Microlensing Events From the 11 Year Observations of the Wendelstein Calar Alto Pixellensing Project

Abstract

We present the results of the decade-long M31 observation from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). WeCAPP has monitored M31 from 1997 till 2008 in both R-and I-filters, thus provides the longest baseline of all M31 microlensing surveys. The data are analyzed with the difference imaging analysis, which is most suitable to study variability in crowded stellar fields. We extracted light curves based on each pixel, and devised selection criteria that are optimized to identify microlensing events. This leads to 10 new events, and sums up to a total of 12 microlensing events from WeCAPP, for which we derive their timescales, flux excesses, and colors from their light curves. The color of the lensed stars fall between (R − I) = 0.56 to 1.36, with a median of 1.0 mag, in agreement with our expectation that the sources are most likely bright, red stars at post main-sequence stage. The event FWHM timescales range from 0.5 to 14 days, with a median of 3 days, in good agreement with predictions based on the model of Riffeser et al. (2006).

Massive Primordial Black Holes

“…A nice review of the state of the art and some new data is presented in ref. [47] with the conclusion that some statistical studies and individual microlensing events point to a non-negligible MACHO population, though the fraction in the halo mass remains uncertain.…”

“…AGAPE collaboration [45], finds the halo MACHO fraction in the range 0.2 < f < 0.9. while MEGA group presented the upper limit f < 0.3 [46]. On the other hand, the recent discovery of 10 new microlensing events [47] is very much in favor of MACHO existence. The authors conclude: "statistical studies and individual microlensing events point to a non-negligible MACHO population, though the fraction in the halo mass remains uncertain".…”

Massive primordial black holes in contemporary and young universe (old predictions and new data)

“…A nice review of the state of the art and some new data are presented in ref. [36] with the conclusion that some statistical studies and individual microlensing events point to a nonnegligible MACHO population, though the fraction in the halo mass remains uncertain.…”

“…AGAPE collaboration [24], finds the halo Macho fraction in the range 0.2 < f < 0.9. while MEGA group presented the upper limit f < 0.3 [25]. On the other hand, the recent discovery of 10 new microlensing events [36] is very much in favor of MACHO existence. The authors conclude: "statistical studies and individual microlensing events point to a non-negligible MACHO population, though the fraction in the halo mass remains uncertain".…”

Rambrain - a library for virtually extending physical memory

“…This applies for example for the difference imaging code presented by Gössl and Riffeser (2002) into which we embed rambrain in order to overcome exactly these limitations set by main memory. High resolution images taken with state of the art instruments (see for example Lee et al, 2012Lee et al, , 2015 can easily be of about 14000 2 pixels in size, each. Typically kernels with several hundreds of free parameters are used which lead to an exemplary memory consumption by kernel matrices of ImageSize · KernelSize · (V alues + Errors) · f loat = 14000 2 · 400 · 2 · 4B ≈ 600GB.…”