Super-Eddington accretion on to a stellar mass ultraluminous X-ray source NGC 4190 ULX1

Abstract

We present the results of high-quality XMM-NEWTON observations of a ULX in the galaxy NGC 4190. The detection of spectral cutoff in NGC 4190 ULX1 spectra rules out the interpretation of the ULX to be in a standard low/hard canonical accretion state. We report that the high quality EPIC spectra can be better described by broad thermal component, such as a slim disk. In addition we found long term spectral and flux variability in the source using several XMM-NEWTON and Swift data. A clear anti-correlation between flux and power-law photon index is found which further confirms the unusual spectral state evolution of the ULX. Spectral properties of the ULX suggest that the source is in a broadened disk state with luminosities (≈(3 − 10) × 1039 ergs s−1) falling in the ultraluminous regime. The positive Luminosity-temperature relation further suggests that the multi colour disk model follows the L∝T4 relation which is expected for a blackbody disk emission from a constant area and the slim disk model seems to favour L∝T2 relation consistent with an advection dominated disk emission . From the broadened disk like spectral feature at such luminosity, we estimated the upper limit of the mass of the central compact object from the inner disk radius and found that the ULX hosts a stellar mass black hole.

Hard X-ray flares and spectral variability in NGC 4395 ULX1

“…In this case, L ∝ L edd [1 + ln ṁ] ṁ2 , because beaming is proportional to 73/ ṁ2 (King 2009;King & Lasota 2016;King et al 2017). Since the luminosity ratio in this case is small (∼ 2), the luminosity-accretion rate relation can be approximated to km, where ξ is the geometric correction factor and κ is the color correction factor, d 10 is the distance in 10 kpc unit, N is the normalization and θ is the inclination angle of the disk (Soria et al 2015;Walton et al 2020;Ghosh & Rana 2021). We estimate the inner radius from the disk normalizations for all the four epochs XM1, XM2, XM3 and XM4.…”

“…The flaring events can have a much more significant up-scattered photon fraction due to proliferation in numbers of inner disk photons. However, quantifying Compton scattering process require high energy data coverage (Ghosh & Rana 2021;Walton et al 2020) which is not available for NGC 4395 ULX1. Future observations with hard X-ray instruments like NuSTAR may uncover the Comptonization scenario with much better constraints.…”

Spectral and Temporal Properties of Ultra-luminous X-ray Source NGC 55 ULX1

“…The inferred high luminosity is considered as strong evidence for the existence of intermediatemass black hole (IMBH) in ULXs with a proposed mass range of 10 2 − 10 5 M⊙ (Colbert & Mushotzky 1999;Coleman Miller & Colbert 2004). The detailed studies in the last couple of decades with XMM-Newton observations do not identify any signatures of the sub-Eddington accretion flow onto the IMBH, instead, these studies favour supercritical accretion onto stellar-mass black hole (e.g., Gladstone et al 2009;Middleton et al 2012;Sutton et al 2013;Middleton et al 2015a;Ghosh & Rana 2021). The radiatively driven optically-thick outflows expected in the super-Eddington accretion systems (Poutanen et al 2007;Middleton et al 2015a) play an important role in understanding the X-ray spectral and temporal properties of ⋆ E-mail: jitheshthejus@gmail.com these sources.…”

Supercritical colliding wind binaries

“…We apply our model to estimate the radiation emitted by the ultraluminous X-ray source NGC 4190 ULX 1 (also known as CXO J121345.2+363754). Although many characteristics of this ULX remain poorly understood, several authors have explored the system and have provided constraints on some of its parameters (see e.g., Liu & Bregman 2005;Gladstone et al 2013;Koliopanos et al 2017;Kosec et al 2018;Ghosh & Rana 2021).…”