J/ApJ/846/L19 115-155MHz radio survey of Fermi sources (Pleunis+, 2017)
A millisecond pulsar discovery in a survey of unidentified Fermi γ-ray
sources with LOFAR.
Pleunis Z., Bassa C.G., Hessels J.W.T., Kondratiev V.I., Camilo F.,
Cognard I., Griessmeier J.-M., Stappers B.W., van Amesfoort A.S., Sanidas S.
<Astrophys. J., 846, L19 (2017)>
=2017ApJ...846L..19P 2017ApJ...846L..19P
ADC_Keywords: Gamma rays ; Pulsars ; Radio sources ; Surveys
Keywords: gamma rays: stars; pulsars: general;
pulsars: individual (PSR J1552+5437); stars: neutron; surveys
Abstract:
Using LOFAR, we have performed a very-low-frequency (115-155MHz) radio
survey for millisecond pulsars (MSPs). The survey targeted 52
unidentified Fermi γ-ray sources. Employing a combination of
coherent and incoherent dedispersion, we have mitigated the dispersive
effects of the interstellar medium while maintaining sensitivity to
fast-spinning pulsars. Toward 3FGLJ1553.1+5437 we have found
PSRJ1552+5437, the first MSP to be discovered (through its pulsations)
at a radio frequency <200MHz. PSR J1552+5437 is an isolated MSP with a
2.43ms spin period and a dispersion measure of 22.9pc/cm3. The
pulsar has a very steep radio spectral index (α-2.8±0.4). We
obtain a phase-connected timing solution combining the 0.74yr of radio
observations with γ-ray photon arrival times covering 7.5yr of
Fermi observations. We find that the radio and γ-ray pulse
profiles of PSR J1552+5437 appear to be nearly aligned. The very steep
spectrum of PSR J1552+5437, along with other recent discoveries, hints
at a population of radio MSPs that have been missed in surveys using
higher observing frequencies. Detecting such steep spectrum sources is
important for mapping the population of MSPs down to the shortest spin
periods, understanding their emission in comparison to slow pulsars,
and quantifying the prospects for future surveys with low-frequency
radio telescopes like SKA-Low and its precursors.
Description:
We have used the Low-Frequency Array (LOFAR) High Band Antennas (HBAs)
of 21 of the 24 LOFAR Core stations to form 7 tied-array beams. This
observational setup has baselines up to 2.3km and provides tied-array
beams of ∼3.5' in diameter (FWHM) at the central frequency, with 7
beams covering a total circular field-of-view (FoV) of about 10' in
diameter (see Figure 1). With this setup we have observed 52 out of
1010 unidentified γ-ray sources from the 3FGL Fermi-LAT
point-source catalog (Acero+ 2015, J/ApJS/218/23).
To maximize sensitivity and FoV we have used signals from 200 subbands
in the 115-155MHz frequency range (39.06MHz bandwidth). See section 2.
Objects:
-------------------------------------------------------------
RA (ICRS) DE Designation(s)
-------------------------------------------------------------
15 52 53.33 +54 37 05.8 PSR J1552+5437 = PSR J1552+5437
-------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 47 52 LOFAR survey of unidentified Fermi-LAT sources:
source information
--------------------------------------------------------------------------------
See also:
B/psr : ATNF Pulsar Catalogue (Manchester+, 2005)
J/ApJ/605/759 : Multifrequency obs. of radio pulse broadening (Bhat+, 2004)
J/ApJS/208/17 : 2nd Fermi LAT cat. of gamma-ray pulsars (2PC) (Abdo+, 2013)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/ApJ/810/85 : Obs. of first Fermi-LAT sources at Parkes (Camilo+, 2015)
J/ApJ/814/128 : Timing noise & astrometry of Fermi-LAT pulsars (Kerr+, 2015)
J/ApJ/829/119 : Known pulsars identified in the TGSS ADR (Frail+, 2016)
J/ApJ/820/8 : 3FGL sources statistical classifications (Saz Parkinson+, 2016)
J/ApJ/838/139 : Radio follow-up on 3FGL unassociated sources (Schinzel+, 2017)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [3FGL]
6- 17 A12 --- 3FGL Source identifier (JHHMM.m+DDMM)
19- 23 I5 d Epoch [57344/57445] Modified Julian Date
of the observation
25- 28 F4.1 deg Alt [40.2/87.1] Altitude (1)
30- 34 F5.1 deg Az [0.7/289.4] Azimuth (1)
36- 39 F4.2 arcmin r95 [2.3/8.2] The 95% confidence radius (2)
41- 43 I3 pc/cm3 DM1 [20/119] NE2001 maximum galactic dispersion
measure (3)
45- 47 I3 pc/cm3 DM2 [12/163] YMW16 maximum galactic dispersion
measure (3)
--------------------------------------------------------------------------------
Note (1): At the midpoint of the LOFAR observation.
Note (2): Semi-major axis of 95% confidence error region in the 3FGL catalog
(Acero+, 2015, J/ApJS/218/23).
Note (3): According to the Cordes & Lazio (2002astro.ph..7156C 2002astro.ph..7156C ; NE2001) and the
Yao+ (2017ApJ...835...29Y 2017ApJ...835...29Y ; YMW16) models for Galactic electron
density.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-May-2018