Time-scales to reach chemical equilibrium in ices at snowline distance around compact objects: the influence of accretion mass in the central object

2021 ◽  
Vol 503 (2) ◽  
pp. 2973-2978
Author(s):  
G A Carvalho ◽  
S Pilling
Keyword(s):  
Time Scales ◽  
Chemical Equilibrium ◽  
Accretion Rate ◽  
Radiation Reaction ◽  
Compact Objects ◽  
Compact Stars ◽  
X Ray ◽  
Accretion Rates ◽  
Central Compact Objects ◽  
Astrophysical Ices

ABSTRACT In this work, we analyse soft X-ray emission due to mass accretion on to compact stars and its effects on the time-scale to reach chemical equilibrium of eventual surrounding astrophysical ices exposed to that radiation. Reaction time-scales due to soft X-ray in water-rich and pure ices of methanol, acetone, acetonitrile, formic acid, and acetic acid were determined. For accretion rates in the range $\dot{m}=10^{-12}\!-\!10^{-8}\,{\rm M}_\odot$ yr−1 and distances in the range 1–3 LY from the central compact objects, the time-scales lie in the range 10–108 yr, with shorter time-scales corresponding to higher accretion rates. Obtained time-scales for ices at snow-line distances can be small when compared to the lifetime (or age) of the compact stars, showing that chemical equilibrium could have been achieved. Time-scales for ices to reach chemical equilibrium depend on X-ray flux and, hence, on accretion rate, which indicates that systems with low accretion rates may not have reached chemical equilibrium.

scholarly journals X-ray photolysis of CH3COCH3 ice: implications for the radiation effects of compact objects towards astrophysical ices

2020 ◽  
Vol 498 (1) ◽  
pp. 689-701 ◽  
Author(s):  
G A Carvalho ◽  
S Pilling
Keyword(s):  
Cross Section ◽  
Time Scales ◽  
Chemical Equilibrium ◽  
Radiation Effects ◽  
Broad Band ◽  
Compact Objects ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Molecular Abundances

ABSTRACT In this study, we employed broad-band X-rays (6–2000 eV) to irradiate the frozen acetone CH3COCH3, at the temperature of 12 K, with different photon fluences up to 2.7 × 1018 photons cm−2. Here, we consider acetone as a representative complex organic molecule (COM) present on interstellar ice grains. The experiments were conduced at the Brazilian Synchrotron facility (LNLS/CNPEN) employing infrared spectroscopy (FTIR) to monitor chemical changes induced by radiation in the ice sample. We determined the effective destruction cross-section of the acetone molecule and the effective formation cross-section for daughter species. Chemical equilibrium, obtained for fluence 2 × 1018 photons cm−2, and molecular abundances at this stage were determined, which also includes the estimates for the abundance of unknown molecules, produced but not detected, in the ice. Time-scales for ices, at hypothetical snow line distances, to reach chemical equilibrium around several compact and main-sequence X-ray sources are given. We estimate time-scales of 18 d, 3.6 and 1.8 months, 1.4 × 109–6 × 1011 yr, 600 and 1.2 × 107 yr, and 107 yr, for the Sun at 5 au, for O/B stars at 5 au, for white dwarfs at 1 LY, for the Crab pulsar at 2.25 LY, for Vela pulsar at 2.25 LY, and for Sagittarius A* at 3 LY, respectively. This study improves our current understanding about radiation effects on the chemistry of frozen material, in particular, focusing for the first time, the effects of X-rays produced by compact objects in their eventual surrounding ices.

scholarly journals Radiative efficiency of hot accretion flow and the radio/X-ray correlation in X-ray binaries

2014 ◽  
Vol 10 (S312) ◽  
pp. 139-140
Author(s):  
Fu-Guo Xie
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
Galactic Nuclei ◽  
X Ray ◽  
Radiative Efficiency ◽  
Accretion Flow ◽  
Accretion Rates ◽  
Distinctive Property ◽  
X Ray Binaries

AbstractSignificant progresses have been made since the discovery of hot accretion flow, a theory successfully applied to the low-luminosity active galactic nuclei (LLAGNs) and black hole (BH) X-ray binaries (BHBs) in their hard states. Motivated by these updates, we re-investigate the radiative efficiency of hot accretion flow. We find that, the brightest regime of hot accretion flow shows a distinctive property, i.e. it has a constant efficiency independent of accretion rates, similar to the standard thin disk. For less bright regime, the efficiency has a steep positive correlation with the accretion rate, while for faint regime typical of advection-dominated accretion flow, the correlation is shadower. This result can naturally explain the observed two distinctive correlations between radio and X-ray luminosities in black hole X-ray binaries. The key difference in systems with distinctive correlations could be the viscous parameter, which determines the critical luminosity of different accretion modes.

scholarly journals Central compact objects and their magnetic fields

2012 ◽  
Vol 8 (S291) ◽  
pp. 101-106 ◽  
Author(s):  
Wynn C. G. Ho
Keyword(s):  
Magnetic Fields ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Compact Objects ◽  
Spectral Measurements ◽  
X Ray ◽  
Surface Field ◽  
Weak Surface ◽  
Central Compact Objects ◽  
Weak Fields

AbstractCentral compact objects (CCOs) are neutron stars that are found near the center of supernova remnants, and their association with supernova remnants indicates these neutron stars are young (≲ 104 yr). Here we review the observational properties of CCOs and discuss implications, especially their inferred magnetic fields. X-ray timing and spectral measurements suggest CCOs have relatively weak surface magnetic fields (~ 1010 − 1011 G). We argue that, rather than being created with intrinsically weak fields, CCOs are born with strong fields and we are only seeing a weak surface field that is transitory and evolving. This could imply that CCOs are one manifestation in a unified picture of neutron stars.

scholarly journals Thermal state of transiently accreting neutron stars with additional heating beyond deep crustal heating

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
Helei Liu ◽  
Masa-aki Hashimoto ◽  
Guoliang Lü ◽  
Yasuhide Matsuo ◽  
Dehua Wen ◽  
...  
Keyword(s):  
Neutron Star ◽  
Heat Source ◽  
Neutron Stars ◽  
High Temperatures ◽  
Accretion Rate ◽  
Thermal State ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Accretion Rates ◽  
Theoretical Predictions

Abstract As some neutron star transients require an additional unknown heat source (referred to as “shallow heating”) to explain their high temperatures at the beginning of quiescence, we investigate the effect of shallow heating as well as compressional heating on the thermal state of transiently accreting neutron stars with the use of evolutionary calculations in the present work. Through comparing our theoretical predictions of the equilibrium redshifted luminosities $(L_{\gamma}^{\infty})$ produced by both deep crustal heating and shallow heating/compressional heating for different time-averaged mass-accretion rates $\langle\dot{M}\rangle$ with 35 updated observations of soft X-ray transients, the results show that both shallow heating and compressional heating make significant contributions to the equilibrium redshifted luminosity. The hotter sources (XTE J1701, MAXI J0556, EXO 0748, Aql X-1 etc.) with higher accretion rates are more likely to be explained with the effect of shallow heating or compressional heating. In addition, for a proper shallow heat $q_\mathrm{sh}$ and mass-accretion rate $\dot{M}$, the effect of shallow heating could be simulated by compressional heating.

scholarly journals On Spin dependence of the Fundamental Plane of black hole activity

2020 ◽  
Vol 495 (1) ◽  
pp. 278-284 ◽  
Author(s):  
Caner Ünal ◽  
Abraham Loeb
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
Galactic Nuclei ◽  
Spin Dependence ◽  
Fundamental Plane ◽  
X Ray ◽  
Dependent Relation ◽  
Accretion Rates ◽  
Jet Power

ABSTRACT The Fundamental Plane (FP) of black hole (BH) activity in galactic nuclei relates X-ray and radio luminosities to BH mass and accretion rate. However, there is a large scatter exhibited by the data, which motivated us for a new variable. We add BH spin as a new variable and estimate the spin dependence of the jet power and disc luminosity in terms of radio and X-ray luminosities. We assume the Blandford–Znajek process as the main source of the outflow, and find that the jet power depends on BH spin stronger than quadratically at moderate and large spin values. We perform a statistical analysis for 10 active galactic nuclei (AGNs) which have sub-Eddington accretion rates and whose spin values are measured independently via the reflection or continuum-fitting methods, and find that the spin-dependent relation describes the data significantly better. This analysis, if supported with more data, could imply not only the spin dependence of the FP relation, but also the Blandford–Znajek process in AGN jets.

scholarly journals Powering central compact objects with a tangled crustal magnetic field

2020 ◽  
Vol 495 (2) ◽  
pp. 1692-1699 ◽  
Author(s):  
Konstantinos N Gourgouliatos ◽  
Rainer Hollerbach ◽  
Andrei P Igoshev
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Initial Conditions ◽  
Supernova Explosion ◽  
Compact Objects ◽  
Dipole Field ◽  
Ohmic Dissipation ◽  
X Ray ◽  
Axisymmetric Structure ◽  
Central Compact Objects

ABSTRACT Central Compact Objects (CCOs) are X-ray sources with luminosity ranging between 1032 and 1034 erg s−1, located at the centres of supernova remnants. Some of them have been confirmed to be neutron stars. Timing observations have allowed the estimation of their dipole magnetic field, placing them in the range ∼1010–1011 G. The decay of their weak dipole fields, mediated by the Hall effect and Ohmic dissipation, cannot provide sufficient thermal energy to power their X-ray luminosity, as opposed to magnetars whose X-ray luminosities are comparable. Motivated by the question of producing high X-ray power through magnetic field decay while maintaining a weak dipole field, we explore the evolution of a crustal magnetic field that does not consist of an ordered axisymmetric structure, but rather comprises a tangled configuration. This can be the outcome of a non-self-excited dynamo, buried inside the crust by fallback material following the supernova explosion. We find that such initial conditions lead to the emergence of the magnetic field from the surface of the star and the formation of a dipolar magnetic field component. An internal tangled magnetic field of the order of 1014 G can provide sufficient Ohmic heating to the crust and power CCOs, while the dipole field it forms is approximately 1010 G, as observed in CCOs.

scholarly journals Black hole mass accretion rates and efficiency factors for over 750 AGN and multiple GBH

2020 ◽  
Vol 500 (1) ◽  
pp. 215-231
Author(s):  
Ruth A Daly
Keyword(s):  
Black Hole ◽  
Radio Emission ◽  
Binary Systems ◽  
Accretion Rate ◽  
Beam Power ◽  
Black Hole Mass ◽  
X Ray ◽  
Accretion Rates ◽  
Efficiency Factors ◽  
The Impact

ABSTRACT Mass accretion rates in dimensionless and physical units, and efficiency factors describing the total radiant luminosity of the disc and the beam power of the outflow are obtained and studied here for samples of black hole systems with outflows. Four samples of sources including 576 LINERs, 100 classical double (FRII) radio sources, 80 relatively local AGN, and 103 measurements of four stellar mass X-ray binary systems, referred to as Galactic Black Holes (GBHs), are included in the study. All of the sources have highly collimated outflows leading to compact radio emission or powerful extended (FRII) radio emission. The properties of each of the full samples are explored, as are those of the four individual GBH, and sub-types of the FRII and local AGN samples. Source types and sub-types that have high, medium, and low values of accretion rates and efficiency factors are identified and studied. A new efficiency factor that describes the relative impact of black hole spin and mass accretion rate on the beam power is defined and studied, and is found to provide a new and interesting diagnostic. Mass accretion rates for 13 sources and efficiency factors for 6 sources are compared with values obtained independently, and indicate that similar values are obtained with independent methods. The mass accretion rates and efficiency factors obtained here substantially increase the number of values available, and improve our understanding of their relationship to source types. The redshift dependence of quantities is presented and the impact on the results is discussed.

scholarly journals Searches for Young Pulsars

2004 ◽  
Vol 218 ◽  
pp. 97-104 ◽  
Author(s):  
Fernando Camilo
Keyword(s):  
Neutron Stars ◽  
Compact Objects ◽  
Pulsar Wind Nebulae ◽  
X Ray ◽  
Γ Ray ◽  
Pulsar Wind ◽  
Central Compact Objects

I review the results of radio and X-ray searches for pulsations from young neutron stars, emphasizing work accomplished in the last five years. I cover undirected searches, as well as directed searches of pulsar wind nebulae, EGRET γ-ray sources, and also the search for pulsations from “isolated neutron stars” and “central compact objects”.

scholarly journals Central Compact Objects in Supernova Remnants

2004 ◽  
Vol 218 ◽  
pp. 239-246 ◽  
Author(s):  
George G. Pavlov ◽  
Divas Sanwal ◽  
Marcus A. Teter
Keyword(s):  
Neutron Stars ◽  
Supernova Remnants ◽  
Compact Objects ◽  
X Ray ◽  
Central Regions ◽  
Supernova Explosions ◽  
Central Compact Objects

There are point-like sources in central regions of several supernova remnants which have not been detected outside the X-ray range. The X-ray spectra of these Central Compact Objects (CCOs) have thermal components with blackbody temperatures of 0.2–0.5 keV and characteristic sizes of 0.3-3 km. Most likely, the CCOs are neutron stars born in supernova explosions. We overview their observational properties, emphasizing the Chandra data, and compare them with magnetars.

scholarly journals Searching for X-ray Pulsations from Neutron Stars Using NICER

2017 ◽  
Vol 13 (S337) ◽  
pp. 187-190 ◽  
Author(s):  
Paul S. Ray ◽  
Zaven Arzoumanian ◽  
Keith C. Gendreau ◽  
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Compact Objects ◽  
Large Area ◽  
Pulse Profile ◽  
Millisecond Pulsars ◽  
X Ray ◽  
Event Time ◽  
Time Stamps ◽  
Central Compact Objects

AbstractThe Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for exploring the modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute event time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for emission and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, low-mass X-ray binaries (LMXBs), accretion-powered millisecond pulsars, central compact objects and other sources. We present our science plan and initial results from the first months of the NICER mission, including the discovery of pulsations from the millisecond pulsar J1231–1411.

Sign in / Sign up

Export Citation Format

Share Document