High Proper Motion Research Articles

First Byurakan Spectral Survey. Late-Type Stars. Dwarfs

A total of 18 lists of the First Byurakan Survey of Late-Type Stars (FBSLTS) were published between 1990 and 2016. The stars were found on FBS low-dispersion spectral plates. A systematic search and selection were carried out on a surface of ∼16 000deg2 on almost the whole area of the FBS. Since 2007, all FBS low-resolution spectral plates have been digitized. The second version of the “Revised And Updated Catalogue of the First Byurakan Survey of Late-Type Stars”, containing data for 1471 M and C (carbon) stars (130 C-type giants, 1105 M– giants, and 236 M dwarfs) was generated. Among the 236 M dwarfs selected, 176 are new discoveries. The Gaia EDR3 G broad-band magnitudes are in the range 11.3 < G < 17.1. New distance information by Bailer-Jones et al. (2021), which is based on the EDR3 parallaxes are used to estimate the G-band absolute magnitudes for M dwarfs. 9 FBS M dwarfs (out of 176 new discovered) lie within 25pc of the Sun. The object FBS 0909-082 is more distant (r = 780˙pc) M dwarf among the sample considered, for which G-band absolute magnitude M(G)=9.18, M= 0.59MSun, L=0.13597 LSun, and Teff = 3844 K. This object can be classified as M1-M2 subtype dwarf. The nearest object is FBS0250+167, a M7 subtype dwarf with very high proper motion (5.13 arcsec/yr) and is located at 3.83pc from the Sun. The TESS estimated masses lie in the range 0.095(±0.02)M⊙ ≤M≤0.7(±0.1)M⊙ and Teff in the range 4000K < Teff < 2790K for FBSM dwarfs. Color-absolute magnitude (CaMD) diagrams are constructed for the FBSM dwarfs based on Gaia EDR3 and TESS data.

XGAPS: a sub-arcsec cross-match of galactic plane surveys

ABSTRACT We present a sub-arcsec cross-match of Gaia Data Release 3 (DR3) against the INT Galactic Plane Surveys (IGAPS) and the United Kingdom Infrared Deep Sky Survey (UKIDSS). The resulting cross-match of Galactic Plane Surveys (XGAPS) provides additional precise photometry (URGO, g, r, i, Hα, J, H, and K) to the Gaia photometry. In building the catalogue, proper motions given in Gaia DR3 are wound back to match the epochs of the IGAPS constituent surveys (INT Photometric HαSurvey of the Northern Galactic Plane, IPHAS, and the UV-Excess Survey of the Northern Galactic Plane, UVEX) and UKIDSS, ensuring high-proper motion objects are appropriately cross-matched. The catalogue contains 33 987 180 sources. The requirement of >3σ parallax detection for every included source means that distances out to 1–1.5 kpc are well covered. In producing XGAPS, we have also trained a Random Forest classifier to discern targets with problematic astrometric solutions. Selection cuts based on the classifier results can be used to clean colour-magnitude and colour–colour diagrams in a controlled and justified manner, as well as producing subsets of astrometrically reliable targets. We provide XGAPS as a 111 column table. Uses of the catalogue include the selection of Galactic targets for multi-object spectroscopic surveys as well as identification of specific Galactic populations.

The Thousand Pulsar Array programme on MeerKAT – X. Scintillation arcs of 107 pulsars

ABSTRACT We present the detection of 107 pulsars with interstellar scintillation arcs at 856–1712 MHz, observed with the MeerKAT Thousand Pulsar Array Programme. Scintillation arcs appear to be ubiquitous in clean, high S/N observations, their detection mainly limited by short observing durations and coarse frequency channel resolution. This led the survey to be sensitive to nearby, lightly scattered pulsars with high effective velocity – from a large proper motion, a screen nearby the pulsar, or a screen near the Earth. We measure the arc curvatures in all of our sources, which can be used to give an estimate of screen distances in pulsars with known proper motion, or an estimate of the proper motion. The short scintillation time-scale in J1731−4744 implies a scattering screen within 12 pc of the source, strongly suggesting the association between this pulsar and the supernova remnant RCW 114. We measure multiple parabolic arcs of five pulsars, all of which are weakly scintillating with high proper motion. Additionally, several sources show hints of inverted arclets suggesting scattering from anisotropic screens. Building on this work, further targeted MeerKAT observations of many of these pulsars will improve understanding of our local scattering environment and the origins of scintillation; annual scintillation curves would lead to robust screen distance measurements, and the evolution of arclets in time and frequency can constrain models of scintillation.

The GAPS programme at TNG

Context. Neptunes represent one of the main types of exoplanets and have chemical-physical characteristics halfway between rocky and gas giant planets. Therefore, their characterization is important for understanding and constraining both the formation mechanisms and the evolution patterns of planets. Aims. We investigate the exoplanet candidate TOI-1422 b, which was discovered by the TESS space telescope around the high proper-motion G2 V star TOI-1422 (V = 10.6 mag), 155 pc away, with the primary goal of confirming its planetary nature and characterising its properties. Methods. We monitored TOI-1422 with the HARPS-N spectrograph for 1.5 yr to precisely quantify its radial velocity (RV) variation. We analyse these RV measurements jointly with TESS photometry and check for blended companions through high-spatial resolution images using the AstraLux instrument. Results. We estimate that the parent star has a radius of R⋆ = 1.019−0.013+0.014 R⊙, and a mass of M⋆ = 1.019−0.013+0.014 M⊙. Our analysis confirms the planetary nature of TOI-1422 b and also suggests the presence of a Neptune-mass planet on a more distant orbit, the candidate TOI-1422 c, which is not detected in TESS light curves. The inner planet, TOI-1422 b, orbits on a period of Pb = 12.9972 ± 0.0006 days and has an equilibrium temperature of Teq,b = 867 ± 17 K. With a radius of Rb = 3.96−0.11+0.13 R⊕, a mass of Mb = 9.0−2.0+2.3 M⊕ and, consequently, a density of ρb = 0.795−0.235+0.290g cm−3, it can be considered a warm Neptune-sized planet. Compared to other exoplanets of a similar mass range, TOI-1422 b is among the most inflated, and we expect this planet to have an extensive gaseous envelope that surrounds a core with a mass fraction around 10% – 25% of the total mass of the planet. The outer non-transiting planet candidate, TOI-1422 c, has an orbital period of Pc = 29.29−0.20+0.21 days, a minimum mass, Mcsin i, of 11.1−2.3+2.6 M⊕, an equilibrium temperature of Teq,c = 661 ± 13 K and, therefore, if confirmed, could be considered as another warm Neptune.

Discovering vanishing objects in POSS I red images using the Virtual Observatory

ABSTRACT In this paper, we report a search for vanishing sources in POSS I red images using virtual observatory (VO) archives, tools, and services. The search, conducted in the framework of the VASCO project, aims at finding POSS I (red) sources not present in recent catalogues like Pan-STARRS DR2 (limiting magnitude r = 21.4) or Gaia EDR3 (limiting magnitude G = 21). We found 298 165 sources visible only in POSS I plates, out of which 288 770 had a cross-match within 5 arcsec in other archives (mainly in the infrared), 189 were classified as asteroids, 35 as variable objects, 3592 as artefacts from the comparison to a second digitization (Supercosmos), and 180 as high proper motion objects without information on proper motion in Gaia EDR3. The remaining unidentified transients (5399) as well as the 172 163 sources not detected in the optical but identified in the infrared regime are available from a VO compliant archive and can be of interest in searches for strong M-dwarf flares, high-redshift supernovae, asteroids, or other categories of unidentified red transients. No point sources were detected by both POSS-I and POSS-II before vanishing, setting the rate of failed supernovae in the Milky Way during 70 yr to less than one in one billion.

The Proper Motion of the Pulsar J1124–5916 in the Galactic Supernova Remnant G292.0+1.8

We present the first direct measurement of the proper motion of pulsar J1124–5916 in the young, oxygen-rich supernova remnant G292.0+1.8. Using deep Chandra ACIS-I observations from 2006 to 2016, we measure a positional change of 0.″21 ± 0.″05 over the ∼10 yr baseline, or ∼0.″02 yr−1. At a distance of 6.2 ± 0.9 kpc, this corresponds to a kick velocity in the plane of the sky of 612 ± 152 km s−1. We compare this direct measurement against the velocity inferred from estimates based on the center of mass of the ejecta. Additionally, we use this new proper-motion measurement to compare the motion of the neutron star to the center of expansion of the optically emitting ejecta. We derive an age estimate for the supernova remnant of ≳2000 yr. The high measured kick velocity is in line with recent studies of high proper motion neutron stars in other Galactic supernova remnants and consistent with a hydrodynamic origin to the neutron star kick.

Serendipitous discovery of radio flaring behaviour from a nearby M dwarf with MeerKAT

ABSTRACT We report on the detection of MKT J174641.0−321404, a new radio transient found in untargeted searches of wide-field MeerKAT radio images centred on the black hole X-ray binary H1743−322. MKT J174641.0−321404 is highly variable at 1.3 GHz and was detected three times during 11 observations of the field in late 2018, reaching a maximum flux density of 590 ± 60 µJy. We associate this radio transient with a high proper motion, M dwarf star SCR 1746−3214 12 pc away from the Sun. Multiwavelength observations of this M dwarf indicate flaring activity across the electromagnetic spectrum, consistent with emission expected from dMe stars, and providing upper limits on quiescent brightness in both the radio and X-ray regimes. TESS photometry reveals a rotational period for SCR 1746−3214 of 0.2292 ± 0.0025 d, which at its estimated radius makes the star a rapid rotator, comparable to other low-mass systems. Dedicated spectroscopic follow up confirms the star as a mid-late spectral M dwarf with clear magnetic activity indicated by strong H α emission. This transient’s serendipitous discovery by MeerKAT, along with multiwavelength characterization, make it a prime demonstration of both the capabilities of the current generation of radio interferometers and the value of simultaneous observations by optical facilities such as MeerLICHT. Our results build upon the literature of M dwarfs’ flaring behaviour, particularly relevant to the habitability of their planetary systems.

Astrometric and Photometric Verification of Faint Blue White Dwarfs in the Gaia Catalog of nearby Stars

Abstract The Gaia catalog of nearby stars (GCNS) divided all objects with parallaxes >10 mas into GCNS-selected and GCNS-rejected 100 pc samples. Below the white dwarf (WD) sequence in the complete GCNS color–magnitude diagram (CMD), at Gabs > 14.7 + 4.7(G − RP), there appear 60 GCNS-selected faint blue white dwarfs (FBWDs). However this CMD region is also populated by 411 GCNS-rejected objects, mainly from crowded regions toward the Galactic center and the Magellanic Clouds. The WD catalog of Gentile et al. lists only 47 GCNS-selected but also 8 GCNS-rejected objects. I confirm 59 of the GCNS-selected but none of the GCNS-rejected objects as FBWDs from visual inspection and a proper motion check using additional optical sky surveys. Hence FBWDs form an additional branch in the CMD. Compared to the full GCNS-selected 100 pc sample, FBWDs have relatively high proper motions and tangential velocities. They represent interesting targets for studies of ultracool or infrared-faint, and possibly also ultramassive WDs.

Hunting wide-area optical surveys for high proper motion isolated neutron stars

ABSTRACT High-velocity neutron stars (HVNSs) that were kicked out from their birth location can be potentially identified with their large proper motions, and possibly with large parallax, when they come across the solar neighborhood. In this paper, we study the feasibility of hunting isolated HVNSs in wide-area optical surveys by modelling the evolution of NS luminosity taking into account spin-down and thermal radiation. Assuming the upcoming 10-yr Vera C. Rubin Observatory’s LSST observation, our model calculations predict that about 10 HVNSs mainly consisting of pulsars with ages of 104–$10^5\, \rm yr$ and thermally emitting NSs with 105–$10^6\, \rm yr$ are detectable. We find that a few NSs with effective temperature $\lt 5 \times 10^5\, \rm K$, which are likely missed in the current and future X-ray surveys, are also detectable, and the detectability highly depends on NS cooling models. In particular, if considering dark matter heating in NS cores, we find that such cold NSs would account for $70{{\ \rm per\ cent}}$ of the whole detectable sample, and they are typically older than $10^6\, \rm yr$ and tend to have slow transverse velocities, $\lesssim 100\, \rm km\, s^{-1}$, compared to already known pulsars. Thus, the future optical observation will give a unique NS sample, which can provide essential constraints on the NS cooling and heating mechanisms. Moreover, we suggest that providing HVNS samples with optical surveys is helpful for understanding the intrinsic kick-velocity distribution of NSs.

Discovery of a Low-mass Comoving System Using NOIRLab Source Catalog DR2

Abstract We present the discovery of a low-mass comoving system found by means of the NOIRLab Source Catalog DR2. The system consists of the high proper-motion star LEHPM 5005 and an ultracool companion 2MASS J22410186-4500298 with an estimated spectral type of L2. The primary (LEHPM 5005) is likely a mid-M dwarf but over-luminous for its color, indicating a possible close equal mass binary. According to the Gaia EDR3 parallax of the primary, the system is located at a distance of 58 ± 2 pc. We calculated an angular separation of 7.″2 between both components, resulting in a projected physical separation of 418 au.

WISEA J052305.94–015356.1: A New EsdT Candidate

Abstract I present WISEA J052305.94–015356.1 as a new candidate extremely metal-poor T subdwarf (esdT), based on its distinctive infrared colors and high proper motion (∼500 mas yr−1). Spectroscopic follow-up is now needed to confirm it is a member of this newly discovered class of substellar objects.

Gaia Early Data Release 3

We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from Gaia DR2. Gaia EDR3 contains celestial positions and the apparent brightness in G for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (G_BP-G_RP) colour are also available. The passbands for G, G_BP, and G_RP are provided as part of the release. For ease of use, the 7 million radial velocities from Gaia DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of Gaia DR3. Finally, Gaia EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the Gaia-CRF3, which is based solely on extragalactic sources. The creation of the source list for Gaia EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for Gaia DR2, but it does feature new sources and there are some notable changes. The source list will not change for Gaia DR3. Gaia EDR3 represents a significant advance over Gaia DR2, with parallax precisions increased by 30 percent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30--40 percent for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for G, G_BP, and G_RP is valid over the entire magnitude and colour range, with no systematics above the 1 percent level.

Extreme adaptive optics astrometry of R136

We compared high-contrast near-infrared images of the core of R136 taken by VLT/SPHERE, in two epochs separated by 3.06 years. For the first time we monitored the dynamics of the detected sources in the core of R136 from a ground-based telescope with adaptive optics. The aim of these observations was to search for High prOper Motion cAndidates (HOMAs) in the central region of R136 (r < 6″) where it has been challenging for other instruments. Two bright sources (K < 15 mag and V < 16 mag) are located near R136a1 and R136c (massive WR stars) and have been identified as potential HOMAs. These sources have significantly shifted in the images with respect to the mean shift of all reliable detected sources and their neighbours, and six times their own astrometric errors. We calculate their proper motions to be 1.36 ± 0.22 mas yr−2 (321 ± 52 km s−1) and 1.15 ± 0.11 mas yr−2 (273 ± 26 km s−1). We discuss different possible scenarios to explain the magnitude of such extreme proper motions, and argue for the necessity to conduct future observations to conclude on the nature of HOMAs in the core of R136.

GaiaEarly Data Release 3

Context.We present the early installment of the thirdGaiadata release,GaiaEDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities fromGaiaDR2.Aims.A summary of the contents ofGaiaEDR3 is presented, accompanied by a discussion on the differences with respect toGaiaDR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use ofGaiaEDR3 results.Methods.The raw data collected with theGaiainstruments during the first 34 months of the mission have been processed by theGaiaData Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect toGaiaDR2 in terms of astrometric and photometric precision, accuracy, and homogeneity.Results. GaiaEDR3 contains celestial positions and the apparent brightness inGfor approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (GBP−GRP) colour are also available. The passbands forG,GBP, andGRPare provided as part of the release. For ease of use, the 7 million radial velocities fromGaiaDR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part ofGaiaDR3. Finally,GaiaEDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, theGaia-CRF3, which is based solely on extragalactic sources. The creation of the source list forGaiaEDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that forGaiaDR2, but it does feature new sources and there are some notable changes. The source list will not change forGaiaDR3.Conclusions. GaiaEDR3 represents a significant advance overGaiaDR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30–40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband forG,GBP, andGRPis valid over the entire magnitude and colour range, with no systematics above the 1% level

GaiaEarly Data Release 3

Context.TheGaiaEarly Data Release 3 (GaiaEDR3) contains results derived from 78 billion individual field-of-view transits of 2.5 billion sources collected by the European Space Agency’sGaiamission during its first 34 months of continuous scanning of the sky.Aims.We describe the input data, which have the form of onboard detections, and the modeling and processing that is involved in cross-matching these detections to sources. For the cross-match, we formed clusters of detections that were all linked to the same physical light source on the sky.Methods.As a first step, onboard detections that were deemed spurious were discarded. The remaining detections were then preliminarily associated with one or more sources in the existing source list in an observation-to-source match. All candidate matches that directly or indirectly were associated with the same source form a match candidate group. The detections from the same group were then subject to a cluster analysis. Each cluster was assigned a source identifier that normally was the same as the identifiers fromGaiaDR2. Because the number of individual detections is very high, we also describe the efficient organising of the processing.Results.We present results and statistics for the final cross-match with particular emphasis on the more complicated cases that are relevant for the users of theGaiacatalogue. We describe the improvements over the earlierGaiadata releases, in particular for stars of high proper motion, for the brightest sources, for variable sources, and for close source pairs.

Bayesian Cross-matching of High Proper-motion Stars in Gaia DR2 and Photometric Metallicities for ∼1.7 million K and M Dwarfs

Abstract We present a Bayesian method to cross-match 5,827,988 high proper-motion Gaia sources (μ > 40 mas yr−1) to various photometric surveys: Two Micron All Sky Survey, AllWISE data release from the Wide-field Infrared Explorer (WISE) mission, Galaxy Evolution Explorer, Radial Velocity Experiment, Sloan Digital Sky Survey, and Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). To efficiently associate these objects across catalogs, we develop a technique that compares the multidimensional distribution of all sources in the vicinity of each Gaia star to a reference distribution of random field stars obtained by extracting all sources in a region on the sky displaced 2′. This offset preserves the local field stellar density and magnitude distribution, allowing us to characterize the frequency of chance alignments. The resulting catalog with Bayesian probabilities >95% has a marginally higher match rate than current internal Gaia data release 2 (DR2) matches for most catalogs. However, a significant improvement is found with Pan-STARRS, where ∼99.8% of the sample within the Pan-STARRS footprint is recovered, as compared to a low ∼20.8% in Gaia DR2. Using these results, we train a Gaussian process regressor to calibrate two photometric metallicity relationships. For dwarfs of 3500 < T eff < 5280 K, we use metallicity values of 4378 stars from the Apache Point Observatory Galactic Evolution Experiment and Hejazi et al. to calibrate the relationship, producing results with a 1σ precision of 0.12 dex and few systematic errors. We then indirectly infer the metallicity of 4018 stars with 2850 < T eff < 3500 K, which are wide companions of primaries whose metallicities are estimated with our first regressor, to produce a relationship with a 1σ precision of 0.21 dex and significant systematic errors. Additional work is needed to better remove unresolved binaries from this second sample to reduce these systematic errors.

Astronomical Analysis on Star Exploration: A Quantitative Research on Luyten’s star based on Proper Motion and Photometric Brightness.

There are many intrinsic properties for the stars and some of them can be investigated by an astronomical way. Through an investigation on one Luyten’s star (LHS33), this paper presents one basic astronomical analysis method and result about its high proper motion, and brightness for four different filters (RC, V, Blue, Ic). It is an essential element when exploring the target star and obtaining its properties. The method used in this study is a measurement of astrometric position and photometry. All of the measurements require the original CCD (Charge-coupled Device) images obtained from the telescope and a series of software processing. The results obtained mainly are about the value of proper motion, apparent magnitude in these 4 filters above. For instance, the proper motion calculated for right ascension (RA) is 0.59 ± 0.10 arcsecs per year and for declination (Dec) is -3.70 ± 0.11 arcsecs per year. The valued calculations suggest an agreement with current published data. It verifies the correction for both operation procedure and data analysis. It gives a specific interpretation on why such the observation happened based on the quantitative analysis.

Second Data Release of the All-sky NOIRLab Source Catalog

Abstract We announce the second data release (DR2) of the NOIRLab Source Catalog (NSC), using 412,116 public images from CTIO-4 m+DECam, the KPNO-4 m+Mosaic3, and the Bok-2.3 m+90Prime. NSC DR2 contains over 3.9 billion unique objects, 68 billion individual source measurements, covers ≈35,000 square degrees of the sky, has depths of ≈23 mag in most broadband filters with ≈1%–2% photometric precision, and astrometric accuracy of ≈7 mas. Approximately 1.9 billion objects within ≈30,000 square degrees of sky have photometry in three or more bands. There are several improvements over NSC DR1. DR2 includes 156,662 (61%) more exposures extending over 2 more years than in DR1. The southern photometric zero-points in griz are more accurate by using the Skymapper DR1 and ATLAS-Ref2 catalogs, and improved extinction corrections were used for high-extinction regions. In addition, the astrometric accuracy is improved by taking advantage of Gaia DR2 proper motions when calibrating the astrometry of individual images. This improves the NSC proper motions to ∼2.5 mas yr−1 (precision) and ∼0.2 mas yr−1 (accuracy). The combination of sources into unique objects is performed using a DBSCAN algorithm and mean parameters per object (such as mean magnitudes, proper motion, etc.) are calculated more robustly with outlier rejection. Finally, eight multi-band photometric variability indices are calculated for each object and variable objects are flagged (23 million objects). NSC DR2 will be useful for exploring solar system objects, stellar streams, dwarf satellite galaxies, quasi-stellar objects, variable stars, high proper-motion stars, and transients. Several examples of these science use cases are presented. The NSC DR2 catalog is publicly available via the NOIRLab’s Astro Data Lab science platform.

The dynamics of the globular cluster NGC 3201 out to the Jacobi radius

ABSTRACT As part of a chemodynamical survey of five nearby globular clusters with 2dF/AAOmega on the Anglo-Australian Telescope (AAT), we have obtained kinematic information for the globular cluster NGC 3201. Our new observations confirm the presence of a significant velocity gradient across the cluster which can almost entirely be explained by the high proper motion of the cluster (${\sim}9\, \mathrm{mas\, yr^{-1}}$). After subtracting the contribution of this perspective rotation, we found a remaining rotation signal with an amplitude of ${\sim}1\, \mathrm{km\, s^{-1}}$ around a different axis to what we expect from the tidal tails and the potential escapers, suggesting that this rotation is internal and can be a remnant of its formation process. At the outer part, we found a rotational signal that is likely a result from potential escapers. The proper motion dispersion at large radii reported by Bianchini et al. ($3.5\pm 0.9\, \mathrm{km\, s^{-1}}$) has previously been attributed to dark matter. Here, we show that the LOS dispersion between 0.5 and 1 Jacobi radius is lower ($2.01\pm 0.18\, \mathrm{km\, s^{-1}}$), yet above the predictions from an N-body model of NGC 3201 that we ran for this study ($1.48\pm 0.14\, \mathrm{km\, s^{-1}}$). Based on the simulation, we find that potential escapers cannot fully explain the observed velocity dispersion. We also estimate the effect on the velocity dispersion of different amounts of stellar-mass black holes and unbound stars from the tidal tails with varying escape rates and find that these effects cannot explain the difference between the LOS dispersion and the N-body model. Given the recent discovery of tidal tail stars at large distances from the cluster, a dark matter halo is an unlikely explanation. We show that the effect of binary stars, which is not included in the N-body model, is important and can explain part of the difference in dispersion. We speculate that the remaining difference must be the result of effects not included in the N-body model, such as initial cluster rotation, velocity anisotropy, and Galactic substructure.

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Spatiokinematics of Water Masers during a Contemporaneous Flare Event

Abstract Following an eruptive accretion event in NGC 6334I-MM1, flares in the various maser species, including water masers, were triggered. We report the observed relative proper motion of the highly variable water masers associated with the massive star-forming region, NGC 6334I. High velocity H2O maser proper motions were detected in five maser clusters, CM2-W2 (bow-shock structure), MM1-W1, MM1-W3, UCHII-W1, and UCHII-W3. The overall average of the derived relative proper motion is 85 km s−1. This mean proper motion is in agreement with the previous results from VLA multiepoch observations. Our position as well as the velocity variance and covariance matrix analyses of the maser proper motions show its major axis to have a position angle of −79.°4, cutting through the dust cavity around MM1B and being aligned in the northwest–southeast direction. We interpret this as the axis of the jet driving the CM2 shock and the maser motion. The complicated proper motions in MM1-W1 can be explained by the combined influence of the MM1 northeast–southwest bipolar outflow, the CS(6−5) north–south collimated bipolar outflow, and the radio jet. The relative proper motions of the H2O masers in UCHII-W1 are likely not driven by the jets of the MM1B protostar but by MM3-UCHII. Overall, the post-accretion burst relative proper motions of the H2O masers trace shocks of jet motion.