The Deep Lens Survey Transient Search. I. Short Timescale and Astrometric Variability

Becker, A. C.; Wittman, David; Boeshaar, P. C.; Clocchiatti, A.; Dell’Antonio, Ian; Frail, D. A.; Halpern, J. P.; Margoniner, V. E.; Norman, Dara; Tyson, J. A.; Schommer, R. A.

doi:10.1086/421994

Cited by 99 publications

(128 citation statements)

References 63 publications

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“…They place a 95% upper limit on the OA rate of 1.9 deg −2 yr −1 at R = 20. The Deep Lensing Survey (DLS; Becker et al 2004) provides a (less constraining) limit of 5.2 deg −2 day −1 for transients with typical duration of a few ksec and 19.5 < R < 23.4. Malacrino et al (2007) obtained a more stringent upper limit from the CFHTLS Very Wide survey: excluding that the three transient they find are GRBs (Malacrino et al 2007), an upper limit of 0.24 deg −2 yr −1 down to R = 23 can be placed.…”

Section: Optical Surveysmentioning

confidence: 99%

Unveiling the population of orphanγ-ray bursts

Ghirlanda

Salvaterra

Campana

et al. 2015

A&A

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Gamma-ray bursts (GRBs) are detectable in the γ-ray band if their jets are oriented toward the observer. However, for each GRB with a typical θ jet , there should be ∼2/θ 2 jet bursts whose emission cone is oriented elsewhere in space. These off-axis bursts can eventually be detected when, due to the deceleration of their relativistic jets, the beaming angle becomes comparable to the viewing angle. Orphan afterglows (OAs) should outnumber the current population of bursts detected in the γ-ray band even if they have not been conclusively observed so far at any frequency. We compute the expected flux of the population of orphan afterglows in the mm, optical, and X-ray bands through a population synthesis code of GRBs and the standard afterglow emission model. We estimate the detection rate of OAs with ongoing and forthcoming surveys. The average duration of OAs as transients above a given limiting flux is derived and described with analytical expressions: in general OAs should appear as daily transients in optical surveys and as monthly/yearly transients in the mm/radio band. We find that ∼2 OA yr −1 could already be detected by Gaia and up to 20 OA yr −1 could be observed by the ZTF survey. A larger number of 50 OA yr −1 should be detected by LSST in the optical band. For the X-ray band, ∼26 OA yr −1 could be detected by the eROSITA. For the large population of OA detectable by LSST, the X-ray and optical follow up of the light curve (for the brightest cases) and/or the extensive follow up of their emission in the mm and radio band could be the key to disentangling their GRB nature from other extragalactic transients of comparable flux density.

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Section: Optical Surveysmentioning

confidence: 99%

Unveiling the population of orphanγ-ray bursts

Ghirlanda

Salvaterra

Campana

et al. 2015

A&A

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“…Detection methods have been optimized for specific variability signals to detect supernovae, microlensing, transits, and other variable sources (e.g. Alard & Lupton 1998;Wozniak 2000;Gössl & Riffeser 2002;Becker et al 2004;Corwin et al 2006;Yuan & Akerlof 2008;Renner et al 2008). An important step to optimising this process is to review the current inventory of variability indices and determine the efficiency level for selecting non-stochastic variations in photometric data.…”

Section: Introductionmentioning

confidence: 99%

New insights into time series analysis

Lopes

Cross

2016

A&A

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Context. The first step when investigating time varying data is the detection of any reliable changes in star brightness. This step is crucial to decreasing the processing time by reducing the number of sources processed in later, slower steps. Variability indices and their combinations have been used to identify variability patterns and to select non-stochastic variations, but the separation of true variables is hindered because of wavelength-correlated systematics of instrumental and atmospheric origin or due to possible data reduction anomalies. Aims. The main aim is to review the current inventory of correlation variability indices and measure the efficiency for selecting nonstochastic variations in photometric data. Methods. We test new and standard data-mining methods for correlated data using public time-domain data from the WFCAM Science Archive (WSA). This archive contains multi-wavelength calibration data (WFCAMCAL) for 216, 722 point sources, with at least ten unflagged epochs in any of five filters (YZJHK), which were used to test the different indices against. We improve the panchromatic variability indices and introduce a new set of variability indices for preselecting variable star candidates. Using the WFCAMCAL Variable Star Catalogue (WVSC1) we delimit the efficiency of each variability index. Moreover we test new insights about these indices to improve the efficiency of detection of time-series data dominated by correlated variations. Results. We propose five new variability indices that display high efficiency for the detection of variable stars. We determine the best way to select variable stars with these indices and the current tool inventory. In addition, we propose a universal analytical expression to select likely variables using the fraction of fluctuations on these indices ( f fluc ). The f fluc can be used as a universal way to analyse photometric data since it displays a only weak dependency with the instrument properties. The variability indices computed in this new approach allow us to reduce misclassification and these will be implemented in an automatic classifier which will be addressed in a forthcoming paper in this series.

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“…We recognize that modern CCD observations have significantly higher precision than photographic images from the past. However, our interest is in the possibility of using this largely neglected observational material on the most densely star-studded regions in the sky to harvest astrophysically interesting targets (for which there would be some baseline temporal information) for follow up by present day surveys (Munn et al 2004;Kilic et al 2006;Finch et al 2007;Becker et al 2004). Figure 10 shows the statistical HRD for the VSC sample of 55 × 10 3 stars using the values of (B − V) 0 This figure illustrates how a statistical HRD allows one to classify a star on the probability, from its kinematical properties, that it is a MS I, RG I, WD I, SD II, RG II or HB II star.…”

Section: Construction Of the Variability Sample Catalog (Vsc)mentioning

confidence: 99%

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

Fresneau

Osborn²

2009

A&A

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Context. A set of 55 × 10 3 stars brighter than about B-magnitude 14 and having at least three observations are identified in the Sydney Observatory Galactic Survey, carried out over the years 1892-1932 along the galactic equator section l ∈ [275. Short-term (30 min) and long-term (decades) magnitude variations in the data set are analyzed. Aims. Evidence is sought for a correlation between short-term and long-term variabilities which would identify stars in a non-quiescent phase. Methods. We use a reduced proper motion diagram to classify the stars in our sample into probable dwarfs, giants and other types. The validity of the kinematical classification is checked using objective-prism spectroscopic classification for 10 × 10 3 early-type stars. A search is made for statistical correlations between our variability indicators and physical and kinematical stellar properties. Results. We find that suspected photospheric activity for giant and dwarf stellar candidates is correlated with the time to cross the galactic thin disk. We estimate a significant apparent B-magnitude variation of ±0.25 over the 40 years of photographic observations, and candidates for monitoring for possible photospheric activity at the present time are selected employing a statistical colour-diagram which uses the total proper motion component as a distance indicator. Conclusions. Follow up studies of our tentative findings are suggested. Toward this aim the derived data for the set of 55 × 10 3 stars with variability information is archived as the variability Sample Catalogue. The data for a set of 2.4 × 10 5 stars along the section of the galactic equator l ∈ [275 • , 335 • ], |b| ≤ 7 • , and a set of of 1.7 × 10 5 stars along the section of the galactic meridian 330 • ± 5 • , b ∈ [−64 • , −7 • ] is also archived as a quick-look facility for seeking long-term magnitude changes since the century-old photographic observations were obtained.

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The Deep Lens Survey Transient Search. I. Short Timescale and Astrometric Variability

Cited by 99 publications

References 63 publications

Unveiling the population of orphanγ-ray bursts

Unveiling the population of orphanγ-ray bursts

New insights into time series analysis

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

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