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Register a new userThe Ages of High Mass X-ray Binaries in NGC 2403 and NGC 300
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Benjamin F. Williams
Publication date
2013
fields
Physics
and research's language is
English
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We have examined resolved stellar photometry from HST imaging surrounding 18 high-mass X-ray binary (HMXB) candidates in NGC 300 and NGC 2403 as determined from combined Chandra/HST analysis. We have fit the color-magnitude distribution of the surrounding stars with stellar evolution models. All but one region in NGC 300 and two in NGC 2403 contain a population with an age between 20 and 70 Myr. One of the candidates is the ultraluminous X-ray source (ULX) in NGC 2403, which we associate with a 60 Myr old population. These age distributions provide additional evidence that 16 of these 18 candidates are HMXBs. Furthermore, our results suggest that the most common HMXB age in these galaxies is 40-55 Myr. This preferred age is similar to observations of HMXBs in the Small Magellanic Cloud, providing new evidence of this formation timescale, but in higher metallicity populations. We suggest that this preferred HMXB age is the result of the fortuitous combination of two physical effects. First, this is the age of a population when the greatest rate of core-collapse events should be occurring, maximizing neutron star production. Second, this is the age when B stars are most likely to be actively losing mass. We also discuss our results in the context of HMXB feedback in galaxies, confirming HMXBs as a potentially important source of energy for the interstellar medium in low-mass galaxies.
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In 2010 May, an intermediate luminosity optical transient was discovered in the nearby galaxy NGC 300 by a South African amateur astronomer. In the decade since its discovery, multi-wavelength observations of the misnamed ``SN 2010da have continually re-shaped our understanding of this high mass X-ray binary system. In this review, we present an overview of the multi-wavelength observations and attempts to understand the 2010 transient event and, later, the re-classification of this system as NGC~300 ULX-1: a red supergiant + neutron star ultraluminous X-ray source.
We present new Chandra observations of the outer halo of the giant elliptical galaxy NGC 4472 (M49) in the Virgo Cluster. The data extend to 130 kpc (28), and have a combined exposure time of 150 ks. After identifying optical counterparts using the Next Generation Virgo Cluster Survey to remove background active galactic nuclei and globular cluster (GC) sources, and correcting for completeness, we find that the number of field low-mass X-ray binaries (LMXBs) per unit stellar V-band light increases significantly with galactocentric radius. Because the flux limit of the complete sample corresponds to the Eddington limit for neutron stars in NGC 4472, many of the ~90 field LMXBs in this sample could host black holes. The excess of field LMXBs at large galactocentric radii may be partially caused by natal kicks on black holes and neutron stars in binary systems in the inner part of the galaxy. Furthermore, since the metallicity in the halo of NGC 4472 strongly decreases towards larger galactocentric radii, the number of field LMXBs per unit stellar mass is anti-correlated with metallicity, opposite to what is observed in GCs. Another way to explain the spatial distribution of field LMXBs is therefore a reversed metallicity effect, although we have not identified a mechanism to explain this in terms of stellar and binary evolution.
We investigate the radial distribution of the low-mass X-ray binary (LMXB) population in the elliptical galaxy NGC 4649, using Chandra and Hubble data to separate the field and globular cluster (GC) populations. GCs with LMXBs have the same radial distribution as the parent red and blue GCs. The radial profile of field LMXBs follows the V-band profile within the D25 of NGC 4649. Using the spatial information provided by our data, we find that the global galaxy-wide relations between cumulative number and luminosity of LMXBs and the integrated stellar mass hold on local scales within D25. An excess of field LMXBs with respect to the V-light is observed in the galaxys outskirt, which may be partially due to unidentified GC sources or to a rejuvenated field LMXB population caused by past merging interactions.
NGC 300 ULX1 is the fourth to be discovered in the class of the ultra-luminous X-ray pulsars. Pulsations from NGC 300 ULX1 were discovered during simultaneous XMM-Newton / NuSTAR observations in Dec. 2016. The period decreased from 31.71 s to 31.54 s within a few days, with a spin-up rate of -5.56 x 10^{-7} s s^{-1}, likely one of the largest ever observed from an accreting neutron star. Archival Swift and NICER observations revealed that the period decreased exponentially from ~45 s to ~17.5 s over 2.3 years. The pulses are highly modulated with a pulsed fraction strongly increasing with energy and reaching nearly 80% at energies above 10keV. The X-ray spectrum is described by a power-law and a disk black-body model, leading to a 0.3-30 keV unabsorbed luminosity of 4.7 x 10^{39} erg s^{-1}. The spectrum from an archival XMM-Newton observation of 2010 can be explained by the same model, however, with much higher absorption. This suggests, that the intrinsic luminosity did not change much since that epoch. NGC 300 ULX1 shares many properties with supergiant high mass X-ray binaries, however, at an extreme accretion rate.
We present the results of a recent (March 2011) 160 ks Chandra-LETGS observation of the Seyfert galaxy NGC 4593, and the analysis of archival X-ray and UV spectra taken with XMM-Newton and HST/STIS in 2002. We find evidence of a multi-component warm absorber (WA) in the X-rays with four distinct ionisation degrees (log xi = 1.0, log xi = 1.7, log xi = 2.4, and log xi = 3.0) outflowing at several hundreds of km/s. In the UV we detect 15 kinematic components in the absorbers, blueshifted with respect to the systemic velocity of the source, ranging from -60 km/s to -1520 km/s. Although the predicted CIV and NV column densities from the low-ionisation X-ray outflow are in agreement with those measured for some components in the STIS spectrum, there are kinematic discrepancies that may prevent both the X-ray and UV absorbers from originating in the same intervening gas. We derive upper limits on the location of the absorbers finding that the high-ionisation gas lie within ~6 - 29 pc from the central ionising source, while the low-ionisation gas is located at several hundreds of pc. This is consistent with our line of sight passing through different parts of a stratified wind. The total kinetic energy of the outflows injected into the surroundings of the host galaxy only accounts for a tiny fraction of the bolometric luminosity of the source, and it is therefore unlikely that they may cause a significant impact in the interstellar medium of NGC 4593 in a given single episode of activity.
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