J/MNRAS/474/219 6.7 GHz methanol masers observations (Szymczak+, 2018)
Monitoring observations of 6.7 GHz methanol masers.
Szymczak M., Olech M., Sarniak R., Wolak P., Bartkiewicz A.
<Mon. Not. R. Astron. Soc., 474, 219-253 (2018)>
=2018MNRAS.474..219S 2018MNRAS.474..219S (SIMBAD/NED BibCode)
ADC_Keywords: Masers ; Radio sources
Keywords: masers - stars: formation - ISM: clouds - radio lines: ISM
Abstract:
We report results of 6.7GHz methanol maser monitoring of 139
star-forming sites with the Torun 32-m radio telescope from 2009 June
to 2013 February. The targets were observed at least once a month,
with higher cadences of two to four measurements per week for
circumpolar objects. Nearly 80 per cent of the sources display
variability greater than 10 per cent on a time-scale between a week
and a few years, but about three quarters of the sample have only one
to three spectral features that vary significantly. Irregular
intensity fluctuation is the dominant type of variability and only
nine objects show evidence for cyclic variations with periods of 120
to 416d. Synchronized and anticorrelated variations of maser
features are detected in four sources with a disc-like morphology.
Rapid and high-amplitude bursts of individual features are seen on
three to five occasions in five sources. Long (>50d to 20 months)
lasting bursts are observed mostly for individual or groups of
features in 19 sources and only one source experienced a remarkable
global flare. A few flaring features display a strong anticorrelation
between intensity and line-width that is expected for unsaturated
amplification. There is a weak anticorrelation between the maser
feature luminosity and variability measure, i.e. maser features with
low luminosity tend to be more variable than those with high
luminosity. The analysis of the spectral energy distribution and
continuum radio emission reveals that the variability of the maser
features increases when the bolometric luminosity and Lyman flux of
the exciting object decreases. Our results support the concept of a
major role for infrared pumping photons in triggering outburst
activity of maser emission.
Description:
A sample of 139 star-forming sites with peak 6.7GHz flux density
greater than 5Jy and declination above -11° was selected from
the Torun methanol source catalogue (TMSC; Szymczak et al.,
2012AN....333..634S 2012AN....333..634S).
We present the results of 3.7yr monitoring observations of large
sample of HMYSOs in the 6.7GHz methanol maser line.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 60 139 List of 6.7GHz methanol maser sites monitored
table2.dat 71 627 Variability properties of 6.7GHz methanol
maser features (for the 139 sources of table1)
table3.dat 37 23 List of short-lived bursts
table4.dat 61 59 List of long-lived bursts
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Name (GLLL.lll+B.bbb)
15 A1 --- r_Name [a-p] Reference for positions (1)
16- 17 A2 --- n_Name Notes (2)
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 29 F5.2 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 41 F4.1 arcsec DEs Declination (J2000)
43- 47 F5.3 arcmin Offset ?=- Offset of the actual pointing from
the maser position
49- 53 F5.1 km/s Vsys Systemic velocity
55 I1 --- r_Vsys [1/2]? References for systemic velocity (3)
57 A1 --- FDist [KT] Distance adopted:
T = Trigonometric, K = Kinematic
59- 60 A2 --- Note Note (4)
--------------------------------------------------------------------------------
Note (1): References for coordinates derived from interferometric observations
(the pointing coordinates are given for other site) as follows::
a = Bartkiewicz et al. (2016A&A...587A.104B 2016A&A...587A.104B)
b = Bartkiewicz et al. (2009A&A...502..155B 2009A&A...502..155B)
c = Breen et al. (2015MNRAS.450.4109B 2015MNRAS.450.4109B)
d = Cyganowski et al. (2009, Cat. J/ApJ/702/1615)
e = Fujisawa et al. (2014PASJ...66...31F 2014PASJ...66...31F)
f = Caswell (2009, Cat. J/other/PASA/26.454
g = Xu et al. (2009A&A...507.1117X 2009A&A...507.1117X)
h = Moscadelli et al. (2013A&A...549A.122M 2013A&A...549A.122M)
i = Pandian et al. (2011ApJ...730...55P 2011ApJ...730...55P)
j = Bartkiewicz et al. (2014A&A...564A.110B 2014A&A...564A.110B)
k = http://bessel.vlbi-astrometry.org
l = Rygl et al. (2010A&A...511A...2R 2010A&A...511A...2R)
m = Reid et al. (2014, Cat. J/ApJ/783/130)
n = Moscadelli et al. (2011A&A...526A..66M 2011A&A...526A..66M)
o = Rygl et al. (2012A&A...539A..79R 2012A&A...539A..79R)
p = Hu et al. (2016, Cat. J/ApJ/833/18)
Note (2): For sites with multiple maser sources (clusters), the number of
sources is given after +.
Note (3): References to systemic velocity as follows:
1 = Szymczak et al. (2007A&A...468..617S 2007A&A...468..617S)
2 = Shirley et al. (2013, Cat. J/ApJS/209/2)
Note (4): The note indicates whether the object was included (Y) or excluded (N)
from statistical analysis and their number for clusters is added.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Name (GLLL.lll+B.bbb)
16- 20 I5 d MJDs Modified Julian Date at the start of the
observation
22- 25 I4 s Ts Total time-span of the observation
27- 29 I3 --- No Total number of observations
31- 36 F6.3 --- C Average observation cadence, in month-1
38- 43 F6.2 km/s Vp Peak velocity at 6.7GHz
45- 49 F5.1 Jy Sp Average peak flux density at 6.7GHz
51- 54 F4.2 --- VI Variability index
56- 59 F4.2 --- FI Fluctuation index
61- 66 F6.2 --- chi2r Reduced chi2
68- 71 F4.2 --- chi299.9 ? Corresponding value of reduced chi2 for a
99.9% significance level of variability
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Name (GLLL.llll+B.bbb)
15- 20 F6.2 km/s Vp Velocity of bursting feature
22- 26 I5 d MJD Time of flare peak (MJD)
28- 32 F5.1 Jy Sp Peak flux density at 6.7GHz
34- 37 F4.1 --- R Relative amplitude
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- No Sequential number
4- 17 A14 --- Name Name (GLLL.llll+B.bbb)
19- 24 F6.2 km/s Vp Velocity of bursting feature
26- 30 I5 d MJD Time of flare peak (MJD)
32- 34 I3 d tr Rise time
36- 38 I3 d td Decay time
40- 43 F4.1 Jy Smax Maximum flux density at 6.7GHz
45- 49 F5.2 --- R Relative amplitude
51- 55 F5.2 --- ln(Deltav)/ln(S) ? Slope fitted to the relationship between
the line-width Δv and flux density
57- 61 F5.2 --- r ? Correlation coefficient of the slope
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Oct-2020