Identification of the Microlens in Event MACHO-LMC-20

Kallivayalil, Nitya; Patten, B. M.; Marengo, Massimo; Alcock, C.; Werner, M. W.; Fazio, G. G.

doi:10.1086/510293

Cited by 14 publications

(14 citation statements)

References 38 publications

(52 reference statements)

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“…5 shows the CMD of LMC stars based on OGLE and Hubble Space Telescope ( HST ) (Holtzman, Afonso & Dolphin 2006) data, along with the determined positions of the sources in the two OGLE candidates. For comparison, we have also included in this figure the candidates from the MACHO collaboration: different colours and shapes differentiate between self‐lensing candidates according to Mancini et al (2004), the binary event MACHO–LMC‐9, the thick‐disc lens candidates MACHO–LMC‐5 (Kallivayalil et al 2004) and MACHO–LMC‐20 (Kallivayalil et al 2006) and the remaining candidates.…”

Section: Resultsmentioning

confidence: 99%

The OGLE view of microlensing towards the Magellanic Clouds - I. A trickle of events in the OGLE-II LMC data

Wyrzykowski¹,

Kozłowski²,

Skowron³

et al. 2009

Monthly Notices of the Royal Astronomical Society

127

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We present the results from the Optical Gravitational Lensing Experiment II (OGLE-II) survey (1996)(1997)(1998)(1999)(2000) towards the Large Magellanic Cloud (LMC), which has the aim of detecting the microlensing phenomena caused by dark matter compact objects in the Galactic halo [massive compact halo objects (MACHOs)].We use high-resolution Hubble Space Telescope images of the OGLE fields and derive the correction for the number of monitored stars in each field. This also yields blending distributions which we use in 'catalogue-level' Monte Carlo simulations of the microlensing events in order to calculate the detection efficiency of the events.We detect two candidates for microlensing events in the All Stars Sample, which translates into an optical depth of 0.43 ± 0.33 × 10 −7 . If both events were due to MACHO, the fraction of mass of compact dark matter objects in the Galactic halo would be 8 ± 6 per cent. This optical depth, however, along with the characteristics of the events seems to be consistent with the self-lensing scenario, i.e. self-lensing alone is sufficient to explain the observed microlensing signal. Our results indicate the non-detection of MACHOs lensing towards the LMC with an upper limit on their abundance in the Galactic halo of 19 per cent for M = 0.4 M and 10 per cent for masses between 0.01 and 0.2 M .

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Section: Resultsmentioning

confidence: 99%

The OGLE view of microlensing towards the Magellanic Clouds - I. A trickle of events in the OGLE-II LMC data

Wyrzykowski¹,

Kozłowski²,

Skowron³

et al. 2009

Monthly Notices of the Royal Astronomical Society

127

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“…Possible close encounters in the last few Gyr may well have stimulated star formation on a global scale in both the SMC and LMC (Murai & Fujimoto 1980; Gardiner, Sawa & Fujimoto 1994; Bekki et al 2004). However, the most recent proper motion values of the Magellanic Clouds (MCs) suggest that they are unbound from each other and only just beginning their first close encounter with the MW (Kallivayalil et al 2006; Piatek, Pryor & Olszewski 2008).…”

Section: Introductionmentioning

confidence: 99%

Washington photometry of 14 intermediate-age to old star clusters in the Small Magellanic Cloud

Piatti

Clariá

Bica

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present CCD photometry in the Washington system C, T1 and T2 passbands down to T1∼ 23 in the fields of L3, L28, HW 66, L100, HW 79, IC 1708, L106, L108, L109, NGC 643, L112, HW 84, HW 85 and HW 86, 14 Small Magellanic Cloud (SMC) clusters, most of them poorly studied objects. We measured T1 magnitudes and C−T1 and T1−T2 colours for a total of 213 516 stars spread throughout cluster areas of 14.7 × 14.7 arcmin2 each. We carried out an in‐depth analysis of the field star contamination of the colour–magnitude diagrams (CMDs) and statistically cleaned the cluster CMDs. Based on the best fits of isochrones computed by the Padova group to the (T1, C−T1) CMDs, as well as from the δ(T1) index and the standard giant branch procedure, we derived ages and metallicities for the cluster sample. With the exception of IC 1708, a relatively metal‐poor Hyades‐age cluster, the remaining 13 objects are between intermediate and old age (from 1.0 to 6.3 Gyr), their [Fe/H] values ranging from −1.4 to −0.7 dex. By combining these results with others available in the literature, we compiled a sample of 43 well‐known SMC clusters older than 1 Gyr, with which we produced a revised age distribution. We found that the present clusters’ age distribution reveals two primary excesses of clusters at t∼ 2 and 5 Gyr, which engraves the SMC with clear signs of enhanced formation episodes at both ages. In addition, we found that from the birth of the SMC cluster system until approximately the first 4 Gyr of its lifetime, the cluster formation resembles that of a constant formation rate scenario.

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“…For example, of 17 lens candidates published by one team (Alcock et al 2000), we now know that at least two events, LMC-5 (Alcock et al 2001a(Alcock et al , 2001bGould 2004;Gould et al 2004;Drake et al 2004;Nguyen et al 2004) and LMC-20 (Kallivayalil et al 2006), were caused by dwarf stars located within 1-2 kpc of Earth. In addition, many Galactic bulge events are of course expected to be caused by stellar lenses in the Galactic disk (see, e.g., An et al 2002).…”

Section: Events In Existing Datamentioning

confidence: 99%

Mesolensing: High‐Probability Lensing without Large Optical Depth

Stefano

2008

Astrophysical Journal

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In a variety of astronomical situations, there is a relatively high probability that a single isolated lens will produce a detectable event. The high probability is caused by some combination of a large Einstein angle, fast angular motion, and a dense background field. We refer to high-probability lenses as ''mesolenses.'' Planetary and stellar masses located within 1-2 kpc are examples of mesolenses. We show that their presence can be detected against a wide variety of background fields, using signatures of both time variability and spatial effects. Time signatures can be identical to those of microlensing, but can also include baseline jitter, extreme apparent chromaticity, photometric events well fit by lens models in which several independent sources are simultaneously lensed, and sequences of events. Spatial signatures include sequential astrometric lensing of surface brightness fluctuations, as well as patterns of time variability that sweep across the background field as the lens moves. Wide-field monitoring programs, such as Pan-STARRS and LSST, are well suited to the study of nearby masses. In addition, targeted high-resolution observations of the region behind a known mass traveling across a dense background field can use lensing effects to measure the lens mass and study its multiplicity.

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Identification of the Microlens in Event MACHO-LMC-20

Cited by 14 publications

References 38 publications

The OGLE view of microlensing towards the Magellanic Clouds - I. A trickle of events in the OGLE-II LMC data

The OGLE view of microlensing towards the Magellanic Clouds - I. A trickle of events in the OGLE-II LMC data

Washington photometry of 14 intermediate-age to old star clusters in the Small Magellanic Cloud

Mesolensing: High‐Probability Lensing without Large Optical Depth

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