The WATCH solar X-ray burst catalogue

Abstract

Abstract. The WATCH experiment aboard the GRANAT satellite provides observations of the Sun in the deka-keV range covering the years 1990 through mid-1992. An introduction to the experiment is given followed by an explanation of how the WATCH solar burst catalogue was created. The different parameters listed for each burst is given and are furthermore explained.Key words: catalogs -sun: activity; flares; X-rays, gamma raysThe Danish Wide Angle Telescope for Cosmic Hard X-rays (WATCH) experiment was launched aboard the Russian GRANAT satellite on the 1st of December 1989 and is composed of four WATCH units. One of these units has the Sun in its field-of-view and observes in the deka-keV range with approximately 6.5 s time resolution. WATCH is based on the rotation-modulation-collimator (RMC) principle. The WATCH instrument contains two independent detectors, one based on a NaI-the other on a CsIscintillator. The direction of the incoming X-rays can thus be derived from the modulation of the detected signal as a function of the rotation phase of the collimator grids. The modulation patterns are used in determining the positions and strengths of the X-ray sources in the field-ofview. In this work observations from the NaI scintillator have been used. For more details on the WATCH experiment see Lund (1985) and for the solar observations see Crosby (1996) and Crosby et al. (1997).The WATCH solar burst catalogue consists of 1551 flares and was created by systematically going through the approximately 2.5 years of count rate time profile obSend offprint requests to: N. CrosbyThe catalogue is available in electronic form only at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html servations. WATCH observations are grouped in dumps associated to telemetry periods.To be characterized as being of solar origin a burst had to pass the following four selection criteria (see Crosby et al. 1997, for more detail):1. The modulation pattern must correspond to the solar one.2. A signature in the GOES data has to be observed (a classified GOES flare or a significant flux enhancement). The corresponding WATCH peak is not necessarily at the same time as that of the GOES peak.3. The peak count rate of the WATCH event has to be above the three sigma WATCH background level. This criterion eliminates 5 very small events.4. The event must not be significantly contaminated by particles.The WATCH solar burst catalogue is divided into months (Tables 2 through 27) and for each month the events are listed in chronological order (one line per event). The information listed in each line (from left to right) is as follows:For each burst the dump number (DN) where the burst is recorded and the day (DAY) when the burst began is listed. Thereafter the total peak count rate (P t ) in counts per bin and the duration in seconds (T acc ) of the bin are indicated. This information refers to observations recorded in the low-energy channel of WATCH. The time accumulation (s/bin) for the count rate...

Untitled

“…Such events may show distinct time differences in absolute values; however, the time difference may be rather small compared to the overall endurance of the event. Moreover, since the importance of a flare and its duration are correlated (e.g., Crosby et al, 1998;Veronig et al, 2002a,c) considering only absolute time differences may introduce a bias towards intense events (for further discussion see Veronig et al, 2002a). From the present data set we derive a median duration of 2.0 min for the BATSE HXR bursts.…”

The transient hard X-ray tail of GX 17+2: New BeppoSAX results

“…On the other hand, if the two electron populations are physically related, a possible origin of the non-thermal component is in processes of magnetohydrodynamic turbulence occurring in the corona (e.g., magnetic reconnection), in analogy with what observed in the solar corona (Crosby et al 1998; see also the review by Coppi 1999). In this case particle acceleration cannot be 100% efficient in the production of non-thermal high-energy particles (e.g., Zdziarski et al 1993).…”

Microflares and the Statistics of X-ray Flares

“…The sensitivity and bias effects (whether instrumental or observational) result in a clear change in the distributions at the extremes, but they can also have a more subtle effect on Table 2.2 (Crosby et al 1993;Crosby et al 1998;) (left to right, top to bottom). Another example (Veronig et al 2002a) is shown in Figure 1 the power law in the mid-regions.…”