Nova rate in spirals

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Nova rate in spirals

• Alessandro Ederoclite
• Dipartimento di Astronomia Università di
  Trieste
• E.S.O. European Southern Observatory

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Collaborators

• Paolo A. Mazzali (INAF - Trieste Observatory)
  official advisor
• Francesca M. Matteucci (Astronomy Department
  Trieste University) official co-advisor
• Roberto Gilmozzi (ESO - Paranal) ESO supervisor
• Elena Mason (ESO - Santiago) ESO unofficial
  supervisor
• Massimo Della Valle (INAF Firenze Observatory)
• Robert E. Williams (STScI)
• Angelo Cassatella (C.N.R. Roma)
• Aldo Altamore (Roma Tre University)

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The physics of a nova explosion

• A white dwarf accretes matter from a less evolved
  companion

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The physics of a nova explosion

• A white dwarf accretes matter from a less evolved
  companion

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The physics of a nova explosion

• A white dwarf accretes matter from a less evolved
  companion
• When pressure at the bottom of the accreted layer
  (mostly H) is P gt 1019 dyne cm-2
• Violent ThermoNuclear Runaway
• Accreted shell ejected ( v 1-5 103 Km/s)
• After the explosion the WD starts to accrete
  material again (Recurrence time time between
  two outbursts)

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Why are novae interesting astrophysical objects?

• The physics of explosions (dynamics and
  chemistry)
• Novae as distance indicators (MMRD Maximum
  Magnitude vs Rate of Decline relation

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Maximum Magnitude vs Rate of Decline Relation
MDVLivio 1995
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MB a log MWD
Della Valle Livio, 1995
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Why are novae interesting astrophysical objects?

• The physics of explosions (dynamics and
  chemistry)
• Novae as distance indicators (MMRD Maximum
  Magnitude vs Rate of Decline relation

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Why are novae interesting astrophysical objects?

• The physics of explosions (dynamics and
  chemistry)
• Novae as distance indicators (MMRD Maximum
  Magnitude vs Rate of Decline relation and
  Buscombe-DeVaucouleurs relation)

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Why are novae interesting astrophysical objects?

• The physics of explosions (dynamics and
  chemistry)
• Novae as distance indicators (MMRD Maximum
  Magnitude vs Rate of Decline relation and
  Buscombe-DeVaucouleurs relation)
• The chemical evolution of the universe (needs
  detailed model of yields and of the nova rate).

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The nova rate

• Nova rate number of novae in a year in a galaxy
• Determined by
• Number of progenitors
• Recurrence time (time between two explosions )
• Recent theoretical estimates (Matteucci et al.,
  2003)
• Irregulars (LMC) 1.7 yr-1
• Spirals (MW) 25 yr-1
• Ellipticals (M87) 100 300 yr-1

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Observed nova rates
from Matteucci et al., 2003
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The strategy how do I look for a nova?

• Need high resolution images of galaxies
• Need long time coverage
• Clean the images (i.e. cosmic rays removal)
• Measure luminosities of objects
• Find the new star (stella nova)
• it must have B-V0 at maximum, expected mmax ,
  expected m15

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Other peoples novae
lt Della Valle Gilmozzi, 2002
Ferrarese et al., 2003 gt
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NGC 3982
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The other galaxies
NGC 4527
NGC 3627
The biggest nova survey in spirals ever done!
NGC 4639
NGC 4496
NGC 4536
?
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How to determine the nova rate(Zwicky, 1942 and
Capaccioli et al., 1989)

• After the counts (obviously)
• Single exposure Control Time
• Global control time
• NRcounts/GCT

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Very preliminary results

• NGC3982
• We have 0 counts !!! ?
• If you assume to have 3 counts, the poissonian
  probability to measure 0 is 5.
• Adopting (arbitrarily)
• ltmdiscgt27
• ltmmaxgt24,72 (slow novae) 22,72 (fast novae)
• ltvdgt 0,032 days (slow novae) 0,317 (fast
  novae)
• We have GCT111,25 days (slow novae) 53,59
  (fast novae)
• That means an upper-limit for the nova rate of
  9,84 (slow novae) and 20,43 (fast novae)

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Galactic novae

• 2 novae recently exploded gt FEROS ?
• Dynamics and 0-order chemistry
• PHOENIX and/or Mazzalis code for a for a better
  chemistry

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Next years

• Obtaining a nova rate for spiral galaxies
• Starting the modelling of the nova explosion gt
  code for synthetic spectra
• Back to 72Kgs and run my 3rd marathon in 3h30.
• WISH ME LUCK!