The monitoring of GRB afterglows and the study of their host galaxies with the SAO RAS 6-m telescope from 1997

V. Sokolov et al.

The review of main results of first optical identifications of gamma-ray bursts (GRBs) under the joint Russian-Spanish observational program.

The first result of the GRB optical identification (with objects already known before): GRBs are identified with ordinary (or the most numerous in the Universe) galaxies up to 28 stellar magnitude and more.

The GRB hosts should not be special, but normal field star forming galaxies at comparable redshifts and magnitudes.

I. Optical identification: GRB host galaxiesand massive SFR at intermediate redshifts

Photometric observation of GRB 970508 in SAO RAS

CCD images of the optical transient of GRB 970508 (Zeiss-1000 and BTA)

Light curves of the optical transient of GRB 970508 in B, V, Rc and Ic bands (Zeiss-1000 and BTA)

Photometry of optical transients

Astronomy of GRBs with the 6-m telescope from 1998

A&A, 337, 356 (1998)BVRcIc light curves of GRB970508 optical remnant and colors of underlying host galaxyS.Zharikov, V. Sokolov, and Yu.Baryshev

A&A, 372, 438 (2001)Properties of the host galaxy of the gamma-ray burst 970508 and local star-forming galaxiesV.Sokolov, S.Zharikov, Yu.Baryshev, M.O. Hanski, K. Nilsson, P. Teerikorpi, L. Nicastro, and E. Palazzi

The Rc band field near GRB 970508 optical source. The image size is 33′′ × 33′′. N -top, E-right. The G1, G2, G3 are nearby galaxies. The arrow denotes an optical remnant of GRB970508.

Multi-color photometry and the Rc image of the GRB 980703 host galaxy field from BTA observations in

July 1998. The comparison of energy distribution obtained from BVRcIc fluxes (with consideration for the

shift in the ultra-violet part of spectrum for z=0.966) of this galaxy with energy distribution in spectra of galaxies of different Hubble types is shown. (The FWHM of each filter for its λ

eff with consideration for its

left shift for z=0.966 are denoted by dotted horizontal segments with bars.)

The massive SFR is seen in rest frame UV part spectra of star-forming galaxies. It is just a light of massive stars in the GRB hosts…

A&A 372, 438 (2001), Host galaxies of gamma-ray bursts:Spectral energy

distributions and internal extinction, V. V. Sokolov, T. A. Fatkhullin, A. J. Castro-Tirado, A. S. Fruchter et al.

A comparison of the GRB 970508 host galaxy broadband rest-frame (z = 0.835) flux spectrum with the SED of S5 template galaxies (see Connoly et al. 1995). The flux of the S5 template was scaled to obtain the best fit. Taking into account z, the FWHM of each filter for λ

eff is marked by dashed

horizontal lines with bars.

The population synthesis modeling: Comparison of modeled and observed fluxes in the filters B, V, R

c, Ic, J, H, K for the GRB 980703 host galaxy (z=0.9662).

If GRBs are associated with an active star formation, then we might expect the light of their host galaxies to be affected by internal extinction.

A&A 372, 438 (2001)

V.Sokolov, T.Fatkhullin, A.J.Castro-Tirado, A.S.Fruchter et al.

Host galaxies of gamma-ray bursts: Spectral energy distributions and internal extinction

Conclusions:

(a) In the case of the host galaxy of GRB 980703 (z=0.9662) the observed deficit in the B-band can be explained by the excess of extinction near 2200 A, which is characteristic of the extinction law similar to that of the Milky Way.

(b) There is a connection between GRB and H II regions (see Sect. 4, Ahn 2000), and together with the association of the host galaxy of GRB 990712 with H II galaxies (Vreeswijk et al. 2000b), again implies strong evidence for massive star formation.

z=0.9662

astro-ph/1102.1469, Fig.A.2 from Tayyaba Zafar, Darach Watson, Johan P. U. Fynbo, Daniele Malesani, Páll Jakobsson , and Antonio de Ugarte Postigo

GRB 070802 (z = 2.4541) afterglow were obtained with the VLT/FORS2. The 2175Å dust extinction feature is clearly seen in the optical spectrum of the afterglow.

A&A, 2001, 372, 438, by V.Sokolov, T.Fatkhullin, A.J.Castro-Tirado, A.S.Fruchter et al.

The best fit for the spectral energy distribution (SED) model to the BVR

cIc photometry of the GRB 970508 host galaxy (z=0.8349),

assuming the Calzetti extinction law. Also the upper limit of HST/NICMOS H-band is plotted (Left-hand). The observed wavelengths are given.

Bull. Spec. Astrophys. Obs., 2001, 51, 48-50

GRB 970508 host, MB rest = – 18.62

GRB 980703 host, MB rest = – 21.27

Bull. Spec. Astrophys. Obs., 2001, 51, 48-60 and 38-47 (astro-ph/0107399)

The observed R-band magnitude vs. spectroscopic redshift for the first 12 GRB host galaxies. The BTA R-band magnitudes (from Sokolov et al, 2001, A&A 372, 438 ) are marked with circles, while asterisks refer to the results of other authors.

Also the HDF F606W magnitude vs.photometrical redshift distribution is plotted. Catalog of the F606W magnitudes and photometrical redshifts was used from Fernández-Soto et al., 1999

A&A 372, 438-455 (2001)

Host galaxies of gamma-ray bursts:Spectral energy distributions and internal extinction

V. V. Sokolov, T. A. Fatkhullin, A. J. Castro-Tirado, A. S. Fruchter et al.

We conclude that long-duration GRBs seem to be closely related to vigorous massive star-forming in their host galaxies.

It should be noted that the SFR in the host galaxies is unlikely to be much higher than in galaxies at the same redshifts (z ≳ 1).

At this redshift the mean star formation rate is ~20-60 Mʘ / yr.

For these reasons we conclude that GRB host galaxies seem to be similar to field galaxies at the same redshift.

It is shown that these galaxies are usual ones with a high star formation rate, they are mainly observed in optical bands at redshifts about 1 and higher.

V. V. Sokolov, T. A. Fatkhullin, A. J. Castro-Tirado, A. S. Fruchter et al., 2001

GRB hosts should not to be special, but normal, faint, star-forming galaxies (the most abundant), detected at any z just because a GRB event has occurred

see S.Savaglio et al., 2008

2001 2008

Savaglio et al.2009 ApJ 691, 182

arXiv:0803.2718

II. The optical identification: The direct connection between long-duration GRBs and massive stars, GRBs and puzzles of Core-Collapse Supernovae (CCSNe)

… there are multiple long lines of evidence that long-duration (~ 1s-100s) GRBs are associated with death of massive stars, occurring in regions of active star formation embedded in dense clouds of dust and gas.

The review of main results of first optical identifications of gamma-ray bursts (GRBs) under the joint Russian-Spanish observational

program. The first result of the GRB optical identification (with objects

already known before): GRBs are identified with ordinary (or the most numerous in the Universe) galaxies up to 28 st. magnitudes and more. The GRB hosts should not be special, but normal field star-forming galaxies at comparable redshifts and magnitudes.

The second result of the GRB identification: now the long-duration GRBs are identified with (may be) ordinary (massive) core-collapse supernovae (CC-SNe, see in the poster report).

So, we have the massive star-forming in GRB hosts and massive star explosions - CCSN/GRB.

The search for differences between nearby SNe identified with GRBs and distant SNe which are to be identified with GRBs can be an additional observational cosmological test. We can ask a question analogous to that on GRB hosts:

do GRB SNe differ from usual (e.g. local) SNe? Generally, what are redshifts at which CC-SNe are quite different from local CC-SNe?

This could be the third important result of the GRB identification.

Thank you.

P.S. See also arXiv: 1111.1406 [astro-ph]