Samuel Lai; Erik Dennihy; Siyi Xu; A. Nitta; S. J. Kleinman; S. K. Leggett; Amy Bonsor; S. T. Hodgkin; A. Rebassa–Mansergas; Laura K. Rogers
The Astrophysical Journal · DOI ↗
Abstract Infrared excesses around white dwarf stars indicate the presence of various astrophysical objects of interest, including companions and debris disks. In this second paper of a series, we present follow-up observations of infrared excess candidates from Gaia and unWISE discussed in the first paper, Paper I. We report space-based infrared photometry at 3.6 and 4.5 micron for 174 white dwarfs from the Spitzer Space Telescope and ground-based near-infrared J , H , and K photometry of 235 white dwarfs from Gemini Observatory with significant overlap between Spitzer and Gemini observations. These data are used to confirm or rule out the observed unWISE infrared excess. From the unWISE-selected candidate sample, the most promising infrared excess sample comes from both color and flux excess, which has a Spitzer confirmation rate of 95%. We also discuss a method to distinguish infrared excess caused by stellar or sub-stellar companions from potential dust disks. In total, we confirm the infrared excess around 62 white dwarfs, 10 of which are likely to be stellar companions. The remaining 52 bright white dwarfs with infrared excess beyond two microns has the potential to double the known sample of white dwarfs with dusty exoplanetary debris disks. Follow-up high-resolution spectroscopic studies of a fraction of confirmed excess white dwarfs in this sample have discovered emission from gaseous dust disks. Additional investigations will be able to expand the parameter space from which dust disks around white dwarfs are found.
J. M. Carrasco; M. Weiler; C. Jordi; C. Fabricius; F. De Angeli; D. W. Evans; F. van Leeuwen; M. Riello; P. Montegriffo
Astronomy and Astrophysics · DOI ↗
Context. The full third Gaia data release will provide, for the first time, the calibrated spectra obtained with the blue and red Gaia slitless spectrophotometers (BP and RP, respectively). Gaia is a very complex mission and cannot be considered as a single instrument, but rather as many instruments. The two lines of sight with wide fields of view introduce strong variations of the observations across the large focal plane with more than one hundred different detectors. The main challenge when facing Gaia spectral calibration is that no lamp spectra or flat fields are available during the mission. Also, the significant size of the line spread function with respect to the dispersion of the prisms produces alien photons contaminating neighbouring positions of the spectra. This makes the calibration special and different from standard approaches. Aims. This work gives a detailed description of the internal calibration model for the spectrophotometric data used to obtain the content of the Gaia catalogue. The main purpose of the internal calibration is to bring all the epoch spectra onto a common flux and pixel (pseudo-wavelength) scale, taking into account variations over the focal plane and with time, producing a mean spectrum from all the observations of the same source. Methods. In order to describe all observations on a common mean flux and pseudo-wavelength scale, we constructed a suitable representation of the internally calibrated mean spectra via basis functions, and we described the transformation between non-calibrated epoch spectra and calibrated mean spectra via a discrete convolution, parametrising the convolution kernel to recover the relevant coefficients. Results. The model proposed here for the internal calibration of the Gaia spectrophotometric observations is able to combine all observations into a mean instrument to allow the comparison of different sources and observations obtained with different instrumental conditions along the mission and the generation of mean spectra from a number of observations of the same source. We derived a calibration model that can handle the self-calibrating nature of the problem. The output of this model provides the internal mean spectra, not as a sampled function (flux and wavelength), but as a linear combination of basis functions, although sampled spectra can easily be derived from them.
N. Mowlavï; L. Rimoldini; D. W. Evans; M. Riello; F. De Angeli; L. Palaversa; M. Audard; L. Eyer; P. García-Lario; P. Gavras; B. Holl; G. Jévardat de Fombelle; I. Lecœur-Taı̈bi; K. Nienartowicz
Astronomy and Astrophysics · DOI ↗
Context. Photometric variability is an essential feature that sheds light on the intrinsic properties of celestial variable sources, the more so when photometry is available in various bands. In this respect, the all-sky Gaia mission is particularly attractive as it collects, among other quantities, epoch photometry measured quasi-simultaneously in three optical bands for sources ranging from a few magnitudes to fainter than magnitude 20. Aims. The second data release (DR2) of the mission provides mean G , G BP , and G RP photometry for ∼1.4 billion sources, but light curves and variability properties are available for only ∼0.5 million of them. Here, we provide a census of large-amplitude variables (LAVs) with amplitudes larger than ∼0.2 mag in the G band for objects with mean brightnesses between 5.5 and 19 mag. Methods. To achieve this, we rely on variability amplitude proxies in G , G BP , and G RP computed from the uncertainties on the magnitudes published in DR2. We then apply successive filters to identify two subsets containing sources with reliable mean G BP and G RP (for studies using colours) and sources having compatible amplitude proxies in G , G BP , and G RP (for multi-band variability studies). Results. The full catalogue gathers 23 315 874 LAV candidates, and the two subsets with increased levels of purity contain, respectively, 1 148 861 and 618 966 sources. A multi-band variability analysis of the catalogue shows that different types of variable stars can be categorized according to their colours and blue-to-red amplitude ratios as determined from the G , G BP , and G RP amplitude proxies. More specifically, four groups are globally identified. They include: long-period variables in a first group with amplitudes more than twice larger in the blue than in the red; hot compact variables in a second group with amplitudes smaller in the blue than in the red; classical instability strip pulsators in a third group with amplitudes larger in the blue than in the red by 50% to 80%; and other non-pulsating variables in a fourth group, mainly achromatic, but 10% of them still having 20% to 50% larger amplitudes in the blue than in the red. Conclusions. The catalogue constitutes the first census of Gaia LAV candidates extracted from the public DR2 archive. The overview presented here illustrates the added value of the mission for multi-band variability studies, even at this stage when epoch photometry is not yet available for all sources.
Rosanna H Tilbrook; M. R. Burleigh; Jean C Costes; Samuel Gill; Louise D. Nielsen; José I Vines; D. Queloz; S. T. Hodgkin; Hannah L. Worters; M. R. Goad; Jack S Acton; Beth A Henderson; D. J. Armstrong; D. R. Anderson; Daniel Bayliss; F. Bouchy; Joshua T Briegal; Edward M. Bryant; S. L. Casewell; Alexander Chaushev; Benjamin F Cooke; Philipp Eigmüller; Edward Gillen; Maximilian N. Günther; Aleisha Hogan; J. S. Jenkins; M. Lendl; J. McCormac; Maximiliano Moyano; Liam Raynard; A. M. S. Smith; S. Udry; C. A. Watson; R. G. West; P. J. Wheatley; H. Breytenbach; Ramotholo Sefako; Jessymol K Thomas; D. R. Alves
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT We report the discovery of four new hot Jupiters with the Next-Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P < 5 d) planets orbiting G-type main-sequence stars, with radii and masses between 1.10 and 1.30RJ and 0.41 and 0.76MJ, respectively. By considering the host star luminosities and the planets’ small orbital separations (0.039–0.052 au), we find that all four hot Jupiters are highly irradiated and therefore occupy a region of parameter space in which planetary inflation mechanisms become effective. Comparison with statistical studies and a consideration of the planets’ high incident fluxes reveal that NGTS-16b, NGTS-17b, and NGTS-18b are indeed likely inflated, although some disparities arise upon analysis with current Bayesian inflationary models. However, the underlying relationships that govern radius inflation remain poorly understood. We postulate that the inclusion of additional hyperparameters to describe latent factors such as heavy element fraction, as well as the addition of an updated catalogue of hot Jupiters, would refine inflationary models, thus furthering our understanding of the physical processes that give rise to inflated planets.
N. Chornay; N. A. Walton
Astronomy and Astrophysics · DOI ↗
Context. Planetary nebulae (PNe) are a brief but important phase of stellar evolution. The study of Galactic PNe has historically been hampered by uncertain distances, but the parallaxes of PN central stars (CSPNe) measured by Gaia are improving the situation. Aims. Gaia ’s Early Data Release 3 (EDR3) offers higher astrometric precision and greater completeness compared to previous releases. Taking advantage of these improvements requires that the CSPNe in the catalogue be accurately identified. Methods. We applied our automated technique based on the likelihood ratio method to cross-match known PNe with sources in Gaia EDR3, using an empirically derived position and colour distribution to score candidate matches. Results. We present a catalogue of over 2000 sources in Gaia EDR3 that our method has identified as likely CSPNe or compact nebula detections. We show how the more precise parallaxes of these sources compare to previous PN statistical distances and introduce an approach to combining them to produce tighter distance constraints. We also discuss Gaia ’s handling of close companions and bright nebulae. Conclusions. Gaia is unlocking new avenues for the study of PNe. The catalogue presented here will remain valid for the upcoming Gaia Data Release 3 (DR3) and thus provide a valuable resource for years to come.
Clare Higgs; Alan W. McConnachie; Nicholaas Annau; M. J. Irwin; G. Battaglia; Patrick Côté; Geraint F. Lewis; Kim A. Venn
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT The Solo (Solitary Local) Dwarf Galaxy survey is a volume-limited, wide-field g- and i-band survey of all known nearby (<3 Mpc) and isolated (>300 kpc from the Milky Way or M31) dwarf galaxies. This set of 44 dwarfs is homogeneously analysed for quantitative comparisons to the satellite dwarf populations of the Milky Way and M31. In this paper, an analysis of the 12 closest Solo dwarf galaxies accessible from the Northern hemisphere is presented, including derivation of their distances, spatial distributions, morphology, and extended structures, including their inner integrated light properties and their outer resolved star distributions. All 12 galaxies are found to be reasonably well described by two-dimensional Sérsic functions, although UGC 4879 in particular shows tentative evidence of two distinct components. No prominent extended stellar substructures, which could be signs of either faint satellites or recent mergers, are identified in the outer regions of any of the systems examined.
E. A. González-Solares; A. Dariush; Carlos González‐Fernández; A. Yoldaş; Mohammad Al Sa’d; Neil S. Millar; Tristan Whitmarsh; N. Chornay; Ilaria Falciatori; Atefeh Fatemi; Daniel Goodwin; Laura Kuett; Claire M. Mulvey; Marta Páez Ribes; Fatime Qosaj; Andrew Roth; Ignacio Vázquez-Garćıa; Spencer S. Watson; Jonas Windhager; Samuel Aparício; Bernd Bodenmiller; Ed Boyden; Carlos Caldas; Owen Harris; Sohrab P. Shah; Simon Tavaré; CRUK IMAXT Grand Challenge Team; Dario Bressan; Gregory J. Hannon; N. A. Walton
bioRxiv (Cold Spring Harbor Laboratory) · DOI ↗
Abstract With the aim of producing a 3D representation of tumours, IMAXT uses a large variety of modalities in order to acquire tumour samples and produce a map of every cell in the tumour and its host environment. With the large volume and variety of data produced in the project we develop automatic data workflows and analysis pipelines and introduce a research methodology where scientists connect to a cloud environment to perform analysis close to where data are located instead of bringing data to their local computers. Here we present the data and analysis infrastructure, discuss the unique computational challenges and describe the analysis chains developed and deployed to generate molecularly annotated tumour models. Registration is achieved by use of a novel technique involving spherical fiducial marks that are visible in all imaging modalities used within IMAXT.
R. Paladini; J. C. Mottram; M. Veneziani; A. Traficante; E. Schisano; Giovanna Giardino; E. Falgarone; J. S. Urquhart; D. L. Harrison; G. Joncas; G. Umana; S. Molinari
The Astrophysical Journal · DOI ↗
Abstract Massive star formation occurs in the interior of giant molecular clouds and proceeds through many stages. In this work, we focus on massive young stellar objects (MYSOs) and ultracompact H ii regions (UCH ii ), where the former are enshrouded in dense envelopes of dust and gas, the latter of which has begun dispersing. By selecting a complete sample of MYSOs and UCH ii from the Red MSX Source (RMS) survey database, we combine Planck and IRAS data and build their spectral energy distributions. With these, we estimate the physical properties (dust temperatures, mass, luminosity) of the sample. Because the RMS database provides unique solar distances, it also allows the instantaneous star formation efficiency (SFE) to be investigated as a function of Galactocentric radius. We find that the SFE increases between 2 and 4.5 kpc, where it reaches a peak, likely in correspondence with the accumulation of molecular material at the end of the Galactic bar. It then stays approximately constant up to 9 kpc, after which it linearly declines, in agreement with predictions from extragalactic studies. This behavior suggests the presence of a significant amount of undetected molecular gas at R G > 8 kpc. Finally, we present diagnostic colors that can be used to identify sites of massive star formation.
Zeeshaan-ul Hasan; Ikhlaaq Ahmed; Rubeta Matin; Victoria Homer; John T. Lear; Ferina Ismail; Tristan Whitmarsh; Adèle C. Green; Jason Thomson; Alan Milligan; Sarah Hogan; Vanessa Van-de-Velde; Liza Mitchell-Worsford; Jonathan Kentley; Claire Gaunt; Yolande Jefferson-Hulme; S. Bowden; Piers Gaunt; Keith Wheatley; Charlotte M. Proby; Catherine Harwood
Discovery Research Portal (University of Dundee) · DOI ↗
BACKGROUND: The risk of cutaneous squamous cell carcinoma (cSCC) is significantly increased in organ transplant recipients (OTRs). Clearance of actinic keratoses (AKs) is generally regarded as a surrogate biomarker for cSCC prevention. OTR-cSCC chemoprevention with topical AK treatments has not been investigated in randomized controlled trials (RCTs), although there is evidence that 5% 5-fluorouracil (5-FU) may be chemoprotective in immunocompetent patients. OBJECTIVES: To assess the feasibility, activity and evaluation outcomes relevant to the design of a future phase III RCT of topical cSCC chemoprevention in OTRs. METHODS: OTRs with 10 or more AKs in predefined areas were randomized 1 : 1 : 1 to topical 5-FU, 5% imiquimod (IMIQ) or sunscreen (sun-protective factor 30+) in a phase II, open-label RCT over 15 months. Feasibility outcomes included proportions of eligible OTRs randomized, completing treatment and willing to be re-treated. AK activity [AK clearance, new AK development, patient-centred outcomes (toxicity, health-related quality of life, HRQoL)] and evaluation methodology (clinical vs. photographic) were assessed. RESULTS: Forty OTRs with 903 AKs were randomized. All feasibility outcomes were met (56% of eligible OTRs were randomized; 89% completed treatment; 81% were willing to be re-treated). AK activity analyses found 5-FU and IMIQ were superior to sunscreen for AK clearance and prevention of new AKs. 5-FU was more effective than IMIQ in AK clearance and prevention in exploratory analyses. Although toxicity was greater with 5-FU, HRQoL outcomes were similar. CONCLUSIONS: Trials of topical AK treatments in OTRs for cSCC chemoprevention are feasible and AK activity results support further investigation of 5-FU-based treatments in future phase III trials. What is already known about this topic? Cutaneous squamous cell carcinoma (cSCC) is significantly more common in immunocompromised individuals including organ transplant recipients (OTRs) compared with immunocompetent populations. cSCC chemoprevention activity of sunscreen and 5-fluorouracil-based (5-FU) actinic keratosis (AK) treatments has been demonstrated in randomized controlled trials (RCTs) in immunocompetent populations but not in OTRs. AKs are cSCC precursors and their clearance and prevention are generally regarded as surrogate endpoint biomarkers for potential cSCC chemoprevention activity. What does this study add? SPOT (SCC Prevention in OTRs using Topical treatments) has confirmed that RCTs of OTR-cSCC chemoprevention with topical AK treatments are feasible. It also suggests that topical 5-FU may be superior to 5% imiquimod and sunscreen in AK clearance and prevention. Together with recent evidence from several RCTs in the general population, these data provide a compelling rationale for further studies of intervention with 5-FU-based topical chemoprevention approaches in OTR-cSCC prevention.
N. Chornay; N. A. Walton; David Jones; H. M. J. Boffin; M. Rejkuba; R. Wesson
Astronomy and Astrophysics · DOI ↗
Context. Many if not most planetary nebulae (PNe) are now thought to be the outcome of binary evolutionary scenarios. However, only a few percent of the PNe in the Milky Way are known to host binary systems. The high-precision repeated observing and long time baseline of Gaia make it well suited for detecting new close binaries through photometric variability. Aims. We aim to find new close binary central stars of PNe (CSPNe) using data from the Gaia mission, building towards a statistically significant sample of post-common envelope, close binary CSPNe. Methods. As the vast majority of Gaia sources do not have published epoch photometry, we used the uncertainty in the mean photometry as a proxy for determining the variability of our CSPN sample in the second Gaia data release. We derived a quantity that expresses the significance of the variability, and considered what is necessary to build a clean sample of genuine variable sources. Results. Our selection recovers a large fraction of the known close binary CSPN population, while other CSPNe lying in the same region of the parameter space represent a promising set of targets for ground-based confirmatory follow-up observations. Gaia epoch photometry for four of the newly identified variable sources confirms that the variability is genuine and consistent with binarity.
Á. Skúladóttir; Stefania Salvadori; A. M. Amarsi; Eline Tolstoy; M. J. Irwin; V. Hill; P. Jablonka; G. Battaglia; Else Starkenburg; D. Massari; A. Helmi; Lorenzo Posti
The Astrophysical Journal Letters · DOI ↗
Abstract Although true metal-free “Population III” stars have so far escaped discovery, their nature, and that of their supernovae, is revealed in the chemical products left behind in the next generations of stars. Here we report the detection of an ultra-metal-poor star in the Sculptor dwarf spheroidal galaxy AS0039. With [Fe/H] LTE = −4.11, it is the most metal-poor star discovered in any external galaxy thus far. Contrary to the majority of Milky Way stars at this metallicity, AS0039 is clearly not enhanced in carbon, with [C/Fe] LTE = −0.75, and A (C) = +3.60, making it the lowest detected carbon abundance in any star to date. Furthermore, it lacks α -element uniformity, having extremely low [Mg/Ca] NLTE = −0.60 and [Mg/Ti] NLTE = −0.86, in stark contrast with the near solar ratios observed in C-normal stars within the Milky Way halo. The unique abundance pattern indicates that AS0039 formed out of material that was predominantly enriched by a ∼20 M ⊙ progenitor star with an unusually high explosion energy E = 10 × 10 51 erg. Therefore, star AS0039 represents some of the first observational evidence for zero-metallicity hypernovae and provides a unique opportunity to investigate the diverse nature of Population III stars.
A. Helmi; F. van Leeuwen; P. J. McMillan; D. Massari; T. Antoja; A. C. Robin; L. Lindegren; U. Bastian; F. Arenou; C. Babusiaux; et al.
Astronomy and Astrophysics · DOI ↗
\n Contains fulltext :\n 225636.pdf (Publisher’s version ) (Open Access)\n
A. Helmi; F. van Leeuwen; P. J. McMillan; D. Massari; T. Antoja; A. C. Robin; L. Lindegren; U. Bastian; F. Arenou; C. Babusiaux; et al.
Astronomy and Astrophysics · DOI ↗
An error occurred during the production process of the original published version. The following names were omitted from theauthor list: R. Haigron, D. Hatzidimitriou, M. Hauser, M. Haywood, U. Heiter, J. Heu, T. Hilger. The original published version hasbeen corrected together with the publication of this corrigendum.
N. Rowell; M. Davidson; L. Lindegren; F. van Leeuwen; J. Castañeda; C. Fabricius; U. Bastian; N. C. Hambly; J. Hernández; A. Bombrun; D. W. Evans; F. De Angeli; M. Riello; D. Busonero; C. Crowley; A. Mora; U. Lammers; G. Gracia; J. Portell; M. Biermann; A. G. A. Brown
Astronomy and Astrophysics · DOI ↗
Context. The unprecedented astrometric precision of the Gaia mission relies on accurate estimates of the locations of sources in the Gaia data stream. This is ultimately performed by point spread function (PSF) fitting, which in turn requires an accurate reconstruction of the PSF, including calibrations of all the major dependences. These include a strong colour dependence due to Gaia ’s broad G band and a strong time dependence due to the evolving contamination levels and instrument focus. Accurate PSF reconstruction is also important for photometry. Gaia Early Data Release 3 (EDR3) will, for the first time, use a PSF calibration that models several of the strongest dependences, leading to signficantly reduced systematic errors. Aims. We describe the PSF model and calibration pipeline implemented for Gaia EDR3, including an analysis of the calibration results over the 34 months of data. We include a discussion of the limitations of the current pipeline and directions for future releases. This will be of use both to users of Gaia data and as a reference for other precision astrometry missions. Methods. We develop models of the 1D line spread function (LSF) and 2D PSF profiles based on a linear combination of basis components. These are designed for flexibility and performance, as well as to meet several mathematical criteria such as normalisation. We fit the models to selected primary sources in independent time ranges, using simple parameterisations for the colour and other dependences. Variation in time is smoothed by merging the independent calibrations in a square root information filter, with resets at certain mission events that induce a discontinuous change in the PSF. Results. The PSF calibration shows strong time and colour dependences that accurately reproduce the varying state of the Gaia astrometric instrument. Analysis of the residuals reveals both the performance and the limitations of the current models and calibration pipeline, and indicates the directions for future development. Conclusions. The PSF modelling and calibration carried out for Gaia EDR3 represents a major step forwards in the data processing and will lead to reduced systematic errors in the core mission data products. Further significant improvements are expected in the future data releases.
A. G. A. Brown; A. Vallenari; T. Prusti; J. H. J. de Bruijne; C. Babusiaux; M. Biermann; O. L. Creevey; D. W. Evans; L. Eyer; A. Hutton; et al.
Astronomy and Astrophysics · DOI ↗
Context. We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from Gaia DR2. Aims. A summary of the contents of Gaia EDR3 is presented, accompanied by a discussion on the differences with respect to Gaia DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of Gaia EDR3 results. Methods. The raw data collected with the Gaia instruments during the first 34 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to Gaia DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity. Results. Gaia EDR3 contains celestial positions and the apparent brightness in G for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the ( G BP − G RP ) colour are also available. The passbands for G , G BP , and G RP are provided as part of the release. For ease of use, the 7 million radial velocities from Gaia DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of Gaia DR3. Finally, Gaia EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the Gaia -CRF3, which is based solely on extragalactic sources. The creation of the source list for Gaia EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for Gaia DR2, but it does feature new sources and there are some notable changes. The source list will not change for Gaia DR3. Conclusions. Gaia EDR3 represents a significant advance over Gaia DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30–40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for G , G BP , and G RP is valid over the entire magnitude and colour range, with no systematics above the 1% level
M. Riello; F. De Angeli; D. W. Evans; P. Montegriffo; J. M. Carrasco; G. Busso; L. Palaversa; P. W. Burgess; C. Diener; M. Davidson; N. Rowell; C. Fabricius; C. Jordi; M. Bellazzini; E. Pancino; D. L. Harrison; C. Cacciari; F. van Leeuwen; N. C. Hambly; S. T. Hodgkin; P. Osborne; G. Altavilla; M. A. Barstow; A. G. A. Brown; M. Castellani; S. Cowell; F. De Luise; G. Gilmore; G. Giuffrida; S. L. Hidalgo; G. Holland; S. Marinoni; C. Pagani; A. M. Piersimoni; L. Pulone; S. Ragaini; M. Rainer; P. J. Richards; N. Sanna; N. A. Walton; M. Weiler; A. Yoldas
Astronomy and Astrophysics · DOI ↗
Context. Gaia Early Data Release 3 ( Gaia EDR3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase. Aims. In this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the Gaia EDR3 catalogue. Methods. The processing broadly followed the same procedure as for Gaia DR2, but with significant improvements in several aspects of the blue and red photometer (BP and RP) preprocessing and in the photometric calibration process. In particular, the treatment of the BP and RP background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. The photometric calibration models have also been updated to account for flux loss over the whole magnitude range. Significant improvements in the modelling and calibration of the Gaia point and line spread functions have also helped to reduce a number of instrumental effects that were still present in DR2. Results. Gaia EDR3 contains 1.806 billion sources with G -band photometry and 1.540 billion sources with G BP and G RP photometry. The median uncertainty in the G -band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2 mmag at magnitude G = 10–14, 0.8 mmag at G ≈ 17, and 2.6 mmag at G ≈ 19. The significant magnitude term found in the Gaia DR2 photometry is no longer visible, and overall there are no trends larger than 1 mmag mag −1 . Using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. A detailed description of the residual systematic effects is provided. Overall the quality of the calibrated mean photometry in Gaia EDR3 is superior with respect to DR2 for all bands.
Z. Kostrzewa-Rutkowska; P. G. Jonker; S. T. Hodgkin; D. Eappachen; D. L. Harrison; S. E. Koposov; G. Rixon; Ł. Wyrzykowski; A. Yoldaş; E. Breedt; A. Delgado; M. van Leeuwen; T. Wevers; P. W. Burgess; F. De Angeli; D. W. Evans; P. Osborne; M. Riello
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT The recent discoveries of gravitational wave events and in one case also its electromagnetic (EM) counterpart allow us to study the Universe in a novel way. The increased sensitivity of the LIGO and Virgo detectors has opened the possibility for regular detections of EM transient events from mergers of stellar remnants. Gravitational wave sources are expected to have sky localization up to a few hundred square degrees, thus Gaia as an all-sky multi-epoch photometric survey has the potential to be a good tool to search for the EM counterparts. In this paper, we study the possibility of detecting EM counterparts to gravitational wave sources using the Gaia Science Alerts system. We develop an extension to current used algorithms to find transients and test its capabilities in discovering candidate transients on a sample of events from the observation periods O1 and O2 of LIGO and Virgo. For the gravitational wave events from the current run O3, we expect that about 16 (25) per cent should fall in sky regions observed by Gaia 7 (10) d after gravitational wave. The new algorithm will provide about 21 candidates per day from the whole sky.
M. Cappetta; R. P. Saglia; Jayne Birkby; J. Koppenhoefer; D. J. Pinfield; S. T. Hodgkin; P. Cruz; G. Kovács; Brigitta Sipőcz; D. Barrado; B. Nefs; Ya. V. Pavlenko; L. Fossati; C. del Burgo; E. L. Martı́n; I. A. G. Snellen; J. R. Barnes; David A. Campbell; S. Catalán; M. C. Gálvez-Ortiz; N. Goulding; C. A. Haswell; O. Ivanyuk; H. R. A. Jones; M. K. Kuznetsov; N. Lodieu; Federico Marocco; D. Mislis; F. Murgas; R. Napiwotzki; Ε. Πάλλη; D. Pollacco; L Sarro Baro; E. Solano; P. R. Steele; H. Stoev; R. Tata; J. Zendejas
Monthly Notices of the Royal Astronomical Society · DOI ↗
<p>This is a correction to: </p><div><a href="https://academic.oup.com/mnras/article/427/3/1877/1094173"><u>… Notices of the Royal Astronomical Society</em>, Volume 427, Issue 3, December 2012, Pages 1877–1890, </u></a><a href="https://doi.org/10.1111/j.1365-2966.2012.21937.x"><u>https://d…;
M. Riello; F. De Angeli; D. W. Evans; P. Montegriffo; J. M. Carrasco; G. Busso; L. Palaversa; P. W. Burgess; C. Diener; M. Davidson; N. Rowell; C. Fabricius; C. Jordi; M. Bellazzini; E. Pancino; D. L. Harrison; C. Cacciari; F. van Leeuwen; N. C. Hambly; S. T. Hodgkin; P. Osborne; G. Altavilla; M. A. Barstow; Brown, AGA; M. Castellani; S. Cowell; F. De Luise; G. Gilmore; G. Giuffrida; S. L. Hidalgo; G. Holland; S. Marinoni; C. Pagani; A. M. Piersimoni; L. Pulone; S. Ragaini; M. Rainer; P. J. Richards; N. Sanna; N. A. Walton; M. Weiler; A. Yoldaş
arXiv (Cornell University) · DOI ↗
Context. Gaia Early Data Release 3 ( Gaia EDR3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase. Aims. In this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the Gaia EDR3 catalogue. Methods. The processing broadly followed the same procedure as for Gaia DR2, but with significant improvements in several aspects of the blue and red photometer (BP and RP) preprocessing and in the photometric calibration process. In particular, the treatment of the BP and RP background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. The photometric calibration models have also been updated to account for flux loss over the whole magnitude range. Significant improvements in the modelling and calibration of the Gaia point and line spread functions have also helped to reduce a number of instrumental effects that were still present in DR2. Results. Gaia EDR3 contains 1.806 billion sources with G -band photometry and 1.540 billion sources with G BP and G RP photometry. The median uncertainty in the G -band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2 mmag at magnitude G = 10–14, 0.8 mmag at G ≈ 17, and 2.6 mmag at G ≈ 19. The significant magnitude term found in the Gaia DR2 photometry is no longer visible, and overall there are no trends larger than 1 mmag mag −1 . Using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. A detailed description of the residual systematic effects is provided. Overall the quality of the calibrated mean photometry in Gaia EDR3 is superior with respect to DR2 for all bands.
N. Rowell; M. Davidson; L. Lindegren; F. van Leeuwen; J. Castañeda; C. Fabricius; U. Bastian; N. C. Hambly; J. Hernández; A. Bombrun; D. W. Evans; F. De Angeli; M. Riello; D. Busonero; C. Crowley; A. Mora; U. Lammers; G. Gracia; J. Portell; M. Biermann; A. G. A. Brown
arXiv (Cornell University) · DOI ↗
Context: The unprecedented astrometric precision of the Gaia mission relies on accurate estimates of the locations of sources in the Gaia data stream. This is ultimately performed by point spread function (PSF) fitting, which in turn requires an accurate reconstruction of the PSF. Gaia Early Data Release 3 (EDR3) will, for the first time, use a PSF calibration that models several of the strongest dependences, leading to signficantly reduced systematic errors. Aims: We describe the PSF model and calibration pipeline implemented for Gaia EDR3, including an analysis of the calibration results over the 34 months of data. We include a discussion of the limitations of the current pipeline and directions for future releases. This will be of use both to users of Gaia data and as a reference for other precision astrometry missions. Methods: We develop models of the 1D line spread function (LSF) and 2D PSF profiles based on a linear combination of basis components. We fit the models to selected primary sources in independent time ranges, using simple parameterisations for the colour and other dependences. Variation in time is smoothed by merging the independent calibrations in a square root information filter, with resets at certain mission events that induce a discontinuous change in the PSF. Results: The PSF calibration shows strong time and colour dependences that accurately reproduce the varying state of the Gaia astrometric instrument. Analysis of the residuals reveals both the performance and the limitations of the current models and calibration pipeline, and indicates the directions for future development. Conclusions: The PSF modelling and calibration carried out for Gaia EDR3 represents a major step forwards in the data processing and will lead to reduced systematic errors in the core mission data products. Further significant improvements are expected in the future data releases.