1. Soft gamma repeaters outside the Local group
S.B. Popov, B.E. Stern
(astro-ph/ ; astro-ph/ )

2. Abstract
We propose that the best sites to search for SGRs outside the Local group are galaxies with active massive star formation.
We searched for giant flares from near-by starforming galaxies (M82, M83, NGC 253, NGC 4945) and from “supernova factories” (Arp 299 and NGC 3256) in the BATSE catalogue. No good candidates are found.
We discuss this result.

3. SGRs: periods and giant flares
P, sec
Giant flare
+candidates
8.0
5 March 1979
6.4
18 June 1998
(?)
7.5
24 Dec 2004
5.2
27 Aug 1998
See a review in
Woods, Thompson
astro-ph/

4. Main types of activity of SGRs
Weak burst. L<1041 erg/s
Intermediate bursts. L=1041–1043 erg/s
Giant bursts. L<1045 erg/s
Hyperflares. L>1046 erg/s
See a review in
Woods, Thompson
astro-ph/

5. SGRs and starformation
Possibility of a SGR detection outside the Local group of galaxies
Starforming galaxies are the best sites to search for extragalactic SGRs
<5 Mpc. M82, M83, NGC 253, NGC 4945
About 40 Mpc. Arp 299, NGC 3256
Possible candidates in the BATSE catalogue of short GRBs

6. Assumed time profiles of the initial spike of the 05 March 1979 event

7. The probability of detection by BATSE of a giant flare

8. BATSE GRBs associated with near-by starbursts

9. The probability of detection by BATSE of a hyperflare

10. BATSE GRBs associated with “supernova factories”

11. Virgo cluster analysis
We also searched for GFs and HFs from
the Virgo cluster direction in BATSE data.
Nothing was found (see astro-ph/ ).
Renormalizing this result to our Galaxy
we obtain that HFs should be as rare as
one in 1000 years.
This estimate is in correspondence with
results obtained by other authors
(Palmer et al. 2005, Ghirlanda et al. 2005).

12. Other ideas about relations between SGR and SF galaxies
Eichler (2005) discussed a possible connection
between SGRs and high energy cosmic rays.
In this sense it is interesting to remember that
several groups (for example, Giller et al.)
reported the discovery of associations
between UHECR and starforming galaxies.
In particular, Giller et al. discussed Arp 299
and NGC 3256.

13. Evolution of SGR activity
Usually the rate of GFs is assumed to be constant.
However, all types of activity of NSs normally decay with time
For example, the rate of starquakes is expected to evolve as t5/2
If the rate of GFs evolves proportionally to time or faster then:
The probability to detect a SGR is higher for younger objects
We can face “an energy crisis”, i.e. there is not enough energy
to support strong burst in SGRs youth.
All these items can be important in estimation of the
probability of detection of extragalactic SGRs.

14. Conclusions Close galaxies with enhanced starformation
rate are the best sites to search for extragalactic SGRs
Our search in the BATSE catalogue did not provide good candidates
Reasons for the non-detection
- overestimates of the peak flux
- naïve scaling of the SGRs number is not valid
- ??????