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EROS light curve data base

C. Afonso, J. -N. Albert, R. Ansari, E. Aubourg, J. P. Beaulieu, T. Blaineau, C. Coutures, F. Derue, J. F. Glicenstein, B. Goldman, C. Hamadache, T. Lasserre, L. Le Guillou, E. Lesquoy, C. Magneville, B. Mansoux, M. Moniez, N. Palanque-Delabrouille, O. Perdereau, J. Rich. M. Spiro, P. Tisserand

TL;DR

The paper presents the public EROS-2 light-curve database, detailing the instrument, observing program, and data processing pipeline used to monitor tens of millions of stars for microlensing and variability. It introduces the four interconnected data products (object catalogs, light curves, and image catalogs) and quantifies photometric and astrometric precision, emphasizing the Gaia-based astrometric alignment. By making 85–86 million stellar light curves publicly available through CDS, the work enables time-domain astronomy applications, cross-validation with LSST-era surveys, and retrospective examination of transient events. The release thereby provides a valuable, long-baseline resource for studying microlensing, variable stars, and other transient phenomena across multiple Galactic environments.

Abstract

The EROS project (Expérience de Recherche d'Objets Sombres) carried out photometric surveys of dense stellar fields towards the Magellanic Clouds (LMC and SMC), the Galactic Bulge and Galactic spiral arms, over the period 1990-2003. The main goal of the experiment was to search for the Galactic Dark Matter in the form of massive compact objects (machos), through the gravitational microlensing effect. The historical record of the flux variations of the monitored stars by EROS-2 will be a unique asset for time domain astronomy and to complement current and future searches of transient sources. We describe the set of light curves obtained by EROS-2 program over the years 1996 to 2003, monitoring more than 86 million stars, which is publicly released through the Centre de Données de Strasbourg (CDS). The numbers of light curves in this data set are 28.7 and 4.0 million in LMC, respectively SMC, 42.9 million in the Galactic Bulge and 10.4 million towards the Galactic spiral arms, with several hundred measurements for each object. Data from EROS-1 is also being released. The object catalog and light curves and images are accessible through the CDS portal. This will be useful for checking the past behavior of newly discovered variable objects.

EROS light curve data base

TL;DR

The paper presents the public EROS-2 light-curve database, detailing the instrument, observing program, and data processing pipeline used to monitor tens of millions of stars for microlensing and variability. It introduces the four interconnected data products (object catalogs, light curves, and image catalogs) and quantifies photometric and astrometric precision, emphasizing the Gaia-based astrometric alignment. By making 85–86 million stellar light curves publicly available through CDS, the work enables time-domain astronomy applications, cross-validation with LSST-era surveys, and retrospective examination of transient events. The release thereby provides a valuable, long-baseline resource for studying microlensing, variable stars, and other transient phenomena across multiple Galactic environments.

Abstract

The EROS project (Expérience de Recherche d'Objets Sombres) carried out photometric surveys of dense stellar fields towards the Magellanic Clouds (LMC and SMC), the Galactic Bulge and Galactic spiral arms, over the period 1990-2003. The main goal of the experiment was to search for the Galactic Dark Matter in the form of massive compact objects (machos), through the gravitational microlensing effect. The historical record of the flux variations of the monitored stars by EROS-2 will be a unique asset for time domain astronomy and to complement current and future searches of transient sources. We describe the set of light curves obtained by EROS-2 program over the years 1996 to 2003, monitoring more than 86 million stars, which is publicly released through the Centre de Données de Strasbourg (CDS). The numbers of light curves in this data set are 28.7 and 4.0 million in LMC, respectively SMC, 42.9 million in the Galactic Bulge and 10.4 million towards the Galactic spiral arms, with several hundred measurements for each object. Data from EROS-1 is also being released. The object catalog and light curves and images are accessible through the CDS portal. This will be useful for checking the past behavior of newly discovered variable objects.

Paper Structure

This paper contains 21 sections, 2 equations, 16 figures, 1 table.

Table of Contents

  1. Introduction
  2. EROS-2 program
  3. The instrument
  4. The survey
  5. Data processing pipeline
  6. PEIDA
  7. Post-processing
  8. Photometric and astrometric precision
  9. The data set description
  10. Conclusions
  11. Data availability
  12. Detailed description of EROS-2 table columns
  13. List of EROS-2 catalogs (xcatinfo)
  14. EROS-2 Object catalog (xcat)
  15. EROS-2 Light curves (xtime)
  16. ...and 6 more sections

Figures (16)

  • Figure 1: The EROS LMC (left) and SMC (right) fields superimposed on images of the full Gaia-dr3 catalog numbers counts gaia_2023AA...674A...1G, extracted using hipstofits. The EROS-2 fields are shown as solid red lines, while the EROS-1 fields are shown in cyan for the survey with the T40/CCD camera and in yellow for the LMC Schmidt plates.
  • Figure 2: Map of the Galactic-plane fields regularly observed by EROS-2. The colored contours correspond to the EROS-2 fields, color-coded for the 5 regions. The background image shows the density of the full Gaia-dr3 sources gaia_2023AA...674A...1G, with a square root scale, as extracted from the CDS using hips2fits. Some artifacts in the form of stripes can be seen in the Galactic bulge area, reflecting Gaia's scanning strategy impact on its source detection threshold.
  • Figure 3: The MARLY telescope, equipped with two EROS CCD cameras.
  • Figure 4: Left: The EROS-2 blue camera cryostat. Right: a view of the mosaic, showing $2 \times 4$ array of $2048 \times 2048$ CCD sensors.
  • Figure 5: The calculated transmission of the EROS-2 optics 1997PhDT.........2B.
  • ...and 11 more figures