J/A+A/635/A75 LOFAR census of non-recycled pulsars sample (Bilous+, 2020)
A LOFAR census of non-recycled pulsars: extending to frequencies below 80 MHz.
Bilous A.V., Bondonneau L., Kondratiev V.I., Griessmeier J.-M., Theureau G.,
Hessels J.W.T., Kramer M., van Leeuwen J., Sobey C., Stappers B.W.,
ter Veen S., Weltevrede P.
<Astron. Astrophys. 635, A75 (2020)>
=2020A&A...635A..75B 2020A&A...635A..75B (SIMBAD/NED BibCode)
ADC_Keywords: Pulsars ; Interstellar medium
Keywords: pulsars: general
Abstract:
We present the results from the low-frequency (40-78MHz) extension of
the first pulsar census of non-recycled pulsars carried out with the
LOw-Frequency ARray (LOFAR). We used the low-band antennas of the
LOFAR core stations to observe 87 pulsars out of 158 that had been
previously detected using high-band antennas. We present flux
densities and flux-calibrated profiles for the 43 pulsars we detected.
Of this sample, 17 have not, to our knowledge, previously been
detected at such low frequencies. Here we recalculate the spectral
indices using the new low-frequency flux density measurements from the
LOFAR census and discuss the prospects of studying pulsars at very low
frequencies using current and upcoming facilities, such as the New
Extension in Nancay Upgrading LOFAR (NenuFAR).
Description:
obssum.dat contains an observing summary for all pulsars in the LOFAR
census sample. DM measurements and mean flux densities in specified
frequency ranges are listed for 43 detected sources. For the
non-detected pulsars the upper limits on mean flux density values are
given.
Spectral fits for the detected pulsars are presented in table1pl.dat
(a single power-law spectral model, 1PL), table2pl.dat (a power-law
with one break, 2PL) or in table3pl.dat (2 breaks, 3PL). For 1PL
models, the measured flux density values were modeled as random
variables, normally distributed in base 10 log space with
meanlgS=lg(S0)+a*lg(f/f0) and dispersion sigma_lgS. For the spectra
consisting of small number of measurements, sigma_lgS was set by the
reported flux density errors. For the spectra consisting of larger
number of measurements, an additional scatter (sigmaunknlgS) was
added in quadrature to sigma_lgS and fitted for. This additional
parameter represents intrinsic flux variability or any kind of
unaccounted propagation or instrumental error. For 2PL models,
mean_logS was defined as lg(S0)+a_lo*lg(f/f0) for f<fbr and as
lg(S0)+ahi*lg(f/fbr)+alo*lg(fbr/f0) for f>fbr. For 3PL models
mean_lgS was modified accordingly. A 2PL or 3PL model was preferred
over a 1PL model in the cases where either of the former gave a
significantly smaller sigmaunknlgS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
obssum.dat 201 87 Observation summary, flux densities,
dispersion measures
refs.dat 74 70 References
table1pl.dat 48 16 Fitted parameters for the pulsars with spectra
modeled with a single power-law
table2pl.dat 73 25 Fitted parameters for the pulsars with spectra
modeled with a broken power-law
table3pl.dat 97 6 Fitted parameters for the pulsars with spectra
modeled with a power-law with two breaks
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See also:
B/psr : ATNF Pulsar Catalogue (Manchester+, 2005)
Byte-by-byte Description of file: obssum.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of pulsar as in ATNF catalogue v.1.51
12- 16 F5.3 s Period Spin period as in ATNF catalogue v.1.51
18- 25 F8.2 d ObsEpoch Observing epoch (MJD)
27- 28 I2 min ObsLength Length of observing session
30- 34 F5.2 MHz MinFreq Lower edge of analysed frequency range
36- 40 F5.2 MHz MaxFreq Upper edge of analysed frequency range
42 I1 --- BestBeam ? Beam with the most clear pulsar signal
44- 47 F4.2 --- MinZap Fraction of zapped data for the least
affected beam (1)
49- 52 F4.2 --- MaxZap Fraction of zapped data for the most
affected beam
54- 56 I3 --- PeakSN ? Peak S/N ratio of the average profile
58- 66 F9.6 pc/cm+3 DM ? Dispersion measure at the epoch of
observation
68- 75 F8.6 pc/cm+3 e_DM ? Dispersion measure uncertainty at the
epoch of observation
77- 81 E5.1 --- TscatFrac Expected scattering time at
60 MHz divided by pulsar period (1)
83- 86 F4.2 --- ModInd Expected flux modulation index due to
scintillation in the interstellar
medium (2)
88 A1 --- l_S [≤] Upper limit flag for flux density
measurement
90- 95 F6.1 --- S Mean flux density in MinFreq-MaxFreq
frequency range or upper limit for
non-detected pulsars
97-100 I4 --- e_S ? Uncertainty in mean flux density
102-201 A100 --- r_S ? Literature flux references,
in refs.dat file
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Note (1): PSRs B0105+68, B0643+80, and B0656+14 were excluded from analysis
because of RFI contamination.
Note (2): Scattering time was calculated within Yao et al. (2017ApJ...835...29Y 2017ApJ...835...29Y)
model.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode BibCode
24- 41 A18 --- Aut Author's name
54- 74 A21 --- Com Comments
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Byte-by-byte Description of file: table1pl.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of pulsar as in ATNF catalogue v.1.51 (1)
12- 13 I2 MHz FreqRngLo Lower edge of the spectral frequency span
15- 19 I5 MHz FreqRngHi Upper edge of the spectral frequency span
21- 22 I2 --- N Number of data points in spectrum
24- 27 I4 MHz f0 Reference frequency
29- 32 F4.1 mJy S0 Fitted mean flux density at the reference
frequency
34- 38 F5.2 --- a Fitted spectral index
40- 43 F4.2 --- e_a Uncertainty in fitted spectral index
45- 48 F4.2 --- sigunlgS ? Fitted extra scatter of lg(S)
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Note (1): PSRs J0611+30, J1238+21, J1313+0931, J1645+1012 have also 2PL fit,
with break frequency fixed at the frequency of the largest measured mean flux
density. See table2pl.dat for the values of fitted parameters.
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Byte-by-byte Description of file: table2pl.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of pulsar as in ATNF catalogue v. 1.51
12- 13 I2 MHz FreqRngLo Lower edge of the spectral frequency span
15- 19 I5 MHz FreqRngHi Upper edge of the spectral frequency span
21- 23 I3 --- N Number of data points in spectrum
25- 28 I4 MHz f0 Reference frequency
30- 34 F5.1 mJy S0 Fitted mean flux density at the reference
frequency
36- 40 F5.2 --- alo Fitted spectral index for f < fbr
42- 45 F4.2 --- e_alo Uncertainty in fitted spectral index for f<fbr
47- 49 I3 MHz frbr Fitted break frequency
51- 53 I3 MHz b_frbr ? Lower limit of 68% uncertainty range for
break frequency
55- 57 I3 MHz B_frbr ? Upper limit of 68% uncertainty range for
break frequency
59- 63 F5.2 --- ahi Fitted spectral index for f > fbr
65- 68 F4.2 --- e_ahi Uncertainty in fitted spectral index for f>fbr
70- 73 F4.2 --- sigunlgS ? Fitted extra scatter of lg(S) (sigmaunknlgS_
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Byte-by-byte Description of file: table3pl.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of pulsar as in ATNF catalogue v.1.51
12- 13 I2 MHz FreqRngLo Lower edge of the spectral frequency span
15- 19 I5 MHz FreqRngHi Upper edge of the spectral frequency span
21- 22 I2 --- N Number of data points in spectrum
24- 26 I3 MHz f0 Reference frequency
28- 32 F5.1 mJy S0 Fitted mean flux density at the reference
frequency
34- 38 F5.2 --- alo Fitted spectral index for f < fbr1
40- 43 F4.2 --- e_alo Uncertainty in fitted spectral index for f<fbr1
45- 47 I3 MHz frbr1 Fitted first break frequency
49- 51 I3 MHz b_frbr1 ? Lower limit of 68% uncertainty range for
the first break frequency
53- 55 I3 MHz B_frbr1 ? Upper limit of 68% uncertainty range for
the first break frequency
57- 61 F5.2 --- amid Fitted spectral index for frbr1<f<fbr2
63- 66 F4.2 --- e_amid Uncertainty in fitted spectral index for
frbr1<f< fbr2
68- 71 I4 MHz frbr2 Fitted second break frequency
73- 76 I4 MHz b_frbr2 ? Lower limit of 68% uncertainty range for
the second break frequency
78- 81 I4 MHz B_frbr2 ? Upper limit of 68% uncertainty range for
the second break frequency
83- 87 F5.2 --- ahi Fitted spectral index for f>fbr2
89- 92 F4.2 --- e_ahi Uncertainty in fitted spectral index for f>fbr2
94- 97 F4.2 --- sigunlgS Fitted extra scatter of lg(S) (sigmaunknlgS)
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Acknowledgements:
Anna Bilous, nna.bilous(at)gmail.com
(End) Anna Bilous [UvA, the Netherlands], Patricia Vannier [CDS] 02-Dec-2019