Description
We query the following data sources to compile the lightcurves of optical transients (introduced with v2.15.0):- Asteroid Terrestrial-impact Last Alert System (ATLAS)
- ASAS-SN
- Fink broker (access to data from the Zwicky Transient Facility (ZTF))
We search for the nearest source around the selected event and retrieve all available photometric observations. ZTF observations are retrieved via the Fink broker and include all available data, i.e. we do not limit ourselves to the Fink data quality criteria. It should be noted that ASAS-SN provides the raw photometric values at the location of sources in the ASAS-SN catalog while ZTF/Fink and ATLAS provide difference magnitudes after substracting archival measurements. In general this means that ASAS-SN provides combined measurement of the host galaxy and the transient, while the other observatories provide direct measurements of the luminosity of the transient event.
Finally, we apply filters to the data points of all observatories to remove entries with (mag < 0.1) as well as entries with large uncertainties (mag_err > 0.5). ATLAS measurements are combined into intervals that are 90 minutes long. The original measurements are shown with semi-transparent markers. ZTF data that is flagged by the Fink broker as 'bad quality' is also shown in the same way. Upper limits are shown as downward facing triangles. The resulting figure shows all selected datapoints. The X-axis of the figure is rescaled to match this data range and therefore does not necessarily correspond to the user-defined time range. An example of the resulting lightcurve figure is shown here:
Default lightcurves are updated twice per day (early morning and mid-day UTC) for all classified optical transients detected within the last 30 days. The lightcurves cover 5 days before the detection of the event and up to 30 days after it. The date of the creation of the figure is given on the figure for reference. Users can create customized lightcurves by opening the small menu indicated by the downward facing arrow (in Science mode). The user can then selected the desired time range and (if sufficient access rights exist) add data from additional observatories and amateur astronomer networks.