ORCID Profile
0000-0001-8357-4453
Current Organisation
University of Amsterdam
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Publisher: American Astronomical Society
Date: 20-10-2008
DOI: 10.1086/591243
Publisher: American Astronomical Society
Date: 10-11-2007
DOI: 10.1086/521336
Publisher: Oxford University Press (OUP)
Date: 21-11-2009
Publisher: American Astronomical Society
Date: 2008
DOI: 10.1086/521975
Publisher: EDP Sciences
Date: 23-07-2008
Publisher: American Astronomical Society
Date: 30-11-2009
Publisher: Oxford University Press (OUP)
Date: 21-03-2010
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
DOI: 10.1038/NATURE24471
Abstract: On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
Publisher: American Astronomical Society
Date: 28-01-2009
Publisher: American Astronomical Society
Date: 19-11-2010
Publisher: Elsevier BV
Date: 06-2015
Publisher: Oxford University Press (OUP)
Date: 09-10-2020
Abstract: The amount of observational data produced by time-domain astronomy is exponentially increasing. Human inspection alone is not an effective way to identify genuine transients from the data. An automatic real-bogus classifier is needed and machine learning techniques are commonly used to achieve this goal. Building a training set with a sufficiently large number of verified transients is challenging, due to the requirement of human verification. We present an approach for creating a training set by using all detections in the science images to be the s le of real detections and all detections in the difference images, which are generated by the process of difference imaging to detect transients, to be the s les of bogus detections. This strategy effectively minimizes the labour involved in the data labelling for supervised machine learning methods. We demonstrate the utility of the training set by using it to train several classifiers utilizing as the feature representation the normalized pixel values in 21 × 21 pixel st s centred at the detection position, observed with the Gravitational-wave Optical Transient Observer (GOTO) prototype. The real-bogus classifier trained with this strategy can provide up to $95{{\\ \\rm per\\ cent}}$ prediction accuracy on the real detections at a false alarm rate of $1{{\\ \\rm per\\ cent}}$.
Publisher: American Astronomical Society
Date: 02-07-2013
Publisher: SPIE
Date: 10-07-2018
DOI: 10.1117/12.2311865
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2020.45
Abstract: The past few decades have seen the burgeoning of wide-field, high-cadence surveys, the most formidable of which will be the Legacy Survey of Space and Time (LSST) to be conducted by the Vera C. Rubin Observatory. So new is the field of systematic time-domain survey astronomy however, that major scientific insights will continue to be obtained using smaller, more flexible systems than the LSST. One such ex le is the Gravitational-wave Optical Transient Observer (GOTO) whose primary science objective is the optical follow-up of gravitational wave events. The amount and rate of data production by GOTO and other wide-area, high-cadence surveys presents a significant challenge to data processing pipelines which need to operate in near-real time to fully exploit the time domain. In this study, we adapt the Rubin Observatory LSST Science Pipelines to process GOTO data, thereby exploring the feasibility of using this ‘off-the-shelf’ pipeline to process data from other wide-area, high-cadence surveys. In this paper, we describe how we use the LSST Science Pipelines to process raw GOTO frames to ultimately produce calibrated coadded images and photometric source catalogues. After comparing the measured astrometry and photometry to those of matched sources from PanSTARRS DR1, we find that measured source positions are typically accurate to subpixel levels, and that measured L -band photometries are accurate to $\\sim50$ mmag at $m_L\\sim16$ and $\\sim200$ mmag at $m_L\\sim18$ . These values compare favourably to those obtained using GOTO’s primary, in-house pipeline, gotophoto , in spite of both pipelines having undergone further development and improvement beyond the implementations used in this study. Finally, we release a generic ‘obs package’ that others can build upon, should they wish to use the LSST Science Pipelines to process data from other facilities.
Publisher: EDP Sciences
Date: 09-01-2008
Publisher: Oxford University Press (OUP)
Date: 21-11-0010
Publisher: EDP Sciences
Date: 04-02-2008
Publisher: American Astronomical Society
Date: 07-2008
DOI: 10.1086/588602
Publisher: American Astronomical Society
Date: 20-12-2011
Publisher: EDP Sciences
Date: 07-2010
Publisher: Oxford University Press (OUP)
Date: 08-2018
Publisher: EDP Sciences
Date: 12-2018
DOI: 10.1051/0004-6361/201833636
Abstract: Context . Long gamma-ray bursts (GRBs) give us the chance to study both their extreme physics and the star-forming galaxies in which they form. Aims . GRB 100418A, at a redshift of z = 0.6239, had a bright optical and radio afterglow, and a luminous star-forming host galaxy. This allowed us to study the radiation of the explosion as well as the interstellar medium of the host both in absorption and emission. Methods . We collected photometric data from radio to X-ray wavelengths to study the evolution of the afterglow and the contribution of a possible supernova (SN) and three X-shooter spectra obtained during the first 60 h. Results . The light curve shows a very fast optical rebrightening, with an litude of ∼3 magnitudes, starting 2.4 h after the GRB onset. This cannot be explained by a standard external shock model and requires other contributions, such as late central-engine activity. Two weeks after the burst we detect an excess in the light curve consistent with a SN with peak absolute magnitude M V = −18.5 mag, among the faintest GRB-SNe detected to date. The host galaxy shows two components in emission, with velocities differing by 130 km s −1 , but otherwise having similar properties. While some absorption and emission components coincide, the absorbing gas spans much higher velocities, indicating the presence of gas beyond the star-forming regions. The host has a star formation rate of SFR = 12.2 M ⊙ yr −1 , a metallicity of 12 + log(O/H) = 8.55, and a mass of 1.6 × 10 9 M ⊙ . Conclusions . GRB 100418A is a member of a class of afterglow light curves which show a steep rebrightening in the optical during the first day, which cannot be explained by traditional models. Its very faint associated SN shows that GRB-SNe can have a larger dispersion in luminosities than previously seen. Furthermore, we have obtained a complete view of the host of GRB 100418A owing to its spectrum, which contains a remarkable number of both emission and absorption lines.
Publisher: Oxford University Press (OUP)
Date: 10-02-2011
Publisher: Elsevier BV
Date: 04-2018
Publisher: American Astronomical Society
Date: 02-2010
Publisher: American Astronomical Society
Date: 18-06-2009
Publisher: Oxford University Press (OUP)
Date: 29-02-2012
Publisher: Oxford University Press (OUP)
Date: 31-08-2011
Publisher: Oxford University Press (OUP)
Date: 10-2007
Publisher: AIP
Date: 2009
DOI: 10.1063/1.3155871
Publisher: Oxford University Press (OUP)
Date: 02-08-2010
Publisher: Oxford University Press (OUP)
Date: 06-2009
Publisher: Oxford University Press (OUP)
Date: 31-12-2015
Publisher: American Astronomical Society
Date: 16-10-2017
Publisher: Oxford University Press (OUP)
Date: 11-02-2009
No related grants have been discovered for Evert Rol.