The Gravitational-wave Optical Transient Observer (GOTO)

Dyer, M.; Steeghs, D.; Galloway, D. K.; Dhillon, V.; O’Brien, P. T.; Ramsay, Gavin; Noysena, K.; Πάλλη, Ε.; Kotak, R.; Breton, R. P.; Nuttall, L. K.; Pollacco, D.; Ulaczyk, K.; Lyman, J. D.; Ackley, K.

doi:10.1117/12.2561008

Cited by 12 publications

(7 citation statements)

References 17 publications

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“…We assume BLAPs to have a -band absolute magnitude = 4.0 (typical of the sample characterised in Ramsay 2018) and we consider two plausible survey depths. A limit of = 20 is the typical 5 depth of individual observations in relatively high cadence (∼ few minute to few day interval) all-sky surveys designed for transient follow-up, such as the Gravitational Wave Optical Transient Observer (GOTO, Dyer et al 2020). A limit of = 23 approximates the depth reached at five per cent photometric uncertainty on individual (2 × 15 s) visits from the Vera Rubin Observatory Legacy Survey of Space and Time (VRO LSST).…”

Section: Predicted Survey Number Densitiesmentioning

confidence: 99%

Binary evolution pathways of blue large-amplitude pulsators

Byrne

Stanway

Eldridge

2021

Monthly Notices of the Royal Astronomical Society

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Blue Large-Amplitude Pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or Roche lobe overflow, with a Main Sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-Solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.

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Section: Predicted Survey Number Densitiesmentioning

confidence: 99%

Binary evolution pathways of blue large-amplitude pulsators

Byrne

Stanway

Eldridge

2021

Monthly Notices of the Royal Astronomical Society

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“…For Fermi-GRB sources a set of four, 90 second exposures are taken using GOTO's wide L filter (400-700 nm). In this work, all GOTO magnitudes have been calibrated in the standard way as described in Dyer et al (2020b).…”

Section: Goto Observing Strategy For Grbsmentioning

confidence: 99%

“…This work is an independent project of GOTO designed to test approaches for GRB afterglow searches, which does not represent the GOTO standard filtering procedures as described in Dyer et al (2020b).…”

Section: Goto Observing Strategy For Grbsmentioning

confidence: 99%

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Searching for Fermi GRB optical counterparts with the prototype Gravitational-wave Optical Transient Observer (GOTO)

Mong

Ackley

Galloway

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The typical detection rate of ∼1 gamma-ray burst (GRB) per day by the Fermi Gamma-ray Burst Monitor (GBM) provides a valuable opportunity to further our understanding of GRB physics. However, the large uncertainty of the Fermi localization typically prevents rapid identification of multi-wavelength counterparts. We report the follow-up of 93 Fermi GRBs with the Gravitational-wave Optical Transient Observer (GOTO) prototype on La Palma. We selected 53 events (based on favourable observing conditions) for detailed analysis, and to demonstrate our strategy of searching for optical counterparts. We apply a filtering process consisting of both automated and manual steps to 60 085 candidates initially, rejecting all but 29, arising from 15 events. With ≈3 GRB afterglows expected to be detectable with GOTO from our sample, most of the candidates are unlikely to be related to the GRBs. Since we did not have multiple observations for those candidates, we cannot confidently confirm the association between the transients and the GRBs. Our results show that GOTO can effectively search for GRB optical counterparts thanks to its large field of view of ≈40 square degrees and its depth of ≈20 mag. We also detail several methods to improve our overall performance for future follow-up programs of Fermi GRBs.

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“…GOTO's default observing mode is the so-called 'survey mode', in which the sky is repeatedly observed in a systematic way. This can be interrupted at any time to undertake prioritised observations to follow-up a transient event, such as a gravitational wave event (Dyer et al 2020a).…”

Section: The Gravitational-wave Optical Transient Observermentioning

confidence: 99%

Processing GOTO survey data with the Rubin Observatory LSST Science Pipelines II: Forced Photometry and lightcurves

Makrygianni

Mullaney

Dhillon

et al. 2021

Publ. Astron. Soc. Aust.

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We have adapted the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Science Pipelines to process data from the Gravitational-wave Optical Transient Observer (GOTO) prototype. In this paper, we describe how we used the LSST Science Pipelines to conduct forced photometry measurements on nightly GOTO data. By comparing the photometry measurements of sources taken on multiple nights, we find that the precision of our photometry is typically better than 20 mmag for sources brighter than 16 mag. We also compare our photometry measurements against colour-corrected Panoramic Survey Telescope and Rapid Response System photometry and find that the two agree to within 10 mmag (1 $\sigma$ ) for bright (i.e., $\sim 14{\rm th} \mathrm{mag}$ ) sources to 200 mmag for faint (i.e., $\sim 18{\rm th} \mathrm{mag}$ ) sources. Additionally, we compare our results to those obtained by GOTO’s own in-house pipeline, gotophoto, and obtain similar results. Based on repeatability measurements, we measure a $5\sigma$ L-band survey depth of between 19 and 20 magnitudes, depending on observing conditions. We assess, using repeated observations of non-varying standard Sloan Digital Sky Survey stars, the accuracy of our uncertainties, which we find are typically overestimated by roughly a factor of two for bright sources (i.e., $< 15{\rm th} \mathrm{mag}$ ), but slightly underestimated (by roughly a factor of 1.25) for fainter sources ( $> 17{\rm th} \mathrm{mag}$ ). Finally, we present lightcurves for a selection of variable sources and compare them to those obtained with the Zwicky Transient Factory and GAIA. Despite the LSST Software Pipelines still undergoing active development, our results show that they are already delivering robust forced photometry measurements from GOTO data.

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The Gravitational-wave Optical Transient Observer (GOTO)

Cited by 12 publications

References 17 publications

Binary evolution pathways of blue large-amplitude pulsators

Binary evolution pathways of blue large-amplitude pulsators

Searching for Fermi GRB optical counterparts with the prototype Gravitational-wave Optical Transient Observer (GOTO)

Processing GOTO survey data with the Rubin Observatory LSST Science Pipelines II: Forced Photometry and lightcurves

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