J/A+A/676/A107 S255IR NIRS3 NIR adaptive optics imaging (Fedriani+, 2023)
The sharpest view on the high-mass star-forming region S255IR.
Near infrared adaptive optics imaging of the outbursting source NIRS3.
Fedriani R., Caratti o Garatti A., Cesaroni R., Tan J.C., Stecklum B.,
Moscadelli L., Koutoulaki M., Cosentino G., Whittle M.
<Astron. Astrophys. 676, A107 (2023)>
=2023A&A...676A.107F 2023A&A...676A.107F (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; YSOs
Keywords: ISM: jets and outflows - ISM: kinematics and dynamics -
stars: pre-main sequence - stars: massive -
stars: individual: S255IR NIRS3 - techniques: high angular resolution
Abstract:
Massive stars have an impact on their surroundings from early in their
formation until the end of their lives. However, very little is known
about their formation. Episodic accretion may play a crucial role in
the process, but only a handful of observations have reported such
events occurring in massive protostars.
We aim to investigate the outburst event from the high-mass
star-forming region S255IR where the protostar NIRS3 recently
underwent an accretion outburst. We follow the evolution of this
source both in photometry and morphology of its surroundings.
We performed near infrared adaptive optics observations on the S255IR
central region using the Large Binocular Telescope in the Ks
broadband as well as the H2 and Brγ narrow-band filters with
an angular resolution of ∼0.06arcsec, close to the diffraction
limit.
We discovered a new near infrared knot north-east of NIRS3 that we
interpret as a jet knot that was ejected during the last accretion
outburst and observed in the radio regime as part of a follow-up after
the outburst. We measured a mean tangential velocity for this knot of
450±50km/s. We analysed the continuum-subtracted images from H2,
which traces jet-shocked emission, and Brγ, which traces
scattered light from a combination of accretion activity and UV
radiation from the central massive protostar. We observed a
significant decrease in flux at the location of NIRS3, with K=13.48mag
being the absolute minimum in the historic series.
Our observations strongly suggest a scenario where the episodic
accretion is followed by an episodic ejection response in the near
infrared, as was seen in the earlier radio follow-up. The ∼2um
photometry from the past 30 years suggests that NIRS3 might have
undergone another outburst in the late 1980s, making it the first
massive protostar with such evidence observed in the near infrared.
Description:
Reduced images from the Large Binocular Telescope (LBT) of the S255IR
massive star-forming region. Below we give further details extracted
from text in the paper. Observations were taken on 13 February 2022
with the Large Binocular Telescope (LBT), in particular the SX
telescope with an 8.4m primary mirror and using the LBT Utility
Camera in the Infrared (LUCI) instrument (programme ID: UV-2022A-004,
PI: J.C. Tan). Adaptive optics assisted mode was used with the
Single conjugated adaptive Optics Upgrade for LBT
SOUL (Pinna et al., 2016, in Adaptive Optics Systems V, ed.
E. Marchetti, L. M. Close, & J.-P. Veran, Vol. 9909, International
Society for Optics and Photonics (SPIE), 99093V).
The N30 camera with a pixel scale of 0.015arcsec and field of view
(FoV) of 30arcsec*30arcsec was used. The filters Ks, H2), and
Brγ, which are centred at the wavelengths 2.163, 2.124, 2.170um,
respectively, were employed.
Images were centred around S255IR NIRS3, with central coordinates of
the image RA(J2000)=06:12:54.355, Dec(J2000)=+17:59:23.748. The AO
guide star we used (i.e. 2MASSJ06125505+1759289
RA(J2000)=06:12:55.049, Dec(J2000)=+17:59:28.896, R=14.8mag) is
located 14arcsec from NIRS3.
The Strehl ratio was 0.2, and the final full width half maximum (FWHM)
at the position of the AO guide star was ∼0.06arcsec for all three
filters (derived by fitting Moffat profiles, namely, close to the LBT
diffraction limit.
The data were reduced and flux calibrated with custom Python scripts
using the Python packages ccdproc, astropy and photutils. The flux
calibration was performed by matching field stars with the UKIRT
Infrared Deep Sky Survey (UKIDSS) point source catalogue, for which we
achieved an accuracy of ∼0.06mag. The data were astrometrically
corrected by matching stars to the Gaia DR3 catalogue retrieved with
astroquery. We were able to match seven Gaia stars in our FoV and have
a final residual for the astrometry of 0.034arcsec.
Objects:
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RA (2000) DE Designation(s)
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06:12:54.355 +17:59:23.748 S255IR-NIRS3 = [TGJ91] S255 NIRS 3
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 135 3 List of fits images
fits/* . 3 *Individual fits images
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Note on fits/*: The images in he filter H2 and BrG have been registered to the
Ks image. They are astrometrically corrected using gaia DR3.
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 25 F6.4 arcsec/pix scale [0.0149] Scale of the image
27- 30 I4 --- Nx [2048] Number of pixels along X-axis
32- 35 I4 --- Ny [2048] Number of pixels along Y-axis
37- 60 A24 "datime" Obs.date Observation date
62- 66 I5 Kibyte size Size of FITS file
68- 82 A15 --- FileName Name of FITS file, in subdirectory fits
84-135 A52 --- Title Title of the FITS file
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Acknowledgements:
Ruben Fedriani, fedriani(at)iaa.es
(End) Patricia Vannier [CDS] 28-Jul-2023