Twenty-five years of using microlensing to study dark matter

Pietrzyński, G.

doi:10.1038/d41586-018-07006-8

Cited by 6 publications

(7 citation statements)

References 10 publications

(10 reference statements)

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“…Only 1 such candidate event was found (Tisserand et al 2007). This confirmed an earlier result (Alcock et al 2000) that MACHOs almost certainly do not have enough mass to account for the missing gravity in our Galaxy, or to stabilize its disc if it obeys Newtonian dynamics (for a historical review of microlensing, we refer the reader to Pietrzyński 2018). Similar conclusions were later reached for primordial black holes over a wide range of mass (Niikura et al 2019).…”

Section: Introductionsupporting

confidence: 87%

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Banik,

Zhao

2021

Preprint

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Astronomical observations reveal a major deficiency in our understanding of physics − the detectable mass is insufficient to explain the observed motions in a huge variety of systems given our current understanding of gravity, Einstein's General theory of Relativity (GR). This missing gravity problem may indicate a breakdown of GR at low accelerations, as posited by Milgromian dynamics (MOND). We review the MOND theory and its consequences, including in a cosmological context where we advocate a hybrid approach involving light sterile neutrinos to address MOND's cluster-scale issues. We then test the novel predictions of MOND using evidence from galaxies, galaxy groups, galaxy clusters, and the large scale structure of the Universe. We also consider whether the standard cosmological paradigm (ΛCDM) can explain the observations, and review several previously published highly significant falsifications of it. Our overall assessment considers both the extent to which the data agree with each theory and how much flexibility each has when accommodating the data, with the gold standard being a clear a priori prediction not informed by the data in question. We also consider some future tests, including on scales much smaller than galaxies. Our conclusion is that MOND is favoured by a wealth of data across a huge range of astrophysical scales, ranging from the kpc scales of galactic bars to the Gpc scale of the local supervoid and the Hubble tension, which is alleviated in MOND through enhanced cosmic variance.

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Section: Introductionsupporting

confidence: 87%

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Banik,

Zhao

2021

Preprint

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“…In the background the positions (grey dots) of some 44000 eclipsing binaries detected by the OGLE project in the LMC (Graczyk et al 2011;Pawlak et al 2016) are shown. The sloping line shows the position of the nodes derived from our 20 eclipsing binaries (Pietrzyński et al 2018). Note.…”

Section: Initial Parameter Choicementioning

confidence: 99%

“…All these eclipsing binaries are composed of G-and K-type normal giant stars. We will derive their individual distances and use them for a new determination of the distance to the LMC with an accuracy of 1% in a follow-up paper (Pietrzyński et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…In order to determine radial velocities of the components of the binaries we employed the Broadening Function (BF) formalism introduced by Rucinski (1992Rucinski ( , 1999 and implemented in the RaveSpan software (Pilecki et al 2013(Pilecki et al , 2017. We used numerous metallic lines in the wavelength regions 4125-4230, 4245-4320, 4350-4840, 4880-5000, 5350-5850, 5920-6250, 6300-6390, and 6600-6800Å to construct the BH profiles.…”

Section: Introductionmentioning

confidence: 99%

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The Late-type Eclipsing Binaries in the Large Magellanic Cloud: Catalog of Fundamental Physical Parameters

Graczyk

Pietrzyński

Thompson

et al. 2018

ApJ

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We present a determination of precise fundamental physical parameters of twenty detached, doublelined, eclipsing binary stars in the Large Magellanic Cloud (LMC) containing G-or early K-type giant stars. Eleven are new systems, the remaining nine are systems already analyzed by our team for which we present updated parameters. The catalogue results from our long-term survey of eclipsing binaries in the Magellanic Clouds suitable for high-precision determination of distances (the Araucaria project). The V-band brightnesses of the systems range from 15.4 mag to 17.7 mag and their orbital periods range from 49 days to 773 days. Six systems have favorable geometry showing total eclipses. The absolute dimensions of all eclipsing binary components are calculated with a precision of better than 3% and all systems are suitable for a precise distance determination. The measured stellar masses are in the range 1.4 to 4.6 M and comparison with the MESA isochrones gives ages between 0.1 and 2.1 Gyr. The systems show an age-metallicity relation with no evolution of metallicity for systems older than 0.6 Gy, followed by a rise to a metallicity maximum at age 0.5 Gy, and then a slow metallicity decrease until 0.1 Gy. Two systems have components with very different masses: OGLE LMC-ECL-05430 and OGLE LMC-ECL-18365. Neither system can be fitted by single stellar evolution isochrone, explained by a past mass transfer scenario in the case of ECL-18365 and a gravitational capture or a hierarchical binary merger scenario in the case of ECL-05430. The longest period system OGLE LMC SC9 230659 shows a surprising apsidal motion which shifts the apparent position of the eclipses. This is a clear sign of a physical companion to the system, however neither investigation of the spectra nor light curve analysis indicate a third light contribution larger than 2-3%. In one spectrum of OGLE LMC-ECL-12669 we noted a peculiar dimming of one of the components by 65% well outside of the eclipses. We interpret this observation as arising from an extremely rare occultation event as a foreground Galactic object covers only one component of an extragalactic eclipsing binary.

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“…These time-domain surveys scan a large portion of the sky, capturing several time-variable phenomena. The data from these variable sources are usually represented as lightcurves that describe underlying astrophysical properties, allowing scientists to identify and label different astronomical objects (Bonanos 2006;Tammann et al 2008;Pietrzyński 2018). For some astrophysical events, it is crucial to obtain this classification in real-time to promptly follow-up individual targets (Abbott et al 2017a;Abbott et al 2017b;Schulze et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The effect of phased recurrent units in the classification of multiple catalogs of astronomical lightcurves

Donoso-Oliva,

Cabrera-Vives,

Protopapas

et al. 2021

Preprint

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In the new era of very large telescopes, where data is crucial to expand scientific knowledge, we have witnessed many deep learning applications for the automatic classification of lightcurves. Recurrent neural networks (RNNs) are one of the models used for these applications, and the LSTM unit stands out for being an excellent choice for the representation of long time series. In general, RNNs assume observations at discrete times, which may not suit the irregular sampling of lightcurves. A traditional technique to address irregular sequences consists of adding the sampling time to the network's input, but this is not guaranteed to capture sampling irregularities during training. Alternatively, the Phased LSTM unit has been created to address this problem by updating its state using the sampling times explicitly. In this work, we study the effectiveness of the LSTM and Phased LSTM based architectures for the classification of astronomical lightcurves. We use seven catalogs containing periodic and nonperiodic astronomical objects. Our findings show that LSTM outperformed PLSTM on 6/7 datasets. However, the combination of both units enhances the results in all datasets.

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Twenty-five years of using microlensing to study dark matter

Cited by 6 publications

References 10 publications

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

The Late-type Eclipsing Binaries in the Large Magellanic Cloud: Catalog of Fundamental Physical Parameters

The effect of phased recurrent units in the classification of multiple catalogs of astronomical lightcurves

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