Proper Motion

In this study, we have used the Gaia Third Data Release (Gaia DR3) to investigate an intermediate-age open cluster Collinder 74. Taking into account the stars with membership probabilities over 0.5 and inside the limiting radius of the cluster, we identified 102 most likely cluster members. The mean proper-motion components of Collinder 74 are estimated as (𝜇 𝛼 cos 𝛿, 𝜇 𝛿 ) = (0.960 ± 0.005, -1.526 ± 0.004) mas yr -1 . We detected previously confirmed four blue straggler stars which show flat radial distribution. Colour excess, distance, and age of the cluster were estimated simultaneously by fitting PARSEC isochrones to the observational data on Gaia based colour magnitude diagram. These values were derived as 𝐸 (𝐺 BP -𝐺 RP ) = 0.425 ± 0.046 mag, 𝑑 = 2831 ± 118 pc and 𝑡 = 1800 ± 200 Myr, respectively. The mass function slope was estimated as Γ = 1.34 ± 0.21 within the mass range 0.65 ≤ 𝑀/𝑀 ⊙ ≤ 1.58 which is well matched with that of Salpeter. Stellar mass distribution indicated that the massive and most likely stars are concentrated around the cluster center. The total mass of the cluster was found to be 365 𝑀/𝑀 ⊙ for the stars with probabilities 𝑃 > 0. Galactic orbit integration shows that the Collinder 74 follows a boxy pattern outside the solar circle and is a member of the thin-disc component of the Galaxy.

We present photometric, astrometric, and kinematic studies of the old open star clusters NGC 1193 and NGC 1798. Both of the clusters are investigated by combining data sets from Gaia Early Data Release 3 (EDR3) and CCD UBV observational data. E(B − V ) color excesses are derived for NGC 1193 as 0.150 ± 0.037 and for NGC 1798 as 0.505 ± 0.100 mag through the use of two-color diagrams. Photometric metallicities are also determined from two-color diagrams with the results of [Fe/H]=−0.30 ± 0.06 dex for NGC 1193 and [Fe/H]=−0.20 ± 0.07 dex for NGC 1798. The isochrone fitting distance and age of NGC 1193 are 5562 ± 381 pc and 4.6±1 Gyr, respectively. For NGC 1798, these parameters are 4451±728 pc and 1.3±0.2 Gyr. Kinematic and dynamic orbital calculations indicate that NGC 1193 and NGC 1798 belong to the thick-disk and thin-disk populations, respectively.

We present reddening, photometric metallicity, age, and distance estimates for the Frolov 1 and NGC 7510 open clusters based on charge‐coupled device (CCD) UBV photometric and Gaia data. Photometric observations were collected using the 1‐m telescope of the TÜBİTAK National Observatory. Gaia data release 2 (DR2) proper motion data in the direction of two groupings were used to identify cluster membership. We determined mean proper motion values of (μα cos δ, μδ) = (− 3.02 ± 0.10, − 1.75 ± 0.08) and (−3.66 ± 0.07, −2.17 ± 0.06) mas year−1 for Frolov 1 and NGC 7510, respectively. We used two‐color diagrams to obtain E(B − V) color excesses for Frolov 1 and NGC 7510 of 0.65 ± 0.06 and 1.05 ± 0.05 mag, respectively. We derived the photometric metallicity of Frolov 1 as [Fe/H] = 0.03 ± 0.03 dex and adopted a solar metallicity for NGC 7510. Based on these reddening and metallicities, we determined the distance moduli and ages of the clusters by fitting stellar tracks and isochrones with t...

The Gaia-ESO Survey (GES) observed many open clusters as part of its programme to spectroscopically characterize the various Milky Way populations. GES spectroscopy and Gaia astrometry from its second data release are used here to assign membership probabilities to targets towards 32 open clusters with ages from 1 to 3800 Myr, based on maximum likelihood modelling of the 3D kinematics of the cluster and field populations. From a parent catalogue of 14 398 individual targets, 5032 stars with uniformly determined 3D velocities, Teff, log g, and chemistry are assigned cluster membership with probability >0.9, and with an average probability of 0.991. The robustness of the membership probabilities is demonstrated using independent membership criteria (lithium and parallax) in two of the youngest clusters. The addition of radial velocities improves membership discrimination over proper motion selection alone, especially in more distant clusters. The kinematically selected nature of th...

A search of more than 3,000 square degrees of high latitude sky by the Sloan Digital Sky Survey has yielded 251 faint high-latitude carbon stars (FHLCs), the large majority previously uncataloged. We present homogeneous spectroscopy, photometry, and astrometry for the sample. The objects lie in the 15.6 < r < 20.8 range, and exhibit a wide variety of apparent photospheric temperatures, ranging from spectral types near M to as early as F. Proper motion measurements for 222 of the objects show that at least 50%, and quite probably more than 60%, of these objects are actually low luminosity dwarf carbon (dC) stars, in agreement with a variety of recent, more limited investigations which show that such objects are the numerically dominant type of star with C 2 in the spectrum. This SDSS homogeneous sample of ∼ 110 dC stars now constitutes 90% of all known carbon dwarfs, and will grow by another factor of 2-3 by the completion of the Survey. As the spectra of the dC and the faint halo giant C stars are very similar (at least at spectral resolution of 10 3 ) despite a difference of 10 mag in luminosity, it is imperative that simple luminosity discriminants other than proper motion be developed. We use our enlarged sample of FHLCs to examine a variety of possible luminosity criteria, including many previously suggested, and find that, with certain important caveats, JHK photometry may segregate dwarfs and giants.

Circa 1980, the most popular world view for explaining bright, variable compact sources asserted that Little Sources were carefully aimed Big Sources, such that real bulk motions enhanced by many times the emission and shortened the time scale for variations, compared to those seen by a co-mover. Superluminality was seen as vindication by the view's boosters; the old light-travel-time canard was relegated to predicting mimimum source sizes following outbursts. BL Lac's new era of powerful variations began in 1980, characterized particularly by its wild, intractable polarization rotations. Our earliest results (Mutel, Aller, Phillips 1980) indicated a source size larger than ct, and Phillips and Mutel (1982) substantiated components that implied a speed of 5c. It was superluminal, but just what did that mean any longer? By 1983, VLBI investigators were beginning to pile up a surfeit of superluminal sources. BL Lac had begun a second career by showing two nearly identical polarization events -events which seemed to be carried by the moving (5c) features that faded before reaching a dozen or so light years from their spot of origin. Both events showed a de-rotated p.a. for fractional linear polarization Ρ (Ε-vector) near the VLBI channel of motion (25 and 20 degrees versus 18 for the channel); the second P-event showed convincing evidence for apparent slowing and stagnation of the moving component. Let us review why we think the moving features are the carriers of P. First, the northern bright spot is always a feature in any map, has a flat spectrum, and can even be modeled as constant in strength (except when a new eruption is confused with it.) It always remains when BL Lac returns to Pquiescence. Finally, the fading of the moving VLBI features corresponds precisely with the fading of P-emission.

In this study, we have used the Gaia Third Data Release (Gaia DR3) to investigate an intermediate-age open cluster Collinder 74. Taking into account the stars with membership probabilities over 0.5 and inside the limiting radius of the cluster, we identified 102 most likely cluster members. The mean proper-motion components of Collinder 74 are estimated as (𝜇 𝛼 cos 𝛿, 𝜇 𝛿 ) = (0.960 ± 0.005, -1.526 ± 0.004) mas yr -1 . We detected previously confirmed four blue straggler stars which show flat radial distribution. Colour excess, distance, and age of the cluster were estimated simultaneously by fitting PARSEC isochrones to the observational data on Gaia based colour magnitude diagram. These values were derived as 𝐸 (𝐺 BP -𝐺 RP ) = 0.425 ± 0.046 mag, 𝑑 = 2831 ± 118 pc and 𝑡 = 1800 ± 200 Myr, respectively. The mass function slope was estimated as Γ = 1.34 ± 0.21 within the mass range 0.65 ≤ 𝑀/𝑀 ⊙ ≤ 1.58 which is well matched with that of Salpeter. Stellar mass distribution indicated that the massive and most likely stars are concentrated around the cluster center. The total mass of the cluster was found to be 365 𝑀/𝑀 ⊙ for the stars with probabilities 𝑃 > 0. Galactic orbit integration shows that the Collinder 74 follows a boxy pattern outside the solar circle and is a member of the thin-disc component of the Galaxy.

We report the 3D kinematics of 27 Mira-like stars in the northern, eastern, and southern periphery of the Large Magellanic Cloud (LMC), based on Gaia proper motions and a dedicated spectroscopic follow-up. Low-resolution spectra were obtained for more than 40 Mira-like candidates, selected to trace known substructures in the LMC periphery. Radial velocities and stellar parameters were derived for all stars. Gaia data release 3 astrometry and photometry were used to discard outliers, derive periods for those stars with available light curves, and determine their photometric chemical types. The 3D motion of the stars in the reference frame of the LMC revealed that most of the stars, in all directions, have velocities consistent with being part of the LMC disc population, out of equilibrium in the radial and vertical directions. A suite of numerical simulations was used to constrain the most likely past interaction history between the Clouds given the phase-space distribution of our ta...

Aims. We produce a clean and well-characterised catalogue of objects within 100 pc of the Sun from the Gaia Early Data Release 3. We characterise the catalogue through comparisons to the full data release, external catalogues, and simulations. We carry out a first analysis of the science that is possible with this sample to demonstrate its potential and best practices for its use. Methods. Theselection of objects within 100 pc from the full catalogue used selected training sets, machine-learning procedures, astrometric quantities, and solution quality indicators to determine a probability that the astrometric solution is reliable. The training set construction exploited the astrometric data, quality flags, and external photometry. For all candidates we calculated distance posterior probability densities using Bayesian procedures and mock catalogues to define priors. Any object with reliable astrometry and a non-zero probability of being within 100 pc is included in the catalogue. Re...

Context.The secondGaiadata release (GaiaDR2) provides precise five-parameter astrometric data (positions, proper motions, and parallaxes) for an unprecedented number of sources (more than 1.3 billion, mostly stars). This new wealth of data will enable the undertaking of statistical analysis of many astrophysical problems that were previously infeasible for lack of reliable astrometry, and in particular because of the lack of parallaxes. However, the use of this wealth of astrometric data comes with a specific challenge: how can the astrophysical parameters of interest be properly inferred from these data?Aims.The main focus of this paper, but not the only focus, is the issue of the estimation of distances from parallaxes, possibly combined with other information. We start with a critical review of the methods traditionally used to obtain distances from parallaxes and their shortcomings. Then we provide guidelines on how to use parallaxes more efficiently to estimate distances by usi...

Millisecond pulsars (MSPs) in binary systems are precise laboratories for tests of gravity and the physics of dense matter. Their orbits can show relativistic effects that provide a measurement of the neutron star mass and the pulsars are included in timing array experiments that search for gravitational waves. Neutron star mass measurements are key to eventually solving the neutron star equation of state and these can be obtained by a measure of the Shapiro delay if the orbit is viewed near edge-on. Here we report on the timing and noise analysis of five MSPs observed with the MeerKAT radio telescope: PSRs J0900-3144, J0921-5202, J1216-6410, J1327-0755 and J1543-5149. We searched for the Shapiro delay in all of the pulsars and obtain weak detections for PSRs J0900-3144, J1216-6410, and J1327-0755. We report a higher significance detection of the Shapiro delay for PSR J1543-5149, giving a precise pulsar mass of 𝑀 p = 1.349 +0.043 -0.061 M ⊙ and companion white-dwarf mass 𝑀 c = 0.223 +0.005 -0.007 M ⊙ . This is an atypically low mass measurement for a recycled MSP. In addition to these Shapiro delays, we also obtain timing model parameters including proper motions and parallax constraints for most of the pulsars.

Context. MWC158 is a star with the B[e] phenomenon that shows strong spectrophotometric variability (in lines and in UV and visible continuum) attributed to phases of shell ejection. The evolutionary stage of this star was never clearly determined. Previous interferometric, spectropolarimetric and spectro-interferometric studies suggest a disk morphology for its environment. Aims. We investigate the origin of the variability within the inner astronomical unit of the central star using near-infrared interferometric observations with PIONIER at the VLTI over a two-year period. Methods. We performed an image reconstruction of the circumstellar environment using the SPARCO method. We discovered that the morphology of the circumstellar environment could vary on timescales of weeks or days. We carried out a parametric fit of the data with a model consisting of a star, a disk and a bright spot that represents a brighter emission in the disk. Results. We detect strong morphological changes in the first astronomical unit around the star, that happen on a timescale of few months. We cannot account for such variability well with a binary model. Our parametric model fits the data well and allows us to extract the location of the asymmetry for different epochs. Conclusions. For the first time, we detect a morphological variability in the environment of MWC158. This variability is reproduced by a model of a disk and a bright spot. The locations of the bright spot suggest that it is located in the disk, but its precise motion is not determined. The origin of the asymmetry in the disk is complex and may be related to asymmetric shell ejections.

SN 1572 (Tycho Brahe's supernova) clearly belongs to the Ia (thermonuclear) type. It was produced by the explosion of a white dwarf in a binary system. Its remnant has been the first of this type to be explored in search of a possible surviving companion, the mass donor that brought the white dwarf to the point of explosion. A high peculiar motion with respect to the stars at the same location in the Galaxy, mainly due to the orbital velocity at the time of the explosion, is a basic criterion for the detection of such companions. Radial velocities from the spectra of the stars close to the geometrical center of Tycho's supernova remnant, plus proper motions of the same stars, obtained by astrometry with the Hubble Space Telescope, have been used so far. In addition, a detailed chemical analysis of the atmospheres of a sample of candidate stars had been made. However, the distances to the stars remained uncertain. Now, the Second Gaia Data Release (DR2) provides unprecedented accurate distances and new proper motions for the stars can be compared with those obtined from the HST. We consider the Galactic orbits that the candidate stars to SN companion would have in the future. We do this to explore any kinematic peculiarity. We also locate a representative sample of candidate stars in the Toomre diagram. Using the new data, we reevaluate here the status of the candidates suggested thus far, as well as the larger sample of the stars seen in the central region of the remnant.

With archival and new Hubble Space Telescope observations, we have refined the spacevelocity measurements of the stars in the central region of the remnant of Tycho's supernova (SN) 1572, one of the historical Galactic Type Ia supernova remnants (SNRs). We derived a proper motion for Tycho-G of (μ αcos δ ; μ δ ) J2000.0 = (-2.63; -3.98) ± (0.06; 0.04) [formal errors] ± (0.18; 0.10) [expected errors] mas yr -1 . If the star were at the distance of the SNR (taken here to be 2.83 kpc), its velocity would be v b = -51 ± 1.5 km s -1 . We also reconstruct the binary orbit that Tycho-G should have followed if it were the surviving companion of SN 1572. We redetermine the Ni abundance of this star and compare it with new abundance data from stars of the Galactic disc, finding that [Ni/Fe] is about 1.7σ above the Galactic trend. From the high velocity of Tycho-G perpendicular to the Galactic plane (-90 ± 3 km s -1 ≤ v b ≤ -45 ± 1 km s -1 , for the allowed range of distances to the star), its metallicity and its Ni excess, we find the probability of it being a chance interloper to be P 0.000 37 at most. The projected rotational velocity of the star should be below current observational limits. The projected position of Tycho-G is, within the uncertainties, consistent with the centroid of the X-ray emission of Tycho's SNR; moreover, its brightness is generally consistent with the postexplosion evolution of the luminosity of an SN companion. Among the other 23 stars having V < 22 mag and located within 42 arcsec from the X-ray centroid, only 4 are at distances compatible with that of the SNR, and none of them shows any peculiarity. Therefore, if even Tycho-G is not the surviving companion of SN 1572, the absence of other viable candidates does favour the merging of two white dwarfs as the producer of the SN.

Context.The secondGaiadata release (GaiaDR2) provides precise five-parameter astrometric data (positions, proper motions, and parallaxes) for an unprecedented number of sources (more than 1.3 billion, mostly stars). This new wealth of data will enable the undertaking of statistical analysis of many astrophysical problems that were previously infeasible for lack of reliable astrometry, and in particular because of the lack of parallaxes. However, the use of this wealth of astrometric data comes with a specific challenge: how can the astrophysical parameters of interest be properly inferred from these data?Aims.The main focus of this paper, but not the only focus, is the issue of the estimation of distances from parallaxes, possibly combined with other information. We start with a critical review of the methods traditionally used to obtain distances from parallaxes and their shortcomings. Then we provide guidelines on how to use parallaxes more efficiently to estimate distances by usi...

This study outlines a detailed investigation using CCD {\it UBV} and {\it Gaia} DR3 data sets of the two open clusters Ruprecht 1 (Rup-1) and Ruprecht 171 (Rup-171). Fundamental astrophysical parameters such as color excesses, photometric metallicities, ages, and isochrone distances were based on {\it UBV}-data analyses, whereas membership probability calculations, structural and astrophysical parameters, as well as the kinematic analyses were based on {\it Gaia} DR3-data. We identified 74 and 596 stars as the most probable cluster members with membership probabilities over 50\% for Rup-1 and Rup-171, respectively. The color excesses $E(B-V)$ were obtained as $0.166\pm0.022$ and $0.301\pm0.027$ mag for Rup-1 and Rup-171, respectively. Photometric metallicity analyses were performed by considering F-G type main-sequence member stars and found to be [Fe/H]=$-0.09\pm 0.16$ and [Fe/H]=$-0.20\pm 0.20$ dex for Rup-1 and Rup-171, respectively. Ages and distances were based on both {\it UBV} and {\it Gaia}-data analyses; according to isochrone-fitting these values were estimated to be $t=580\pm60$ Myr, $d=1469\pm57$ pc for Rup-1 and $t=2700\pm200$ Myr, $d=1509\pm69$ pc for Rup-171. The present-day mass function slope of Rup-1 was estimated as $1.26\pm0.32$ and Rup-171 as $1.53\pm1.49$. Galactic orbit integration analyses showed that both of the clusters \tr{might be} formed outside the solar circle.

Using photometry and proper motions from Gaia Early Data Release 3, we detect a 45 • -long trailing stellar debris stream associated with the old, metal-poor globular cluster NGC 7089. With a width on the order of 100 pc, the extended stream appears to be as dynamically cold as the coldest known streams found to date. There is some evidence for an extended leading tail extending between 28 • and 37 • from the cluster, though the greater distance of this tail, combined with proper motions that are virtually indistinguishable from those of foreground stars, make the detection much less certain. The proper motion profile and the path on the sky of the trailing tail are not well matched using a simple Galactic potential comprised purely of a disk, bulge, and spherical halo. However, the addition of a moving, massive (M = 1.88 × 10 11 M ⊙ ) Large Magellanic Cloud brings the model predictions into much better agreement with the observables. We provide tables of the most highly ranked candidate stream stars for follow-up by ongoing and future spectroscopic surveys.

Context. The study of the younger, and brighter, pulsars is important for understanding the optical emission properties of isolated neutron stars through observations which, even in the 10 m-class telescope era, are much more challenging for older and fainter objects. PSR B0540-69, the second brightest (V ∼ 22) optical pulsar, is obviously a primary target for these investigations. Aims. The aims of this work are several: (i) constraining the pulsar proper motion and its velocity on the plane of the sky and improving the determination of the pulsar coordinates through optical astrometry; (ii) obtaining a more precise characterisation of the pulsar optical spectral energy distribution (SED) through a consistent set of multi-band, high-resolution, imaging photometry observations and studying the relation with the X-ray spectrum, including the presence of a spectral turnover between the two bands. Last, we aim at (iii) measuring the pulsar optical phase-averaged linear polarisation, for which only a preliminary and uncertain measurement has been obtained so far from ground-based observations, and at testing the predictions of different neutron star magnetosphere models. Methods. We performed high-resolution observations of PSR B0540-69 with the Wide Field and Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope (HST), in both direct imaging and polarimetry modes. Results. From multi-epoch astrometry we set a 3σ upper limit of 1 mas yr -1 on the pulsar proper motion, implying a transverse velocity <250 km s -1 at the 50 kpc LMC distance. Moreover, we determined the pulsar absolute position with an unprecedented accuracy of 70 mas. From multi-band photometry we characterised the pulsar power-law spectrum and derived the most accurate measurement of the spectral index (α O = 0.70 ± 0.07), which indicates a spectral turnover between the optical and X-ray bands. Finally, from polarimetry we obtained a new measurement of the pulsar phase-averaged polarisation degree (PD = 16% ± 4%), consistent with magnetosphere models, depending on the actual intrinsic polarisation degree and depolarisation factor, and we found that the polarisation vector (22 • ± 12 • position angle) is possibly aligned with the semi-major axis of the pulsar-wind nebula and with the apparent proper motion direction of its bright emission knot. Conclusions. Deeper studies with the HST can only be possible with the refurbished Advanced Camera for Surveys (ACS) and with the new Wide Field Camera 3 (WFC3).

We present a proper-motion study on models of the dwarf spheroidal galaxy Sculptor, based on the predicted proper-motion accuracy of Gaia measurements. Gaia will measure proper motions of several hundreds of stars for a Sculptor-like system. Even with an uncertainty on the proper motion of order 1.5 times the size of an individual proper-motion value of ∼ 10 mas/century, we find that it is possible to recover Sculptor's systemic proper motion at its distance of 79 kpc.

We show that a string of H I clouds that form part of the high-velocity cloud complex known as GCN is a probable gaseous stream extending over more than 50 • in the Galactic halo. The radial velocity gradient along the stream is used to deduce transverse velocities as a function of distance, enabling a family of orbits to be computed. We find that a direction of motion towards the Galactic disc coupled with a mid-stream distance of ∼20 kpc provides a good match to the observed sky positions and radial velocities of the H I clouds comprising the stream. With an estimated mass of 10 5 M , its progenitor is likely to be a dwarf galaxy. However, no stellar counterpart has been found amongst the currently known Galactic dwarf spheroidal galaxies or stellar streams and the exact origin of the stream is therefore currently unknown.

We imaged silicon monoxide masers toward the asymptotic giant branch star R Cas at 23 intervals covering almost 2 pulsation cycles. The masers are concentrated in a shell within 4 stellar radii. Between 19 and 62 features were identified per epoch and 184 of these were matched at 3 or more epochs, forming 38 series. The features probably survive more epochs than their detectable masers. We compared the proper motions and polarization of these clumps, providing the first complete assessment of the net expansion velocity over more than one cycle and the significance of the magnetic field. Proper motions are irregular, dominated by outflow (infall) in the first (second) cycles. Sixty-five matched pairs had maser polarization angles consistent within π/8. A small excess (22) of this subsample has proper motion vectors within ±22°. 5 of being parallel to the inferred magnetic field, 10 of which have approximately radial proper motions. The average field strength needed to provide a magnetic energy density equivalent to the bulk kinetic and thermal energy densities of a clump is ∼2 G, similar to direct magnetic field measurements. While some clumps possess a consistent magnetic field, capable of influencing the direction of motion, only a minority flow along magnetic field lines. The resultant SiO expansion proper motion over the entire periods is ∼0.4 km s -1 (taking ∼67 yr to cross the shell), which, compared with the mass in the shell, implies a wind similar to mass-loss rates from the literature measured on larger scales.

We present a proper motion investigation of a sample of Be star candidates towards the Magellanic Clouds, which has resulted in the identification of separate populations, in the Galactic foreground and in the Magellanic background. Be stars are broadly speaking B-type stars that have shown emission lines in their spectra. In this work, we studied a sample of 2446 and 1019 Be star candidates towards the LMC and SMC respectively, taken from the literature and proposed as possible Be stars due to their variability behaviour in the OGLE-II I band. JHKs magnitudes from the IRSF catalog and proper motions from the SPM4 catalog, were obtained for 1188 and 619 LMC and SMC Be stars candidates, respectively. Color-color and vector-point diagrams were used to identify different populations among the Be star candidates. In the LMC sample, two populations with distinctive infrared colours and kinematics were found, the bluer sample is consistent with being in the LMC and the redder one with belonging to the Milky Way disk. This settles the nature of the redder sample which had been described in previous publications as a possible unknown subclass of stars among the Be candidates in the LMC. In the SMC sample, a similar but less evident result was obtained, since this apparent unknown subclass was not seen in this galaxy. We confirm that in the selection of Be stars by their variability, although generally successful, there is a higher risk of contamination by Milky Way objects towards redder B-V and V-I colors.

Actively accreting young stellar objects show Hα emission line in their spectra. We present the results of survey for Hα emission-line stars in the star-forming region IC 5070 taken with 2-m Himalyan Chandra Telescope. Based on the Hα slitless spectroscopy data, we identified 131 emission-line stars in ∼ 0.29 square degrees area of the IC 5070 region. Using Gaia Early Data Release 3, we estimated the mean proper motion and parallax of the emission-line stars. We also estimated the mean distance and reddening toward the region using the emission-line stars, that are ∼ 833 pc and ∼2 mag, respectively. By examining the locations of these stars in the color-magnitude diagrams constructed using Gaia and PanSTARRS1 data, we found that a majority of the Hα emitters are young low-mass (< 1.5 M ) stars. We also compared our catalog of emission-line stars with the available young stellar catalogs and found that most of them are Class II/ flat spectrum sources with the spectral type ranging from K to M. Based on the proper motion/ parallax values and locations on the color-magnitude diagrams, about 20 emission-line stars are flagged as non-members. The relative proper motion of the emissionline stars with respect to the ionizing source suggest the possibility of the 'rocket effect' scenario in the remnant cloud (BRC 31).

We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tycho's supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the remnant (i.e., the forward shock and protruding ejecta knots) varies from 0 ′′ .20 yr -1 (expansion index m = 0.33, where R = t m ) to 0 ′′ .40 yr -1 (m = 0.65) with azimuthal angle in 2000-2007 measurements, and 0 ′′ .14 yr -1 (m = 0.26) to 0 ′′ .40 yr -1 (m = 0.65) in 2003-2007 measurements. The azimuthal variation of the proper motion and the average expansion index of ∼0.5 are consistent with those derived from radio observations. We also find proper motion and expansion index of the reverse-shocked ejecta to be 0 ′′ .21-0 ′′ .31 yr -1 and 0.43-0.64, respectively. From a comparison of the measured m-value with Type Ia supernova evolutionary models, we find a pre-shock ambient density around the remnant of 0.2 cm -3 .

We present comprehensive characterization of the Galactic open cluster M 36. Some 200 member candidates, with an estimated contamination rate of ∼8%, have been identified on the basis of proper motion and parallax measured by the Gaia DR2. The cluster has a proper motion grouping around ( mas yr−1, and μ δ = − 3.35 ± 0.02 mas yr−1), distinctly separated from the field population. Most member candidates have parallax values 0.7–0.9 mas, with a median value of 0.82 ± 0.07 mas (distance ∼1.20 ± 0.13 kpc). The angular diameter of determined from the radial density profile then corresponds to a linear extent of 9.42 ± 0.14 pc. With an estimated age of ∼15 Myr, M 36 is free of nebulosity. To the southwest of the cluster, we discover a highly obscured (A V up to ∼23 mag), compact (∼ ) dense cloud, within which three young stellar objects in their infancy (ages ≲0.2 Myr) are identified. The molecular gas, 3.6 pc in extent, contains a total mass of (2–3) × 102 M ⊙, and has a uniform velocity...

We have obtained a second epoch observation of the Cassiopeia A supernova remnant (SNR) with the Chandra X-ray Observatory to measure detailed X-ray proper motions for the first time. Both epoch observations are 50 ks exposures of the ACIS-S3 chip and they are separated by 2 years. Measurements of the thin Xray continuum dominated filaments located around the edge of the remnant (that are identified with the forward shock) show expansion rates from 0.02% yr −1 to 0.33% yr −1. Many of these filaments are therefore significantly decelerated. Their median value of 0.21% yr −1 is equal to the median expansion of the bright ring (0.21% yr −1) as measured with Einstein and ROSAT. This presents a conundrum if the motion of the bright ring is indicative of the reverse shock speed. We have also re-evaluated the motion of the radio bright ring with emphasis on angle-averaged emissivity profiles. Our new measurement of the expansion of the angle-averaged radio bright ring is 0.07 ± 0.03% yr −1 , somewhat slower than the previous radio measurements of 0.11% yr −1 which were sensitive to the motions of small-scale features. We propose that the expansion of the small-scale bright ring features in the optical, X-ray, and radio do not represent the expansion of the reverse shock, but rather represent a brightness-weighted average of ejecta passing through and being decelerated by the reverse shock. The motion of the reverse shock, itself, is then represented by the motion of the angle-averaged emissivity profile of the radio bright ring.

The interpretation of the old, cool white dwarfs recently found by Oppenheimer et al. is still controversial. Whereas these authors claim that they have finally found the elusive ancienthalo white dwarf population that contributes significantly to the mass budget of the galactic halo, there have been several other contributions that argue that these white dwarfs are not genuine halo members but, instead, thick-disc stars. We show here that the interpretation of this sample is based on the adopted distances, which are obtained from a colour-magnitude calibration, and we demonstrate that when the correct distances are used a sizeable fraction of these putative halo white dwarfs belong indeed to the disc population. We also perform a maximum likelihood analysis of the remaining set of white dwarfs and we find that they most probably belong to the thick-disc population. However, another possible explanation is that this sample of white dwarfs has been drawn from a 1 : 1 mixture of the halo and disc white dwarf populations.

We report optical spectroscopic observations of the Low Mass X-ray Binary GRO J1655−40 during outbursts in August−September 1994 and in June 1996. The spectra show emission and absorption lines from the accretion disk surrounding the X-ray source, which have enabled us to measure the motion of the black hole candidate in this system. It is the first time among black-hole candidates that an emission-line radial velocity curve is seen in phase with the expected motion of the primary. The projected radial velocity semi-amplitude determined for the primary (K X = 76.2 ± 7.5 km/s), combined with estimates of the projected radial velocity semi-amplitude of the companion star from previous observations (K C = 228.2±3.0 km/s), yields a 95% confidence limit, derived purely from kinematics, of M X > 5.1M for the mass of the compact object in GRO J1655−40, confirming its black hole nature.

We present Spitzer/IRAC observations of the L5 dwarf, 2MASSI J1315309-264951 (2M1315). This ultracool dwarf is known to display strong emission in the Hα line. The SED for this object does not show any IR excess, that would indicate the presence of an accretion disk. Although the IRAC colors for 2M1315 are consistent with other L dwarfs, they seem to be redder by ∼0.1 mag compared to the other L5 dwarfs, and more like the late-type L dwarfs. The existing six epochs of spectroscopy suggest that the emission in Hα is not persistent, but shows long-term variability between a flare value of ∼100Å and a quiescent value of ∼25Å. Chromospheric activity seems to be the most likely cause, which is also indicated by the detection of Na I D lines in emission (Fuhrmeister et al.). We have measured a proper motion of 0.79 ′′ ± 0.06 ′′ /yr, that corresponds to a tangential velocity of ∼81 km/s, at a distance of ∼22 pc. The high V tan for this object suggests an old age. Evolutionary models indicate lower limits of 3.3 Gyr (Chabrier et al.) or 1.4 Gyr (Burrows et al.) for this magnetically active L dwarf to be a stable hydrogen-burning star. There seem to be no observational differences between this old L dwarf that has Hα emission and the other field L dwarfs without it.

Context. TMR-1C is a candidate protoplanet that lies at a separation of about 10 (∼1000 AU) from the Class I protobinary TMR-1 (IRAS 04361+2547) located in the Taurus molecular cloud. A narrow filament-like structure was observed in the discovery HST/NICMOS images, extending southeast from the central proto-binary system towards TMR-1C, suggesting a morphology in which the candidate protoplanet may have been ejected from the TMR-1 system. Follow-up low-resolution spectroscopy, however, could not confirm if this object is a protoplanet or a low-luminosity background star. Aims. We present two epochs of near-infrared photometric observations obtained at the CFHT of TMR-1C. The time span of ∼7 years between the two sets of observations provides an opportunity to (a) check for any photometric variability similar to that observed among young stellar objects, which would indicate the youth of this source, and to (b) determine the proper motion. Results. TMR-1C displays large photometric variability between 1 and 2 mag in both the Hand K s-bands. From our 2002 observations, we find a (H − K s) color of 0.3 mag, which is much bluer than the value of 1.3 mag reported by T98 from HST observations. Also, we observe brightening in both the Hand K s-bands when the colors are bluer; i.e., the object gets redder as it becomes fainter. We have explored the possible origins for the observed variability, and find extinction due to the presence of circumstellar material to be the most likely scenario. The observed large-amplitude photometric variations and the possible presence of a circumstellar disk are strong arguments against this object being an old background star.

We present HST/ACS observations of 19 nearby M subdwarfs in a search for binary systems. Other than the wide common proper motion pair LHS 2140/2139, none of our sdM and esdM targets are found to be binaries. Our survey is sensitive to equal-luminosity companions at close (2-8 AU) separations, while sub-stellar secondaries could have been detected at separations in the range of 6-30 AU. To check for wide binaries, we have compared the POSS I and II images in a field of view as large as 10 ′ ×10 ′ , but could not detect a single comoving star for any of the targets. Combining our results with those from Gizis & Reid, we have a binary fraction of 3% (1/28). Detection of a small number of M subdwarf binaries reported in the literature suggests a higher fraction than the one obtained here, probably comparable to that found for the more massive solar-type stars in the halo (13-15%). Comparison with the disk M dwarf fraction (∼25%) however suggests multiplicity to be rare among the lowest mass halo stars, implying the two populations formed under different initial conditions. The low binary fraction in our survey could be explained by selection biases. A decrease in multiplicity has been observed in the disk for masses below 0.1M ⊙ , the peak in the disk mass function (MF). The globular cluster MF is found to peak at about 0.33M ⊙ , with a decrease in the number of stars per unit mass below the peak mass. Our sample being composed of stars with masses between ∼0.2 and 0.085 M ⊙ suggests that a decrease in multiplicity similar to the disk may also be true for the halo stars, but perhaps below a mass of ∼0.3M ⊙. A higher M subdwarf binary fraction may be obtained if the selected primaries have masses near or higher than the peak in the MF.

In constellation Orion I observed interesting stellar pairs. Most of these stars have a similar brightness of about 10 magnitudes. An analysis of the proper motion between the components gives information of possible physical relationship between some of them. Observation of Interesting Stellar Pairs in the Constellation Orion with a Possible New CPM Pair At a distance of 185.0 arcseconds a third component C, TYC 1283-00546-1 with a magnitude of 10.15 can be seen. The proper motion is very similar to component A and therefore a physical relationship between the A and C components is possible. A f o u r t h c o m p o n e n t D ( 2 M A S S J05122896+1614415) is at a distance of 159.1 arcseconds. The position angle is 77.5 degrees. There is no information about proper motion in the SIMBAD database [2]. In comparison with my own measurements, component D has a different proper motion and we can expect it to be an optical component. At a distance of 11.3 arcseconds, I found a fifth compo...

The halo of the Milky Way galaxy hosts multiple dynamically coherent substructures known as stellar streams that are remnants of tidally disrupted orbiting systems such as globular clusters (GCs) and dwarf galaxies (DGs). A particular case is that of the Jhelum stream, which is known for its unusual and complex morphology. Using the available data from the Gaia DR3 catalog, we extracted a region on the sky that contains Jhelum, and fine-tuned this selection by enforcing limits on the magnitude and proper motion of the selected stars. We then applied the novel Locally Aligned Ant Technique (LAAT) on the position and proper motion space of stars belonging to the selected region to highlight the stars that are closely aligned with a local manifold in the data and the stars belonging to regions of high local density. We find that the overdensity representing the stream in proper motion space is composed of two components, and show the correspondence of these two signals to the previously reported narrow and broad spatial components of Jhelum. We then made use of the radial velocity measurements provided by the S 5 survey and confirm, for the first time, a separation between the stars belonging to the two components in radial velocity. We show that the narrow and broad components have velocity dispersions of 4.84 +1.23 −0.79 km/s and 19.49 +2.19 −1.84 km/s, and metallicity dispersions of 0.15 +0.18 −0.10 and 0.34 +0.13 −0.09 , respectively. These measurements, as well as the given difference in component widths, could be explained with a probable scenario where Jhelum is the remnant of a GC embedded within a DG where both were accreted onto the Milky Way during their infall. Although the properties of Jhelum could be explained with this merger scenario, other progenitors of the narrow component remain possible such as a nuclear star cluster or a DG. To rule these possibilities out, we would need more observational data of member stars of the stream. Our analysis shows that the internal structure of streams holds great information on their past formation history, and therefore provides further insight into the merger history of the Milky Way.

We report the discovery of 141 new high proper motion systems (1.0 ′′ /yr > µ ≥ 0.4 ′′ /yr) in the southern sky (δ = -90 • to -47 • ) brighter than UKST plate R 59F = 16.5 via our SuperCOSMOS-RECONS (SCR) search. When combined with the nine systems having µ ≥ 1.0 ′′ /yr and/or late spectral type from the initial phases of this effort , we find that 73 of the 150 total systems are moving faster than 0.5 ′′ /yr, and are therefore new members of the classic "LHS" (Luyten Half Second) sample. These constitute a 21% increase in the sample of stars with µ ≥ 0.5 ′′ /yr in the declination region searched, thereby comprising an important addition to this long-neglected region of the sky. Distance estimates are provided for the entire sample, based upon a combination of photographic plate magnitudes and 2MASS photometry, using the relations presented in for the presumed main sequence stars. Three systems are anticipated to be within 10 pc, and an additional 15 are within 25 pc. Eight of these 18 nearby systems have proper motions falling between 0.4 ′′ /yr and 0.6 ′′ /yr, hinting at a large population of nearby stars with fast, but not extremely high, proper motions that have not been thoroughly investigated.

Photometric (V J R C I C ) and spectroscopic (6000-9500 Å) observations of high proper motion stars discovered during the first phase of the SuperCOSMOS RECONS (SCR) search are used to estimate accurate distances to eight new nearby red dwarfs, including probable 10 pc sample members SCR 1845-6357 (M8.5V at 4.6 pc), the binary SCR 0630-7643AB (M6.0VJ at 7.0 pc), and SCR 1138-7721 (M5.0V at 9.4 pc). Distance estimates are determined using a suite of new photometric color-M Ks relations defined using a robust set of nearby stars with accurate V RIJHK s photometry and trigonometric parallaxes. These relations are utilized, with optical and infrared photometry, to estimate distances on a uniform system (generally good to 15%) for two additional samples of red nearby star candidates: several recently discovered members of the solar neighborhood, and known faint stars with proper motions in excess of 1.0 ′′ /yr south of DEC = -57.5. Of those without accurate trigonometric parallax measurements, there are five stars in the first sample and three in the second that are likely to be within 10 pc. The two nearest are SO 0253+1652 (M7.0V at 3.7 pc) and DEN 1048-3956 (M8.5V at 4.5 pc). When combined with SCR 1845-6357, these three stars together represent the largest increase in the 5 pc sample in several decades. Red spectra are presented for the red dwarfs and types are given on the RECONS standard spectral system. Red spectra are also given for two new nearby white dwarfs for which we estimate distances from the photometry of less than 20 pc -WD 0141-675 (LHS 145, 9.3 pc) and SCR 2012-5956 (17.4 pc). WD 0141-675 brings the total number of systems nearer than 10 pc discussed in this paper to 12.

We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnards Star, a nearby, well-characterized mid-M dwarf. By comparing colors, optical and near-infrared spectra, we find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion and no quiescent Hα emission-all of which is consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 ± 0.05 M ⊙ ), radius (0.17 ± 0.04 R ⊙ ) and luminosity (2.40 × 10 -3.0±0.3 L ⊙ ). We calculate KOI 961's distance (38.7 ± 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet-candidate, and find a less than 1 % chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1 R ⊕ , with KOI 961.03 being Mars-sized (R P = 0.57 ± 0.18 R ⊕ ), and they represent some of the smallest exoplanets detected to date.

We present a spectroscopic catalog of the 1,564 brightest (J < 9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1,408 of the candidates to be late-K and M dwarfs with spectral subtypes K7-M6. From the low (µ >40 mas yr -1 ) proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes > 90% of all existing, northern-sky M dwarfs with apparent magnitude J < 9. Only 682 stars in our sample are listed in the Third Catalog of Nearby Stars (CNS3); most others are relative unknowns and have spectroscopic data presented here for the first time. Spectral subtypes are assigned based on spectral index measurements of CaH and TiO molecular bands; a comparison of spectra from the same stars obtained at different observatories however reveals that spectral band index measurements are dependent on spectral resolution, spectrophotometric calibration, and other instrumental factors. As a result, we find that a consistent classification scheme requires that spectral indices be calibrated and corrected for each observatory/instrument used. After systematic corrections and a recalibration of the subtype-index relationships for the CaH2, CaH3, TiO5, and TiO6 spectral indices, we find that we can consistently and reliably classify all our stars to a half-subtype precision. The use of corrected spectral indices further requires us to recalibrate the ζ parameter, a metallicity indicator based on the ratio of TiO and CaH optical bandheads. However, we find that our ζ values are not sensistive enough to diagnose metallicity variations in dwarfs of subtypes M2 and earlier (±0.5dex accuracy) and are only marginally useful at later M3-M5 subtypes (±0.2dex accuracy). Fits of our spectra to the Phoenix atmospheric model grid are used to estimate effective temperatures. These suggest the existence of a plateau in the M1-M3 subtype range, in agreement with model fits of infrared spectra but at odds with photometric determinations of T e f f . Existing geometric parallax measurements are extracted from the literature for 624 stars, and are used to determine spectroscopic and photometric distances for all the other stars. Active dwarfs are identified from measurements of Hα equivalent widths, and we find a strong correlation between Hα emission in M dwarfs and detected X-ray emission from ROSAT and/or a large UV excess in the GALEX point source catalog. We combine proper motion data and photometric distances to evaluate the (U,V,W) distribution in velocity space, which is found to correlate tighly with the velocity distribution of G dwarfs in the Solar Neighborhood. However, active stars show a smaller dispersion in their space velocities, which is consistent with those stars being younger on average. Our catalog will be most useful to guide the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.

Spectroscopy from the final internal data release of the Gaia–ESO Survey (GES) has been combined with Gaia EDR3 to assign membership probabilities to targets observed towards 63 Galactic open clusters and 7 globular clusters. The membership probabilities are based chiefly on maximum likelihood modelling of the 3D kinematics of the targets, separating them into cluster and field populations. From 43 211 observed targets, 13 985 are identified as highly probable cluster members (P &gt; 0.9), with an average membership probability of 0.993. The addition of GES radial velocities successfully drives down the fraction of false positives and we achieve better levels of discrimination in most clusters over the use of astrometric data alone, especially those at larger distances. Since the membership selection is almost purely kinematic, the union of this catalogue with GES and Gaia is ideal for investigating the photometric and chemical properties of clusters as a function of stellar mass, a...

The Gaia-ESO Survey (GES) observed many open clusters as part of its programme to spectroscopically characterize the various Milky Way populations. GES spectroscopy and Gaia astrometry from its second data release are used here to assign membership probabilities to targets towards 32 open clusters with ages from 1 to 3800 Myr, based on maximum likelihood modelling of the 3D kinematics of the cluster and field populations. From a parent catalogue of 14 398 individual targets, 5032 stars with uniformly determined 3D velocities, Teff, log g, and chemistry are assigned cluster membership with probability &gt;0.9, and with an average probability of 0.991. The robustness of the membership probabilities is demonstrated using independent membership criteria (lithium and parallax) in two of the youngest clusters. The addition of radial velocities improves membership discrimination over proper motion selection alone, especially in more distant clusters. The kinematically selected nature of th...

The methods of secular and statistical parallax for homogeneous groups of Galactic stars are applied in a practical (classroom) exercise to establish the luminosity of bright B3 V stars. The solar motion of 20 km s -1 relative to group stars exceeds their random velocities of ±10 km s -1 , a condition adopted for preference of secular parallax to statistical parallax. The group parallax of ⟨π ups ⟩ = 5.81 ± 0.83 mas and derived luminosity ⟨M V ⟩ = -0.98 ± 0.33 for B3 V stars from upsilon components of proper motion should be close to the true value. The weighted mean Hipparcos parallax of ⟨π Hip ⟩ = 5.75 ± 0.27 mas for the same sample, and implied luminosity of ⟨M V ⟩ = -1.00 ± 0.15, confirm the secular parallax solution. Both solutions are close to M V = -0.83 for ZAMS stars of the same type, implying that Malmquist bias in the selection of stars mainly accounts for the presence of unresolved binaries, slightly evolved objects, and rapidly rotating stars in the sample.

FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of 4 ×10 7 stars with 5 < m V < 15. For bright stars, 5 < m V < 9, FAME will determine positions and parallaxes accurate to < 50 µas, with proper motion errors < 50 µas/year. For fainter stars, 9 < m V < 15, FAME will determine positions and parallaxes accurate to < 500 µas, with proper motion errors < 500 µas/year. It will also collect photometric data on these 4 ×10 7 stars in four Sloan DSS colors.

FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of 4 ×10 7 stars with 5 < m V < 15. For bright stars, 5 < m V < 9, FAME will determine positions and parallaxes accurate to < 50 µas, with proper motion errors < 50 µas/year. For fainter stars, 9 < m V < 15, FAME will determine positions and parallaxes accurate to < 500 µas, with proper motion errors < 500 µas/year. It will also collect photometric data on these 4 ×10 7 stars in four Sloan DSS colors.

The detection and accurate astrometry of fast-moving near-Earth objects (NEOs) has been a challenge for the follow-up community. Their fast apparent motion results in streaks in sidereal images, thus affecting the telescope’s limiting magnitude and astrometric accuracy. A widely adopted technique to mitigate trailing losses is non-sidereal tracking, which transfers the streaking to background reference stars. However, no existing publicly available astrometry software is configured to detect such elongated stars. We present Astreaks, a streaking source detection algorithm, to obtain accurate astrometry of NEOs in non-sidereal data. We validate the astrometric accuracy of Astreaks on 371 non-sidereally tracked images for 115 NEOs with two instrument set-ups of the GROWTH-India Telescope. The observed NEOs had V-band magnitude in the range [15, 22] with proper motion up to 140 arcsec min−1, thus resulting in stellar streaks as high as 6.5 arcmin (582 pixels) in our data. Our method ob...

We present WISEA J114724.10-204021.3, a young, low-mass, high-probability member of the TW Hya association (TWA). WISEA J114724.10-204021.3 was discovered based on its red AllWISE color (W1 − W2 = 0.63 mag) and extremely red 2MASS J−K S color (>2.64 mag), the latter of which is confirmed with nearinfrared photometry from the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey (J − K S = 2.57 ± 0.03). Follow-up near-infrared spectroscopy shows a spectral type of L7±1 as well as several spectroscopic indicators of youth. These include a peaked H-band shape and a steeper K-band slope, traits typically attributed to low surface gravity. The sky position, proper motion, and distance estimates of WISEA J114724.10-204021.3 are all consistent with membership in the ∼10 Myr old TWA. Using the age of the TWA and evolutionary models, we estimate the mass of WISEA J114724.10-204021.3 to be 5-13 M Jup , making it one of the youngest and lowest-mass free-floating objects yet discovered in the Solar neighborhood.

In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 ± 0.7) ×10 −20 s s −1 ; from these, we derive a characteristic age of > 9.1 Gyr and a surface magnetic field strength of < 2.6 ×10 9 G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric (e = 0.17) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, ω = 0.07686 ± 0.00046 • yr −1. Assuming general relativity accurately describes the orbital motion, this implies a total system mass M = 2.538 ± 0.022 M. The minimum companion mass is 0.92 M and the maximum pulsar mass is 1.62 M. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW 170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.

al. EROS 2 proper motion survey: a brown dwarf and an L dwarf companion to LHS 102 abstract We report the discovery of two L dwarfs (the new spectral class defined for dwarfs cooler than the M type) in a two-epoch CCD proper motion survey of 413 square degrees, complemented by infrared photometry from DENIS. One of them has a strong lithium line and is therefore a brown dwarf. The other is a common proper motion companion to the mid-M dwarf LHS 102 (GJ 1001), which has a well determined trigonometric parallax. LHS 102B is thus the coolest L dwarf of known distance and luminosity. : Galaxy: kinematics and dynamics-dark matter-stars: low-mass, brown dwarfs 1

The AllWISE processing pipeline has measured motions for all objects detected on WISE images taken between 2010 January and 2011 February. In this paper, we discuss new capabilities made to the software pipeline in order to make motion measurements possible, and we characterize the resulting data products for use by future researchers. Using a stringent set of selection criteria, we find 22,445 objects that have significant AllWISE motions, of which 3,525 have motions that can be independently confirmed from earlier 2MASS images yet lack any published motions in SIMBAD. Another 58 sources lack 2MASS counterparts and are presented as motion candidates only. Limited spectroscopic follow-up of this list has already revealed eight new L subdwarfs. These may provide the first hints of a "subdwarf gap" at mid-L types that would indicate the break between the stellar and substellar populations at low metallicities (i.e., old ages). Another object in the motion list-WISEA J154045.67−510139.3-is a bright (J ≈ 9 mag) object of type M6; both the spectrophotometric distance and a crude preliminary parallax place it ∼6 pc from the Sun. We also compare our list of motion objects to the recently published list of 762 WISE motion objects from Luhman (2014). While these first large motion studies with WISE data have been very successful in revealing previously overlooked nearby dwarfs, both studies missed objects that the other found, demonstrating that many other nearby objects likely await discovery in the AllWISE data products.

We present measurements of positions and relative proper motions in the 30 Doradus region of the Large Magellanic Cloud (LMC). We detail the construction of a single-epoch astrometric reference frame, based on specially-designed observations obtained with the two main imaging instruments ACS/WFC and WFC3/UVIS onboard the Hubble Space Telescope (HST). Internal comparisons indicate a sub milli-arc-second (mas) precision in the positions and the presence of semi-periodic systematics with a mean amplitude of ∼0.8 mas. We combined these observations with numerous archival images taken with WFPC2 and spanning 17 years. The precision of the resulting proper motions for well-measured stars around the massive cluster R 136 can be as good as ∼20 µas yr −1 , although the true accuracy of proper motions is generally lower due to the residual systematic errors. The observed proper-motion dispersion for our highest-quality measurements is ∼0.1 mas yr −1. Our catalog of positions and proper motions contains 86,590 stars down to V ∼ 25 and over a total area of ∼70 square arcmin. We examined the proper motions of 105 relatively bright stars and identified a total of 6 candidate runaway stars. We are able to tentatively confirm the runaway status of star VFTS 285, consistent with the findings from line-of-sight velocities, and to show that this star has likely been ejected from R 136. This study demonstrates that with HST it is now possible to reliably measure proper motions of individual stars in the nearest dwarf galaxies such as the LMC.

Multiple observations were made of six faint common proper motion pairs with the 2-meter Faulkes Telescope North on Haleakala by Maui middle school and high school students and their supporters. Of the six pairs, two are reported as newly discovered proper motion binaries. Individual reductions versus a single 'track and stack' reduction were compared.