discovery of a highly eccentric binary millisecond pulsar in a gamma-ray-detected globular cluster
DESCRIPTION
Discovery of a Highly Eccentric Binary Millisecond Pulsar in a Gamma-Ray-Detected Globular Cluster. Megan DeCesar (UWM) In collaboration with Scott Ransom (NRAO), Paul Ray (NRL), Paul Demorest (NRAO), David Kaplan (UWM), and the Fermi LAT Collaboration. - PowerPoint PPT PresentationTRANSCRIPT
Discovery of a Highly Eccentric Binary Millisecond Pulsar in a Gamma-Ray-
Detected Globular Cluster
Megan DeCesar (UWM)In collaboration with Scott Ransom (NRAO), Paul Ray (NRL), Paul Demorest (NRAO), David Kaplan
(UWM), and the Fermi LAT Collaboration
Discovery of a Highly Eccentric Binary Millisecond Pulsar
Big PicturePulsars as Extreme Physical Laboratories Physics of very dense matter Gravitational physics in weak and
strong fields
NS Equation of State
Constraints on EOS from: Maximum NS mass
(binary pulsar timing) Radius estimates
(thermal X-ray emission)
Emission: NS-NS, NS-BH mergersDetection:
Indirect (binary pulsar timing) Direct (pulsar timing array)
Gravitational Waves
Lattimer+Prakash’04
Weisberg+’10
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Gamma-ray pulsars with the Fermi Large Area Telescope
http://www.nasa.gov/externalflash/fermipulsar/
Saz Parkinson 2009Abdo+ 2009 (MSPs)
Young/normal pulsars
Millisecond pulsars (MSPs)
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Fifty new MSPs discovered in Fermi LAT sources
Image: P. S. Ray
Several new MSPs for GW searches
All show gamma-ray pulsations
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Gamma-ray detections of globular clusters
Many MSPs in globular clusters (GCs)
GCs should be gamma- ray sources with pulsar- like spectra (Venter+ 2008, 2009)
Ter 5 (35 MSPs), 47 Tuc (26 MSPs), and several others with known MSPs were detected by the LAT (Abdo+ 2009, Kong+ 2010, Abdo+ 2010, Tam+ 2011)
Several more were detected that had no known MSPs (Abdo+ 2010, Tam+ 2011)
Abdo+ 2009
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Discovery of PSR J1835-3259A
Searched NGC 6388 and NGC 6652 with the NRAO Green Bank Telescope (GBT)
Found 1 MSP in NGC 6652
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Estimating the orbit of PSR J1835-3259A
NGC 6652A has a highly eccentric orbit. Pulsar timing is needed to accurately determine the
orbital parameters.
Circular orbit Eccentric orbit
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Basic idea: Use measured pulse arrival times to find a function (the timing solution) that accurately predicts future pulse arrival times.
Timing solution depends on pulsar properties.
Pulsar timing
Solitary pulsar
Frequency, frequency derivative (spin parameters)
Binary pulsar
Spin parameters + orbital parameters: Orbital period, Pb Pulsar’s projected semimajor axis, x
= ap sin(i) Eccentricity, e Epoch of periastron, T0 Longitude of periastron, ω
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Initial timing solution of NGC 6652A
!!!
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An exotic, relativistic binary system
Mass function
High eccentricity implies companion exchange in the past,
common in dense environments of globular clusters.
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An exotic, relativistic binary system
mc ~ 0.7 – 2.9 Msun
1.4 Msun
90% confidence
Midwest Relativity Meeting 2013
An exotic, relativistic binary system
Roche lobe is smaller than MS radius for all companion masses. Companion cannot be MS star; must be compact object.
Midwest Relativity Meeting 2013
An exotic, relativistic binary system
Mass function
High eccentricity implies companion exchange in the past,
common in dense environments of globular clusters.
Companion is compact object with min. mass ~ 0.7 Msun
Midwest Relativity Meeting 2013
An exotic, relativistic binary system
Mass function
High eccentricity implies companion exchange in the past,
common in dense environments of globular clusters.
Companion is compact object with min. mass ~ 0.7 Msun
System is relativistic Measure Post-Keplerian parameters.
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Post-Keplerian parameters
Rate of periastron advanceEinstein delay
Shapiro delay
Orbital decay (due to GWs)
Measure 2 PK parameters pulsar, companion masses Measure 3+ PK parameters test GR
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Post-Keplerian parameters: γ, dPb/dt, and dω/dt
Comparison with Hulse-Taylor pulsar
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An exotic, relativistic binary system
Mass function
High eccentricity implies companion exchange in the past,
common in dense environments of globular clusters.
Companion is compact object with min. mass ~ 0.7 Msun
System is relativistic Measure Post-Keplerian parameters.Einstein delay and dPb/dt ~5x larger than PSR B1913+16.
Might also measure dω/dt.There is real potential to measure pulsar mass and test
GR.
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Conclusions and Future
PSR J1835-3259A is the most eccentric binary MSP known.
It has undergone one or more companion exchanges. Its current companion is a compact object with minimum mass ~ 0.7 Msun, likely a massive white dwarf or a neutron star.
Two PK parameters, γ and dPb/dt, are ~5x larger than those of Hulse-Taylor pulsar, so are likely measurable. May be able to measure the neutron star mass and test GR.
We are currently investigating feasibility of measuring PK parameters.
We have proposed for GBT observations to better determine the timing solution and measure PK parameters.
Thank you!