Chandra's First Decade of Discovery

Session 5: Keynote

[PDF of Riccardo Giacconi's keynote address] [Video of the keynote address]

Progenitors of Type Ia Supernovae in early type galaxies.

Marat Gilfanov, Max-Planck-Institute for Astrophysics
Akos Bogdan (MPA, Garching)

Although there is a nearly universal agreement that SNeIa are associated with the thermonuclear disruption of a CO white dwarf reaching the Chandrasekhar mass limit, the exact nature of their progenitors is still unknown. The single degenerate scenario envisages a white dwarf accreting matter from a non-degenerate companion in a binary system. Gravitational and nuclear energy of the accreted matter is released in the form of electromagnetic radiation and/or kinetic power of Classical Novae explosions prior to the Supernova event. We show that combined X-ray output of SNIa progenitors and statistics of Classical Novae predicted in the single degenerate scenario are inconsistent with X-ray and optical observations of nearby early type galaxies. No more than ~5-10 percent of SNeIa associated with old stellar population can be produced via single degenerate evolutionary channel, unless our understanding of accretion and nuclear fusion on the white dwarf surface is fundamentally flawed.

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M31 in the Chandra Era: A High Definition Movie of a Nearby Galaxy

Albert Kong, National Tsing Hua University, Taiwan
Rosanne Di Stefano (CfA)

M31 has been a prime targets for all X-ray missions since the first detection in 1974. With its superb spatial resolution, Chandra is unique in resolving dense source regions and detecting faint sources. Since the launch of Chandra, M31 has been regularly observed. It is perhaps the only nearby galaxy which is observed by an X-ray telescope regularly throughout operation. With 10 years of observations, the center of M31 has been observed with Chandra for nearly 1 Msec. The X-ray skies of M31 not only consist of many transients and variables, globular cluster X-ray sources in M31 are also different from our Milky Way. They are in general more luminous and one of them may even host an intermediate-mass black hole. Supersoft and quasi-soft X-ray sources in M31 are the best kept secret to unlock the nature of the progenitor of Type Ia supernova. In this talk, I will review some of the important Chandra discoveries in M31 in the past 10 years.

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X-ray source populations in nearby spiral and star-forming galaxies

Andreas Zezas, Harvard-Smithsonian Center for Astrophysics, University of Crete (Greece)
V. Antoniou (CfA), K. Gazeas (CfA), P. Sell (U. Wisconsin), G. Fabbiano (CfA), V. Kalogera (Northwestern U.), D. Pooley (U. Wisconsin)

We present results on the X-ray source populations of nearby spiral and star-forming galaxies. The sample of galaxies includes the nearby spiral galaxy M81 and star-forming galaxies with stellar populations in the 10-100Myr range. We use HST data in order to classify the X-ray sources to HMXBs, LMXBs and globular clusters, and identify any SNRs or background AGNs. We discuss the spectral and temporal characteristics of the different sub-populations in these galaxies, and their implications for the sources' nature. We present the X-ray luminosity functions (XLF) of the discrete sources from the individual as well as the co-added observations and we discuss the dependence of the XLF on the age of the stellar populations. In the case of M81 we find a population of sources in the 1036-1037 erg s-1 luminosity range with early-type counterparts, while the HMXBs in the star-forming galaxies have generally higher luminosities. We also present results from Chandra observations of the SMC which extend the XLFs down to luminosities of 1032 erg s-1 and show evidence for the onset of the propeller effect at low luminosities.

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