J/ApJ/940/L26 GTC 8-13um spectropolarimetry toward CygOB2-12 (Telesco+, 2022)
Mid-infrared polarization of the diffuse interstellar medium toward CygOB2-12.
Telesco C.M., Varosi F., Wright C., Draine B.T., Fernandez Acosta S.J.,
Packham C.
<Astrophys. J., 940, L26 (2022)>
=2022ApJ...940L..26T 2022ApJ...940L..26T
ADC_Keywords: Stars, giant; Polarization; Spectra, infrared; Interstellar medium
Keywords: Diffuse interstellar clouds ; Spectropolarimetry ; Silicate grains
Abstract:
We present the first mid-IR detection of the linear polarization
toward the star CygOB2-12, a luminous blue hypergiant that, with
AV∼10mag of foreground extinction, is a benchmark in the study of
the properties of dust in the diffuse interstellar medium. The
8-13µm spectropolarimetry, obtained with the CanariCam multimode
camera at the Gran Telescopio CANARIAS shows clear trends with
wavelength characteristic of silicate grains aligned in the
interstellar magnetic field. The maximum polarization, detected with
7.8σ statistical significance near 10.2µm, is (1.24±0.28)%
with position angle 126°±8°. We comment on these
measurements in the context of recent models for the dust composition
in the diffuse interstellar medium.
Description:
We obtained spectropolarimetry of CygOB2-12 on UT 2020 August 5 and
October 28 with CanariCam, the mid-IR multimode facility camera on the
10.4m Gran Telescopio CANARIAS (GTC) in La Palma, Spain.
Our low-resolution (R∼50) spectropolarimetry spans the wavelength
range 8.1-13.0um and consists of nine individual data sets obtained
using a 1.02" wide slit. The total on-source integration time was
2979s.
Objects:
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RA (ICRS) DE Designation(s)
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20 32 40.95 +41 14 29.2 CygOB2-12 = NAME Cyg OB2 12
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 43 272 CanariCam 8-13um intensity spectrum
fig2.dat 53 12 CanariCam 8-13um spectropolarimetry of CygOB2-12
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See also:
B/mk : Catalogue of Stellar Spectral Classifications (Skiff, 2009-)
II/225 : Catalog of Infrared Observations, Edition 5 (Gezari+ 1999)
VIII/99 : Catalogue of Radio Stars (Wendker, 2001)
J/AJ/101/1408 : Massive stars in Cyg OB2. (Massey+ 1991)
J/A+A/281/161 : Radio emission from stars at 250GHz (Altenhoff+, 1994)
J/A+A/390/1033 : The ISO-SWS post-helium atlas (Vandenbussche+, 2002)
J/AZh/81/1104 : Optical spectrum of Cyg OB2 No. 12 (Klochkova+, 2004)
J/ApJS/151/299 : Spectra classification from ISO PHT-S database (Hodge+, 2004)
J/ApJ/664/1102 : Radial velocity survey of Cyg OB2 association (Kiminki+, 2007)
J/BaltA/17/125 : Interstellar reddening in 3 HII regions (Straizys+, 2008)
J/AJ/137/3358 : Speckle interferometry of massive stars (Mason+, 2009)
J/ApJ/708/1628 : Diffuse interstellar bands. IV. (McCall+, 2010)
J/ApJ/713/871 : Sources in star-forming reg Cyg-OB2 from X-ray (Wright+, 2010)
J/A+A/536/A31 : Cyg OB2 XMM observations (Rauw, 2011)
J/ApJ/751/4 : Radial velocities of massive stars in Cyg OB2 (Kiminki+, 2012)
J/MNRAS/449/741 : The massive star population of Cygnus OB2 (Wright+, 2015)
J/A+A/598/A108 : Variability survey of brightest stars (Laur+, 2017)
J/ApJ/850/194 : Equivalent widths of 8 DIBs for 186 O & B stars (Fan+, 2017)
J/MNRAS/484/1838 : Spatial substructure of Cygnus OB2 (Berlanas+, 2019)
J/ApJ/895/38 : MIR extinction toward Cyg OB2-12 ISM (Hensley+, 2020)
J/A+A/637/A64 : Cygnus OB2 e-MERLIN 21cm survey (COBRaS) (Morford+, 2020)
J/AJ/160/115 : JHK obs. of 75 OB stars in Cyg OB2 (Caballero-Nieves+, 2020)
J/MNRAS/493/2339 : Internal motions in OB-associations (Melnik+, 2020)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 um lambda [7.76/12.96] Wavelength
8- 13 F6.3 Jy Flux [5.3/17.2] Flux density
15- 17 I3 --- SNR [101/732] Signal-to-Noise
19- 24 F6.3 % q [-1.62/2.4] The q Stokes parameter; Q/I
26- 31 F6.3 % u [-3.34/1.93] The u Stokes parameter; U/I
33- 37 F5.3 % Pol [0.1/3.52] Percentage polarization
39- 43 F5.1 deg PA [37.8/210] Position angle; East of North
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 um lambda [8.2/12.6] Wavelength
7- 11 F5.3 % Pol [0.3/1.3] Percentage polarization
13- 17 F5.3 % e_Pol [0.16/0.6] Uncertainty in Pol
19- 23 F5.1 deg PA [111.7/127.4] Position angle; East of North
25- 28 F4.1 deg e_PA [5.1/37.1] Uncertainty in PA
30- 34 F5.3 % q [0.41/1.23] The q Stokes parameter; Q/I
36- 40 F5.3 % e_q [0.16/0.6] Uncertainty in q
42- 47 F6.3 % u [-0.15/0.28] The u Stokes parameter; U/I
49- 53 F5.3 % e_u [0.16/0.6] Uncertainty in u
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Nov-2024