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J/A+A/601/A83       GRB 140506A X-shooter spectra               (Heintz+, 2017)

Steep extinction towards GRB 140506A reconciled from host galaxy observations: Evidence that steep reddening laws are local. Heintz K.E., Fynbo J.P.U., Jakobsson P., Kruehler T., Christensen L., Perley D.A., Ledoux C., Noterdaeme P., Watson D., Selsing J., Rhodin H., Schulze S., Tanvir N.R., Moller P., Goldoni P., Xu D., Milvang-Jensen B. <Astron. Astrophys. 601, A83 (2017)> =2017A&A...601A..83H (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Spectroscopy Keywords: gamma-ray burst: general - gamma-ray burst: individual: GRB140506A - dust, extinction - galaxies: individual: GRB 140506A host Abstract: We present the spectroscopic and photometric late-time follow-up of the host galaxy of the long-duration Swift γ-ray burst GRB140506A at z=0.889. The optical and near-infrared afterglow of this GRB had a peculiar spectral energy distribution (SED) with a strong flux-drop at 8000Å (4000Å rest-frame) suggesting an unusually steep extinction curve. By analysing the contribution and physical properties of the host galaxy, we here aim at providing additional information on the properties and origin of this steep, non-standard extinction.We find that the strong flux-drop in the GRB afterglow spectrum at <8000Å and rise at <4000Å (observers frame) is well explained by the combination of a steep extinction curve along the GRB line of sight and contamination by the host galaxy light at short wavelengths so that the scenario with an extreme 2175Å extinction bump can be excluded. We localise the GRB to be at a projected distance of approximately 4kpc from the centre of the host galaxy. Based on emission-line diagnostics of the four detected nebular lines, Hα, Hβ, [OII] and [OIII], we find the host to be a modestly star forming (SFR=1.34±0.04M/yr) and relatively metal poor (Z=0.35+0:150.11Z) galaxy with a large dust content, characterised by a measured visual attenuation of AV=1.74±0.41mag. We compare the host to other GRB hosts at similar redshifts and find that it is unexceptional in all its physical properties. We model the extinction curve of the host-corrected afterglow and show that the standard dust properties causing the reddening seen in the Local Group are inadequate in describing the steep drop. We thus conclude that the steep extinction curve seen in the afterglow towards the GRB is of exotic origin and is sightline-dependent only, further confirming that this type of reddening is present only at very local scales and that it is solely a consequence of the circumburst environment. Description: We acquired late-time photometry with the FOcal Reducer and low dispersion Spectrograph 2 (FORS2) instrument at the ESO/VLT on 2015 April 29 and June 16. To supplement the FORS2 and Spitzer imaging we acquired additional spectra centred on the host galaxy using the X-shooter spectrograph mounted at the ESO/VLT, covering a wavelength range of 3000-24800Å (3000-5600, 5500-10200 and 10200-24800Å for the UVB, VIS and NIR arm, respectively). The follow-up observations of this host were spread out over three nights, on 2015 May 15, June 15 and September 30. Objects: ---------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------- 18 27 06.04 -55 38 08.7 GRB140506A = GRB 140506A ---------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file nir.dat 44 18355 X-shooter NIR spectrum uvb.dat 44 6399 X-shooter UVB spectrum vis.dat 44 11750 X-shooter VIS spectrum
Byte-by-byte Description of file: nir.dat uvb.dat vis.dat
Bytes Format Units Label Explanations
1- 11 E11.6 0.1nm Lambda Wavelength 13- 24 E12.6 0.1mW/m2/nm Flux Flux (in erg/s/cm2/Å) 26- 36 E11.6 0.1mW/m2/nm e_Flux rms uncertainty on Flux 38- 44 F7.5 --- Corr Error slit loss correction
Acknowledgements: Kasper Elm Heintz, heintz(at)dark-cosmology.dk
(End) Patricia Vannier [CDS] 28-Apr-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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