Search for: All records

IC 10 is a dwarf galaxy in Cassiopeia, located at a distance of 660 kpc, and hosts a young stellar population, a large number of Wolf–Rayet stars, and a large number of massive stars in general. Utilizing a series of 11 Chandra observations (spanning 2003–2021, with a total exposure of 235.1 ks), 375 point sources of X-ray emission were detected. Similar studies have been conducted earlier in the central region of IC 10. Here, we consider all regions covered by Chandra-ACIS. By comparing our catalog of X-ray sources with a published optical catalog, we found that 146 sources have optical counterparts. We also created a list of 60 blue supergiant (SG) candidates with X-ray binary (XRB) companions by using an optical color–magnitude selection criterion to isolate the blue SGs. Blue SG-XRBs form a major class of progenitors of double-degenerate binaries. Hence, their numbers are an important factor in modeling the rate of gravitational-wave sources. Identifying the nature of individual sources is necessary as it paves the way toward a comprehensive census of XRBs in IC 10, thus enabling meaningful comparisons with other Local Group galaxies exhibiting starbursts, such as the Magellanic Clouds. 

Abstract We present an analysis of ∼235 ks of Chandra observations obtained over ∼19 yr of the nearby dwarf starburst galaxy IC 10 in order to study the X-ray variability and X-ray luminosity function (XLF) of its X-ray binary (XRB) population. We identify 23 likely XRBs within the Two Micron All Sky SurveyK_Sisophotal radius and find the distributions of their dynamic ranges and duty cycles are consistent with a young, high-mass XRB (HMXB) population dominated by supergiant-fed systems, consistent with previous work. In general, we find that brighter HMXBs (those withL_X≳ several ×10³⁶erg s⁻¹) have higher duty cycles (i.e., are more persistent X-ray sources) than fainter objects, and the dynamic ranges of the sgHMXBs in the lower-metallicity environment of IC 10 are higher than what is observed for comparable systems in the Milky Way. After filtering out foreground stars on the basis of Gaia parallaxes, we construct, for the first time, the XLF of IC 10. We then use the XLF to model the star formation history of the galaxy, finding that a very recent (3–8 Myr) burst of star formation with a rate of ∼0.5M_⊙yr⁻¹is needed to adequately explain the observed bright end (L_X∼ 10³⁷erg s⁻¹) of the HMXB XLF. 

ABSTRACT We present an analysis of the two-point spatial correlation functions of high-mass X-ray binary (HMXB) and young star cluster (YSC) populations in M31 and M33. We find evidence that HMXBs are spatially correlated with YSCs to a higher degree than would be expected from random chance in both galaxies. When supplemented with similar studies in the Milky Way, Small Magellanic Cloud, and NGC 4449, we find that the peak value of the spatial correlation function correlates strongly with the specific star formation rate of the host galaxy. We additionally perform an X-ray stacking analysis of 211 non-X-ray detected YSCs in M31 and 463 YSCs in M33. We do not detect excess X-ray emission at the stacked cluster locations down to 3σ upper limits of ∼1033 erg s−1 (0.35–8 keV) in both galaxies, which strongly suggests that dynamical formation within YSCs is not a major HMXB formation channel. We interpret our results in the context of (1) the recent star formation histories of the galaxies, which may produce differences in the demographics of compact objects powering the HMXBs, and (2) the differences in natal kicks experienced by compact objects during formation, which can eject newly formed HMXBs from their birth clusters. 

Abstract We present multiwavelength characterization of 65 high-mass X-ray binary (HMXB) candidates in M33. We use the Chandra ACIS survey of M33 (ChASeM33) catalog to select hard X-ray point sources that are spatially coincident with UV-bright point-source optical counterparts in the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region catalog, which covers the inner disk of M33 at near-IR, optical, and near-UV wavelengths. We perform spectral energy distribution fitting on multiband photometry for each point-source optical counterpart to measure its physical properties including mass, temperature, luminosity, and radius. We find that the majority of the HMXB companion star candidates are likely B-type main-sequence stars, suggesting that the HMXB population of M33 is dominated by Be X-ray binaries (Be-XRBs), as is seen in other Local Group galaxies. We use spatially resolved recent star formation history maps of M33 to measure the age distribution of the HMXB candidate sample and the HMXB production rate for M33. We find a bimodal distribution for the HMXB production rate over the last 80 Myr, with a peak at ∼10 and ∼40 Myr, which match theoretical formation timescales for the most massive HMXBs and Be-XRBs, respectively. We measure an HMXB production rate of 107–136 HMXBs/(M_⊙yr⁻¹) over the last 50 Myr and 150–199 HMXBs/(M_⊙yr⁻¹) over the last 80 Myr. For sources with compact object classifications from overlapping NuSTAR observations, we find a preference for giant/supergiant companion stars in black hole HMXBs and main-sequence companion stars in neutron star HMXBs. 

ABSTRACT Citizen science has helped astronomers comb through large data sets to identify patterns and objects that are not easily found through automated processes. The Milky Way Project (MWP), a citizen science initiative on the Zooniverse platform, presents internet users with infrared (IR) images from Spitzer Space Telescope Galactic plane surveys. MWP volunteers make classification drawings on the images to identify targeted classes of astronomical objects. We present the MWP second data release (DR2) and an updated data reduction pipeline written in python. We aggregate ∼3 million classifications made by MWP volunteers during the years 2012–2017 to produce the DR2 catalogue, which contains 2600 IR bubbles and 599 candidate bow shock driving stars. The reliability of bubble identifications, as assessed by comparison to visual identifications by trained experts and scoring by a machine-learning algorithm, is found to be a significant improvement over DR1. We assess the reliability of IR bow shocks via comparison to expert identifications and the colours of candidate bow shock driving stars in the 2MASS point-source catalogue. We hence identify highly reliable subsets of 1394 DR2 bubbles and 453 bow shock driving stars. Uncertainties on object coordinates and bubble size/shape parameters are included in the DR2 catalogue. Compared with DR1, the DR2 bubbles catalogue provides more accurate shapes and sizes. The DR2 catalogue identifies 311 new bow shock driving star candidates, including three associated with the giant H ii regions NGC 3603 and RCW 49.