| BZs >gnuplot.ps Acta Polytechnica Vol. 51 No. 2/2011 Cosmology and the Subgroups of Gamma-ray Bursts A. Mészáros, J. Ř́ıpa, L. G. Balázs, Z. Bagoly, P. Veres, I. Horváth Abstract Both short and intermediate gamma-ray bursts are distributed anisotropically in the sky (Mészáros, A. et al. ApJ, 539, 98 (2000), Vavrek, R. et al. MNRAS, 391, 1741 (2008)). Hence, in the redshift range, where these bursts take place, the cosmological principle is in doubt. It has already been noted that short bursts should be mainly at redshifts smaller than one (Mészáros, A. et al. Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1133, 483 (2009); Mészáros, A. et al. Baltic Astron., 18, 293 (2009)). Here we show that intermediate bursts should be at redshifts up to three. Introduction In several papers, the authors have shown that there are three subgroups of gamma-ray bursts (GRBs); see Horváth, I. et al, ApJ, 713, 552 (2010) and the references therein. The three subgroups are shown in Figures 1–3 for different instruments (BATSE on the Compton Gamma-Ray Observa- tory, http://heasarc.gsfc.nasa.gov/docs/cgro/batse/; RHESSI satellite, http://science.nasa.gov/missions/ rhessi/; Swift satellite, http://heasarc.nasa.gov/docs/ swift/swiftsc.html). -0.5 0 0.5 1 1.5 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 lo g H 3 2 log T90 Fig. 1: Three subgroups of BATSEGRBs separated with respect to duration and hardness. T90 is in seconds; for definitions of hardness, durationT90 and formore details see Horváth et al.: A & A, 447, 23 (2006) Angular distribution of the BATSE GRBs The biggest number of detected GRBs is in the BATSE database. If the cosmological principle holds, then they should be distributed isotropically in the sky. In other words, these bursts may well serve as a test of isotropical distribution. These sky distribu- tions are shown in Figures 4–6. Fig. 2: Three similar subgroups of RHESSI GRBs. T90 is in seconds; Ř́ıpa et al.: A & A, 498, 399 (2009) −1 0 1 2 − 0 .2 0 .0 0 .2 0 .4 logT90 lo g H R Fig. 3: Three similar subgroups of Swift GRBs. T90 is in seconds; Horváth, I. et al.: ApJ, 713, 552 (2010) 82 Acta Polytechnica Vol. 51 No. 2/2011 0 360180 90 -90 short Fig. 4: Celestial distribution of short BATSE GRBs. These short GRBs are not distributed isotropically; Vavrek, R. et al.: MNRAS, 391, 1741 (2008) 0 360180 90 -90 medium Fig. 5: Celestial distribution of intermediate BATSE GRBs. They are also not distributed isotropically; Mészáros, A. et al.: ApJ, 539, 98 (2000); Vavrek, R. et al.: MNRAS, 391, 1741 (2008) 0 360180 90 -90 long Fig. 6: Celestial distribution of longBATSEGRBs. Long GRBs seem to be distributed isotropically; Vavrek, R. et al.: MNRAS, 391, 1741 (2008) Redshifts of short and intermediate GRBs In two previous papers it was already suggested that short GRBs are mainly at z < 1 (z is the red- shift); Mészáros, A. et al.: Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1133, 483 (2009); Mészáros, A. et al.: Baltic Astron., 18, 293 (2009). Hence, up to z ∼ 1 the cosmological principle is in doubt. In this paper we have also acquired the red- shifts of intermediate GRBs (from the Swift satellite; Horváth, I.: et al, ApJ, 713, 552 (2010)). The red- shifts of known Swift GRBs are shown in Figure 7. It is seen that these redshifts are up to z ∼ 3. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 1 2 3 4 5 6 7 z Fig. 7: Redshift distributions of Swift GRBs (short GRBs=solid line; intermediateGRBs=dashed line; long GRBs=dotted line). Intermediate GRBs are at even higher redshifts than short ones; Horváth, I. et al.: ApJ, 713, 552 (2010) Conclusion Of course, it is not fully necessary that the redshifts of intermediate GRBs from two different experiments (BATSE vs. Swift) are the same in the statistical sense. However, keeping this eventuality in mind, it seems that anisotropies exist up to z ∼ 3 in the spa- tial distribution of GRBs. Acknowledgement This study was supported by OTKA grant K77795, by Grant Agency of the Czech Republic grants No. 205/08/H005 and P209/10/0734, by project SVV 261301 of Charles University in Prague, and by Re- search Program MSM0021620860 of the Ministry of Education of the Czech Republic. References [1] Horváth, I., et al.: A & A, 447, 23 (2006). 83 Acta Polytechnica Vol. 51 No. 2/2011 [2] Horváth, I., et al.: ApJ, 713, 552 (2010). [3] http://heasarc.gsfc.nasa.gov/docs/cgro/batse/ [4] Mészáros, A., et al.: ApJ, 539, 98 (2000). [5] Mészáros, A., et al.: Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1133, 483 (2009). [6] Mészáros, A., et al.: Baltic Astron., 18, 293 (2009). [7] Řı́pa, J., et al.: A & A, 498, 399 (2009). [8] http://heasarc.nasa.gov/docs/swift/swiftsc.html. [9] Vavrek, R., et al.: MNRAS, 391, 1741 (2008). Attila Mészáros E-mail: meszaros@cesnet.cz Charles University Faculty of Mathematics and Physics Astronomical Institute V Holešovičkách 2, 180 00 Prague 8, Czech Republic Jakub Řı́pa E-mail: ripa@sirrah.troja.mff.cuni.cz Charles University Faculty of Mathematics and Physics Astronomical Institute V Holešovičkách 2, 180 00 Prague 8, Czech Republic Lajos G. Balázs E-mail: balazs@konkoly.hu Konkoly Observatory PO BOX 67, H-1525 Budapest, Hungary Zsolt Bagoly E-mail: zsolt@yela.elte.hu Lab. for Information Technology Eötvös University Pázmány P. s. 1/A, H-1518 Budapest, Hungary Péter Veres E-mail: veresp@elte.hu Lab. for Information Technology Eötvös University Pázmány P. s. 1/A, H-1518 Budapest, Hungary István Horváth E-mail: Horvath.Istvan@zmne.hu Dept. of Physics Bolyai Military University H-1581 Budapest, POB 15, Hungary 84