J/ApJ/750/170 6.035GHz OH observations of two IRAS (Al-Marzouk+, 2012)
Discovery of 6.035 GHz hydroxyl maser flares in IRAS 18566+0408.
Al-Marzouk A.A., Araya E.D., Hofner P., Kurtz S., Linz H., Olmi L.
<Astrophys. J., 750, 170 (2012)>
=2012ApJ...750..170A 2012ApJ...750..170A (SIMBAD/NED BibCode)
ADC_Keywords: Masers ; Radio lines ; H II regions ; Interstellar medium
Keywords: H II regions - ISM: individual: IRAS18566+0408 -
ISM: molecules - masers - radio lines: ISM - stars: formation
Abstract:
We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward
the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which
is the only region known to show periodic formaldehyde (4.8GHz H2CO)
and methanol (6.7GHz CH3OH) maser flares. The observations were
conducted between 2008 October and 2010 January with the 305m Arecibo
Telescope in Puerto Rico. We detected two flare events, one in 2009
March and one in 2009 September to November. The OH maser flares are
not simultaneous with the H2 CO flares, but may be correlated with
CH3 OH flares from a component at corresponding velocities. A
possible correlated variability of OH and CH3 OH masers in
IRAS 18566+0408 is consistent with a common excitation mechanism (IR
pumping) as predicted by theory.
Description:
The observations were conducted with the 305m Arecibo Telescope in
Puerto Rico between 2008 October and 2010 January. We monitored the
6.035GHz main excited-state line of hydroxyl (OH;
ν0=6035.0932MHz, 2Π3/2, J=5/2, F=3--3+)9 toward the
young massive stellar object IRAS 18566+0408 (pointing position,
RA=18:59:09.98, DEC=+04:12:15.6, J2000) for a total of 24 epochs. We
used the WAPP spectrometer.
We also observed the 6.035GHz OH maser source G34.26+0.15 (pointing
position, RA=18:53:18.5, DEC=+01:14:59, J2000; 40km/s LSR central
bandpass velocity) in most of the runs with the same spectral setup as
the IRAS 18566+0408 observations.
Objects:
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RA (2000) DE Designation(s) (Table)
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18 53 18.54 +01 14 57.9 G34.26+0.15 = IRAS 18507+0110 (table1)
18 59 10.02 +04 12 14.7 IRAS 18566+0408 = GAL 037.55+00.20 (table2)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 98 Line Parameters of 6.035GHz OH in G34.26+0.15
table2.dat 51 25 Line Parameters of the 6.035GHz OH Masers in
IRAS 18566+0408 (G37.55+0.20)
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See also:
J/AN/333/634 : Torun methanol source catalogue (Szymczak+, 2012)
J/AZh/89/611 : Class I methanol maser catalog (Bayandina+, 2012)
J/ApJ/717/L133 : Formaldehyde maser flares in IRAS 18566+0408 (Araya+, 2010)
J/ApJ/669/435 : Arecibo Methanol Maser GP Survey. II. (Pandian+, 2007)
J/ApJ/656/255 : Arecibo methanol maser Galactic Plane Survey (Pandian+, 2007)
J/AZh/84/839 : Methanol emission of isolated maser condensations (Larionov+,
2007)
J/A+A/432/737 : General Cat. of 6.7GHz Methanol Masers (Pestalozzi+, 2005)
J/A+A/414/235 : OH maser emission from star forming regions (Szymczak+, 2004)
J/A+A/358/257 : Molecular clouds SO and CS obs. II. (Nilsson+, 2000)
J/A+AS/133/29 : Molecular line survey towards UC HII (Hatchell+ 1998)
J/A+A/325/1163 : 330-360GHz spectral lines of G 34.3+0.15. II. (Millar+ 1997)
J/A+A/325/255 : 5cm OH masers survey (Baudry+ 1997)
J/A+AS/110/81 : Methanol masers towards IRAS sources (van der Walt+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "YYYY/MMM/DD" Date Date of observation
13- 15 I3 mJy rms [23/282] Root-mean-square noise (1)
17- 19 I3 mJy Snu [100/640]? OH peak flux density (2)
21- 25 F5.2 km/s VLSR [55.8/62.5]? LSR Velocity (1)
27- 30 F4.2 km/s e_VLSR [0.01/0.5]? VLSR 1σ uncertainty
32- 35 F4.2 km/s Width [0.17/0.9]? Line width
37- 40 F4.2 km/s e_Width [0.03/0.3]? Width 1σ uncertainty (1)
42- 46 F5.1 mJy.km/s Snudv [0/443]? Integrated flux density of the
6.035GHz line (1)
48- 51 F4.1 mJy.km/s e_Snudv [0/74]? Snudv 1σ uncertainty
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Note (1): Line parameters and rms noise were obtained after smoothing the
spectra to a final channel width of 0.15 km/s. Only spectral lines
brighter than 4σ; are reported. The OH components at
58.3 and 62.3km/s are superposition of narrower lines, however
single Gaussian profiles gave acceptable fits given the channel
width and signal-to-noise.
Note (2): After smoothing the data to a channel width of ∼1km/s, we found
evidence in most of the scans for a broad, weak OH absorption line
at ∼50km/s LSR peak velocity. After averaging all the data and
smoothing the spectrum to a channel width of 1.2km/s (6mJy rms),
the line parameters of the absorption line were:
Sν=-65mJy, VLSR=50km/s, FWHM=18km/s.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "YYYY/MMM/DD" Date Date of observation
13- 15 I3 mJy rms [9/261]? Root-mean-square noise
17- 19 I3 mJy Snu [106/251]? OH peak flux density
21- 25 F5.2 km/s VLSR [85.82/90.03]? Local Standard of Rest Velocity
27- 30 F4.2 km/s e_VLSR [0.01/0.02]? VLSR 1σ uncertainty
32- 35 F4.2 km/s Width [0.2/0.3]? Line width
37- 40 F4.2 km/s e_Width [0.02/0.06]? Width 1σ uncertainty
42- 46 F5.1 mJy.km/s Snudv [23/81]? Integrated flux density of the
6.035GHz line
48- 51 F4.1 mJy.km/s e_Snudv [4/6]? Snudv 1σ uncertainty
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 11-Dec-2013