XRF 080109

Atish Kamble (University of Amsterdam), Sabyasachi Pal (NCRA/TIFR), D.
Bhattacharya (IUCAA,Pune), Ishwara-Chandra (NCRA/TIFR) report on behalf
of a larger GRB collaboration :

The Giant Metrewave Radio Telescope (GMRT), India observed the field of
XRF 080109/SN2008D (GCN 7159
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 , GCN 7178
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 ) on 11 Feb. 2008 (between 14.0 UT
and 19.0 UT) at 1280 MHz using a bandwidth of 32 MHz. The radio transient
was not detected down to a 3-sigma upper limit of 165 microJy at the
source location.

We thank GMRT and the National Centre for Radio Astrophysics (NCRA) staff.
This TOO was done under the GMRT Director's Discretionary Time.
GMRT is run by NCRA-TIFR, Pune (INDIA).

This messege may be cited.

Sabyasachi Pal (NCRA/TIFR), A. Kamble (University of Amsterdam) and
Dipankar Bhattacharya report on behalf of a larger collaboration

The position of XRF 080109 / SN 2008D was observed by Giant
Meterwave Radio Telescope (GMRT) as ToO at 1280 MHz. The observation took
place from UT 20.68 to 21.00 January, 2008. It was started after 11.11
days of the beginning of the burst (GCN 7172
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 ). The preliminary
analysis suggest that the upper limit of the flux density at the
position of XRF 080109 (GCN 7190
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 , GCN 7178
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 ) is 160 microJy with 235
micro Jy three sigma noise level. One sigma rms noise of the image is
45 microJy.

We thank the staffs of the GMRT who have made this ToO observation
possible and have given the data to us. GMRT is run by the National Centre 
for Radio Astrophysics of the Tata Institute of Fundamental Research.

A.J. van der Horst, C. Kouveliotou (NASA/MSFC) and A. Kamble (University
of Amsterdam) report on behalf of a larger collaboration:

"We observed the position of the NGC 2770 transient (GCN 7159
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 ) at 1.4 GHz
with the Westerbork Synthesis Radio Telescope at January 18 19.30 UT to
January 19 6.86 UT.
The galaxy NGC 2770 is resolved and the flux density of the galaxy core is
~4.4 mJy. The flux at the position of XRF 080109 / SN 2008D (GCN 7178
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 ) is
~1.1 mJy. There is no significant detection of a point source at this
position.
The one-sigma rms noise in the map is 48 microJy per beam.

We would like to thank the WSRT staff for scheduling and obtaining these
observations."

A.J. van der Horst, C. Kouveliotou (NASA/MSFC), R.A.M.J. Wijers and
A. Kamble (Univ. of Amsterdam) report on behalf of a larger collaboration:

"We observed the position of the NGC 2770 transient (GCN 7159
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 ) at 4.9 GHz
with the Westerbork Synthesis Radio Telescope at January 15 19.38 UT to
January 16 7.06 UT.
We detect a source with a flux density of 369 +/- 33 microJy at the
position of the radio counterpart reported at 8.46 GHz (GCN 7178
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 ).

We would like to thank the WSRT staff for scheduling and obtaining these
observations."

E. Pavlenko, A. Litvinchova, Yu. Efimov (CrAO),   A. Pozanenko (IKI) report
on behalf of a larger collaboration:

We observed the optical transient of XRF 080109/SN 2008D in NGC 2770
(Berger,  Soderberg, GCN 7159
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 ; Deng, Zhu, GCN 7160
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 ) on January 11,12,13 with
CrAO 2.6 telescope  (ZTSh).  On Jan. 11 observations were completed in BVRI
and on Jan. 12-13 in BR filters under good weather conditions.

Preliminary photometry of the transient XRF 080109/SN 2008D obtained after
galaxy subtracion and assuming  reference stars from USNO-A2.0
1200-06240802,  R=17.3, B=17.7 (the same star used in GCN 7162
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  (D'Elia et
al)):

Mid time (UT), Filter, magnutude

Jan. 12.04 B 18.63
Jan. 12.04 R 17.98
Jan. 13.01 B 18.74
Jan. 12.99 R 18.04
Jan. 13.93 B 18.84
Jan. 14.01 R 17.98

Typical statistical uncertainties of magnitude in the table above is better
than 0.01.  Magnitudes are not corrected for Galaxy reddening.

Within our observations  B magnitude is fading  on Jan. 11-13, while the R
brightness has a minimum on the night on Jan. 12/13.  Color (B-R) gradually
increasing from 0.65 (Jan. 12) to 0.86 (Jan. 14) which aslo may support of
SN dominance in light  curve of the transient (Malesani et al. GCN 7184
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 ).

D. Malesani (DARK), J. Sollerman (DARK and Univ. Stockolm), J.P.U. 
Fynbo, C.C. Thoene, D. Xu, J. Hjorth, G. Leloudas, P.M. Vreeswijk, D.J. 
Watson (DARK), P. Jakobsson (Univ. Herfordshire), T. Augusteijn, C. 
Villforth, S.-M. Niemi (NOT), report on behalf of a larger collaboration:

We observed SN 2008D with the Nordic Optical Telescope on Jan 13.05 and 
Jan 15.16 UT. Spectra were acquired covering the range 3700-7500 AA.

The spectra have evolved when compared to earlier epochs (Malesani et 
al., GCN 7169
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 ; Blondin et al., CBET 1205; Valenti et al., CBET 1205). 
The spectrum of Jan 15 now appears similar to that of the normal type-Ic 
SN 1994I a few days before maximum (Clocchiatti et al. 1996, ApJ, 462, 
462). In particular, the spectral features are clearly narrower than 
those of SN 1998bw and SN 2006aj at comparable epochs.

A plot of the NOT spectrum of Jan 15, compared with that of SN 1994I 
dereddened by A_V = 0.7 mag, is shown at the following URL:

http://www.astro.ku.dk/~malesani/GRB/080109/spec_Jan15.png

N. R. Tanvir, K. Wiersema (U. Leicester), A. J. Levan (U. Warwick),
A. Adamson and C. Davis (JACH) report on behalf of a larger collaboration:

We observed the field of XRF080109/SN2008D (GCN7159
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 , GCN7160
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 , GCN7169
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 )
with UKIRT/UFTI on 2008-01-12 (13 UT) and on 2008-01-15 (14 UT) in
good conditions, using the JHK filters on each occasion.  Between the
two epochs we estimate that the optical transient brightened by
approximately 0.35+/-0.05 mag in each band, confirming the onset of a
slowly rising supernova component.

M. Nysewander (STScI), D. Reichart, K. Ivarsen, J.A. Crain, A. LaCluyze (UNC) report:


We observed the optical transient of XRF 080109/SN 2008D in NGC
2770 (Berger & Soderberg, GCN 7159
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 ; Deng & Zhu, 7160) on
January 12 & 13 with two PROMPT telescopes.  Observations were
taken under good conditions, but at high airmass.


On both nights, the P5 telescope took continuous 60s R-band
exposures for ~3 hrs, while P4 cycled through repeated sequences of
15x60s in BVI for a total of ~1 hr in each filter.   
Assuming the star at RA: 09:09:37.28 Dec: +33:09:35.1 (to be
consistent with D'Elia et al. GCN 7162
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 ) to have B=17.25, V=16.71,
R=17.20, and I=16.67 (NOMAD and USNOB), we find the following
preliminary magnitudes for the OT at Jan 12.3 and 13.3:


Filter:   Exposure:  Mag1:   Mag2:


B         12 x 60s   18.6    18.3

V         5 x 60s    17.9    17.7

R         5 x 60s    18.0    18.0

I         5 x 60s    17.2    17.1



These values may suggest a slight brightening over the two nights, but are consistent with no variation. 


Observations are ongoing.

L.A. Antonelli (INAF/OAR), S. Valenti (Universita'  di  Ferrara),  D. 
Fugazza (INAF/OABr), V. D'Elia (INAF/OAR), E. Maiorano (INAF/IASF Bo), 
A. Magazzu' and N. Pinilla-Alonso (INAF/TNG), report on behalf of the 
CIBO collaboration:

We imaged the field of the galaxy NGC 2770 with the Telescopio 
Nazionale Galileo (TNG) [La Palma (Canary Islands)] equipped with NICS 
in the J,H,K  bands. Observations were performed on 2008 Jan 11, 
starting at 05:04:25 UT  for a total exposure  time of about 360 s in 
each filter.

The source reported by Deng & Zhu (GCN 7160
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 ), Thoene et al. (GCN 7161
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 ) 
and D'Elia et al. (GCN7162
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 ), is clearly detected in all bands with the 
following magnitudes: J=16.60+-0.13, H=16.33+-0.12, K=16.09+-0.12 
extimated using the 2MASS catalogue.  TNG NIR measures are consistent
with those reported by Modjaz et al. (GCN 7175
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  ).

Further analysis is underway.

GCN OPS NOTE(15jan08):  Per author's request, the last sentence in the
second paragraph was added.]

Shlomo Dado (Technion), Arnon Dar (Technion and CERN) and A. De Rujula (CERN) 
Report:

The source of XRF 080109 in NGC2770 (GCN 7159
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 ) may, for months or even 
years, be moving at a constant superluminal angular velocity of the order 
of ~ 10 mas / month , should XRF 080109 be an ordinary long GRB viewed 
off-axis (DDD2004). The Doppler factor, delta, the Lorentz factor, gamma, 
and the viewing angle, theta, for XRFs and GRBs are related by,
delta ~ 2 gamma / [ 1 + (gamma theta)^2 ].

For the average GRB gamma*theta ~ 1 and the isotropic energy is,
E_{iso} ~ 8 E52 erg. For GRBs and XRFs, E_{iso} scales with delta^3 (DD2004).
For XRF 080109, E_{iso} ~ E45 erg (GCN 7159
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 ) , resulting in delta ~ 2, and 
gamma*theta ~ 30, for a typical gamma ~ 500 to 1000. The angular velocity 
cited above is v/d, with v ~ gamma*delta*theta*c, and d = 27 Mpc.

Interpreted in the same way, GRB 980425 had delta ~ 20 and gamma*theta ~ 10.
Its X-ray plateau (which we attributed to the GRB's jetted source and 
NOT to SN1998bw, DDD2002,3,7) was flat for a few months, implying a 
constant gamma, delta and v for that period. For XRF 080109 this 
approximate result may be valid for ten times a longer period, the ratio 
of Doppler factors. For single-pulse events, this ratio is also an 
estimate of the ratio of pulse durations, ~ 50 s in the 1.5-10 keV X-ray 
band for GRB 980425, and ~ 500 s for XRF 080109. If XRF 080109 and
GRB  980425 are identical, but for distance and viewing angle, the prompt 
peak X-ray luminosity of GRB 980425 (Pian et al. 2000) can also be scaled
as in the above to predict 5 E42 erg/s in the Swift XRT band, in agreement
with the observed ~ 4 E52 erg/s (GCN 7159
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 ).

The energy flux of the X-ray plateau of XRF 080901 is expected to be 
suppressed relative to that of GRB 980425 by the ratio (10) of Doppler 
factors to the power 4.1 (DDD2007) and may be hard to detect, unless it is 
compensated by a large ISM density around SN2007D in NGC2770.

If the radio emission of the GRB980425/SN1998bw pair was dominated by the jet 
which produced its off-axis GRB (DDD2003), scaling the observed peak flux 
density at t ~ 10 days of GRB 980425 (F_p = 50 mJy at 3.5 cm, Kulkarni et al. 
1998) yields, for XRF 080109a in a similar environment, a rough estimate of a 
peak date at ~100 days and a 35-cm peak flux of ~1.4 mJy, which may be 
observable at this wavelenght and nearby ones. Radio observations could even 
resolve two separated radio sources, SN2008D and the moving source of XRF 
090109. It is also not excluded that there is more than one moving source.

DDD2002: A&A, 388, 1079 (2002)
DDD2003: A&A, 401, 243 (2003)
DDD2004: A&A, 422, 381 (2004)
DDD2007: arXiv0712.1527 (2007)
Kulkarni, S. R., et al. 1998, astro-ph/9807001
Pian, E., et al. 2000, ApJ, 536, 778