Possible gravitational microlensing of a star in the Large Magellanic Cloud

Alcock, C.; Akerlof, C.; Allsman, R. A.; Axelrod, T. S.; Bennett, D. P.; Chan, S. K.; Cook, K. H.; Freeman, K. C.; Griest, K.; Marshall, S.; Park, H. S.; Perlmutter, S.; Peterson, Bruce A.; Pratt, M. R.; Quinn, Peter J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, William J.

doi:10.1038/365621a0

Cited by 783 publications

(546 citation statements)

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“…The nature of the sources has been studied for hundreds of years. However, the advent of large-scale microlensing surveys, such as massive compact halo object (Alcock et al 1993) and Optical Gravitational Lensing Experiment (OGLE; Udalski et al 1994), revolutionized this work by greatly increasing the quantity and quality of variable star information. Nevertheless, the coverage of the microlensing surveys was limited to the Galactic bulge and the Magellanic Clouds and thus left most of the sky to be explored.…”

Section: Introductionmentioning

confidence: 99%

The Catalina Surveys Southern periodic variable star catalogue

Drake

Djorgovski

Catelan

et al. 2017

Monthly Notices of the Royal Astronomical Society

167

133

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Here, we present the results from our analysis of 6 yr of optical photometry taken by the Siding Spring Survey (SSS). This completes a search for periodic variable stars within the 30 000 deg 2 of the sky covered by the Catalina Surveys. The current analysis covers 81 million sources with declinations between −20 • and −75 • with median magnitudes in the range 11 < V < 19.5. We find approximately 34 000 new periodic variable stars in addition to the ∼9000 RR Lyrae that we previously discovered in SSS data. This brings the total number of periodic variables identified in Catalina data to ∼110 000. The new SSS periodic variable stars mainly consist of eclipsing binaries, RR Lyrae, LPVs, RS CVn stars, δ Scutis, and Anomalous Cepheids. By cross-matching these variable stars with those from prior surveys, we find that ∼90 per cent of the sources are new discoveries and recover ∼95 per cent of the known periodic variables in the survey region. For the known sources, we find excellent agreement between our catalogue and prior values of luminosity, period, and amplitude. However, we find many variable stars that had previously been misclassified. Examining the distribution of RR Lyrae, we find a population associated with the Large Magellanic Cloud (LMC) that extends more than 20 • from its centre confirming recent evidence for the existence of a very extended stellar halo in the LMC. By combining SSS photometry with Dark Energy Survey data, we identify additional LMC halo RR Lyrae, thus confirming the significance of the population.

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Section: Introductionmentioning

confidence: 99%

The Catalina Surveys Southern periodic variable star catalogue

Drake

Djorgovski

Catelan

et al. 2017

Monthly Notices of the Royal Astronomical Society

167

133

View full text Add to dashboard Cite

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“…Several groups like the MACHO collaboration (Alcock et al 1993), OGLE (Udalski et al 1993), EROS (Aubourg et al 1993) and DUO (Alard et al 1995) followed the suggestion of Paczynski (1986) and surveyed millions of stars in the Large and Small Magellanic Clouds (LMC, SMC) and in the Galactic bulge for variability induced by gravitational microlensing. Although all of them discovered events compatible with gravitational lensing by MACHOs (Massive Astrophysical Compact Halo Objects) (Paczynski et al 1994;Ansari et al 1996;Alcock et al 1997;Alard & Guibert 1997;Palanque-Delabrouille et al 1998;Afonso et al 1999;Alcock et al 2000a;Alcock et al 2000;Udalski et al 2000) they were not able to derive unambiguous constraints on the amount of baryonic dark matter and its distribution in the Galactic halo (e.g.…”

Section: Introductionmentioning

confidence: 99%

WeCAPP -Wendelstein Calar Alto pixellensing project I

Riffeser

Fliri

Gössl

et al. 2001

A&A

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Abstract. We present WeCAPP, a long term monitoring project searching for microlensing events towards M 31. Since 1997 the bulge of M 31 was monitored in two different wavebands with the Wendelstein 0.8 m telescope. In 1999 we extended our observations to the Calar Alto 1.23 m telescope. Observing simultaneously at these two sites we obtained a time coverage of 53% during the observability of M 31. To check thousands of frames for variability of unresolved sources, we used the optimal image subtraction method (OIS) by Alard & Lupton (1998). This enabled us to minimize the residuals in the difference image analysis (DIA) and to detect variable sources with amplitudes at the photon noise level. Thus we can detect microlensing events with corresponding amplifications A > 10 of red clump giants with MI = 0.

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“…The search for what are commonly called MACHOS -massive, compact, halo objects, a term coined by Kim Griest -has been undertaken by several groups. Since the St. Malo meeting, two groups have reported the first, probable microlensing events of background Large Magellanic Cloud giants by halo objects -the EROS group (Aubourg et al 1993) and the Livermore group (Alcock et al 1993). A Polish project tied more directly to Paczynski has also reported a similar detection from the Galactic bulge (Udalski, A. et al 1993).…”

Section: Halo Stars Brown Dwarfs and Machosmentioning

confidence: 84%