Search for a radio pulsar in the AMXPs XTE J0929314 XTE J1751306 XTE J1814338

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Search for a radio pulsar in the AMXPs XTE
J0929-314 XTE J1751-306 - XTE J1814-338
Maria Noemi Iacolina
Supervisors Marta Burgay - Luciano Burderi
Andrea Possenti - Tiziana Di Salvo
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Millisecond Pulsars
Recycling Model
AMXP ? ? MSP
Proof
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Search for radio millisecond pulsations in
__________________________________________________
_____________ Name Ps Porb
Ref. (ms) (hr) ----------------------------
--------------------------------------------------
----------------------------------- XTE
J0929-314 5.4 0.73 (Galloway et al. 2002)
XTE J1751-306 2.3 0.71 (Markwardt et al. 2002)
XTE J1814-338 3.2 4.27 (Markwardt et al.
2003) ___________________________________________
_____________________
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The choice of the observing frequency

• Which is the suitable frequency searching for
  radio pulsar in this systems?
• Because of the matter enclosing the system
• We have to fight with the free-free absorption

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The choice of the observing frequency

• Optical depth at various radio frequencies
• due to matter engulfing a AMXP in its quiescent
  phase

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XTE J0929-314 The choice of the observing
frequency
For this source we get tff (1.4 GHz) 6 1.4
GHz ? typical ?obs for radio pulsar searching
Search at higher frequencies
tff (6.5 GHz) 0.2 tff (8.5 GHz) 0.1
ltlt 1
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XTE J0929-314 - The data series
Three data series 8hr (2003 December)

• Parkes 64 m radio telescope (Australia)

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XTE J0929-314 The search
Search on 3 steps
1. Correcting for the dispersion effects
2. Deorbiting and solar system barycentering
3. Folding
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1. Dispersion
The signal is more delayed at lower
frequency Minimize the damage due to ISM
Subdivide the receiver bandwidth in channels In
everyone the dedispersion effect result less
important
pulse drift
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1. Dedispersion

• Correct this drift with DM value
• Integrate the signal on the bandwidth following
  the line joining the pulse peaks channel by
  channel

Signal emerges from the noise
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1. Dedispersion

• DM not precisely known
• 72 trial DM values 6 400 pc cm-3 ?
  6.4 GHz
• 33 trial DM values 12 400 pc cm-3 ?
  8.5 GHz
• d 6 kpc
• Taylor Cordes and Cordes Lazio models
• Distribution of free electrons in the ISM

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2. Deorbit

• Binary pulsars
• eliminate effects orbital motion
• barycenter time series - eliminate the effect
  earth
• orbit

DEORBIT fortran software
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2. Deorbit

• Orbital parameters date from X observation,
• Check propagation error of X ephemeris on radio
  ephemeris
• Simulation of dedispersed time series
• Deorbit using parameters at 1s error
• Propagation dPorb over ?TXR ( 2 104 orbits)
• producing broadening of 0.4 in pulse phase
• affecting the detectability of the pulsation
• Max broadening 0.1
• 8 trial values of the orbital period
• covering the 1s uncertainty range

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3. Folding
Radio pulses superimposed on a more intense noise
Fold the deorbited time series according to the
spin parameters
DEFOLDING fortran software
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3. Folding

• X observation ? 2002 May
• Radio observation ? 2003 December
• ?T 19 months
• Explored range period
• Choosing 40 trial values of folding period

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XTE J0929-314 - Results

• 5 104 plots
• Plot with the highest signal to noise
• S/N 6
• Pulse
• Grayscale
• Folding -
• observation
• parameters

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XTE J0929-314 - Results

• No radio pulsation with millisecond periodicity
  has been found in XTE J0929-314 in its quiescent
  phase.

Flux upper limits
P Pulsar spin period
??MHz Frequency Band (MHz)
6.4 GHz
68 µJy
?t Integration Time (s)
ns Minimum S/N 6
Tsys System Temperature (K)
8.5 GHz
Tsky Sky Temperature (K)
26 µJy
G Gain (K/Jy)
e Digit number
Np Polarization number
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XTE J0929-314 - Results

• Flux density upper limit
• versus
• duty cycle

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Discussion

• Radio pulsar emission on
• Possible explanations

• 1. Beaming factor
• Unfavorable geometry of the radio emission with
  respect to the observer
• Probability of 50

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2. Luminosity
The source possesses an intrinsic luminosity
smaller than the upper limits determined in this
work 90 of MSP are below our upper limit
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XTE J0929-314 Conclusions

• No radio pulsation
• down to the limits mentioned above

6.4GHz ? 68 µJy
8.5GHz ? 26 µJy
Radio emission was on
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XTE J0929-314 Conclusions

• The free-free absorption cannot be the reason

• The beaming factor is a viable explanation

• The luminosity, lower than ours limits, is the
  most likely reason of a negative result

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XTE J0929-314 Future perspectives
Get round to these problems Intermediate
frequency 1.4 - 6.4 GHz
maximum mass transfer rate outburst value lower
limit in frequency (tff 1) is 3 GHz
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XTE J0929-314 Future perspectives
Luminosity upper limit for an observation at 3
GHz Sample more than a half of the known MSPs
luminosity distribution
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XTE J1751-306 - XTE J1814-338
Work in progress We hope to finish it as soon as
possible
THANK YOU