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Vela X-1: Flares & Off States. West Orange High School Manthan Kothari, Lucy Zipf, Neil Savalia, Brian Meise, Krish Pillai. IN TODAY’S PRESENTATION, WE WILL:. Discuss how we chose our project. Describe the Vela X-1 system.

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vela x 1 flares off states

Vela X-1: Flares & Off States

West Orange High School

Manthan Kothari, Lucy Zipf, Neil Savalia, Brian Meise, Krish Pillai

in today s presentation we will
IN TODAY’S PRESENTATION, WE WILL:
  • Discuss how we chose our project.
  • Describe the Vela X-1 system.
  • Present the Characteristics & Models for flaring behavior for the 20-40 keV range.
  • Present the Characteristics & Models for “off-states for the 20-40 keV range.
  • Present our findings regarding flares and off-states for the 1-10 keV range.
why flares off states
Why Flares & Off States?
  • Literature Review
    • Kreykenbohm et al., 2008

Discusses flaring behavior of Vela X-1 for 20-40 keV X-Ray energy range based on data from the INTEGRAL (International Gamma-Ray Astrophysics Laboratory, Launched in 2002) satellite.

  • RAI:

We look at X-Rays in the 1-10 keV range from the Exosat (European Space Agency X-Ray Observatory, finished its mission in 1986). So, we decided to compare Vela X-1’s flaring behavior in this energy range versus Kreykenbohm’s findings.

parameters of vela x 1
Parameters of Vela X-1

1. Compact Object

  • Period (from the Power Spectrum) of the compact object is ~283 seconds and it is not changing.
  • The compact object is a neutron star based on its luminosity (from the energy spectrum flux) of ~1036 ergs sec-1
  • It is a pulsar because it is in a MXRB and has a Power law Model fit.

Literature support: Kretschmar, 2004, Charles and Seward, 1995, Kreykenbohm, 2008.

slide6
2. Companion OB Star
  • The luminosity (from the distance modulus) of the OB star companion HD77581 is

63,000 times that of the sun.

  • The radius is (using Stephan-Boltzmann)

21 times that of the sun.

Literature support: Kaper, 1997, Kretschmar, 2004.

slide7
3. System

-- Using values for the orbital speed and the orbital period (from literature), we found the orbital radius of HD77581 to be 2.6x109 m and the orbital radius of the neutron star to be 3.45x1010 m.

  • Therefore the radius of the neutron star’s orbit is

~50 solar radii (~1.7RHD77581).

  • MHD77581~24Msun(using Kepler’s 3rd Law and Center of Mass independently)
  • This tells us this is a close MXRB meaning solar winds account for accretion of matter onto the NS.

Literature support: Quaintrall et al., 2003, Van Paradijs et al., 1976. Kretschmar et al.,2004, Willems et al., 2005.

kreykenbohm s flares 20 40 kev
Kreykenbohm’s Flares (20-40 keV)
  • Characteristics
    • Long Flares
      • TRise/TTotal > 0.5
      • Hardness Plotdoes not change.
slide11
Short Flares
    • TRise/TTotal < 0.3
    • Hardness Plot does change:

the soft x-rays increase

slide12
Kreykenbohm’s Flare Models

Flip-Flop Instability

The Lucy Situation

kreykenbohm s off states
Kreykenbohm’s Off-States
  • Characteristics
    • Occurs suddenly without a transition phase (almost like a switch)
    • Not an eclipse but count rate drops to below detection limits, almost 0.
kreykenbohm s off state models
Kreykenbohm’s Off-State Models
  • The “Biggest Loser” Model
    • Dense blobs of stellar winds (thanks to the close binary)
  • Propeller Effect
    • Inhibition of Accretion via balancing of infallingram pressure and the magnetic pressure.
our research questions
Do light curves in the 1-10 keV range exhibit flaring and off-state behaviors?

If these behaviors are present, do they have the same characteristics as in the 20-40 keV range?

If they’re present but with different characteristics, what model(s) might account for the difference?

Our Research Questions
flaring behaviors
Flaring Behaviors

Average cts/sec ~ 40 cts/sec +/- 0.03 cts/sec

Rise Time = ~2500 secs.

Flare Time = ~5000 secs.

Therefore, this is a LONG FLARE.

Fall Time

Rise time

Pre-Rise Time: 40 cts/sec +/- .447cts/sec

slide19

Average cts/sec ~ 38 cts/sec +/- 0.031 cts/sec

Rise Time = ~1000 secs.

Flare Time = ~3000 secs.

Therefore, this is a SHORT FLARE.

Pre-Rise Time:

25 cts/sec +/- .35 cts/sec

slide22

Hardness plot fluctuates for an off-state which is consistent with Kreykenbohm’s results.

summary of our findings
Summary of Our Findings
  • Flares
    • Flare behavior for 1-10 keV range isconsistent with Kreykenbohm’s 20-40 keV data.
    • Hardness plots for flaring behavior were just the opposite of the Kreykenbohm results!!!!
    • Result: we have evidence that

(1) supports the flare models but

(2) is inconsistent with hardness plot

results found bytheKreykenbohm study

slide24
Off-States
    • One of the off-states was consistent with Kreykenbohm time wise while the other one was not (for a longer period of time).
    • The hardness plots for both off-states are consistent with Kreykenbohm’s 20-40 keV range results.
future research
Future Research
  • Write a paper presenting our findings
  • Look at other MXRB to compare Vela X-1 flaring behaviors with those sources.
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