A Search for Pulsar Companions Around Extremely Low Mass White Dwarfs - 14th BONN workshop
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A Search for Pulsar Companions Around
Extremely Low Mass White Dwarfs
14th BONN workshop
17 Feb.2020
Tilemachos M. Athanasiadis
Supervisors: Dr. John Antoniadis, Prof. Dr. Michael Kramer
• Usually
• Single star evolution needs more than a Hubble time to create a LMWD
• 50% of the LMWDs of ~0.4M☉ are expected to exist in binaries
or ELM WDs should exist
• Possible dark companions:
• Another WD
• Black hole
• Optical surveys have discovered LMWDs and through optical spectroscopy orbital
parameters are measured.
LMWD+MSPs are ideal for
through timing of the MSP and optical spectroscopy of the
LMWD (for example Antoniadis et al. 2013). Very few NS
mass measurements are currently available.
Observational
among the double-degenerate population.
This information is a crucial missing input in stellar-
evolution and population synthesis models.
Outline
PROJECTS
ELM follow-up Survey
Effelsberg
GAIA follow-up Survey
Effelsberg
GAIA follow-up Survey
Arecibo
• ELM survey
target selection:
• Sloan Digital Sky Survey (SDSS) photometric catalog by color.
• Objects with
• Our target selection:
• ELM WDs in binaries with a dark companion with mass > 0.8M☉.
for MSP companions observed by M. Berezina & L. Spitler
(Effelsberg-2014)
• For these systems there are also spectroscopic observations .
Athanasiadis et al. 2020 (in prep.)
90 min 30 min Porb*10%
• The 3 most compact systems was observed
for 90 minutes each. J0751-0141 J+A J+A A
• 5 systems was observed multiple times J0755+4800 n.o. A -
for 30 minutes per session.
• SIGPROC: Acceleration (A) and/or Jerk J0755+4906 J+A J+A A
(J) search applied based on the orbital
period. J0811+0225 n.o. A -
• Acceleration and jerk range based on
each system J1233+1602 n.o. J+A A
• DM range: 0-100 (calc. based on NE2001) J1443+1509 n.o. J+A A
J1741+6526 J+A J+A A
J2132+0754 n.o. A -
Our SIGPROC-PRESTO pipeline are based on the HTRU-N pipeline (M. Cruces)
• Inject simulated pulsar signals into real Effelsberg noise. • We have used that tool to have a better understanding of the sensitivity of our survey. • ~0.1 mJy error before RFI mitigation • ~0.05 mJy error after RFI mitigation
We simulate 10000
MONTE CARLO SIMULATION OF companions for
COMPANIONS FOR EACH SYSTEM every LMWD in a
specific distance d assuming a
(GAIA) percentance of NSs
within the
using random Luminosity
(Svd2) from distribution companions based on
(Gonthier 2018) the mass function
Flux density Sv
using random Pspin from
Flux density Sv Compare Sv with the survey
distribution
(Lorimer 2015) Spin period Ps sensitivity as function of Ps
using a beaming fraction Flux density Sv
model Spin period Ps
(Tauris & Manchester 1998) Beaming
DETECTION
RATE
Assumption: The acceleration range that we use in Probability for each
our search is enough to detect the systems that we
are looking for. system to host a NS.
Flux Density (mJy)
Flux Density (mJy)
Athanasiadis et al. 2020A
(paper A)Flux Density (mJy)
Flux Density (mJy)
Athanasiadis et al. 2020AProbability of PNS PNS
detection mass func after obs
Athanasiadis et al. 2020APrecise proper motions for 1.5 billion objects in
the Galaxy.
~500,000 WDs with hydrogen atmospheres,
~30,000 LMWDs with M < 0.25 solar masses
EFFELSBERG GAIA FOLLOW UP SURVEY
Well known and small distances (Athanasiadis et al. 2020b
NS fraction is the percentance of the
LMWD/NS binaries compared to other double
GAIA follow up survey
degenerate binaries. 104 targets
Upper limit:
Binomial distribution: PNS < 0.031
L ~ (1 Pdet PNS ) N
Upper limit based on van Leewen et al. ELM follow up survey
2007: 8 targets
Upper limit:
1 1 / 2
1/ N PNS < 0.35
PNS 0.0073 GAIA
Pdet survey
1 1 / 2
1/ N
ELM
PNS 0.09
Pdet survey• We have strong motivation to search for radio pulsars at the positions of low mass white
dwarfs.
• Both detections and non-detections are useful:
• Detection > Precise NS mass measurements
• Non-detections > Constraints on the LMWD/NS population
• Survey sensitivity, beaming fraction and distance are the most important factors regarding
the detection rate.
• Based on our results, we expect the fraction of LMWD/NS systems to be close to zero
and not higher than ~3%.TARGET SELECTION: High tranverse velocities High galactic latitudes Cross-matched with 3FGL Fermi catalog (
THANK YOU
BACKUP SLIDES
Beaming fraction model for MSPs
MSPs are considered to have large
beaming fraction values
Tauris & Manchester (1998)
Consistent with Kramer et al 1999
MSPs• Pdet= NMSPs/NNS
Athanasiadis et al. 2020
• We simulate a population of
NS companions for a LMWD in
different (well known)
parallaxes.
• We calculate how many
pulsars the survey would
have detected.
• For systems with parallax
higher than 0.5 mas (d• For each NS companion (MSP candidate), we assume
a random:
from a spin distribution based on
Lorimer 2015.
based on
Tauris & Manchester 1998.
(based on Gonthier et al. 2018)
within the distance error based on
GAIA DR2. MSPs
• From the Luminosity (L) and distance (r) we
calculate the : (L/4πr2)
• Comparing the flux density with the sensitivity
of the survey provide us with the Lorimer (2008)Athanasiadis et al. (paper A)
Athanasiadis et al. (paper A)Li et al. 2019 Li et al. 2019
• Possible companions of LMWDs: • Another WD • Neutron star • Black hole • No hydrogen shell flashes occur during the ELM WD cooling stage in contrast with more massive WDs. • In the latter case the hydrogen-rich envelope is loosing mass, therefore they have thiner envelopes. • WDs have thicker envelopes which allow for significantly higher stable hydrogen burning rates, • ELM WDs are much more luminous than their more massive companions (Driebe et al. 1999).
Athanasiadis et al. (paper A)
Athanasiadis et al. (paper A)
EFFELSBERG GAIA FOLLOW UP SURVEY
Telescope Effelsberg Radio Telescope
The DATA are archived and easily accesible on
HERCULES cluster. Receiver 7-beam receiver (21 cm)
Useful scripts for easy retrieval and reprocessing Targets 104 selected GAIA white dwarfs
Obs. time 2x30 min
Sensitivity 0.125 mJy
Acceleration-Jerk on 30 min observ. Acceleration search on 10 min FFA with acceleration search
observations (in coop. with T. Gautam)
Sensitive to systems with
Porb > 5 hours Sensitive to systems with Period range:
Porb > 1,6 hours 0.5-30 seconds
Acceleration range: ± 100 km/s2
Acceleration range: ± 500 km/s2 random discoveries
Jerk range: ± 4cm/s3
DM range: 0-2000 Single pulse search (PRESTO)
DM range: 0-2000
Our SIGPROC-PRESTO pipelines are based on the HTRU-N pipeline (M. Cruces)Test pulsars
Known MSPS-WD systems observed as tests of the pipeline:
Binary Period DM P_orb S1400
(ms) (pc*cm^-3) (hours) (mJy)
J2053+4650 12.58 98.08 2.4
J1738+0333 5.85 33.77 8.5 0.67
J0751+1807 3.47 30.24 6.3 3.2
J0348+0432 3.9 40.46 2.4Acceleration range
We need to be sure that the acceleration
range that we use is enough for the
objects that we are looking for.
(Handbook, Lorimer & Kramer)
Acceleration range depends on masses
and the orbital period:
Red: MSP+WD (1+0.25 solar masses)
Green: NS+NS (1+2 solar masses)
Black: BH+BH (10+10 solar masses)
Athanasiadis et al. 2019 (in prep.)Expected Orbital Periods (MSPs+He WDs)
Tauris et al. 1999ARECIBO OBSERVATIONS PART II
Graphical example of our selection method. Clustering based
on a gaussian mixture model based on their transverse
velocity and galactic latitude. Our algorithm clusters nearby
GAIA LMWDs into 4 distinct in the galactic latitute/velocity
plane. Known MSPs (in green) belong exclusively in two of
these clusters.Luminosity distribution for MSPs
Based on all-sky surveys carried
out in the 90s and for pulsars
observed at 430 MHz within 1.5
kpc of the Sun.
Severe undersampling of low-
luminosity pulsars.
The observed (dashed line) and
corrected (solid line) luminosity
distribution for MSPs.
Power law with a slope of -1
Lorimer 2008• For every system:
• Known parameters:
orbital period, mass function
• For random orientations:
MC simulation of companions
neutron stars
1.4 < M < 2.5
Ozel & Freire 2016
Athanasiadis et al. (paper A)Spin Period distribution for MSPs
It's important to simulate accurately
the spin period distribution
We can compare with the sensitivity in
specific spin periods.
This distribution is gaussian centered
at 4 ms
Tauris 2015You can also read
