MUSE integral field unit observation of NGC 6397

Compact Binaries

Cataclysmic Variable/ Low-mass X-ray Binary

• White dwarf / Neutron star as primary:
• MS star companion
• Accretion (usually) via a disk:
• Disk instability outbursts. Increase several magnitudes

Binaries in Globular Clusters

• Globular Clusters
  • The binary population drives the dynamical evolution of GCs
• Cataclysmic Variables:
  • Potentially very different from field CVs
  • A lot of open questions
• Neutron Stars:
  • Known distance binary in GC
  • Estimate equation of state (mass-radius relation)
• Gravitational Waves:.
  • Neutron stars binaries sources for LIGO
  • White dwarf degenerate sources for eLISA

Lack data and understanding CVs in GCs

Binaries in NGC 6397

Known X-ray sources

• Cataclysmic Variables
  • 15 CV Candidates
  • Two Bimodal Population:
  • Bright and Faint (Cohn et al. 2011)
• Millisecond Pulsars (MSPs):
  • One radio confirmed and one candidate
• Neutron Stars:
  • One qLMXB and possibly ultracompact

Characterize and find new binaries

MUSE

Integral Field Unit (IFU)

• Data cube:

$ \text{FoV:}(1^ \prime \times 1 ^ \prime )$

$(0.\!\!^{\prime\prime}2 \times 0.\!\!^{\prime\prime}2 \times 1.25 \, \unicode{x212B} $)

$4800-9300 \, \unicode{x212B} $

Newer data
• June 3 2018
• Longer exposures (250-300 s)
• Total 1.5 h
MUSE Commissioning
• July 26th to August 3rd, 2014
• Very short exposures (25-60 s)
• Total 95 minutes

NGC 6397

Credit: ESO's

Data reduction

Pre-processing to remove instrumental signatureCredit: MUSE Pipeline User Manual

Post-processing for observation calibration and produce data cubes
Credit: MUSE Pipeline User Manual

The Data

White Image		H$\alpha - $continuum (H$\alpha$ - continuum) + Chandra X-ray Contours

Detected CVs

Compact Binaries in NGC 6397

Spectral Analysis

Work in progress

• CVs:
• Mass ratio:
• From the H$\alpha$ double peaked emission (Casares 2016)
• Magnetism:
• No He II. Strongest He II outside range (4686 Å)
• qLMXB:
• Place limit on the H$\alpha$ flux
• MSPs:
• Nature of accretion(?) from H$\alpha$ line (narrow vs broad)

Future Work

• Follow up Observations
  • MUSE Adaptive Optics and extended range
  • Deeper observation for qLMXB
• Variability:
  • Lot of Hubble data in Optical and UV
• Datacube:
  • Systematically search for emission:
  • Helium emitters (AM CVn ?)
  • Planetary Nebula
  • Active Binaries

Conclusion