We have conducted a statistical analysis of the ultra-luminous X-ray point sources (ULXs; L_X_>=10^39^erg/s) in a sample of galaxies selected from the Arp Atlas of Peculiar Galaxies (1996, Cat. VII/192; Webb, 1996, Cat. VII/192). We find a possible enhancement of a factor of ~2-4 in the number of ULXs per blue luminosity for the strongly interacting subset. Such an enhancement would be expected if ULX production is related to star formation, as interacting galaxies tend to have enhanced star formation rates on average. For most of the Arp galaxies in our sample, the total number of ULXs compared to the far-infrared luminosity is consistent with values found earlier for spiral galaxies. This suggests that for these galaxies, ULXs trace recent star formation. However, for the most infrared-luminous galaxies, we find a deficiency of ULXs compared to the infrared luminosity. For these very infrared-luminous galaxies, active galactic nuclei may contribute to powering the far-infrared; alternatively, ULXs may be highly obscured in the X-ray in these galaxies and therefore not detected by these Chandra observations. We determined local UV/optical colors within the galaxies in the vicinity of the candidate ULXs using Galaxy Evolution Explorer UV and Sloan Digitized Sky Survey optical images. In most cases, the distributions of colors are similar to the global colors of interacting galaxies. However, the u-g and r-i colors at the ULX locations tend to be bluer on average than these global colors, suggesting that ULXs are preferentially found in regions with young stellar populations. In the Arp sample there is a possible enhancement of a factor of ~2-5 in the fraction of galactic nuclei that are X-ray-bright compared to more normal spirals.
One hundred seven ultraluminous X-ray sources (ULXs) with 0.3-10.0keV luminosities in excess of 10^39^erg/s are identified in a complete sample of 127 nearby galaxies. The sample includes all galaxies within 14.5Mpc above the completeness limits of both the Uppsala Galaxy Catalogue (Cat. VII/26) and the Infrared Astronomical Satellite survey (Cat. II/125). The galaxy sample spans all Hubble types, a four-decade range in mass, 7.5<log(M/M_{sun}_)<11.4, and in star formation rate, 0.0002<SFR(M_{sun}_/yr)<=3.6. ULXs are detected in this sample at rates of one per 3.2x10^10^M_{sun}_, one per ~0.5M_{sun}_/yr star formation rate, and one per 57Mpc^3^ corresponding to a luminosity density of ~2x10^37^erg/s/Mpc^3^. At these rates we estimate as many as 19 additional ULXs remain undetected in fainter dwarf galaxies within the survey volume. An estimated 14 objects, or 13%, of the 107 ULX candidates are expected to be background sources. The differential ULX luminosity function shows a power-law slope {alpha}~-0.8 to -2.0 with an exponential cutoff at ~20x10^39^erg/s with precise values depending on the model and on whether the ULX luminosities are estimated from their observed numbers of counts or, for a subset of candidates, from their spectral shapes. Extrapolating the observed luminosity function predicts at most one very luminous ULX, L_X_~10^41^erg/s, within a distance as small as 100Mpc. The luminosity distribution of ULXs within the local universe cannot account for the recent claims of luminosities in excess of 2x10^41^erg/s, requiring a new population class to explain these extreme objects.
We present the results of an archival XMM-Newton study of the bright X-ray point sources (LX>10^38^ergs/s) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the ultraluminous X-ray (ULX) population, searching for a soft-hard state dichotomy similar to that known for Galactic X-ray binaries and testing the specific predictions of the intermediate-mass black hole (IMBH) hypothesis. To this end, we searched for low-state objects, which we defined as objects within our sample that had a spectrum well fitted by a simple absorbed power law, and high-state objects, which we defined as objects better fitted by a combined blackbody and a power law.
We search for ultra luminous X-ray source (ULXs) radio counterparts located in nearby galaxies in order to constrain their physical nature. Our work is based on a systematic cross-identification of the most recent and extensive available ULX catalogues and archival radio data. A catalogue of 70 positional coincidences is reported. Most of them are located within the galaxy nucleus. Among them, we find 11 new cases of non-nuclear ULX sources with possibly associated radio emission.
We present a mid-infrared (IR) sample study of nearby ultraluminous X-ray sources (ULXs) using multiepoch observations with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. Spitzer/IRAC observations taken after 2014 were obtained as part of the Spitzer Infrared Intensive Transients Survey. Our sample includes 96 ULXs located within 10 Mpc. Of the 96 ULXs, 12 have candidate counterparts consistent with absolute mid-IR magnitudes of supergiants, and 16 counterparts exceeded the mid-IR brightness of single supergiants and are thus more consistent with star clusters or non-ULX background active galactic nuclei. The supergiant candidate counterparts exhibit a bimodal color distribution in a Spitzer/IRAC color-magnitude diagram, where "red" and "'blue" ULXs fall in IRAC colors [3.6]-[4.5]~0.7 and [3.6]-[4.5]~0.0, respectively. The mid-IR colors and absolute magnitudes of four "red" and five "blue" ULXs are consistent with those of supergiant B[e] (sgB[e]) and red supergiant (RSG) stars, respectively. Although "blue," RSG-like mid-IR ULX counterparts likely host RSG mass donors; we propose that "red" counterparts are ULXs exhibiting the "B[e] phenomenon" rather than hosts of sgB[e] mass donors. We show that the mid-IR excess from the "red" ULXs is likely due to thermal emission from circumstellar or circumbinary dust. Using dust as a probe for total mass, we estimate mass-loss rates of dM/dt~1x10^-4^M_{sun}_/yr in dust-forming outflows of red ULXs. Based on the transient mid-IR behavior and its relatively flat spectral index, {alpha}=-0.19+/-0.1, we suggest that the mid-IR emission from Holmberg IX X-1 originates from a variable jet.
Ulysses Jupiter Encounter Cospin Anisotropy Telescope (AT) Flux Data
Collection
Short Name:
ulysses_cospin_a
Date:
25 Apr 2025 02:02:21
Publisher:
Planetary Data System
Description:
This collection contains data submitted to the Planetary Data System
(PDS) by the Ulysses COSPIN investigators, for the Ulysses Jupiter
Encounter, 1992-01-25 to 1992-02-17 (days 25-48 inclusive).
Ulysses Jupiter Encounter Cospin High Energy Telescope (HET) Flux Data
Collection
Short Name:
ulysses_cospin_h
Date:
25 Apr 2025 02:00:49
Publisher:
Planetary Data System
Description:
This file contains data submitted to the Planetary Data System (PDS)
by the Ulysses COSPIN investigators, for the Ulysses Jupiter
Encounter, 1992-01-25 to 1992-02-17 (days 25-48 inclusive). All data
on this volume are from the High Energy Telescope (HET) detector.
Ulysses Jupiter Encounter Cospin High Flux Telescope (HFT) Flux Data
Collection
Short Name:
ulysses_cospin_h
Date:
25 Apr 2025 02:08:17
Publisher:
Planetary Data System
Description:
This file contains data submitted to the Planetary Data System (PDS)
by the Ulysses COSPIN investigators, for the Ulysses Jupiter
Encounter, 1992-01-25 to 1992-02-18 (days 25-48 inclusive). All data
on this volume are from the High Flux Telescope (HFT) detector.
Ulysses Jupiter Encounter Cospin Kiel Electron Telescope (KET)
Intensity Data Collection
Short Name:
ULY-COSPIN-KET-I
Date:
04 Mar 2024 19:10:39
Publisher:
Planetary Data System
Description:
This file contains data submitted to the Planetary Data System (PDS)
by the Ulysses COSPIN investigators, for the Ulysses Jupiter
Encounter, 1992-01-24 to 1992-02-17 (days 25-48 inclusive). All data
on this volume are from the Kiel Electron Telescope (KET) detector.
Ulysses Jupiter Encounter Cospin Kiel Electron Telescope (KET) Raw
Data Collection
Short Name:
ulysses_cospin_k
Date:
25 Apr 2025 02:06:52
Publisher:
Planetary Data System
Description:
This file contains data submitted to the Planetary Data System (PDS)
by the Ulysses COSPIN investigators, for the Ulysses Jupiter
Encounter, 1992-01-24 to 1992-02-17 (days 25-48 inclusive). All data
on this volume are from the Kiel Electron Telescope (KET) detector.
