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.
Jaroslav Merc; J. Mikołajewska; M. Gromadzki; C. Gałan; Krystian Iłkiewicz; J. Skowron; Ł. Wyrzykowski; S. T. Hodgkin; Krzysztof A. Rybicki; Paweł Zieliński; K. Kruszyńska; V. Godunova; A. Simon; V. Reshetnyk; Fraser Lewis; U. Kolb; M. Morrell; A. J. Norton; Supachai Awiphan; S. Poshyachinda; D. E. Reichart; M. Greet; J. Kolgjini
Astronomy and Astrophysics · DOI ↗
Context. Besides the astrometric mission of the Gaia satellite, its repeated and high-precision measurements also serve as an all-sky photometric transient survey. The sudden brightenings of the sources are published as Gaia Photometric Science Alerts and are made publicly available, allowing the community to photometrically and spectroscopically follow up on the object. Aims. The goal of this paper is to analyze the nature and derive the basic parameters of Gaia18aen, a transient detected at the beginning of 2018. This object coincides with the position of the emission-line star WRAY 15-136. The brightening was classified as a “nova?” on the basis of a subsequent spectroscopic observation. Methods. We analyzed two spectra of Gaia18aen and collected the available photometry of the object covering the brightenings in 2018 and also the preceding and following periods of quiescence. Based on this observational data, we derived the parameters of Gaia18aen and discussed the nature of the object. Results. Gaia18aen is the first symbiotic star discovered by Gaia satellite. The system is an S-type symbiotic star and consists of an M giant of a slightly super-solar metallicity, where T eff ∼ 3500 K, a radius of ∼230 R ⊙ , and a high luminosity L ∼ 7400 L ⊙ . The hot component is a hot white dwarf. We tentatively determined the orbital period of the system ∼487 d. The main outburst of Gaia18aen in 2018 was accompanied by a decrease in the temperature of the hot component. The first phase of the outburst was characterized by the high luminosity L ∼ 27 000 L ⊙ , which remained constant for about three weeks after the optical maximum, later followed by the gradual decline of luminosity and increase of temperature. Several re-brightenings have been detected on the timescales of hundreds of days.
Romain Lucchesi; C. Lardo; F. Primas; P. Jablonka; P. North; G. Battaglia; Else Starkenburg; V. Hill; M. J. Irwin; P. François; Matthew Shetrone; Eline Tolstoy; Kim A. Venn
Springer Link (Chiba Institute of Technology) · DOI ↗
We present the high-resolution spectroscopic analysis of two new extremely metal-poor star (EMPS) candidates in the dwarf spheroidal galaxy Sextans. These targets were preselected from medium-resolution spectra centered around the Ca <ns0:sc>II</ns0:sc> triplet in the near-infrared and were followed-up at higher resolution with VLT/UVES. We confirm their low metallicities with [Fe/H] = −2.95 and [Fe/H] = −3.01, which place them among the most metal-poor stars known in Sextans. The abundances of 18 elements, including C, Na, the α, Fe-peak, and neutron-capture elements, are determined. In particular, we present the first unambiguous detection of Zn in a classical dwarf at extremely low metallicity. Previous indications were made of a large scatter in the abundance ratios of the Sextans stellar population around [Fe/H] ∼ − 3 when compared to other galaxies, particularly with very low observed [α/Fe] ratios. We took the opportunity of reanalyzing the full sample of EMPS in Sextans and find a [α/Fe] Milky Way-like plateau and a ∼0.2 dex dispersion at fixed metallicity.
M. Monguió; R. Greimel; J. E. Drew; Geert Barentsen; P. Groot; M. J. Irwin; J. Casares; B. T. Gänsicke; Philip J. Carter; J. M. Corral-Santana; N. P. Gentile-Fusillo; S. Greiss; L. M. van Haaften; Mark Hollands; David Jones; Thomas Kupfer; Christopher J. Manser; D. N. A. Murphy; Anna F. McLeod; T. Oosting; Q. A. Parker; S. Pyrzas; P. Rodríguez-Gil; Jan van Roestel; Simone Scaringi; P. Schellart; Odette Toloza; O. Văduvescu; L. van Spaandonk; K. Verbeek; N. J. Wright; J. Eislöffel; J. Fabregat; A. Harris; R. A. H. Morris; S. Phillipps; R. Raddi; L. Sabin; Y. C. Unruh; J. S. Vink; R. Wesson; A. Cardwell; A. de Burgos; R. K. Cochrane; Saeed Doostmohammadi; Teo Močnik; H. Stoev; L. Suárez-Andrés; Vlad Tudor; T. G. Wilson; Tarik Zegmott
Astronomy and Astrophysics · DOI ↗
The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i , r , narrow-band H α , g , and U RGO . The IGAPS footprint fills the Galactic coordinate range, | b | &lt; 5° and 30° &lt; ℓ &lt; 215°. A uniform calibration, referred to as the Pan-STARRS system, is applied to g , r , and i , while the H α calibration is linked to r and then is reconciled via field overlaps. The astrometry in all five bands has been recalculated in the reference frame of Gaia Data Release 2. Down to i ∼ 20 mag (Vega system), most stars are also detected in g , r , and H α . As exposures in the r band were obtained in both the IPHAS and UVEX surveys, typically a few years apart, the catalogue includes two distinct r measures, r I and r U . The r 10 σ limiting magnitude is approximately 21, with median seeing of 1.1 arcsec. Between approximately 13th and 19th mag in all bands, the photometry is internally reproducible to within 0.02 mag. Stars brighter than r = 19.5 mag are tested for narrow-band H α excess signalling line emission, and for variation exceeding | r I − r U | = 0.2 mag. We find and flag 8292 candidate emission line stars and over 53 000 variables (both at &gt; 5 σ confidence).
Laura K. Rogers; Siyi Xu; Amy Bonsor; S. T. Hodgkin; K. Y. L. Su; Ted von Hippel; Michael Jura
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT The inwards scattering of planetesimals towards white dwarfs is expected to be a stochastic process with variability on human time-scales. The planetesimals tidally disrupt at the Roche radius, producing dusty debris detectable as excess infrared emission. When sufficiently close to the white dwarf, this debris sublimates and accretes on to the white dwarf and pollutes its atmosphere. Studying this infrared emission around polluted white dwarfs can reveal how this planetary material arrives in their atmospheres. We report a near-infrared monitoring campaign of 34 white dwarfs with infrared excesses with the aim to search for variability in the dust emission. Time series photometry of these white dwarfs from the United Kingdom Infrared Telescope (Wide Field Camera) in the J-, H-, and K-bands was obtained over baselines of up to 3 yr. We find no statistically significant variation in the dust emission in all three near-infrared bands. Specifically, we can rule out variability at ∼1.3 per cent for the 13 white dwarfs brighter than 16th mag in K-band, and at ∼10 per cent for the 32 white dwarfs brighter than 18th mag over time-scales of 3 yr. Although to date two white dwarfs, SDSS J095904.69−020047.6 and WD 1226+110, have shown K-band variability, in our sample we see no evidence of new K-band variability at these levels. One interpretation is that the tidal disruption events that lead to large variabilities are rare occur on short time-scales, and after a few years the white dwarfs return to being stable in the near-infrared.
Z. Kostrzewa-Rutkowska; P. G. Jonker; S. T. Hodgkin; D. Eappachen; D. L. Harrison; S. E. Koposov
Monthly Notices of the Royal Astronomical Society · DOI ↗
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