Sloan Digital Sky Survey (SDSS), and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of m_r_~20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate its positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are linear. By simultaneously fitting the positions of stars at different epochs of-Gaia DR1, PS1, SDSS, and 2MASS-we construct an extensive catalog of proper motions dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3mas/yr and a typical precision of 1.5-2.0mas/yr. The proper motions have been validated using galaxies, open clusters, distant giant stars, and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error (<0.3mas/yr) should be nearly an order of magnitude better than that of PPMXL and UCAC4 (>2.0mas/yr). Similarly, its precision (~1.5mas/yr) is a four-fold improvement relative to PPMXL and UCAC4 (~6.0mas/yr). For QSOs, the precision of GPS1 is found to be worse (~2.0-3.0mas/yr), possibly due to their particular differential chromatic refraction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/501/1116
- Title:
- GAIA pulsars and where to find them
- Short Name:
- J/MNRAS/501/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While the majority of massive stars have a stellar companion, most pulsars appear to be isolated. Taken at face value, this suggests that most massive binaries break apart due to strong natal kicks received in supernova explosions. However, the observed binary fraction can still be subject to strong selection effects, as monitoring of newly discovered pulsars is rarely carried out for long enough to conclusively rule out multiplicity. Here, we use the second Gaia data release to search for companions to 1534 rotation-powered pulsars with positions known to better than 0.5arcsec. We find 22 matches to known pulsars, including 1 not reported elsewhere, and 8 new possible companions to young pulsars. We examine the photometric and kinematic properties of these systems and provide empirical relations for identifying Gaia sources with potential millisecond pulsar companions. Our results confirm that the observed multiplicity fraction is small. However, we show that the number of binaries below the sensitivity of Gaia and radio timing in our sample could still be significantly higher. We constrain the binary fraction of young pulsars to be f^true^_young_<5.3(8.3) per cent under realistic (conservative) assumptions for the binary properties and current sensitivity thresholds. For massive stars (>10M_{sun}_) in particular, we find f^true^_OB_<3.7 per cent, which sets a firm independent upper limit on the Galactic neutron star merger rate, <=7.2x10^-4^/yr. Ongoing and future projects, such as the CHIME/pulsar program, MeerTime, HIRAX, and ultimately the SKA, will significantly improve these constraints in the future.
- ID:
- ivo://CDS.VizieR/VI/137
- Title:
- GaiaSimu Universe Model Snapshot
- Short Name:
- VI/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context: This study has been developed in the framework of the computational simulations that are executed for the preparation of the ESA Gaia astrometric mission. Aims: We focus on describing the objects and characteristics that Gaia will potentially observe without taking into consideration instrumental effects (detection efficiency, observing errors). Methods: The theoretical Universe Model prepared for the Gaia simulation has been statistically analysed at a given time. Ingredients of the model are described, with the greatest emphasis on the stellar content, the double and multiple stars, and variability. Results: In this simulation the errors have not yet been included. Hence we estimated the number of objects and their theoretical photometric, astrometric and spectroscopic characteristics if they are perfectly detected.We show that Gaia will be able to potentially observe 1.1 billion of stars (single or part of multiple star systems) of which about 2% are variable stars and 3% have one or two exoplanets. At the extragalactic level, observations will be potentially composed of several millions of galaxies, half a million to 1 million quasars and about 50,000 supernovae that will occur during the five years of the mission.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1767
- Title:
- Gaia spectrophotometric standard stars I.
- Short Name:
- J/MNRAS/426/1767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe two ground-based observing campaigns aimed at building a grid of approximately 200 spectrophotometric standard stars (SPSS), with an internal =~1% precision and tied to Vega within =~3%, for the absolute flux calibration of data gathered by Gaia, the European Space Agency (ESA) astrometric mission. The criteria for the selection and a list of candidates are presented, together with a description of the survey strategy and the adopted data analysis methods. We also discuss a short list of notable rejected SPSS candidates and difficult cases, based on identification problems, literature discordant data, visual companions and variability. In fact, all candidates are also monitored for constancy (within +/-5mmag, approximately). In particular, we report on a CALSPEC standard, 1740346, that we found to be a {delta} Scuti variable during our short-term monitoring (1-2h) campaign.
- ID:
- ivo://CDS.VizieR/J/AJ/160/186
- Title:
- Gaia survey of stars associated with Lupus Clouds
- Short Name:
- J/AJ/160/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I have used high-precision photometry and astrometry from the second data release of the Gaia mission to perform a survey for young stars associated with the Lupus clouds, which have distances of ~160pc and reside within the Scorpius-Centaurus (Sco-Cen) OB association. The Gaia data have made it possible to distinguish Lupus members from most of the stars in other groups in Sco-Cen that overlap with the Lupus clouds, which have contaminated previous surveys. The new catalog of candidate Lupus members should be complete for spectral types earlier than M7 at AK<0.2 within fields encompassing clouds 1-4. I have used that catalog to characterize various aspects of the Lupus stellar population. For instance, the sequence of low- mass stars in Lupus is ~0.4mag brighter than the sequence for Upper Sco, which implies an age of ~6Myr based an adopted age of 10-12Myr for Upper Sco and the change in luminosity with age predicted by evolutionary models. I also find that the initial mass function in Lupus is similar to that in other nearby star-forming regions based on a comparison of their distributions of spectral types.
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/1890
- Title:
- Gaia white dwarfs within 40pc. II.
- Short Name:
- J/MNRAS/499/1890
- Date:
- 14 Jan 2022 00:10:10
- Publisher:
- CDS
- Description:
- We present an overview of the sample of northern hemisphere white dwarfs within 40pc of the Sun detected from Gaia Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from Gaia DR2 and followed-up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection in the Gaia DR2 Hertzsprung-Russell diagram (HRD). Atmospheric parameters are calculated from Gaia and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population (MDAZ_avg_=0.59M_{sun}_, MDA_avg_=0.66M_{sun}_). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallised white dwarfs in the mass range from 0.6<=M/M_{sun}_<=1.0 and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallisation alone. We also detect 26 double degenerates and white dwarf components in 56 wide binary systems.
- ID:
- ivo://CDS.VizieR/VIII/100
- Title:
- GaLactic and Extragalactic All-sky MWA survey
- Short Name:
- VIII/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilising the first year of observations. The catalogue covers 24,402 square degrees, over declinations south of +30{deg} and Galactic latitudes outside 10{deg} of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307,456 radio sources with 20 separate flux density measurements across 72-231MHz, selected from a time- and frequency- integrated image centred at 200MHz, with a resolution of ~=2'. Over the catalogued region, we estimate that the catalogue is 90% complete at 170mJy, and 50% complete at 55mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97% above the detection threshold of 5{sigma}, which itself is typically 50mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low frequency flux density scale of the southern sky to better than 10%. This paper presents details of the flagging, imaging, mosaicking, and source extraction/characterisation, as well as estimates of the completeness and reliability. All source measurements and images are available online. This is the first in a series of publications describing the GLEAM survey results.
