15 research outputs found
The orbital period of the recurrent nova V2487 Oph revealed
We present the first reliable determination of the orbital period of the
recurrent nova V2487 Oph (Nova Oph 1998). We derived a value of d ( h) from the radial velocity curve of the intense He II
4686 emission line as detected in time-series X-shooter spectra. The
orbital period is significantly shorter than earlier claims, but it makes V2487
Oph one of the longest period cataclysmic variables known. The spectrum of
V2487 Oph is prolific in broad Balmer absorptions that resemble a white dwarf
spectrum. However, we show that they come from the accretion disc viewed at low
inclination. Although highly speculative, the analysis of the radial velocity
curves provides a binary mass ratio and a donor star mass M, assuming the reported white dwarf mass
M. A subgiant M-type star is tentatively suggested as the donor star.
We were lucky to inadvertently take some of the spectra when V2487 Oph was in a
flare state. During the flare, we detected high-velocity emission in the Balmer
and He II 4686 lines exceeding km s at close to orbital
phase 0.4. Receding emission up to km s at about phase 0.3 is
also observed. The similarities with the magnetic cataclysmic variables may
point to magnetic accretion on to the white dwarf during the repeating flares.Comment: Accepted for publication in MNRAS (October 9, 2023
A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars
We present DECam imaging combined with Gaia DR2 data to study the Canis Major
overdensity. The presence of the so-called Blue Plume stars in a low-pollution
area of the color-magnitude diagram allows us to derive the distance and proper
motions of this stellar feature along the line of sight of its hypothetical
core. The stellar overdensity extends on a large area of the sky at low
Galactic latitudes, below the plane, and between 230. According to the orbit derived for Canis Major, it presents an
on-plane rotation around the Milky Way. Moreover, additional overdensities of
Blue Plume stars are found around the plane and across the Galaxy, proving that
these objects are not only associated with that structure. The spatial
distribution of these stars, derived using Gaia astrometric data, confirms that
the detection of the Canis Major overdensity results more from the warped
structure of the Milky Way disk than from the accretion of a dwarf galaxy.Comment: 11 pages, 9 figures, accepted for publication in MNRA
Stellar streams around the Magellanic Clouds in 4D
We carried out a spectroscopic follow-up program of the four new stellar
stream candidates detected by Belokurov & Koposov (2016) in the outskirts of
the Large Magellanic Cloud (LMC) using FORS2 (VLT). The medium-resolution
spectra were used to measure the line-of-sight velocities, estimate stellar
metallicities and to classify stars into Blue Horizontal Branch (BHB) and Blue
Straggler (BS) stars. Using the 4-D phase-space information, we attribute
approximately one half of our sample to the Magellanic Clouds, while the rest
is part of the Galactic foreground. Only two of the four stream candidates are
confirmed kinematically. While it is impossible to estimate the exact levels of
MW contamination, the phase-space distribution of the entire sample of our
Magellanic stars matches the expected velocity gradient for the LMC halo and
extends as far as 33 deg (angular separation) or 29 kpc from the LMC center.
Our detections reinforce the idea that the halo of the LMC seems to be larger
than previously expected, and its debris can be spread in the sky out to very
large separations from the LMC center. Finally, we provide some kinematic
evidence that many of the stars analysed here have likely come from the Small
Magellanic Cloud.Comment: 15 pages, 13 figures, accepted for publication in MNRA
Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)
Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters.
Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs).
Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001).
Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio
IGAPS: The merged IPHAS and UVEX optical surveys of the northern Galactic plane
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 Hα, g, and URGO. The IGAPS footprint fills the Galactic coordinate range, |b| 5σ confidence).MM, JED and GB acknowledge the support of research grants funded by the Science, Technology and Facilities Council of the UK (STFC, grants ST/M001008/1 and ST/J001333/1). MM was partially supported by the MINECO (Spanish Ministry of Economy) through grant ESP2016-80079-C2-1-R and RTI2018-095076-B-C21 (MINECO/FEDER, UE), and MDM-2014-0369 of ICCUB (Unidad de Excelencia “María de Maeztu”). RG benefitted from support via STFC grant ST/M001334/1 as a visitor to UCL. PJG acknowledges support from the Netherlands Organisation for Scientific Research (NWO), in contributing to the Isaac Newton Group of Telescopes and through grant 614.000.601. JC acknowldges support by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) under grant AYA2017-83216-P. DJ and PR-G acknowledge support from the State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU) and the European Regional Development Fund (FEDER) under grant AYA2017-83383-P. RR acknowledges funding by the German Science foundation (DFG) through grants HE1356/71-1 and IR190/1-1. We thank Eugene Magnier for providing support on Pan-STARRS data. This research has made use of the University of Hertfordshire high-performance computing facility (https://uhhpc.herts.ac.uk/) located at the University of Hertfordshire (supported by STFC grants including ST/P000096/1). We thank Martin Hardcastle for his support and expertise in connection with our use of the facility. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www. cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Much of the analysis presented has been carried out via TopCat and stilts (Taylor et al. 2006). We thank the referee for comments on this paper that have improved its content
Whiting 1: Confirmation of its accretion by the Milky Way
We investigate the association of Whiting 1 with the Sagittarius tidal stream by obtaining radial velocities for a sample of 101 stars observed with VIMOS. Our results reveal the presence of a component of the Sagittarius tidal stream with a radial velocity - and distance - compatible with that of the globular cluster. Therefore, we conclude that Whiting1 was formed in the interior of the Sagittarius dwarf spheroidal galaxy and later accreted by the Milky Way. In addition, our data also reveal the detection for the first time of an ancient wrap of the Sagittarius tidal stream along the same line-of-sight and at the same heliocentric distance
Whiting 1: Confirmation of its accretion by the Milky Way
We investigate the association of Whiting 1 with the Sagittarius tidal stream by obtaining radial velocities for a sample of 101 stars observed with VIMOS. Our results reveal the presence of a component of the Sagittarius tidal stream with a radial velocity – and distance – compatible with that of the globular cluster. Therefore, we conclude that Whiting1 was formed in the interior of the Sagittarius dwarf spheroidal galaxy and later accreted by the Milky Way. In addition, our data also reveal the detection for the first time of an ancient wrap of the Sagittarius tidal stream along the same line-of-sight and at the same heliocentric distance
A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars
We present the Dark Energy Camera (DECam) imaging combined with Gaia Data Release 2 (DR2) data to study the Canis Major overdensity. The presence of the so-called Blue Plume stars in a low-pollution area of the colour-magnitude diagram allows us to derive the distance and proper motions of this stellar feature along the line of sight of its hypothetical core. The stellar overdensity extends on a large area of the sky at low Galactic latitudes, below the plane, and in the range 230° < ℓ < 255°. According to the orbit derived for Canis Major, it presents an on-plane rotation around the Milky Way. Moreover, additional overdensities of Blue Plume stars are found around the plane and across the Galaxy, proving that these objects are not only associated with that structure. The spatial distribution of these stars, derived using Gaia astrometric data, confirms that the detection of the Canis Major overdensity results more from the warped structure of the Milky Way disc than from the accretion of a dwarf galaxy. © 2020 The Author(s).Authors thank the anonymous referee for helpful comments and suggestions. They also thank Santi Cassisi for his help to compute the synthetic colour-magnitude diagram used in this study and to X. Chen for kindly providing the positions of their sample of Cepheids. JAC-B acknowledges financial support to CAS-CONICYT 17003. DM-D acknowledges support from the Spanish Ministry for Science, Innovation and Universities and FEDER funds through grant AYA2016-81065-C2-2. EJA and DM-D acknowledge financial support from the State Agency for Research of the Spanish MCIU through the 'Centre of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and from grant PGC2018-095049-B-C21. DECam was constructed by the Dark Energy Survey (DES) collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, theMinistry of Science and Education of Spain, the Science and Technology Facilities Council of theUnited Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo 'a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Ministerio da Ciencia, Tecnologia e Inovacao, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. Funding for the Gaia DPC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.Peer reviewe