Constraints on the number of X‐ray pulsars in IC 10 from a deep XMM‐Newton observation

Abstract

We report the most sensitive search yet for X-ray pulsars in the dwarf starburst galaxy IC 10, which is known to contain a population of young, high-mass X-ray binaries. We searched for pulsations in 207 point-like X-ray sources in the direction of IC 10 by a 2012 XMM-Newton observation with a total exposure time of 134.5 ks. Pulsation searches in faint objects can be sensitive to the energy bands of the light curves, as well as the source and background extraction areas. We analyzed separately the PN and metal-oxide-semiconductor barycenter corrected 0.2-12 keV data, with good time interval filtering. Different schemes for source and background extraction were compared, and the search was repeated in the narrower 0.5-8 keV energy band to increase the signal-to-noise ratio. For the most conservative parameters, five point sources produced significant peaks in the Lomb-Scargle periodogram (99% significance, single trial, assuming white noise). A similar number of different candidates result from alternative analyses. A ∼4,100 s period seen in all three instruments for the black hole (BH) + Wolf-Rayet binary IC 10 X-1 is probably due to red noise of astrophysical origin. Considering the periods, luminosities, and spatial distribution of the pulsar candidates in the direction of IC 10, they do not belong to the same distribution as the ones in the Magellanic Clouds and Milky Way. This result holds even if the candidates are spurious, since if the Small Magellanic Cloud were placed at the distance of IC 10, we would expect to see nearly five pulsars at L x > 10 36 erg s -1 inside the D 25 contour, and their periods would be of order 100 s, rather than the mostly ∼1 s periods for the candidates reported here, which lie outside the main body of the galaxy. KEYWORD galaxies: individual (IC 10) -stars: neutron -X-rays: binaries 1

Young Black Hole and Neutron Star Systems in the Nearby Star-forming Galaxy M33: The NuSTAR View

“…To confirm the nature of M33 X-8, we searched for pulsations in both NuSTAR epochs using Lomb-Scargle periodograms (the same method described in Yang et al 2017aYang et al , 2019a. We found that a periodic signal was independently detected in both telescopes FPMA (769.42 ± 4.87 s) and FPMB (724.82 ± 5.22 s) with 99% significance during the first NuSTAR epoch (ObsID 50310002001).…”

TV Cassiopeiae with Chandra and XMM–Newton X-ray Observations

“…The X-ray Multi-Mirror Mission (XMM-Newton) observation in 2003 has the longest exposure time. We used the standard procedure (see [20][21][22][23][24]) to extract the source. The folded light curve shows two double peaks and double troughs.…”

Monitoring the X-Ray Variability of Bright X-Ray Sources in M33

“…Extensive studies of X-ray variability in the SMC sample have been performed (e.g., Laycock et al 2005;Eger & Haberl 2008;Galache et al 2008;Haberl & Sturm 2016;Lazzarini et al 2019;Haberl et al 2022). HMXBs have also been studied in the Large Magellanic Cloud (LMC; Lang et al 1998;Coe et al 2015b;Antoniou & Zezas 2016;van Jaarsveld et al 2018;Maitra et al 2023), the dwarf starburst galaxy IC 10 ( Massey et al 2007;Laycock et al 2017;Noori et al 2017;Yang et al 2019), the spiral galaxy NGC 300 (Kang et al 2016;Binder et al 2017), and M31 (Williams et al 2004;Lazzarini et al 2021).…”