Upper Mass Limit Research Articles

Expanding Orbitrap Collision Cross-Section Measurements to Native Protein Applications Through Kinetic Energy and Signal Decay Analysis.

The measurement of collision cross sections (CCS, σ) offers supplemental information about sizes and conformations of ions beyond mass analysis alone. We have previously shown that CCSs can be determined directly from the time-domain transient decay of ions in an Orbitrap mass analyzer as ions oscillate around the central electrode and collide with neutral gas, thus removing them from the ion packet. Herein, we develop the modified hard collision model, thus deviating from the prior FT-MS hard sphere model, to determine CCSs as a function of center-of-mass collision energy in the Orbitrap analyzer. With this model, we aim to increase the upper mass limit of CCS measurement for native-like proteins, characterized by low charge states and presumed to be in more compact conformations. We also combine CCS measurements with collision induced unfolding and tandem mass spectrometry experiments to monitor protein unfolding and disassembly of protein complexes and measure CCSs of ejected monomers from protein complexes.

TOI-1442 b and TOI-2445 b: Two potentially rocky ultra-short period planets around M dwarfs

Context. Exoplanets with orbital periods of less than one day are known as ultra-short period (USP) planets. They are relatively rare products of planetary formation and evolution processes, but especially favourable for characterisation with current planet detection methods. At the time of writing, 125 USP planets have already been confirmed. Aims. Our aim is to validate the planetary nature of two new transiting planet candidates around M dwarfs announced by the NASA Transiting Exoplanet Survey Satellite (TESS), registered as TESS Objects of Interest (TOIs) TOI-1442.01 and TOI-2445.01. Methods. We used TESS data, ground-based photometric light curves, and Subaru/IRD spectrograph radial velocity (RV) measurements to validate both planetary candidates and to establish their physical properties. Results. TOI-1442 bis a validated exoplanet with an orbital period of P = 0.4090682 ± 0.0000004 day, a radius of Rp = 1.15 ± 0.06 R⊕, and equilibrium temperature of Tp,eq = 1357−42+49 K. TOI-2445 b is also validated with an orbital period of P = 0.3711286 ± 0.0000004 day, a radius of Rp = 1.33 ± 0.09 R⊕, and equilibrium temperature of Tp,eq = 1330−56+61 K. Their physical properties align with current empirical trends and formation theories of USP planets. Based on the RV measurements, we set 3σ upper mass limits of 8 M⊕ and 20 M⊕, thus confirming the non-stellar, sub-Jovian nature of both transiting objects. More RV measurements will be needed to constrain the planetary masses and mean densities, and the predicted presence of outer planetary companions. These targets extend the small sample of USP planets orbiting around M dwarfs up to 21 members. They are also among the 20 most suitable terrestrial planets for atmospheric characterisation via secondary eclipse with the James Webb Space Telescope, according to a widespread emission spectroscopy metric.

Constraints on the cosmological coupling of black holes from Gaia

Recent work has suggested that black holes (BHs) could be cosmologically coupled to the accelerated expansion of the Universe, potentially becoming a candidate for origin of dark energy. This would imply that BH mass growth follows cosmological expansion, with the masses of individual BHs growing as MBH ∝ (1 + z)3. In this Letter, we discuss the binary systems Gaia BH1 and Gaia BH2, which contain ∼9 M⊙ BHs orbited by ∼1 M⊙ stars in widely separated orbits. The ages of both systems can be constrained by the properties of the luminous stars. If BH masses are indeed growing as (1 + z)3, the masses of both BHs at formation would have been significantly smaller than today. We find a 77% probability that the mass of the BH in Gaia BH2 would have been below 2.2 M⊙ at formation. This is below the classical Tolman–Oppenheimer–Volkov limit, though it is not yet clear whether or not BHs subject to cosmological coupling should obey this limit. For Gaia BH1, the same probability is 70%. This analysis is consistent with results from two BHs in the globular cluster NGC 3201, but unlike the NGC 3201 BHs, the Gaia BHs have well-constrained inclinations and therefore firm upper mass limits. The discovery of more BHs in binary systems with Gaia astrometry in the coming years will allow us to test the cosmological coupling hypothesis decisively.

Validation of TOI-1221 b: A Warm Sub-Neptune Exhibiting Transit Timing Variations around a Sun-like Star

We present a validation of a long-period ( days) transiting sub-Neptune planet, TOI-1221 b (TIC 349095149.01), around a Sun-like (m V = 10.5) star. This is one of the few known exoplanets with a period >50 days, and belongs to the even smaller subset of which have bright enough hosts for detailed spectroscopic follow-up. We combine Transiting Exoplanet Survey Satellite light curves and ground-based time-series photometry from the Perth Exoplanet Survey Telescope (0.3 m) and Las Cumbres Observatory global telescope network (1.0 m) to analyze the transit signals and rule out nearby stars as potential false-positive sources. High-contrast imaging from the Southern Astrophysical Research Telescope and Gemini/Zorro rule out nearby stellar contaminants. Reconnaissance spectroscopy from CHIRON sets a planetary scale upper mass limit on the transiting object (1.1 and 3.5 M Jup at 1σ and 3σ, respectively) and shows no sign of a spectroscopic binary companion. We determine a planetary radius of , placing it in the sub-Neptune regime. With a stellar insolation of , we calculate a moderate equilibrium temperature of T eq = 440 K, assuming no albedo and perfect heat redistribution. We find a false-positive probability from the TRICERATOPS tool of FPP = 0.0014 ± 0.0003 as well as other qualitative and quantitative evidence to support the statistical validation of TOI-1221 b. We find significant evidence (>5σ) of oscillatory transit timing variations, likely indicative of an additional nontransiting planet.

Abundances of CNO elements in z ∼ 0.3–0.4 Lyman continuum leaking galaxies

ABSTRACT We present observations with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope (HST) of 11 Lyman continuum (LyC) leaking galaxies at redshifts, z, in the range 0.29–0.43, with oxygen abundances 12+log(O/H) = 7.64–8.16, stellar masses M⋆ ∼ 107.8–109.8 M⊙, and O32 = [O iii] λ5007/[O ii] λ3727 of ∼ 5–20 aiming to detect the C iii] λ1908 emission line. We combine these observations with the optical Sloan Digital Sky Survey (SDSS) spectra for the determination of carbon, nitrogen, and oxygen abundances. Our sample was supplemented by 31 galaxies from the literature, for which carbon, nitrogen, and oxygen abundances can be derived from the HST and SDSS spectra. These additional galaxies, however, do not have LyC observations. We find that log(C/O) for the entire sample at 12+log(O/H) < 8.1 does not depend on metallicity, with a small dispersion of ∼0.13 dex around the average value of ∼−0.75 dex. On the other hand, the log(N/O) in galaxies at z > 0.1, including LyC leakers, is systematically higher compared to the rest of the sample with lower metallicity. We find that log(C/O) slightly decreases with increasing M⋆ from ∼ −0.65 at M⋆ = 106 M⊙ to ∼ −0.80 at M⋆ = 109–1010 M⊙, whereas log(N/O) is considerably enhanced at M⋆ > 108 M⊙. The origin of these trends remains basically unknown. A possible solution would be to assume that the upper mass limit of the stellar initial mass function in more massive galaxies is higher. This would result in a higher production of oxygen and a larger fraction of massive stars with stellar wind polluting the interstellar medium with nitrogen.

Analytical model of low-mass strange stars in $$2+1$$ space–time

It is quite fascinating to study the low-mass compact stars because of their enigmatic behaviour. In this paper, we have modelled this kind of low-mass strange stars based on the Heintzmann ansatz in $$(2+1)$$ dimensions. Attractive anisotropic force plays a significant role in restricting the upper mass limit (which is comparatively low) of the strange star. We have applied our model to some low-mass strange stars. Our model is useful to predict important parameters of the low-mass strange stars.

Weak Interaction Dependent Super Gravity of Galactic Baryon Mass

Considering our light speed growing Planck scale universe, it seems possible to develop a practical model of Hubble-Hawking Universe by using which cosmic temperature and Hubble parameter can be correlated accurately. Without considering galactic dark matter, galactic flat rotation speeds can be addressed with ‘super gravity’ of galactic baryonic mass. In this context, (180 to 200) million solar masses can be considered as a characteristic upper mass limit of ordinary gravity. Considering the proposed current upper mass limit of ordinary gravity as a characteristic weak interaction mass unit, hypothecated galactic dark matter can be quantified. Clearly speaking, weak interaction boosts the gravity of galaxies in proportion to their virtual dark mass as (galactic baryonic mass)3/2 / (200 million solar masses)1/2. Based on cosmic recombination temperature and baryon acoustic bubble radius, upper mass limit of gravity can also be fitted. With further study, dark matter existence and physical properties can be explored.

A 3.8 yr optical quasi-periodic oscillations in blue quasar SDSS J132144+033055 through combined light curves from CSS and ZTF

ABSTRACT In the manuscript, a 3.8 yr optical quasi-periodic oscillations (QPOs) is reported in blue quasar SDSS J132144+033055 (= SDSS J1321) at z = 0.269, based on 16.3yr-long light curve from both CSS and ZTF directly described by a sinusoidal function. The 3.8 yr QPOs can be confirmed through the Generalized Lomb–Scargle periodogram with confidence level higher than 5σ, through properties of the phase-folded light curve and the WWZ technique. Moreover, the collected Pan-STARRS light curves well follow the sinusoidal function described best fitting results to the Catalina Sky Survey (CSS) and Catalina Sky Survey (ZTF) light curves. The optical QPOs strongly indicate a central binary black hole (BBH) system in SDSS J1321, with expected space separation smaller than 0.018 pc, through the estimated upper limit of total BH mass 3.3 × 109 M⊙ through the correlation between BH mass and continuum luminosity. Meanwhile, we check disc precession applied to explain the optical QPOs. However, under the disc precession assumption, the determined optical emission regions from central BH have sizes about 37RG similar as the sizes 35RG of the expected NUV emission regions through the correlation between disc size and BH mass, indicating the disc precession is not preferred. And due to undetected radio emissions, jet precession can be ruled out. Furthermore, only 0.1 per cent probability can determined as the QPOs mis-detected through CAR process randomly created light curves related to intrinsic AGN activities, re-confirming the optical QPOs with significance level higher than 3σ. Therefore, combining long-term light curves from CSS and ZTF can lead to more QPOs candidates in the near future.

Simultaneous determination of Os, Ir, Pt and Au in sorbent phases by total reflection X-ray fluorescence

Simultaneous determination of trace and ultra-trace noble metal (NM) contents is a challenging analytical problem. Quantification of NMs in a solid sorbent phase by total reflection X-ray fluorescence (TXRF) was propounded to exclude the problematic stage of analytes desorption. In this study, line overlapping and spectra processing were discussed, theoretical upper limit of area-related mass of the sorbent on a reflector was evaluated, and different quantification procedures were compared. A procedure for the simultaneous determination of Os, Ir, Pt and Au in the solid sorbent phase was developed. This procedure includes sorption of NMs from a diluted solution of a digested sample, TXRF determination of analytes directly in the sorbent phase and data processing using empirical calibration or multivariate regression algorithms (principal component regression, projection on latent structures or partial least squares regression). The procedure allows determining Os, Ir, Pt, Au with a relative error of 15%. Calculated limits of quantification (LOQ) for rocks, considering our sample decomposition procedure, were equal to 0.43, 0.39, 0.43 and 0.31 μg g−1 for Os, Ir, Pt and Au, respectively. The procedure was verified using certificated reference materials and ICP-MS as a reference method.

Extinguishing the FIRE: environmental quenching of satellite galaxies around Milky Way-mass hosts in simulations

ABSTRACT The star formation and gas content of satellite galaxies around the Milky Way (MW) and Andromeda (M31) are depleted relative to more isolated galaxies in the Local Group (LG) at fixed stellar mass. We explore the environmental regulation of gas content and quenching of star formation in z = 0 galaxies at $M_{*}=10^{5\!-\!10}\, \rm {M}_{\odot }$ around 14 MW-mass hosts from the Feedback In Realistic Environments 2 (FIRE-2) simulations. Lower mass satellites ($M_{*}\lesssim 10^7\, \rm {M}_{\odot }$) are mostly quiescent and higher mass satellites ($M_{*}\gtrsim 10^8\, \rm {M}_{\odot }$) are mostly star forming, with intermediate-mass satellites ($M_{*}\approx 10^{7\!-\!8}\, \rm {M}_{\odot }$) split roughly equally between quiescent and star forming. Hosts with more gas in their circumgalactic medium have a higher quiescent fraction of massive satellites ($M_{*}=10^{8\!-\!9}\, \rm {M}_{\odot }$). We find no significant dependence on isolated versus paired (LG-like) host environments, and the quiescent fractions of satellites around MW-mass and Large Magellanic Cloud (LMC)-mass hosts from the FIRE-2 simulations are remarkably similar. Environmental effects that lead to quenching can also occur as pre-processing in low-mass groups prior to MW infall. Lower mass satellites typically quenched before MW infall as central galaxies or rapidly during infall into a low-mass group or a MW-mass galaxy. Most intermediate- to high-mass quiescent satellites have experienced ≥1–2 pericentre passages (≈2.5–5 Gyr) within a MW-mass halo. Most galaxies with $M_{*}\gtrsim 10^{6.5}\, \rm {M}_{\odot }$ did not quench before falling into a host, indicating a possible upper mass limit for isolated quenching. The simulations reproduce the average trend in the LG quiescent fraction across the full range of satellite stellar masses. Though the simulations are consistent with the Satellites Around Galactic Analogs (SAGA) survey’s quiescent fraction at $M_{*}\gtrsim 10^8\, \rm {M}_{\odot }$, they do not generally reproduce SAGA’s turnover at lower masses.

The Discovery of a Planetary Companion Interior to Hot Jupiter WASP-132 b

Hot Jupiters are generally observed to lack close planetary companions, a trend that has been interpreted as evidence for high-eccentricity migration. We present the discovery and validation of WASP-132 c (TOI-822.02), a 1.85 ± 0.10 R ⊕ planet on a 1.01 day orbit interior to the hot Jupiter WASP-132 b. Transiting Exoplanet Survey Satellite and ground-based follow-up observations, in conjunction with vetting and validation analysis, enable us to rule out common astrophysical false positives and validate the observed transit signal produced by WASP-132 c as a planet. Running the validation tools vespa and TRICERATOPS on this signal yields false-positive probabilities of 9.02 × 10−5 and 0.0107, respectively. Analysis of archival CORALIE radial velocity data leads to a 3σ upper limit of 28.23 ms−1 on the amplitude of any 1.01 day signal, corresponding to a 3σ upper mass limit of 37.35 M ⊕. Dynamical simulations reveal that the system is stable within the 3σ uncertainties on the planetary and orbital parameters for timescales of ∼100 Myr. The existence of a planetary companion near the hot Jupiter WASP-132 b makes the giant planet’s formation and evolution via high-eccentricity migration highly unlikely. Being one of just a handful of nearby planetary companions to hot Jupiters, WASP-132 c carries with it significant implications for the formation of the system and hot Jupiters as a population.

The Discovery of a Planetary Companion Interior to Hot Jupiter WASP-132 b

Hot Jupiters are generally observed to lack close planetary companions, a trend that has been interpreted as evidence for high-eccentricity migration. We present the discovery and validation of WASP-132 c (TOI-822.02), a 1.85 $\pm$ 0.10 $R_{\oplus}$ planet on a 1.01 day orbit interior to the hot Jupiter WASP-132 b. Transiting Exoplanet Survey Satellite (TESS) and ground-based follow-up observations, in conjunction with vetting and validation analysis, enable us to rule out common astrophysical false positives and validate the observed transit signal produced by WASP-132 c as a planet. Running the validation tools \texttt{vespa} and \texttt{triceratops} on this signal yield false positive probabilities of $9.02 \times 10^{-5}$ and 0.0107, respectively. Analysis of archival CORALIE radial velocity data leads to a 3$\sigma$ upper limit of 28.23 ms$^{-1}$ on the amplitude of any 1.01-day signal, corresponding to a 3$\sigma$ upper mass limit of 37.35 $M_{\oplus}$. Dynamical simulations reveal that the system is stable within the 3$\sigma$ uncertainties on planetary and orbital parameters for timescales of $\sim$100 Myr. The existence of a planetary companion near the hot Jupiter WASP-132 b makes the giant planet's formation and evolution via high-eccentricity migration highly unlikely. Being one of just a handful of nearby planetary companions to hot Jupiters, WASP-132 c carries with it significant implications for the formation of the system and hot Jupiters as a population.

Constraints on the stellar upper mass limit from simulations of UV disk ablation

Constraints on the stellar upper mass limit from simulations of UV disk ablation

Type II supernovae from the Carnegie Supernova Project-I

Linking supernovae to their progenitors is a powerful method for furthering our understanding of the physical origin of their observed differences while at the same time testing stellar evolution theory. In this second study of a series of three papers where we characterise type II supernovae (SNe II) to understand their diversity, we derive progenitor properties (initial and ejecta masses and radius), explosion energy, and56Ni mass and its degree of mixing within the ejecta for a large sample of SNe II. This dataset was obtained by the Carnegie Supernova Project-I and is characterised by a high cadence of SNe II optical and near-infrared light curves and optical spectra that were homogeneously observed and processed. A large grid of hydrodynamical models and a fitting procedure based on Markov chain Monte Carlo methods were used to fit the bolometric light curve and the evolution of the photospheric velocity of 53 SNe II. We infer ejecta masses of between 7.9 and 14.8M⊙, explosion energies between 0.15 and 1.40 foe, and56Ni masses between 0.006 and 0.069M⊙. We define a subset of 24 SNe (the ‘gold sample’) with well-sampled bolometric light curves and expansion velocities for which we consider the results more robust. Most SNe II in the gold sample (∼88%) are found with ejecta masses in the range of ∼8−10M⊙, coming from low zero-age main-sequence masses (9−12M⊙). The modelling of the initial-mass distribution of the gold sample gives an upper mass limit of 21.3$ ^{+3.8}_{-0.4} $M⊙and a much steeper distribution than that for a Salpeter massive-star initial mass function (IMF). This IMF incompatibility is due to the large number of low-mass progenitors found – when assuming standard stellar evolution. This may imply that high-mass progenitors lose more mass during their lives than predicted. However, a deeper analysis of all stellar evolution assumptions is required to test this hypothesis.

A Snowball in Hell: The Potential Steam Atmosphere of TOI-1266c

Abstract TOI-1266c is a recently discovered super-Venus in the radius valley orbiting an early M dwarf. However, its notional bulk density (∼2.2 g cm−3) is consistent with a large volatile fraction, suggesting that it might have volatile reservoirs that have survived billions of years at more than twice Earth’s insolation. On the other hand, the upper mass limit paints a picture of a cool super-Mercury dominated by >50% iron core (∼9.2 g cm−3) that has tiptoed up to the collisional stripping limit and into the radius gap. Here we examine several hypothetical states for TOI-1266c using a combination of new and updated open-source atmospheric escape, radiative−convective, and photochemical models. We find that water-rich atmospheres with trace amounts of H2 and CO2 are potentially detectable (S/N > ∼ 5) in less than 20 hr of James Webb Space Telescope (JWST) observing time. We also find that water vapor spectral features are not substantially impacted by the presence of high-altitude water or ice clouds owing to the presence of a significant amount of water above the cloud deck, although further work with self-consistent cloud models is needed. Regardless of its mass, however, TOI-1266c represents a unique proving ground for several hypotheses related to the evolution of sub-Neptunes and Venus-like worlds, particularly those near the radius valley.

The Transit Timing and Atmosphere of Hot Jupiter HAT-P-37b

Abstract We perform transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting a G-type star. Nine new transit light curves are obtained and analyzed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV analyses show a possibility that the system has an additional planet that induced the TTVs amplitude signal of 1.74 ± 0.17 minutes. If the body is located near the 1:2 mean-motion resonance orbit, the sinusoidal TTV signal could be caused by the gravitational interaction of a sub-Earth-mass planet with mass of 0.06 M ⊕. From the analysis of an upper-mass limit for the second planet, a Saturn-mass planet with orbital period less than 6 days is excluded. The broadband transmission spectra of HAT-P-37b favors a cloudy atmospheric model with an outlier spectrum in the B filter.

A pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 characterized with CHEOPS

ABSTRACT We report the discovery and characterization of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in the Transiting Exoplanet Survey Satellite (TESS) photometry. To characterize the system, we performed and retrieved the CHaracterising ExOPlanets Satellite (CHEOPS), TESS, and ground-based photometry, the High Accuracy Radial velocity Planet Searcher (HARPS) high-resolution spectroscopy, and Gemini speckle imaging. We characterize the host star and determine $T_{\rm eff, \star }=4734\pm 67\,\mathrm{ K}$, $R_{\star }=0.726\pm 0.007\, \mathrm{ R}_{\odot }$, and $M_{\star }=0.748\pm 0.032\, \mathrm{ M}_{\odot }$. We present a novel detrending method based on point spread function shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of Pb = 6.44387 ± 0.00003 d, a radius of Rb = 2.59 ± 0.04 R⊕, and a mass of $M_{\rm b} = 13.5_{-1.8}^{+1.7}$ M⊕, whilst TOI-1064 c has an orbital period of $P_{\rm c} = 12.22657^{+0.00005}_{-0.00004}$ d, a radius of Rc = 2.65 ± 0.04 R⊕, and a 3σ upper mass limit of 8.5 M⊕. From the high-precision photometry we obtain radius uncertainties of ∼1.6 per cent, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterized sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further radial velocities are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of mass–radius space, and it allow us to identify a trend in bulk density–stellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets.

The Estimation of Fundamental Physics Parameters for Fermi-LAT Blazars

Abstract Aiming to delineate the physical framework of blazars, we present an effective method to estimate four important parameters based on the idea proposed by Becker & Kafatos, including the upper limit of central black hole mass M, the Doppler factor δ, the distance along the axis to the site of the γ-ray production d (which then can be transformed into the location of γ-ray-emitting region R γ ) and the propagation angle with respect to the axis of the accretion disk Φ. To do so, we adopt an identical sample with 809 Fermi-LAT-detected blazars which had been compiled in Pei et al. These four derived parameters stepping onto the stage may shed new light on our knowledge regarding γ-ray blazars. With regard to the paper of Becker & Kafatos, we obtain several new perspectives, mainly in (1) putting forward an updated demarcation between BL Lacs and FSRQs based on the relation between broad-line region luminosity and disk luminosity both measured in Eddington units, i.e., L disk/L Edd = 4.68 × 10−3, indicating that there are some differences between BL Lacs and FSRQs on the accretion power in the disk; (2) proposing that there is a so-called “appareling zone,” a potential transition field between BL Lacs and FSRQs where the changing-look blazars perhaps reside; (3) the location of γ-ray emission region is principally constrained outside the broad-line region, and for some BL Lacs are also away from the dusty molecular torus, which means the importance of emission components in the jet.

Maximum baryon masses for static neutron stars in f(R) gravity

We investigate the upper mass limit predictions of the baryonic mass for static neutron stars in the context of f(R) gravity. We use the most popular f(R) gravity model, namely the R 2 gravity, and calculate the maximum baryon mass of static neutron stars adopting several realistic equations of state and one ideal equation of state, namely that of causal limit. Our motivation is based on the fact that neutron stars with baryon masses larger than the maximum mass for static neutron star configurations inevitably collapse to black holes. Thus with our analysis, we want further to enlighten the predictions for the maximum baryon masses of static neutron stars in R 2 gravity, which, in turn, further strengthens our understanding of the mysterious mass gap region. As we show, the baryon masses of most of the equations of states studied in this paper lie in the lower limits of the mass gap region –, but intriguingly enough, the highest value of the maximum baryon masses we found is of the order of . This upper mass limit also appears as a maximum static neutron star gravitational mass limit in other contexts. Combining the two results which refer to baryon and gravitational masses, we point out that the gravitational mass of static neutron stars cannot be larger than three solar masses, while based on maximum baryon masses results of the present work, we can conspicuously state that it is highly likely the lower mass limits of astrophysical black holes in the range of –. This, in turn, implies that maximum neutron star masses in the context of R 2 gravity are likely to be in the lower limits of the range of –. Hence our work further supports the General Relativity claim that neutron stars cannot have gravitational masses larger than and then, to explain observations comparable or over this limit, we need alternative extensions of General Relativity, other than f(R) gravity.

Using action space clustering to constrain the recent accretion history of Milky Way-like galaxies

ABSTRACT In the currently favoured cosmological paradigm galaxies form hierarchically through the accretion of satellites. Since a satellite is less massive than the host, its stars occupy a smaller volume in action space. Actions are conserved when the potential of the host halo changes adiabatically, so stars from an accreted satellite would remain clustered in action space as the host evolves. In this paper, we identify recently disrupted accreted satellites in three Milky Way-like disc galaxies from the cosmological baryonic FIRE-2 simulations by tracking satellites through simulation snapshots. We try to recover these satellites by applying the cluster analysis algorithm Enlink to the orbital actions of accreted star particles in the z = 0 snapshot. Even with completely error-free mock data we find that only 35 per cent (14/39) satellites are well recovered while the rest (25/39) are poorly recovered (i.e. either contaminated or split up). Most (10/14 ∼70 per cent) of the well-recovered satellites have infall times <7.1 Gyr ago and total mass >4 × 108M⊙ (stellar mass more than 1.2 × 106 M⊙, although our upper mass limit is likely to be resolution dependent). Since cosmological simulations predict that stellar haloes include a population of in situ stars, we test our ability to recover satellites when the data include 10–50 per cent in situ contamination. We find that most previously well-recovered satellites stay well recovered even with 50 per cent contamination. With the wealth of 6D phase space data becoming available we expect that cluster analysis in action space will be useful in identifying the majority of recently accreted and moderately massive satellites in the Milky Way.