arXiv subjects

Mario Cadelano

Publications and source records attributed to Mario Cadelano.

At least 19 recordsLinked to original sources

arXiv2026

The first MeerKAT S-band globular cluster pulsar survey

Globular clusters are efficient factories of recycled pulsars, but searches toward high-dispersion-measure (DM) clusters can be strongly limited near 1 GHz by dispersive smearing and interstellar scattering. We present the first MeerKAT S-band (nu ~ 2.4 GHz) pulsar survey of 14 globular clusters. High time- and frequency-resolution observations were searched using segmented acceleration and jerk techniques, followed by candidate folding and targeted folding with available timing ephemerides. We re-detected 39 known pulsars and discovered four new millisecond pulsars in Glimpse-C01: J1848-0129C, D, E, and F. Multi-epoch follow-up enabled preliminary Keplerian orbital fits for J1848-0129C and J1848-0129D. J1848-0129C is an eclipsing MSP in a ~5 d orbit, placing it among long-period eclipsing systems known as huntsman binaries, while J1848-0129D is in a ~3.4 d nearly circular orbit with a massive white-dwarf companion of about 1 solar mass. Two Glimpse-C01 pulsars show large DM offsets from the cluster average. Comparison with other Galactic globular clusters indicates that intracluster DM spreads tend to increase with foreground DM, implying that narrow DM search windows may be sub-optimal for high-DM clusters. From detections and non-detections, we infer a practical single-epoch MeerKAT S-band tied-array detectability scale of about 10-20 microJy. These results demonstrate the value of high-frequency searches for pulsars in strongly dispersed and scattered cluster environments.

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arXiv2026

The youngest white dwarf companion to a millisecond pulsar: Insights from NGC 362D

We report on the identification of the optical counterpart to the recently discovered millisecond pulsar (MSP) NGC362D in the Galactic globular cluster NGC362 based on deep, multi-band, and multi-epoch Hubble Space Telescope observations. Our analysis robustly shows that this object is a very low-mass ($\sim0.18 M_{\odot}$) He white dwarf (WD) still in the pre-cooling phase. Interestingly, a detailed comparison with updated binary evolution models indicates that this object completed the mass-transfer phase only recently ($\sim0.6$ Gyr ago), thus strongly suggesting that COM-NGC362D is the youngest WD companion to a MSP identified to date. Remarkably, in this respect, the photometric properties of NGC362D show, for the first time in this class of objects, significant wavelength-dependent variations that are consistent with the presence of residual circumstellar material. This system therefore provides a valuable test case to directly probe the immediate aftermath of the MSP recycling process and to constrain the early evolutionary stages of proto-WD companions and their radio and optical properties. Our results suggest that residual material can produce radio and optical signatures that mimic those of systems with non-degenerate companions, potentially leading to the misclassification of young MSPs.

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arXiv2026

Exploring the optical properties of redback pulsars: The case of J1717+4308A in the globular cluster M92

Binary millisecond pulsars (MSPs) in globular clusters (GCs) are key for binary and stellar evolution studies under extreme conditions. The identification of their optical companion stars is instrumental in order to characterise these systems and to constrain the possible recycling mechanisms. For this work, we searched for the optical counterpart to PSR J1717+4308A (hereafter M92A) in the GC M92. To this end, we exploited a multi-epoch, multi-wavelength dataset obtained with the Hubble Space Telescope. We constructed colour--magnitude diagrams, investigated proper motions to assess cluster membership, and modelled the observed light curves. We identified an object located at only 0.02 arcsec from the nominal radio position as the likely optical companion to M92A. The star is significantly bluer than the main sequence at the same luminosity level and exhibits clear photometric variability with a periodicity in agreement with the orbital motion of the binary. The light curve displays two maxima and two minima, indicative of strong tidal distortion and only mild irradiation. Such mild irradiation is consistent with the ratio of the pulsar spin-down to the companion flux ($f_\mathrm{sd}$), which for M92A lies close to the boundary between ellipsoidal- and irradiation-dominated regimes ($f_\mathrm{sd} \approx 2.71$). From the light curve modelling we inferred the main physical properties of the companion star. The best-fit model indicates a high-inclination system with a relatively low-mass companion and a massive neutron star. With a base temperature of $\sim7200$ K, the companion ranks among the hottest redbacks known to date. This object therefore adds additional pieces to the puzzle of MSP companion properties and contributes to outlining the characteristics of redbacks across the different classes.

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arXiv2026

The one and the only: the pulsar - white dwarf system in NGC 6749

PSR J1905+0154A is a binary millisecond pulsar located in the globular cluster (GC) NGC 6749. It was discovered in 2004 in a search for pulsars in GCs carried out with the Arecibo 305-m radio telescope. The pulsar has a spin period of 3.2 ms, an orbital period of 0.81 days, and is in a low-eccentricity orbit with a low-mass WD companion. Combining early Arecibo and latter Five Hundred meter Aperture Spherical Telescope (FAST) data, we were able to derive a phase-coherent timing solution for this pulsar, which now spans 20 years. This includes a precise measurement of the astrometric, spin and orbital parameters of the system. The small range of predicted accelerations expected from the gravitational field of this GC allows an estimate of the intrinsic spin-down: the inferred magnetic field at the surface (2.2 - 2.4 * 10^8 G) and characteristic age (2.8 - 3.5 Gyr) are typical of what one finds among MSPs in the Galactic field. The position of this pulsar coincides with the position of one of the very few candidate white dwarfs (WDs) in the whole HST dataset on this GC. The position of the companion in the colour-magnitude diagram is consistent with a Helium WD with a mass of 0.17 - 0.19 M_sun, a cooling age of 0.4 - 0.7 Gyr, and a surface temperature of 11,600 - 14,800 K. A comparison with the characteristic age of the pulsar indicates that at the time of Roche lobe detachment, the spin period was between 1.98 and 2.62 ms.. The velocity of the system relative to the GC, which is 4.5-sigma significant and an order of magnitude larger than the escape velocity, raises the possibility that, despite its location close to the centre of the GC, the pulsar might not be associated with it. Finally, our effort to confirm a second pulsar candidate in this GC did not yield a positive confirmation, nor the discovery of any additional pulsar in this GC.

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arXiv2026

A joint MeerKAT and Parkes view of Omega Centauri: New TRAPUM Searches and Pulsar Timing

Millisecond pulsars (MSPs) are powerful probes of globular clusters (GCs), tracing stellar evolution, cluster dynamics, and the local gravitational potential. We investigate the MSP population in GC Omega Centauri. We perform Fourier-domain acceleration and jerk searches on MeerKAT observations, and carry out pulsar timing using MeerKAT and Parkes Murriyang data spanning 2021-2025. We fold Fermi LAT and NICER photons using updated radio ephemerides to search for high-energy pulsations. We discover a new isolated MSP, PSR J1326-4728S (hereafter S), with a spin period of 4.538 ms and a dispersion measure of 96.24 cm$^3$pc. We update the orbital parameters of all known binary systems, with those of I, N, and Q differing significantly from previous estimates, and obtain new timing solutions for G, H, and K. Pulsars B, G, H, K, and L exhibit black widow-like properties, I, N and Q are found in wider binaries, with N and Q having >0.2 M$_\odot$ companions, and N showing a significant orbital eccentricity (e=0.093). Significant spin period derivatives are measured for eight pulsars and interpreted as arising from the cluster gravitational potential. No pulsed high-energy emission is detected from individual pulsars. The inferred line-of-sight accelerations are consistent with a King-model gravitational potential. While our measurements are insensitive to an intermediate-mass black hole with mass 10$^3$-10$^4$ M$_\odot$, they place an upper limit of <10$^5$ M$_\odot$ at 90% confidence. The high fraction of isolated MSPs and black widows systems, and possibly the eccentricity of N, are difficult to reconcile with MSP population predictions based solely on encounter rates. Instead, these properties likely reflect the complex evolutionary history of Omega Centauri, with part of its MSP population having formed in denser environments than the one observed today.

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arXiv2025

Fast Rotating Blue Straggler Stars in the globular cluster NGC 1851

In this work we study the rotational velocities of a sample of blue straggler stars (BSSs) and reference stars belonging to the Galactic globular cluster NGC 1851, using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT. After field decontamination based on radial velocities and proper motions, the final sample of member stars is composed of 15 BSSs and 45 reference stars populating the red giant and horizontal branches of the cluster. In agreement with previous findings, the totality of reference stars has negligible rotation (lower than 15 km/s). In contrast, we find high values of rotational velocity (up to $\sim$ 150 km/s) for a sub-sample of BSSs. By defining the threshold for fast rotating BSSs at 40 km/s, we found 4 fast-rotating BSSs out of 15, corresponding to a percentage of 27 $\pm$ 14 %. This results delineates a monotonically decreasing trend (instead of a step function) between the percentage of fast spinning BSSs and the central concentration and density of the host cluster, supporting a scenario where recent BSS formation preferentially occurs in low-density environments from the evolution of binary systems.

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arXiv2025

Identification and characterization of optical companions to the population of millisecond pulsars in the globular cluster M3

The study of binary millisecond pulsars (MSPs) in globular clusters (GCs) is a key ingredient to study binary and stellar evolution under extreme conditions. In this context, an accurate analysis of the optical emission, which is mostly dominated by the companion star, is essential for a comprehensive characterization of these systems and their role within their environment. In this work, we present a multi-wavelength investigation of five binary MSPs in the Galactic GC M3 (NGC 5272) using archival Hubble Space Telescope (HST) data. Our analysis builds on the timing solutions obtained with the FAST radio Telescope by Li et al. (2024). For each MSP, we carry out precise astrometric cross-matching with the accurate radio positions to identify potential counterparts. When a match is found, we analyse its location in the colour-magnitude diagrams and compare the results with updated binary evolution models to infer the system properties. We confirm the identification of the optical companion to M3B, matching the source previously reported by Cadelano et al. (2019), and successfully identify and characterize the optical companions to M3D and M3F. All three are consistent with helium white dwarfs, as expected from the canonical formation scenario. For M3A and M3E, no reliable counterparts are found, but we place strong upper limits on the brightness and mass of the undetected companion. In the case of M3E, we detect a red object near the radio position in two F814W observations; however, astrometric measurements over a 15-year baseline reveal a significant proper motion inconsistent with cluster membership, identifying the source as a foreground contaminant. This study highlights the effectiveness of combining precise radio timing with deep, multi-band HST images to uncover and constrain the nature of MSP companions in GCs, offering insights into their formation and evolutionary histories.

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arXiv2025

A candidate to the long sought optical counterpart to the Rapid Burster in the bulge fossil fragment Liller 1

We report on the possible identification of the optical counterpart of the Rapid Burster MXB 1730-335 in the stellar system Liller 1. The identification was performed by taking advantage of a set of images acquired with the Hubble Space Telescope/Advanced Camera for Surveys in the optical band, and with the Gemini South Telescope in the near-infrared. The analysis of these images revealed the presence of a star with a position possibly compatible with the X-ray and radio band coordinates of the Rapid Burster, and showing significant optical variability. According to its location in the color-magnitude diagram, the candidate companion appears to belong to the young (~ 1-2 Gyr old) super-solar metallicity ([M/H]= +0.3) sub-population recently discovered in Liller 1. We discuss the main characteristics of the candidate counterpart and the Rapid Burster binary system as derived from the available data, also highlighting the need for further coordinated observations to solidly confirm their association and better clarify their physical properties.

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arXiv2025

Detection of a white dwarf orbiting a Carbon-Oxygen depleted blue straggler in 47 Tucanae

We have employed deep far-UV observations secured with the Solar Blind Channel of the Advanced Camera for Surveys onboard the Hubble Space Telescope to search for hot companions to five blue stragglers stars (BSSs) showing significant surface depletion of carbon (C) and oxygen (O), in the Galactic globular cluster 47 Tucanae. Such a chemical pattern has been interpreted as the chemical signature of the mass transfer formation process for the observed blue stragglers. The mass transfer origin is also expected to leave a "photometric signature" in the form of a UV-excess, as the stripped core of the donor star should be observable as a white dwarf (WD) companion orbiting the newborn BSS. We found strong evidence for the presence of a hot (T > 20000 K) WD companion to one of the investigated BSS, indicating that it likely formed through mass transfer less than 12 Myr ago. This is the first simultaneous evidence of the chemical and the photometric signatures of the mass-transfer formation channel. The lack of evidence for a hot companion to the other investigated blue stragglers is consistent with the expectation that the photometric signature (as well as the chemical one) is a transient phenomenon.

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arXiv2025

A binary-related origin mediated by environmental conditions for blue straggler stars

Blue stragglers are anomalously massive core hydrogen-burning stars that, according to the theory of single star evolution, should not exist. They are suspected to form in mass-enhancement processes, involving binary evolution or stellar collisions. In dynamically active systems like globular clusters, the number of blue stragglers originated by collisions is expected to increase with the local density and the rate of stellar encounters. Here we analyse more than 3000 blue stragglers in 48 Galactic globular clusters with different structures, finding that their number normalized to the sampled luminosity anti-correlates (instead of correlating) with the central density, collision rate, and dynamical age of the parent cluster. Similar trends are also found for the cluster binary fraction. Once inserted in the context of the current knowledge of the BSS phenomenon, these correlations indicate that low-density regions (possibly because of a higher binary production/survival rate) are the natural habitat of both BSSs and binary systems, and the observed BSSs mostly have a binary-related origin mediated by the environmental conditions.

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arXiv2025

Structural parameters, chronological age and dynamical age of the LMC globular cluster NGC 1754

In the context of a new systematic study of the properties of the most compact and massive star clusters in the Large Magellanic Cloud (LMC), here we present the determination of the chronological age, the structural parameters, and the dynamical age of NGC 1754. We used high-resolution images taken with the WFC3/HST instrument, both in optical and near-ultraviolet filters. The high quality of the images made it possible to construct the star density profile from resolved star counts, and to fit the observed profile with an appropriate King model to obtain the structural parameters (e.g. core, half-mass, and tidal radii). Our findings confirm that NGC 1754 is a very compact globular cluster with a core radius of only 0.84 pc. The analysis of the same dataset allowed us to confirm a very old age ($t=12.8\pm0.4$ Gyr) for this system, thus further consolidating the indication that the process of globular cluster formation started at the same cosmic time both in the LMC and in the Milky Way, independently of the characteristics of the host environment. We have also used the empirical method called ``dynamical clock'' to estimate the dynamical age of the system. This consists of quantifying the degree of central segregation of blue straggler stars (BSSs) using the $A^+_{rh}$ parameter, which is defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference (lighter) population. This method yielded a value of $A^+_{rh}=0.31\pm0.07$, which is the highest measured so far for LMC clusters, pointing to an advanced dynamical age for the cluster, possibly on the verge of core collapse. The results presented here for NGC 1754 confirm that the natural dynamical evolution of globular clusters plays a role in shaping the age-core radius distributions observed in the LMC.

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arXiv2025

Stellar rotation in the intermediate-age massive cluster NGC 1783: clues on the nature of UV-dim stars

Over the past decade, stellar rotation has emerged as a key factor in shaping the morphology of color-magnitude diagrams of young and intermediate-age star clusters. In this study, we use MUSE integral-field spectroscopy to investigate the stellar rotation of ~2300 stars in the 1.5 Gyr old cluster NGC 1783 in the Large Magellanic Cloud. The effective temperature, surface gravity, radial velocity, and projected rotational velocity ($v\mathrm{sin}i$) of the entire sample were obtained within a Bayesian framework to derive robust estimates of these parameters along with their associated errors. The analysis shows that stars along the extended main sequence turn-off (eMSTO) cover a wide range of rotational velocities, from values consistent with no/slow rotation up to $v\mathrm{sin}i$ ~ 250 km/s. The distribution of stellar rotation velocities appears to play a crucial role in explaining the broadening of the eMSTO in this cluster, and a correlation is observed between $v\mathrm{sin}i$ and the color of the eMSTO stars, with $v\mathrm{sin}i$ increasing as the color becomes redder. Among the eMSTO stars, we investigate the peculiar population of stars strongly dimmed in the UV (so-called UV-dim stars), recently discovered in NGC 1783. UV-dim stars show clear photometric evidence of self-extinction and mild spectroscopic signatures typically observed in shell stars, thus suggesting that they have likely a decretion disc observed nearly equator-on. Interestingly, the study also shows that a significant fraction of UV-dim stars are slow rotators. We discuss potential implications these results may have on our understanding of the formation and evolution of UV-dim stars and we propose that the rotational properties of the UV-dim stars should vary with cluster age.

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arXiv2025

Searching for exotic object companions in the dense core of NGC 362: a multi-wavelength and multi-epoch photometric analysis

The dense cores of globular clusters (GCs) are efficient environments for the production of exotic stellar populations, including millisecond pulsars (MSPs), low-mass X-ray binaries (LMXBs) and cataclysmic variables (CVs). Most of these objects likely form through two- and three-body interactions and are useful tracers of the cluster's dynamical evolution. In this work we explore the exotic object population in the galactic GC NGC 362, searching for the optical counterpart of 33 X-ray sources identified within 1 arcmin from the cluster center. To this aim, we exploit a large Hubble Space Telescope (HST) data-set, obtained in eight different epochs and covering a wavelength range from near UV to the optical I band. To identify the most promising counterparts we follow a multi-step analysis, which is based on four main ingredients, namely positional coincidence, position in the colour-magnitude-diagrams (CMDs), H$\alpha$ excess and photometric variability. In addition, we complement the photometric analysis with spectroscopic information coming from the analysis of MUSE radial velocity (RV) curves. Thanks to this multi-diagnostic approach, we are able to identify 28 high-confidence optical counterparts, including several candidate MSPs, active binaries (ABs) and CVs. The most intriguing counterparts include a candidate black widow (BW) system, an eclipsing binary blue straggler, and a system in outburst, potentially representing either a LMXB or a nova eruption from a CV. The candidate MSPs proposed in this work will contribute to ongoing radio analyses with MeerKAT for the identification and detailed study of MSPs in NGC 362.

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arXiv2025

The bulge globular cluster Terzan 6 as seen from multi-conjugate adaptive optics and HST

This work consists of the first detailed photometric study of Terzan 6, one of the least known globular clusters in the Galactic bulge. Through the analysis of high angular resolution and multi-wavelength data obtained from adaptive optics corrected and space observations, we built deep, optical and near-infrared color-magnitude diagrams reaching $\approx 4$ magnitudes below the main-sequence turnoff. Taking advantage of 4 different epochs of observations, we measured precise relative proper motions for a large sample of stars, from which cluster members have been solidly distinguished from Galactic field interlopers. A non-canonical reddening law (with $R_V=2.85$) and high-resolution differential reddening map, with color excess variations up to $\delta E(B-V) \approx 0.8 $ mag, have been derived in the direction of the system. According to these findings, new values of the extinction and distance modulus have been obtained: respectively, $E(B-V)=2.36\pm0.05$ and $(m-M)_0=14.46 \pm 0.10$ (corresponding to $d=7.8 \pm 0.3$ kpc). We also provide the first determinations of the cluster center and projected density profile from resolved star counts. The center is offset by more than $7$ arcsec to the east from the literature value, and the structural parameters obtained from the King model fitting to the density profile indicate that Terzan 6 is in an advanced stage of its dynamical evolution. We also determined the absolute age of the system, finding $t=13\pm 1 $ Gyr, in agreement with the old ages found for the globular clusters in the Galactic bulge. From the re-determination of the absolute magnitude of the red giant branch bump and the recent estimate of the cluster global metallicity, we find that Terzan 6 nicely matches the tight relation between these two parameters drawn by the Galactic globular cluster population.

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arXiv2025

Thirty-five years of timing of M53A with Arecibo and FAST

PSR B1310+18A is a 33-ms binary pulsar in a 256-day, low eccentricity orbit with a low-mass companion located in NGC 5024 (M53). In this Letter, we present the first phase-coherent timing solution for this pulsar (designated as M53A) derived from a 35-year timing baseline; this combines the archival Arecibo Observatory data with the recent observations from the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We find that the spin period derivative of the pulsar is between 6.1 and $7.5 \times 10^{-19} \rm \, s\, s^{-1}$, which implies a characteristic age between 0.70 and 0.85 Gyr. The timing solution also includes a precise position and proper motion for the pulsar, enabling the identification of the companion of M53A in Hubble Space Telescope data as a Helium white dwarf (He WD) with a mass of $M_{\rm WD}=0.39^{+0.05}_{-0.07} \, \rm M_{\odot}$ and a cooling age of $0.14^{+0.04}_{-0.03}\, \rm Gyr$, confirming that the system formed recently in the history of the GC. The system resembles, in its spin and orbital characteristics, similarly wide pulsar - He WD systems in the Galactic disk. We conclude by discussing the origin of slow pulsars in globular clusters, showing that none of the slow pulsars in low-density globular clusters are as young as the systems observed in the densest known globular clusters.

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arXiv2024

Rotational velocities of Blue Straggler Stars in the Globular Cluster M55

By using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT, we measured radial and rotational velocities of 115 stars in the Galactic globular cluster M55. After field decontamination based on the radial velocity values, the final sample of member stars is composed of 32 blue straggler stars (BSSs) and 76 reference stars populating the red giant and horizontal branches of the cluster. In agreement with previous findings, the totality of red giant branch stars has negligible rotation ($<$ 10 km s$^{-1}$), and horizontal branch stars have rotational velocities of 40 km s$^{-1}$ at most. In contrast, the BSS rotational velocity distribution shows a long tail extending up to $\sim$ 200 km s$^{-1}$, with 15 BSSs (out of 32) spinning faster than 40 km s$^{-1}$. By defining the threshold for fast rotating BSSs at 40 km s$^{-1}$, this sets the percentage of these stars at 47 $\pm$ 14 %. Such a large value has never been found before in any globular clusters. It is roughly comparable to that measured in other loose systems ($\omega$ Centauri, M4, and NGC 3201) and significantly larger than that observed in high-density clusters (as 47 Tucanae, NGC 6397, NGC 6752, and M30). This evidence supports a scenario where recent BSS formation is occurring in low-density environments. We also find that the BSS rotational velocity tends to decrease for decreasing luminosity, as found for another loose cluster of the sample (namely, NGC 3201).

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arXiv2024

The ESO-VLT MIKiS survey reloaded: the internal kinematics of the core of M75

We present the results of a study aimed at characterizing the kinematics of the inner regions of the halo globular cluster M75 (NGC 6864) based on data acquired as part of the ESO-VLT Multi-Instrument Kinematic Survey (MIKiS) of Galactic globular clusters. Our analysis includes the first determination of the line-of-sight velocity dispersion profile in the core region of M75. By using MUSE/NFM observations, we obtained a sample of $\sim 1900$ radial velocity measurements from individual stars located within $16''$ (corresponding to about $r < 3 r_c$ where $r_c$ is the estimated core radius of the system) from the cluster center. After an appropriate selection of the most accurate velocity measures, we determined the innermost portion of the velocity dispersion profile, finding that it is characterized by a constant behavior and a central velocity dispersion of $\sigma_0\sim 9$ km s$^{-1}$. The simultaneous King model fitting to the projected velocity dispersion and density profiles allowed us to check and update previous determinations of the main structural parameters of the system. We also detected a mild hint of rotation in the central $\sim 7''$ from the center, with an amplitude of just $\sim 1.0$ km s$^{-1}$ and a position angle of the rotation axis of PA$_0 = 174\deg$. Intriguingly, the position angle is consistent with that previously quoted for the suspected rotation signal in the outer region of the cluster. Taking advantage of the high quality of the photometric catalog used for the analysis of the MUSE spectra, we also provide updated estimates of the cluster distance, age, and reddening.

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arXiv2024

The dynamical age of the LMC globular cluster NGC 1835 using the "dynamical clock"

In the context of the study of the size-age relationship observed in star clusters in the Large Magellanic Cloud and the investigation of its origin, here we present the determination of the structural parameters and the dynamical age of the massive cluster NGC 1835. We have used a powerful combination of optical and near-ultraviolet images acquired with the WFC3 onboard the HST to construct the star density profile from resolved star counts, determining the values of the core, half-mass and tidal radii through the comparison with the King model family. The same data also allowed us to evaluate the dynamical age of the cluster by using the 'dynamical clock'. This is an empirical method that quantifies the level of central segregation of blue stragglers stars (BSSs) within the cluster half-mass radius by means of the A+ parameter, which is defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference (lighter) population. The results confirm that NGC 1835 is a very compact cluster with a core radius of only 0.84 pc. The estimated value of A+ ($0.30\pm 0.04$) is the largest measured so far in the LMC clusters, providing evidence of a highly dynamically evolved stellar system. NGC 1835 nicely fits into the correlation between A+ and the central relaxation time and in the anti-correlation between A+ and the core radius defined by the Galactic and the Magellanic Cloud clusters investigated to date.

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