[vsnet-grb-info 8479] GRB 091003: WHT ACAM observations

GCN Circulars gcncirc at capella.gsfc.nasa.gov
Tue Oct 6 02:11:50 JST 2009 

TITLE:   GCN CIRCULAR
NUMBER:  9995
SUBJECT: GRB 091003: WHT ACAM observations
DATE:    09/10/05 17:11:44 GMT
FROM:    Klaas Wiersema at U of Leicester  <kw113 at star.le.ac.uk>

K. Wiersema, N. Tanvir (Leicester), A. Levan (Warwick) and C. Benn (ING) 
report on behalf of a larger collaboration:

We observed the afterglow of Fermi GRB 091003 (Rau GCN 9983; McEnery et al 
GCN 9985; Starling & Beardmore GCN 9986) with the William Herschel 
Telescope, using the ACAM instrument. We took a 60 and a 250 second 
exposure in imaging mode, starting at 21:11 UT, October 4 (1.69 days after 
burst).
The afterglow is clearly detected, with r = 21.33 +/- 0.11 (calibrated to 
SDSS field stars), at position:

RA (J2000) = 16:46:04.687
Dec (J2000) = +36:37:30.76
with uncertainty 0.3 arcseconds.

We obtained spectroscopy with ACAM immediately after, at high airmass. Two 
900 second exposures were obtained using the 400V grism and a 1 arcsecond 
slit. Faint continuum emission is detected over the 4000-9300 A range. No 
strong absorption or emission lines are detected. The detection of 
continuum at 4000A gives a upper limit to the redshift of 2.3.










> 
> Hi guys
> 
> Attached the wavelength calibrated spectrum of the afterglow (disp.fits) - I 
> can't get it much better than this. Too bad they put the afterglwo right on 
> that crappy part of the slit. No lines that I believe, with EW<10 A between 
> 4000-7500A. Continuum is detected over the whole range, so the redshift will 
> be less than z< (4000/1215)-1 = 2.3.
> 
> Attached also the bright source spectrum (dstar.fits) - it's clearly a star 
> (it has balmer lines at z=0).
> 
> I'll do the photometry now.
> 
> K
> 
> 
> 
> 
> 
> 
> 
> 
>> I've put the bias subtracted images (and the bias frame I subtracted)
>> in:  /h/nrt3/RAID/GRB/grb091003
>> 
>> good luck!
>> 
>> N.
>> 
>> On Oct 05, 2009 12:50 PM, Klaas Wiersema <kw113 at star.le.ac.uk> wrote:
>> 
>>> 
>>> I'm happy to give it a go, after lunch.
>>> 
>>> K
>>> 
>>> 
>>>> Hi all,
>>>> 
>>>> I've taken a look at the WHT data from last night.  It doesn't look as if 
>>>> it
>>>> will be easy to deal with.  The slit profile must be a bit ratty (or 
>>>> dusty),
>>>> which is the first problem -- and dealing with that isn't so simple since
>>>> the spectrum is tilted and the sky lines curved.  I don't know if there
>>>> are existing spectral extraction packages that can easily (and 
>>>> efficiently)
>>>> deal with this.
>>>> 
>>>> Anyway, I only got as far as debiasing all the frames, so if anyone else
>>>> wants to have a go, starting with those frames, let me know. 
>>>> 
>>>> Unfortunately it looks like there is probably little or nothing there 
>>>> anyway,
>>>> but it is hard to be quite sure of that without pushing the reduction a 
>>>> little
>>>> further.
>>>> 
>>>> cheers
>>>> Nial
>>>> 
>>>> -------- Original Message --------
>>>> From: Chris Benn <crb at ing.iac.es>
>>>> To: Nial Tanvir <nrt3 at star.le.ac.uk>
>>>> Date: Oct 05, 2009 07:14 AM
>>>> Subject: Re: GRB 091003
>>>> 
>>>> 
>>>> Hi Nial
>>>> 
>>>> We tried this at high airmass through light cirrus. The GRB was clearly
>>>> visible on R-band images, but there's only a hint of a detection in the
>>>> raw spectroscopic frame.
>>>> 
>>>> If we have better conditions tonight (Oct 5), is it worth trying again,
>>>> or will it have faded?
>>>> 
>>>> In case you want to look at the data, ftp to ftp.ing.iac.es and log in as
>>>> ftpwht1, password ftpCOMPTE1. The run numbers start with the digits
>>>> 1372:
>>>> 013-015 - images (Sloan R)
>>>> 017-018 - spectra (2 * 900 sec) 017-018
>>>> The object should lie near x = 1059
>>>> 020-024 - W flats
>>>> 025-026 - CuNe arcs (no CuAr available)
>>>> 027-031 - biases
>>>> 
>>>> Chris
>>>> 
>>>> 
>>>> On Sun, 4 Oct 2009, Nial Tanvir wrote:
>>>> 
>>>>> The star to the NE of the afterglow is at:
>>>>> 
>>>>> 16 46 05.86   +36 37 44.0
>>>>> 
>>>>> good luck.
>>>>> 
>>>>> N.
>>>>> 
>>>>> On Oct 04, 2009 10:23 PM, Chris Benn <crb at ing.iac.es> wrote:
>>>>> 
>>>>>> Clearly visible in 60 sec, looks as though R < 23, but slit
>>>>>> acquisition will be challenging. Do you have the coordinates of one of
>>>>>> the bright stars, so that I can blind offset?
>>>>>> 
>>>>>> Chris
>>>>>> 
>>>>>> 
>>>>>> On Sun, 4 Oct 2009, Nial Tanvir wrote:
>>>>>> 
>>>>>>> great, thanks Chris.
>>>>>>> 
>>>>>>> I realised I forgot to put the GRB name in the subject line
>>>>>>> of the request, so here it is above!
>>>>>>> 
>>>>>>> cheers
>>>>>>> Nial
>>>>>>> 
>>>>>>> On Oct 04, 2009 09:47 PM, Chris Benn <crb at ing.iac.es> wrote:
>>>>>>> 
>>>>>>>> Thanks Nial, we'll have a go.
>>>>>>>> 
>>>>>>>> Cheers
>>>>>>>> 
>>>>>>>> Chris
>>>>>>>> 
>>>>>>>> 
>>>>>>>> On Sun, 4 Oct 2009, Nial Tanvir wrote:
>>>>>>>> 
>>>>>>>>> Dear Chris
>>>>>>>>> 
>>>>>>>>> we realise it is a commissioning night, but we are forwarding
>>>>>>>>> information on a recent GRB in case there is an opportunity
>>>>>>>>> to observe it.
>>>>>>>>> 
>>>>>>>>> The coordinates are:
>>>>>>>>> 
>>>>>>>>> RA (J2000): 16 46 4.75
>>>>>>>>> Dec (J2000): +36 37 29.0
>>>>>>>>> as you can see, it is only available early in
>>>>>>>>> the night (i.e. as soon as possible, as it is already
>>>>>>>>> going down).
>>>>>>>>> 
>>>>>>>>> Our suggestion would be to first attempt an R-band image
>>>>>>>>> with ACAM (e.g. 5 minutes), and then if the afterglow
>>>>>>>>> seems bright enough (e.g. R<23), a 2x15 minute low resolution
>>>>>>>>> spectrum.
>>>>>>>>> 
>>>>>>>>> For your information, the interest in this burst lies in
>>>>>>>>> the fact that it was initially detected at high (GeV) energies
>>>>>>>>> by the Fermi/LAT. The LAT does not detect many GRBs,
>>>>>>>>> and those which are detected provide new constraints on
>>>>>>>>> theoretical models, and potentially tests of quantum gravity
>>>>>>>>> models -- but interpretation is critically dependent on obtaining
>>>>>>>>> a redshift.
>>>>>>>>> 
>>>>>>>>> A finder based on the DSS is attached -- the position
>>>>>>>>> of the afterglow being marked. The field is North up and
>>>>>>>>> East left, and 3 arcmin on a side.
>>>>>>>>> 
>>>>>>>>> Best regards
>>>>>>>>> Nial
>>>>>>>>> 
>>>>>>>>> nrt3 at star.le.ac.uk
>>>>>>>>> +44 7980 136499
>>>>>>>>> 
>>>>>>>>> a.j.levan at warwick.ac.uk
>>>>>>>>> +44 7714250373
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>>> --
>>> **********************************************************
>>> dr. Klaas Wiersema
>>> X-Ray and Observational Astronomy Group
>>> Department of Physics and Astronomy
>>> University of Leicester
>>> University Road, Leicester, LE1 7RH, United Kingdom
>>> tel: +44 116 252 2377 (Leics)
>>> **********************************************************
>> 
>> 
>> 
>> 
> 
>

-- 
**********************************************************
dr. Klaas Wiersema
X-Ray and Observational Astronomy Group
Department of Physics and Astronomy
University of Leicester
University Road, Leicester, LE1 7RH, United Kingdom
tel: +44 116 252 2377   (Leics)
**********************************************************

More information about the vsnet-grb-info mailing list