Publications (58)
High-mass X-ray binaries and OB-runaway stars
Lex Kaper
High-mass X-ray binaries (HMXBs) represent an important phase in the evolution of massive binary systems. HMXBs provide unique diagnostics to test massive-star evolution, to probe…
Fermi/GBM Observations of SGR J0501+4516 Bursts
Lin Lin, Chryssa Kouveliotou, Matthew G. Baring +27
We present our temporal and spectral analyses of 29 bursts from SGR J0501+4516, detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope during the 13…
First constraint on cosmological variation of the proton-to-electron mass ratio from two independent telescopes
Freek van Weerdenburg, Michael T. Murphy, Adrian L. Malec +2
A high signal-to-noise spectrum covering the largest number of hydrogen lines (90 H2 lines and 6 HD lines) in a high redshift object was analyzed from an observation along the sigh…
The promise of recent and future observatories and instruments
Lex Kaper
The identification of the carrier(s) of diffuse interstellar bands (DIBs) is one of the oldest mysteries in stellar spectroscopy. With the advent of 8-10m-class telescopes substant…
Constraint on a variation of the proton-to-electron mass ratio from H2 absorption towards quasar Q2348-011
Julija Bagdonaite, Michael T. Murphy, Lex Kaper +1
Molecular hydrogen (H2) absorption features observed in the line-of-sight to Q2348-011 at redshift zabs = 2.426 are analysed for the purpose of detecting a possible variation of th…
VLT/X-shooter spectroscopy of the candidate black-hole X-ray binary MAXI J1659-152 in outburst
Ramanpreet Kaur, Lex Kaper, Lucas E. Ellerbroek +15
We present the optical to near-infrared spectrum of MAXI J1659-152, during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO - Very Large Te…
The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment
Nick Cox, Jan Cami, Amin Farhang +27
The carriers of the diffuse interstellar bands (DIBs) are largely unidentified molecules ubiquitously present in the interstellar medium (ISM). After decades of study, two strong a…
Modelling the orbital modulation of ultraviolet resonance lines in high-mass X-ray binaries
Jacco Th. van Loon, Lex Kaper, Godelieve Hammerschlag-Hensberge
The stellar-wind structure in high-mass X-ray binaries (HMXBs) is investigated through modelling of their ultraviolet (UV) resonance lines. For the OB supergiants in two systems, V…
BlueMUSE: Project Overview and Science Cases
Johan Richard, Roland Bacon, Jérémy Blaizot +59
We present the concept of BlueMUSE, a blue-optimised, medium spectral resolution, panoramic integral field spectrograph based on the MUSE concept and proposed for the Very Large Te…
MOSAIC: the high-multiplex and multi-IFU spectrograph for the ELT
Rubén Sánchez-Janssen, Francois Hammer, Simon Morris +40
MOSAIC is the planned multi-object spectrograph for the 39m Extremely Large Telescope (ELT). Conceived as a multi-purpose instrument, it offers both high multiplex and multi-IFU ca…
ELT-MOS White Paper: Science Overview & Requirements
Chris Evans, Mathieu Puech, Beatriz Barbuy +18
The workhorse instruments of the 8-10m class observatories have become their multi-object spectrographs (MOS), providing comprehensive follow-up to both ground-based and space-born…
On the origin of the difference between the runaway velocities of the OB-supergiant X-ray Binaries and the Be/X-ray Binaries
Edward P. J. van den Heuvel, Simon F. Portegies Zwart, Dipankar Bhattacharya +1
The recent finding by Chevalier & Ilovaisky (1998) that OB-supergiant X-ray binaries have relatively large runaway velocities whereas Be/X-ray binaries have low runaway velocities,…
The wind properties of O-type stars at sub-SMC metallicity
Ciarán Furey, O. Grace Telford, Alex de Koter +7
Radiation-driven winds heavily influence the evolution and fate of massive stars. Feedback processes from these winds impact the properties of the interstellar medium of their host…
The early evolution of young massive clusters: The kinematic history of NGC6611 / M16
Mitchel Stoop, Lex Kaper, Alex de Koter +3
In the first few Myr the massive stars dynamically interact, produce runaways and affect the initial binary population. Observing and interpreting the dynamics of young massive clu…
Fine structure in the luminosity function in young stellar populations with Gaia DR2
Difeng Guo, Alex de Koter, Lex Kaper +2
A pioneering study showed that the fine structure in the luminosity function (LF) of young star clusters contains information about the evolutionary stage (age) and composition of…
The R136 star cluster dissected with Hubble Space Telescope/STIS. III. The most massive stars and their clumped winds
Sarah A. Brands, Alex de Koter, Joachim M. Bestenlehner +17
Context: The star cluster R136 inside the LMC hosts a rich population of massive stars, including the most massive stars known. The strong stellar winds of these very luminous star…
The early evolution of young massive clusters. II. The kinematic history of NGC 6618 / M 17
Mitchel Stoop, Annelotte Derkink, Lex Kaper +5
The fraction of massive stars in young stellar clusters is of importance as they are the dominant sources of both mechanical and radiative feedback, strongly influencing the therma…
Massive Young Stellar Objects in high-mass star-forming regions
Arjan Bik, Lex Kaper, Wing-Fai Thi +1
High-quality K-band spectra of point sources, deeply embedded in massive star-forming regions, have revealed a population of 20 young massive stars showing no photospheric absorpti…
Massive pre-main sequence stars in M17
MarÃa Claudia RamÃrez-Tannus, Lex Kaper, Alex de Koter +6
The formation process of massive stars is still poorly understood. Massive young stellar objects (mYSOs) are deeply embedded in their parental clouds, they are rare and thus typica…
Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
Adrian L. Malec, Ruth Buning, Michael T. Murphy +7
Molecular transitions recently discovered at redshift z_abs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-elect…
Design of a Full-Stokes Polarimeter for VLT/X-shooter
Frans Snik, Gerard van Harten, Ramon Navarro +3
X-shooter is one of the most popular instruments at the VLT, offering instantaneous spectroscopy from 300 to 2500 nm. We present the design of a single polarimetric unit at the pol…
Two waves of massive stars running away from the young cluster R136
Mitchel Stoop, Alex de Koter, Lex Kaper +10
Massive stars are predominantly born in stellar associations or clusters. Their radiation fields, stellar winds, and supernovae strongly impact their local environment. In the firs…
Discovery of a bow shock around Vela X-1
Lex Kaper, Jacco van Loon, Thomas Augusteijn +4
We report the discovery of a symmetric bow shock around the well-known high-mass X-ray binary (HMXB) Vela X-1. Wind bow shocks are a ubiquitous phenomenon around OB-runaway stars,…
The ELT-MOS (MOSAIC): towards the construction phase
Simon Morris, François Hammer, Pascal Jagourel +50
When combined with the huge collecting area of the ELT, MOSAIC will be the most effective and flexible Multi-Object Spectrograph (MOS) facility in the world, having both a high mul…
Search for a drifting proton--electron mass ratio from H
Wim Ubachs, Julija Bagdonaite, Edcel J. Salumbides +2
An overview is presented of the H quasar absorption method to search for a possible variation of the proton--electron mass ratio on a cosmological time scale. Deta…
The Highly Energetic Expansion of SN2010bh Associated with GRB 100316D
Filomena Bufano, Elena Pian, Jesper Sollerman +50
We present the spectroscopic and photometric evolution of the nearby (z = 0.059) spectroscopically confirmed type Ic supernova, SN 2010bh, associated with the soft, long-duration g…
X-Shooting ULLYSES: massive stars at low metallicity: XII. The clumped winds of O-type (super)giants in the Large Magellanic Cloud
Sarah A. Brands, Frank Backs, Alex de Koter +23
Mass loss governs the evolution of massive stars and shapes the stellar surroundings. To quantify the impact of the stellar winds we need to know the exact mass-loss rates; however…
Diffuse Interstellar Bands in NGC 1448
Jesper Sollerman, Nick Cox, Seppo Mattila +4
We present spectroscopic VLT/UVES observations of two emerging supernovae, the Type Ia SN 2001el and the Type II SN 2003hn, in the spiral galaxy NGC 1448. Our high resolution and h…
Spectroscopy of High Energy BL Lac Objects with X-shooter on the VLT
Santiago Pita, Paolo Goldoni, Catherine Boisson +6
Context. The study of BL Lac objects (BLL) detected in gamma-rays gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool to constrain the…
The origin of the most recently ejected OB runaway star from the R136 cluster
Simon Portegies Zwart, Michel Stoop, Lex Kaper +3
The solar-mass (\MSun) star-cluster R136 (NGC~2070) in the Tarantula Nebula in the Large Magellanic Cloud is the host of at least 55 massive stars ($M \apgt 10$\,\MS…
Winds in OB-type stars
Lex Kaper
The International Ultraviolet Explorer satellite has made a tremendous contribution to the study of hot-star winds. Its long lifetime has resulted in the collection of ultraviolet…
Stellar Physics with High-Resolution UV Spectropolarimetry
Julien Morin, Jean-Claude Bouret, Coralie Neiner +26
Current burning issues in stellar physics, for both hot and cool stars, concern their magnetism. In hot stars, stable magnetic fields of fossil origin impact their stellar structur…
The EDIBLES survey VI. Searching for time variations of interstellar absorption features
Amin Farhang, Jonathan Smoker, Nick L. J. Cox +10
Interstellar lines observed toward stellar targets change slowly over long timescales, mainly due to the proper motion of the background target relative to the intervening clouds.…
HST/COS Spectra of the Wind Lines of VFTS 102 and 285
Katherine Shepard, Douglas R. Gies, Kathryn V. Lester +5
Rapid rotation in massive stars imposes a latitudinal variation in the mass loss from radiatively driven winds that can lead to enhanced mass loss at the poles (with little angular…
First VLT/X-shooter spectroscopy of early-type stars outside the Local Group
Olga Hartoog, Hugues Sana, Alex de Koter +1
As part of the VLT/X-shooter science verification, we obtained the first optical medium-resolution spectrum of a previously identified bright O-type object in NGC55, an LMC-like ga…
Spectroscopic Line Modeling of the Fastest Rotating O-type Stars
Katherine Shepard, Douglas R. Gies, Lex Kaper +1
We present a spectroscopic analysis of the most rapidly rotating stars currently known, VFTS 102 ( km s; O9: Vnnne+) and VFTS 285 ($v_{e} \sin i =…
Properties of intermediate- to high-mass stars in the young cluster M17 -- Characterizing the (pre-)zero-age main sequence
Frank Backs, S. A. Brands, M. C. RamÃrez-Tannus +5
The outcome of the formation of massive stars is an important anchor point in their evolution. It provides insight into the physics of the assembly process, and sets the conditions…
Confirming NGC 6231 as the parent cluster of the runaway high-mass X-ray binary HD 153919/4U 1700-37 with Gaia DR2
Vincent van der Meij, Difeng Guo, Lex Kaper +1
A significant fraction of the most massive stars move through space with a high velocity. One of the possible physical explanations is that a supernova in a compact binary system r…
Metallicities of Young Massive Clusters in NGC 5236 (M83)
Svea Hernandez, Søren Larsen, Scott Trager +2
We present integrated-light spectra of 8 Young Massive Clusters (YMCs) in the metal-rich spiral galaxy NGC 5236 (M 83). The observations were taken with the X-Shooter spectrograph…
Search for cosmological mu variation from high redshift H2 absorption; a status report
Wim Ubachs, Julija Bagdonaite, Michael T. Murphy +2
Observations of H2 spectra in the line-of-sight of distant quasars may reveal a variation of the proton-electron mass ratio mu=m_p/m_e at high redshift, typically for z>2. Currentl…
The Science Case for Multi-Object Spectroscopy on the European ELT
Chris Evans, Mathieu Puech, Jose Afonso +68
This White Paper presents the scientific motivations for a multi-object spectrograph (MOS) on the European Extremely Large Telescope (E-ELT). The MOS case draws on all fields of co…
On the absence of wind bow-shocks around OB-runaway stars: probing the physical conditions of the interstellar medium
Fredrik Huthoff, Lex Kaper
High-resolution IRAS maps are used to search for the presence of stellar-wind bow-shocks around high-mass X-ray binaries (HMXBs). Their high space velocities, recently confirmed wi…
The stellar velocity dispersion of a compact massive galaxy at z=1.80 using X-Shooter: confirmation of the evolution in the mass-size and mass-dispersion relations
Jesse van de Sande, Mariska Kriek, Marijn Franx +7
Recent photometric studies have shown that early-type galaxies at fixed stellar mass were smaller and denser at earlier times. In this paper we assess that finding by deriving the…
A search for close companions in Sco OB2
Thijs Kouwenhoven, Anthony Brown, Hans Zinnecker +3
Using adaptive optics we study the binary population in the nearby OB association Scorpius OB2. We present the first results of our near-infrared adaptive optics survey among 199 (…
Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): PDS 111, an old T Tauri star with a young-looking disk
Annelotte Derkink, Christian Ginski, Paola Pinilla +20
The interplay between T Tauri stars and their circumstellar disks, and how this impacts the onset of planet formation has yet to be established. We studied a seemingly old T Tauri…
The Intermediate-mass Young Stellar Object 08576nr292: Discovery of a disk-jet system
Lucas E. Ellerbroek, Lex Kaper, Arjan Bik +5
We present observations of the embedded massive young stellar object (YSO) candidate 08576nr292, obtained with X-shooter and SINFONI on the ESO Very Large Telescope (VLT). The flux…
The VLTI/MIDI survey of massive young stellar objects - Sounding the inner regions around intermediate- and high-mass young stars using mid-infrared interferometry
Paul A. Boley, Hendrik Linz, Roy van Boekel +10
We aim to characterize the distribution and composition of circumstellar material around young massive stars, and to investigate exactly which physical structures in these objects…
The host-galaxy response to the afterglow of GRB 100901A
Olga E. Hartoog, Klaas Wiersema, Paul M. Vreeswijk +16
For Gamma-Ray Burst 100901A, we have obtained Gemini-North and Very Large Telescope optical afterglow spectra at four epochs: one hour, one day, three days and one week after the b…
The extremely low-metallicity tail of the Sculptor dwarf spheroidal galaxy
Else Starkenburg, Vanessa Hill, Eline Tolstoy +10
We present abundances for seven stars in the (extremely) low-metallicity tail of the Sculptor dwarf spheroidal galaxy, from spectra taken with X-shooter on the ESO VLT. Targets wer…
Investigating silicate, carbon, and water in the diffuse interstellar medium: the first shots from WISCI
S. T. Zeegers, Jonathan P. Marshall, Karl D. Gordon +33
The dusty interstellar medium (ISM) of the Milky Way is distributed in a complex, cloudy structure. It is fundamental to the radiation balance within the Milky Way, provides a reac…
Extinction towards the cluster R136 in the Large Magellanic Cloud: An extinction law from the near-infrared to the ultraviolet
Sarah A. Brands, Alex de Koter, Joachim M. Bestenlehner +4
The cluster R136 in the giant star-forming region 30 Doradus in the Large Magellanic Cloud (LMC) offers a unique opportunity to resolve a stellar population in a starburst-like env…
Discovery and Identification of MAXI J1621-501 as a Type I X-ray Burster with a Super-Orbital Period
Nicholas M. Gorgone, Chryssa Kouveliotou, Hitoshi Negoro +26
MAXI J1621-501 is the first Swift/XRT Deep Galactic Plane Survey transient that was followed up with a multitude of space missions (NuSTAR, Swift, Chandra, NICER, INTEGRAL, and MAX…
A very energetic supernova associated with the gamma-ray burst of 29 March 2003
Jens Hjorth, Jesper Sollerman, Palle Møller +24
Over the past five years evidence has mounted that long-duration (> 2 s) gamma-ray bursts (GRBs)--the most brilliant of all astronomical explosions--signal the collapse of massive…
LMC X-1: A New Spectral Analysis of the O-star in the binary and surrounding nebula
Elaina A. Hyde, David M. Russell, Andreas Ritter +4
We provide new observations of the LMC X-1 O star and its extended nebula structure using spectroscopic data from VLT/UVES as well as H imaging from the Wide Field Imager on th…
Massive binaries in high-mass star-forming regions: A multi-epoch radial velocity survey of embedded O-stars
Daniel Apai, Arjan Bik, Lex Kaper +3
We present the first multi-epoch radial velocity study of embedded young massive stars using near-infrared spectra obtained with ISAAC mounted at the ESO Very Large Telescope, with…
New limit on a varying proton-to-electron mass ratio from high-resolution optical quasar spectra
Adrian L. Malec, Ruth Buning, Michael T. Murphy +7
Molecular transitions recently discovered at redshift z_abs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-elect…
Chemical Abundances of Globular Clusters in NGC 5128 (Centaurus A)
Svea Hernandez, Søren Larsen, Scott Trager +2
We perform a detailed abundance analysis on integrated-light spectra of 20 globular clusters (GCs) in the early-type galaxy NGC 5128 (Centaurus A). The GCs were observed with X-Sho…
The star formation history of RCW 36
Lucas E. Ellerbroek, Lex Kaper, Arjan Bik +2
Recent studies of massive-star forming regions indicate that they can contain multiple generations of young stars. These observations suggest that star formation in these regions i…