52119
2018
2018
eng
3456
3476
21
3
479
article
Oxford Univ. Press
Oxford
1
--
2018-06-04
--
Highly ionized metals as probes of the circumburst gas in the natal regions of gamma-ray bursts
We present here a survey of high-ionization absorption lines in the afterglow spectra of long-duration gamma-ray bursts (GRBs) obtained with the VLT/X-shooter spectrograph. Our main goal is to investigate the circumburst medium in the natal regions of GRBs. Our primary focus is on the N vλλ 1238, 1242 line transitions, but we also discuss other high-ionization lines such as O vi, C iv, and Si iv. We find no correlation between the column density of N v and the neutral gas properties such as metallicity, H i column density, and dust depletion; however, the relative velocity of N v, typically a blueshift with respect to the neutral gas, is found to be correlated with the column density of H i. This may be explained if the N v gas is part of an H ii region hosting the GRB, where the region’s expansion is confined by dense, neutral gas in the GRB’s host galaxy. We find tentative evidence (at 2σ significance) that the X-ray derived column density, NH, X, may be correlated with the column density of N v, which would indicate that both measurements are sensitive to the column density of the gas located in the vicinity of the GRB. We investigate the scenario where N v (and also O vi) is produced by recombination after the corresponding atoms have been stripped entirely of their electrons by the initial prompt emission, in contrast to previous models where highly ionized gas is produced by photoionization from the GRB afterglow.
Monthly notices of the Royal Astronomical Society
10.1093/mnras/sty1447
0035-8711
1365-2966
wos:2018
WOS:000441382300045
Heintz, KE (reprint author), Univ Iceland, Inst Sci, Ctr Astrophys & Cosmol, Dunhagi 5, IS-107 Reykjavik, Iceland.; Heintz, KE (reprint author), Univ Copenhagen, Cosm Dawn Ctr, Niels Bohr Inst, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark.; Heintz, KE (reprint author), Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark., keh14@hi.is
Icelandic Research Fund [162948-051]; Danish Council for Independent Research (EU-FP7 under the Marie-Curie grant) [600207, DFF-MOBILEX-5051-00115]; NOVA; NWO-FAPESP grant; Slovenian Research AgencySlovenian Research Agency - Slovenia [P1-0031, J1-8136]; Spanish Ministry of Economy and Competitivity [AYA 2014-58381-P]; Ramon y Cajal fellowshipsSpanish Government [RyC-2012-09975, RyC-2012-09984]; BBVA foundation for researchers and cultural creatorsBBVA Foundation; Juan de la Cierva Incorporacion fellowship [IJCI-2014-21669]; Spanish research project [AYA 2014-58381-P]; ASI (Italian Space Agency)Italian Space Agency [2015-046-R.0]; European Union Horizon 2020 Programme under the AHEAD project [654215]
2021-10-08T13:28:53+00:00
sword
importub
filename=package.tar
03db281bb67fbe27a0c62330062cded2
false
true
Kasper Elm Heintz
D. Watson
P. Jakobsson
J. P. U. Fynbo
J. Bolmer
M. Arabsalmani
Zach Cano
S. Covino
A. Gomboc
J. Japelj
L. Kaper
J. -K. Krogager
G. Pugliese
R. Sanchez-Ramirez
J. Selsing
Martin Sparre
N. R. Tanvir
C. C. Thone
A. de Ugarte Postigo
S. D. Vergani
eng
uncontrolled
gamma-ray bursts: general
eng
uncontrolled
ISM: abundances
Physik
Institut für Physik und Astronomie
Referiert
Import
Green Open-Access
15103
2004
2004
eng
article
1
--
--
--
Inference of hot star density stream properties from data on rotationally recurrent DACs
The information content of data on rotationally periodic recurrent discrete absorption components (DACs) in hot star wind emission lines is discussed. The data comprise optical depths tau(w,phi) as a function of dimensionless Doppler velocity w=(Deltalambda/lambda(0))(c/v(infinity)) and of time expressed in terms of stellar rotation angle phi. This is used to study the spatial distributions of density, radial and rotational velocities, and ionisation structures of the corotating wind streams to which recurrent DACs are conventionally attributed. The simplifying assumptions made to reduce the degrees of freedom in such structure distribution functions to match those in the DAC data are discussed and the problem then posed in terms of a bivariate relationship between tau(w, phi) and the radial velocity v(r)(r), transverse rotation rate Omega(r) and density rho(r, phi) structures of the streams. The discussion applies to cases where: the streams are equatorial; the system is seen edge on; the ionisation structure is approximated as uniform; the radial and transverse velocities are taken to be functions only of radial distance but the stream density is allowed to vary with azimuth. The last kinematic assumption essentially ignores the dynamical feedback of density on velocity and the relationship of this to fully dynamical models is discussed. The case of narrow streams is first considered, noting the result of Hamann et al. (2001) that the apparent acceleration of a narrow stream DAC is higher than the acceleration of the matter itself, so that the apparent slow acceleration of DACs cannot be attributed to the slowness of stellar rotation. Thus DACs either involve matter which accelerates slower than the general wind flow, or they are formed by structures which are not advected with the matter flow but propagate upstream (such as Abbott waves). It is then shown how, in the kinematic model approximation, the radial speed of the absorbing matter can be found by inversion of the apparent acceleration of the narrow DAC, for a given rotation law. The case of broad streams is more complex but also more informative. The observed tau(w,phi) is governed not only by v(r)(r) and Omega(r) of the absorbing stream matter but also by the density profile across the stream, determined by the azimuthal (phi(0)) distribution function F- 0(phi(0)) of mass loss rate around the stellar equator. When F-0(phi(0)) is fairly wide in phi(0), the acceleration of the DAC peak tau(w, phi) in w is generally slow compared with that of a narrow stream DAC and the information on v(r)(r), Omega(r) and F-0(phi(0)) is convoluted in the data tau(w, phi). We show that it is possible, in this kinematic model, to recover by inversion, complete information on all three distribution functions v(r)(r), Omega(r) and F- 0(phi(0)) from data on tau(w, phi) of sufficiently high precision and resolution since v(r)(r) and Omega(r) occur in combination rather than independently in the equations. This is demonstrated for simulated data, including noise effects, and is discussed in relation to real data and to fully hydrodynamic models
0004-6361
allegro:1991-2014
10097754
Astronomy and astrophysics <Berlin> : an European journal. - ISSN 0004-6361. - 413 (2004), S. 959 - 986
John C. Brown
R. K. Barrett
Lida M. Oskinova
S. P. Owocki
Wolf-Rainer Hamann
J. A. de Jong
L. Kaper
H. F. Henrichs
Institut für Physik und Astronomie
Referiert
Institut für Physik
49955
2019
2019
eng
42
623
article
EDP Sciences
Les Ulis
1
2019-03-12
2019-03-12
--
The X-shooter GRB afterglow legacy sample (XS-GRB)
In this work we present spectra of all gamma-ray burst (GRB) afterglows that have been promptly observed with the X-shooter spectrograph until 31/03/2017. In total, we have obtained spectroscopic observations of 103 individual GRBs observed within 48 hours of the GRB trigger. Redshifts have been measured for 97 per cent of these, covering a redshift range from 0.059 to 7.84. Based on a set of observational selection criteria that minimise biases with regards to intrinsic properties of the GRBs, the follow-up effort has been focused on producing a homogeneously selected sample of 93 afterglow spectra for GRBs discovered by the Swift satellite. We here provide a public release of all the reduced spectra, including continuum estimates and telluric absorption corrections. For completeness, we also provide reductions for the 18 late-time observations of the underlying host galaxies. We provide an assessment of the degree of completeness with respect to the parent GRB population, in terms of the X-ray properties of the bursts in the sample and find that the sample presented here is representative of the full Swift sample. We have constrained the fraction of dark bursts to be <28 per cent and confirm previous results that higher optical darkness is correlated with increased X-ray absorption. For the 42 bursts for which it is possible, we have provided a measurement of the neutral hydrogen column density, increasing the total number of published HI column density measurements by similar to 33 per cent. This dataset provides a unique resource to study the ISM across cosmic time, from the local progenitor surroundings to the intervening Universe.
Astronomy and astrophysics : an international weekly journal
10.1051/0004-6361/201832835
1432-0746
0004-6361
wos:2019
A92
WOS:000460890300002
Selsing, J (reprint author), Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Marius Vej 30, DK-2100 Copenhagen O, Denmark.; Selsing, J (reprint author), Univ Copenhagen, Niels Bohr Inst, Cosm Dawn Ctr DAWN, Juliane Marius Vej 30, DK-2100 Copenhagen O, Denmark.; Selsing, J (reprint author), Tech Univ Denmark, DTU Space, Elektrovej 327, DK-2800 Lyngby, Denmark., jselsing@dark-cosmology.dk
ERC-StG grant [EGGS-278202]; Danish National Research FoundationDanmarks Grundforskningsfond; VILLUM FONDEN Investigator grant [16599]; European Commission under the Marie Curie Intra-European Fellowship Programme in FP7European Union (EU); NOVA; NWO-FAPESP grant for advanced instrumentation in astronomy; Icelandic Research Fund [162948-051]; Slovenian Research AgencySlovenian Research Agency - Slovenia [P1-0031, J1-8136]; Spanish National Research Grant of Excellence [AYA 2014-58381-P]; Ramon y Cajal fellowshipSpanish Government [RyC-2012-09984]; BBVA Foundation Grant for Researchers and Cultural CreatorsBBVA Foundation; Spanish Ministry of Economy and Competitiveness [AYA2014-58381-P]; Spanish research project [AYA 2014-58381-P]; Juan de la Cierva Incorporacion [IJCI-2014-21669, IJCI-2015-26153]; ASI (Italian Space Agency)Italian Space Agency [2015-046-R.0]; European Union Horizon 2020 Programme under the AHEAD project [654215]; VILLUM FONDEN [19054]; French National Research Agency (ANR)French National Research Agency (ANR) [ANR-16-CE31-0003 BEaPro]; Instrument Center for Danish Astrophysics (IDA); National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA) [NNX08AR22G]; National Science FoundationNational Science Foundation (NSF) [AST-1238877]
2021-03-16T12:43:30+00:00
sword
importub
filename=package.tar
bcbd730f90d55b93bb200db377b66ea3
false
true
Jonatan Selsing
D. Malesani
P. Goldoni
Johan Fynbo
T. Krühler
L. A. Antonelli
M. Arabsalmani
J. Bolmer
Z. Cano
L. Christensen
S. Covino
A. De Cia
A. de Ugarte Postigo
H. Flores
M. Fliis
A. Gomboc
J. Greiner
P. Groot
F. Hammer
O. E. Hartoog
K. E. Heintz
J. Hjorth
P. Jakobsson
J. Japelj
D. A. Kann
L. Kaper
C. Ledoux
G. Leloudas
A. J. Levan
E. Maiorano
A. Melandri
B. Milvang-Jensen
E. Palazzi
J. T. Palmerio
D. A. Perley
E. Pian
S. Piranomonte
G. Pugliese
R. Sanchez-Ramirez
S. Savaglio
P. Schady
S. Schulze
J. Sollerman
Martin Sparre
G. Tagliaferri
N. R. Tanvir
C. C. Thone
S. D. Vergani
P. Vreeswijk
D. Watson
K. Wiersema
R. Wijers
D. Xu
T. Zafar
eng
uncontrolled
gamma-ray burst: general
eng
uncontrolled
galaxies: high-redshift
eng
uncontrolled
ISM: general
eng
uncontrolled
techniques: spectroscopic
eng
uncontrolled
catalogs
eng
uncontrolled
galaxies: star formation
Physik
Institut für Physik und Astronomie
Referiert
Import
Bronze Open-Access
8778
2015
eng
109
112
article
0
--
--
--
Massive Wolf-Rayet stars on the verge to explode
The enigmatic oxygen-sequence Wolf-Rayet stars represent a rare stage in the evolution of massive stars. Their properties can provide unique constraints on the pre-supernova evolution of massive stars. This work presents the results of a quantitative spectroscopic analysis of the known single WO stars, with the aim to obtain the key stellar parameters and deduce their evolutionary state.X-Shooter spectra of the WO stars are modeled using the line-blanketed non-local thermal equilibrium atmosphere code cmfgen. The obtained stellar parameters show that the WO stars are very hot, with temperatures ranging from 150 kK to 210 kK. Their chemical composition is dominated by carbon (>50%), while the helium mass fraction is very low (down to 14%). Oxygen mass fractions reach as high as 25%. These properties can be reproduced with dedicated evolutionary models for helium stars, which show that the stars are post core-helium burning and very close to their eventual supernova explosion. The helium-star masses indicate initial masses or approximately 40 - 60M⊙.Thus, WO stars represent the final evolutionary stage of stars with estimated initial masses of 40 - 60M⊙. They are post core-helium burning and may explode as type Ic supernovae within a few thousand years.
Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
the properties of the WO stars
urn:nbn:de:kobv:517-opus4-87786
online registration
Keine öffentliche Lizenz: Unter Urheberrechtsschutz
F. Tramper
S. M. Straal
D. Sanyal
Hugues Sana
A. de Koter
G. Gräfener
N. Langer
J. S. Vink
S. E. de Mink
L. Kaper
Astronomie und zugeordnete Wissenschaften
open_access
Institut für Physik und Astronomie
Universitätsverlag Potsdam
Wolf-Rayet Stars: Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015 / Wolf-Rainer Hamann, Andreas Sander, Helge Todt (Eds.)
WR spectral analysis, parameters, and wind theory
Universität Potsdam
https://publishup.uni-potsdam.de/files/8778/proceedings_S109-112.pdf
41522
2012
2019
eng
29
601
postprint
1
2019-02-14
2019-02-14
--
Very massive stars in the local universe
Recent studies have claimed the existence of very massive stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.
Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
10.25932/publishup-41522
urn:nbn:de:kobv:517-opus4-415220
1866-8372
online registration
Proceedings of the International Astronomical Union 10 (2012) 16 (Higlights of Astronomy), pp. 51–79 DOI 10.1017/S1743921314004657
Keine öffentliche Lizenz: Unter Urheberrechtsschutz
Jorick Sandor Vink
Alexander Heger
Mark R. Krumholz
Joachim Puls
Shiladitya Banerjee
Norberto Castro
K.-J. Chen
A.-N. Chenè
P. A. Crowther
A. Daminelli
G. Gräfener
J. H. Groh
Wolf-Rainer Hamann
S. Heap
A. Herrero
L. Kaper
F. Najarro
Lida M. Oskinova
A. Roman-Lopes
A. Rosen
A. Sander
M. Shirazi
Y. Sugawara
F. Tramper
D. Vanbeveren
R. Voss
A. Wofford
Y. Zhang
Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
601
eng
uncontrolled
stars: massive stars
eng
uncontrolled
stars: mass-loss
eng
uncontrolled
stars: stellar evolution
Astronomie und zugeordnete Wissenschaften
open_access
Mathematisch-Naturwissenschaftliche Fakultät
Referiert
Open Access
Cambridge University Press (CUP)
Universität Potsdam
https://publishup.uni-potsdam.de/files/41522/pmnr601.pdf