Why are X-ray sources in the M31 Bulge so close to Planetary Nebulae?

Abstract

We compare a deep (37 ks) Chandra ACIS-S image of the M31 bulge to deep [O III] Local Group Survey data of the same region. Through precision image alignment using globular cluster X-ray sources, we are able to improve constraints on possible optical/X-ray associations suggested by previous surveys. Our image registration allows us to rule out several emission-line objects, previously suggested to be the optical counterparts of X-ray sources, as true counterparts. At the same time, we find six X-ray sources peculiarly close to strong [O III] emission-line sources, classified as planetary nebulae (PNe) by previous optical surveys. Our study shows that, while the X-rays are not coming from the same gas as the optical line emission, the chances of these six X-ray sources lying so close to cataloged PNe is only ~1%, suggesting that there is some connection between these [O III] emitters (possibly PNe) and the X-ray sources. We discuss the possibility that these nebulae are misidentified supernova remnants, and we rule out the possibility that the X-ray sources are ejected X-ray binaries. There is a possibility that some cases involve a PN and an LMXB that occupy the same undetected star cluster. Beyond this unconfirmed possibility, and the statistically unlikely one that the associations are spatial coincidences, we are unable to explain these [O III]/X-ray associations.

arXiv comment21 pages, 3 figures, 2 tables, accepted for publication in AJ

References in corpus (24)

• Catalogue of cataclysmic binaries, low-mass X-ray binaries and related objects (Seventh edition)
• The Velocity Distribution of Isolated Radio Pulsars
• Sherpa: a Mission-Independent Data Analysis Application
• Dynamical Evolution of the Mass Function of Globular Star Clusters
• The Mass Function of Young Star Clusters in the "Antennae" Galaxies
• Type Ia Supernovae: Influence of the Initial Composition on the Nucleosynthesis, Light Curves, Spectra and Consequences for the Determination of Omega_M & Lambda
• Neutron Star Population Dynamics.II: 3D Space Velocities of Young Pulsars
• The SN 1006 Remnant: Optical Proper Motions, Deep Imaging, Distance, and Brightness at Maximum
• X-ray Point Sources in The Central Region of M31 as seen by Chandra
• The Symbiotic Neutron Star Binary GX 1+4/V2116 Ophiuchi
• Discovery of Extended X-ray Emission from the Planetary Nebula NGC 7027 by the Chandra X-ray Observatory
• The Enigmatic X-ray Point Sources at the Central Stars of NGC 6543 and NGC 7293
• A Chandra High-Resolution Camera Observation of X-Ray Point Sources in M31
• The Recent Star Formation History of the M31 Disk
• A Synoptic X-ray Study of M31 with the Chandra-HRC
• ROSAT observations of X-ray emission from planetary nebulae
• The Stellar Content of M31's Bulge
• WFPC2 Observations of Massive and Compact Young Star Clusters in M31
• Detection of CO in the inner part of M31's bulge
• Discovery of Radio/X-ray/Optical Resolved Supernova Remnants in the Center of the Andromeda Galaxy
• X-ray behaviour of Circinus X-1 - I: X-ray Dips as a diagnostic of periodic behaviour
• The discovery of 2.78 hour periodic modulation of the X-ray flux from globular cluster source Bo 158 in M31
• The Discovery of a Spatially-Resolved Supernova Remnant in M31 with Chandra
• HST observations rule out the association between Cir X-1 and SNR G321.9-0.3

Cited by in corpus (3)

• A study of the population of LMXBs in the bulge of M31
• A Close Look at the Population of Supersoft and Quasi-Soft X-Ray Sources Observed in M31 with XMM-Newton
• The interior of the SNR RX J0852.0-4622 (Vela Jr) at radio wavelengths