Search

We present the discovery of TOI-2136b, a sub-Neptune planet transiting every 7.85 days a nearby M4.5V-type star, identified through photometric measurements from the TESS mission. The host star is located $33$ pc away with a radius of $R_{\ast} = 0.34\pm0.02\ R_{\odot}$, a mass of $0.34\pm0.02\ M_{\odot}$ and an effective temperature of $\rm 3342\pm100\ K$. We estimate its stellar rotation period to be $75\pm5$ days based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multi-wavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from CFHT/SPIRou. Our joint analysis reveals that the planet has a radius of $2.19\pm0.17\ R_{\oplus}$, and a mass measurement of $6.4\pm2.4\ M_{\oplus}$. The mass and radius of TOI2136b is consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136b falls close to the radius valley for low-mass stars predicted by the thermally driven atmospheric mass loss models, making it an interesting target for future studies of its interior structure and atmospheric properties., Comment: 19 pages, 15 figures, submitted to MNRAS

We present a curated sample of 6688 resolved binaries containing M and L dwarf companions within 400 pc of the Sun, including 121 systems within 100 pc. These sources were selected from the Gaia EDR3 compilation of El-Badry et al., and further vetted using photometric and astrometric data from SDSS, Pan-STARRS, 2MASS, UKIDSS, and WISE, as well as visual examination of imaged fields. Only 13% of these systems were reported as co-moving pairs prior to Gaia, and only 4% of the primaries and 1% of the secondaries have published spectral classifications, including just 9 of 109 late-M and L dwarf secondaries within 100 pc. Follow-up of this expanded low-mass companion sample will provide valuable benchmark systems for precisely calibrating empirical diagnostics of the physical properties of the lowest-mass stars and brown dwarfs.

We present moderate-resolution ($R\sim4000$) $K$ band spectra of the planetary-mass companion VHS 1256 b. The data were taken with the OSIRIS integral field spectrograph at the W.M. Keck Observatory. The spectra reveal resolved molecular lines from H$_{2}$O and CO. The spectra are compared to custom $PHOENIX$ atmosphere model grids appropriate for young, substellar objects. We fit the data using a Markov Chain Monte Carlo forward modeling method. Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of 1240 K, with a range of 1200--1300 K, a surface gravity of $\log{g}=$ 3.25, with a range of 3.25--3.75 and a cloud parameter of $\log P_{cloud}=$ 6, with a range of 6.0--6.6. These values are consistent with previous studies, regardless of the new, larger system distance from GAIA EDR3 (22.2$^{+1.1}_{-1.2}$ pc). We derive a C/O ratio of 0.590$_{-0.354}^{+0.280}$ for VHS 1256b. Both our OSIRIS data and spectra from the literature are best modeled when using a larger 3 $\mu$m grain size for the clouds than used for hotter objects, consistent with other sources in the L/T transition region. VHS 1256 b offers an opportunity to look for systematics in the modeling process that may lead to the incorrect derivation of properties like C/O ratio in the high contrast regime., Comment: 16 pages, 10 figures. arXiv admin note: text overlap with arXiv:2009.08959

Ultracool spectral binaries are unresolved pairs of low-mass stars and brown dwarfs revealed by peculiarities in their combined light spectra. Methods to identify these systems have relied on spectral indices, which have known selection biases. We report on a pilot study examining the application of machine learning methods to identify ultracool spectral binaries. Using a sample of single and binary templates constructed from low-resolution, near-infrared spectra, we trained a random forest model to identify binaries composed of M7–L7 primaries and T1–T8 secondaries. We find that uniform data preparation and balancing of the training sample are critical to building an effective model. Our model achieves precisions of ≥95%, confirms known spectral binaries, and identifies new spectral features sensitive to multiplicity, illustrating the utility of machine learning methods to identify these rare systems.

Through the Backyard Worlds: Planet 9 citizen science project, we have identified a wide-separation ($\sim$10', $\sim$9900 au projected) substellar companion to the nearby ($\sim$17.5 pc), mid-M dwarf Ross 19. We have developed a new formalism for determining chance alignment probabilities based on the BANYAN $\Sigma$ tool, and find a 100% probability that this is a physically associated pair. Through a detailed examination of Ross 19A, we find that the system is metal-poor ([Fe/H]=$-$0.40$\pm$0.12) with an age of 7.2$^{+3.8}_{-3.6}$ Gyr. Combining new and existing photometry and astrometry, we find that Ross 19B is one of the coldest known wide-separation companions, with a spectral type on the T/Y boundary, an effective temperature of 500$^{+115}_{-100}$ K, and a mass in the range 15-40 $M_{\rm Jup}$. This new, extremely cold benchmark companion is a compelling target for detailed characterization with future spectroscopic observations using facilities such as the Hubble Space Telescope or James Webb Space Telescope., Comment: Accepted to ApJ

We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs. We combine these with prior studies to build a list of 525 known L, T, and Y dwarfs within 20 pc of the Sun, 38 of which are presented here for the first time. Using published photometry and spectroscopy as well as our own follow-up, we present an array of color-magnitude and color-color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. Using these characterizations, we assign each object a $T_{\rm eff}$ value and judge sample completeness over bins of $T_{\rm eff}$ and spectral type. Except for types $\ge$ T8 and $T_{\rm eff}, Comment: 101 pages, 31 figures, accepted for publication in the Astrophysical Journal Supplement Series

We present medium-resolution (λ/Δλ = 2700), near-infrared spectral standards for field L0–L2, L4, and L7–Y0 dwarfs obtained with the Near-Infrared Echellette Spectrometer on the Keck II 10 m telescope. These standards allow for detailed spectral comparative analysis of cold brown dwarfs discovered through ongoing ground-based projects such as Backyard Worlds: Planet 9, and forthcoming space-based spectral surveys such as the James Webb Space Telescope, SPHEREx, Euclid, and the Nancy Grace Roman Space Telescope.

We report multi-epoch radial velocities, rotational velocities, and atmospheric parameters for 37 T-type brown dwarfs observed with Keck/NIRSPEC. Using a Markov Chain Monte Carlo forward-modeling method, we achieve median precisions of 0.5 km s$^{-1}$ and 0.9 km s$^{-1}$ for radial and rotational velocities, respectively. All of the T dwarfs in our sample are thin disk brown dwarfs. We confirm previously reported moving group associations for four T dwarfs. However, the lack of spectral indicators of youth in two of these sources suggests that these are chance alignments. We confirm two previously un-resolved binary candidates, the T0+T4.5 2MASS J11061197+2754225 and the L7+T3.5 2MASS J21265916+7617440, with orbital periods of 4 yr and 12 yr, respectively. We find a kinematic age of 3.5$\pm$0.3 Gyr for local T dwarfs, consistent with nearby late-M dwarfs (4.1$\pm$0.3 Gyr). Removal of thick disk L dwarfs in the local ultracool dwarf sample gives a similar age for L dwarfs (4.2$\pm$0.3 Gyr), largely resolving the local L dwarf age anomaly. The kinematic ages of local late-M, L, and T dwarfs can be accurately reproduced with population simulations incorporating standard assumptions of the mass function, star formation rate, and brown dwarf evolutionary models. A kinematic dispersion break is found at the L4$-$L6 subtypes, likely reflecting the terminus of the stellar Main Sequence. We provide a compilation of precise radial velocities for 172 late-M, L, and T dwarfs within $\sim$20 pc of the Sun., Comment: 84 pages, 33 figures. Accepted for publication in ApJS

The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provides valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4' of the core of the Orion Nebula Cluster (ONC). We also re-measure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using $HST$ ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities measured are consistent with a normal distribution in all three components. We measure intrinsic velocity dispersions of ($\sigma_{v_\alpha}$, $\sigma_{v_\delta}$, $\sigma_{v_r}$) = ($1.64\pm0.12$, $2.03\pm0.13$, $2.56^{+0.16}_{-0.17}$) km s$^{-1}$. Our computed intrinsic velocity dispersion profiles are consistent with the dynamical equilibrium models from Da Rio et al. (2014) in the tangential direction, but not in the line of sight direction, possibly indicating that the core of the ONC is not yet virialized, and may require a non-spherical potential to explain the observed velocity dispersion profiles. We also observe a slight elongation along the north-south direction following the filament, which has been well studied in previous literature, and an elongation in the line of sight to tangential velocity direction. These 3-D kinematics will help in the development of realistic models of the formation and early evolution of massive clusters., Comment: Accepted to ApJ; 33 pages, 5 tables; 15 figures

We present moderate-resolution ($R\sim4000$) $K$ band spectra of the "super-Jupiter," $\kappa$ Andromedae b. The data were taken with the OSIRIS integral field spectrograph at Keck Observatory. The spectra reveal resolved molecular lines from H$_{2}$O and CO. The spectra are compared to a custom $PHOENIX$ atmosphere model grid appropriate for young planetary-mass objects. We fit the data using a Markov Chain Monte Carlo forward modeling method. Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of $T_\mathrm{eff}$ = 1950 - 2150 K, a surface gravity of $\log g=3.5 - 4.5$, and a metallicity of [M/H] = $-0.2 - 0.0$. These values are consistent with previous estimates from atmospheric modeling and the currently favored young age of the system ($, Comment: 23 pages, 18 figures. Accepted for publication in AJ

We present a volume-limited, spectroscopically-verified sample of M7$-$L5 ultracool dwarfs within 25\,pc. The sample contains 410 sources, of which $93\%$ have trigonometric distance measurements ($80\%$ from \textit{Gaia} DR2), and $81\%$ have low-resolution ($R\sim120$), near-infrared (NIR) spectroscopy. We also present an additional list of 60 sources which may be M7$-$L5 dwarfs within 25\,pc when distance or spectral type uncertainties are taken into account. The spectra provide NIR spectral and gravity classifications, and we use these to identify young sources, red and blue $J-K_S$ color outliers, and spectral binaries. We measure very low gravity and intermediate gravity fractions of $2.1^{+0.9}_{-0.8}\%$ and $7.8^{+1.7}_{-1.5}\%$, respectively; fractions of red and blue color outliers of $1.4^{+0.6}_{-0.5}$\% and $3.6^{+1.0}_{-0.9}$\%, respectively; and a spectral binary fraction of $1.6^{+0.5}_{-0.5}\%$. We present an updated luminosity function for M7$-$L5 dwarfs continuous across the hydrogen burning limit that agrees with previous studies. We estimate our completeness to range between $69-80\%$ when compared to an isotropic model. However, we find that the literature late-M sample is severely incomplete compared to L dwarfs, with completeness of $62^{+8}_{-7}\%$ and $83^{+10}_{-9}\%$, respectively. This incompleteness can be addressed with astrometric-based searches of ultracool dwarfs with \textit{Gaia} to identify objects previously missed by color- and magnitude-limited surveys., 71 pages, 27 figures, and 18 tables

We report resolved optical spectroscopy for the nearby low-mass stellar system BD-08 2582AB. We confirm prior unpublished reports of the existence of the secondary, and the spectral data indicate a secondary type of M6 Ve, consistent with spectrophotometric estimates from Gaia astrometry. The secondary exhibits Hα emission at a level equivalent to other M6 dwarfs, and has a metallicity index in line with its well-studied solar-metallicity K7/M0 primary.

We present a parallax solution for WISE J135501.90-825838.9, a spectral binary with spectral types L7+T7.5 and a candidate AB Doradus member. Using Wide-field Infrared Survey Explorer (WISE) astrometry, we obtain a distance of d = 16.7 ± 5.3 pc. This preliminary parallax solution provides further evidence that WISE J135501.90-825838.9 is a member of AB Doradus (130–200 Myr), and when combined with evolutionary models predicts masses of 11 M Jup and 9 M Jup for each component.

The Orion Nebula Cluster (ONC) is the nearest site of ongoing massive star formation, which allows us to study the kinematics and dynamics of the region in detail and constrain star formation theories. Using HST ACS/WFPC2/WFC3IR and Keck II NIRC2 data, we have measured the proper motions of 701 stars within an $\sim6'\times6'$ field of view around the center of the ONC. We have found more than 10 escaping star candidates, concentrated predominantly at the core of the cluster. The proper motions of the bound stars are consistent with a normal distribution, albeit elongated North-South along the Orion filament, with proper motion dispersions of $(\sigma_{\mu,\alpha^*}, \sigma_{\mu,\delta}) = (0.83\pm0.02,\,1.12\pm0.03)$ mas yr$^{-1}$ or intrinsic velocity dispersions of $(\sigma_{v,\alpha^*}, \sigma_{v,\delta}) = (1.57\pm0.04,\,2.12\pm0.06)$ km s$^{-1}$ assuming a distance of 400 pc to the ONC. The cluster shows no evidence for tangential-to-radial anisotropy. Our velocity dispersion profile agrees with the prediction from the observed stellar + gas density profile from Da Rio et al. (2014), indicating that the ONC is in virial equilibrium. This finding suggests that the cluster was formed with a low star formation efficiency per dynamical timescale based on comparisons with current star formation theories. Our survey also recovered high-velocity IR sources BN, x, and n in the BN/KL region. The estimated location of the first two sources $\sim500$ years ago agrees with that of the radio source I, consistent with their proposed common origin from a multi-stellar disintegration. However, source n appears to have a small proper motion and is unlikely to have been involved in the event., Comment: 20 pages, 11 figures, 5 tables. AJ, in press. Changes w.r.t v1: the mass of source I in Section 5.3, the order of tables, and minor language corrections

We present the results of an investigation into the occurrence and properties (stellar age and mass trends) of low-mass field stars exhibiting extreme mid-infrared (MIR) excesses ($L_\mathrm{IR} / L_\ast \gtrsim 0.01$). Stars for the analysis were initially selected from the Motion Verified Red Stars (MoVeRS) catalog of photometric stars with SDSS, 2MASS, and $WISE$ photometry and significant proper motions. We identify 584 stars exhibiting extreme MIR excesses, selected based on an empirical relationship for main sequence $W1-W3$ colors. For a small subset of the sample, we show, using spectroscopic tracers of stellar age (H$\alpha$ and Li ${\rm{\small I}}$) and luminosity class, that the parent sample is likely comprised of field dwarfs ($\gtrsim$ 1 Gyr). We also develop the Low-mass Kinematics ($LoKi$) galactic model to estimate the completeness of the extreme MIR excess sample. Using Galactic height as a proxy for stellar age, the completeness corrected analysis indicates a distinct age dependence for field stars exhibiting extreme MIR excesses. We also find a trend with stellar mass (using $r-z$ color as a proxy). Our findings are consistent with the detected extreme MIR excesses originating from dust created in a short-lived collisional cascade ($\lesssim$ 100,000 years) during a giant impact between two large planetismals or terrestrial planets. These stars with extreme MIR excesses also provide support for planetary collisions being the dominant mechanism in creating the observed $Kepler$ dichotomy (the need for more than a single mode, typically two, to explain the variety of planetary system architectures $Kepler$ has observed), rather than different formation mechanisms., Comment: 33 pages, 26 figures, 10 tables. Accepted for publication in AJ

This paper uses the multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE) to demonstrate a method to measure proper motions and trigonometric parallaxes with precisions of $\sim$4 mas yr$^{-1}$ and $\sim$7 mas, respectively, for low-mass stars and brown dwarfs. This method relies on WISE single exposures (Level 1b frames) and a Markov Chain Monte Carlo method. The limitations of Gaia in observing very low-mass stars and brown dwarfs are discussed, and it is shown that WISE will be able to measure astrometry past the 95% completeness limit and magnitude limit of Gaia (L, T, and Y dwarfs fainter than $G\approx19$ and $G=21$, respectively). This method is applied to WISE data of 20 nearby ($\lesssim17$ pc) dwarfs with spectral types between M6-Y2 and previously measured trigonometric parallaxes. Also provided are WISE astrometric measurements for 23 additional low-mass dwarfs with spectral types between M6-T7 and estimated photometric distances $, Accepted to ApJ

We present the Late-Type Extension to the Motion Verified Red Stars (LaTE-MoVeRS) catalog, containing 46,463 photometric late-type ($>$ M5) dwarfs within the Sloan Digital Sky Survey (SDSS) footprint. Proper motions were computed for objects combining astrometry from the SDSS Data Release 12 (DR12), the Two-Micron All-Sky Survey (2MASS) Point Source Catalog (PSC), and the \emph{Wide-field Infrared Survey Explorer} (\emph{WISE}) AllWISE datasets. LaTE-MoVeRS objects were required to have significant proper motion ($��_\mathrm{tot} \geqslant 2��_{��_\mathrm{tot}}$). Using the LaTE-MoVeRS sample and \emph{Gaia} Data Release 1, we estimate \emph{Gaia} will be $\sim$64\% complete for very-low-mass objects ($>$ M5) in comparison to the combined SDSS+2MASS+\emph{WISE} dataset ($i < 21.3$). We computed photometric distances and estimated stellar effective temperatures for the LaTE-MoVeRS catalog. The majority of the dwarfs in the sample have distances $< 150$ pc and $T_\mathrm{eff} < 3000$ K. Thirteen objects were identified within LaTE-MoVeRS with estimated photometric distances within 25 pc that have not been previously identified as nearby objects. We also identified one new object with a large amount of excess mid-infrared flux that has not been previously identified (2MASS J11151597$+$1937266). This object appears to be an L2$��$ at $\sim$50 pc showing spectroscopic signs of a flaring event (e.g., strong Hydrogen Balmer emission lines). This object does not exhibit kinematics similar to any known kinematic association. The LaTE-MoVeRS catalog is available through SDSS CasJobs and VizieR., Accepted for publication in AJ. 18 pages including 14 figures and 5 tables

We present a photometric catalog of 8,735,004 proper motion selected low-mass stars (KML-spectral types) within the Sloan Digital Sky Survey (SDSS) footprint, from the combined SDSS Data Release 10 (DR10), Two-Micron All-Sky Survey (2MASS) Point Source Catalog (PSC), and Wide-field Infrared Survey Explorer (WISE) AllWISE catalog. Stars were selected using $r-i$, $i-z$, $r-z$, $z-J$, and $z-W1$ colors, and SDSS, WISE, and 2MASS astrometry was combined to compute proper motions. The resulting 3,518,150 stars were augmented with proper motions for 5,216,854 earlier type stars from the combined SDSS and United States Naval Observatory B1.0 catalog (USNO-B). We used SDSS+USNO-B proper motions to determine the best criteria for selecting a clean sample of stars. Only stars whose proper motions were greater than their $2$$\sigma$ uncertainty were included. Our Motion Verified Red Stars (MoVeRS) catalog is available through SDSS CasJobs and VizieR., Comment: 24 pages, 18 figures, 8 tables, accepted for publication in AJ

We present a sample of 20 runaway M dwarf candidates (RdMs) within 1 kpc of the Sun whose Galactocentric velocities exceed 400 km s$^{-1}$. The candidates were selected from the SDSS DR7 M Dwarf Catalog of West et al. (2011). Our RdMs have SDSS+USNO-B proper motions that are consistent with those recorded in the PPMXL, LSPM, and combined WISE+SDSS+2MASS catalogs. Sixteen RdMs are classified as dwarfs, while the remaining four RdMs are subdwarfs. We model the Galactic potential using a bulge-disk-halo profile (Kenyon et al. 2008; Brown et al. 2014). Our fastest RdM, with Galactocentric velocity 658.5 $\pm$ 236.9 km s$^{-1}$, is a possible hypervelocity candidate, as it is unbound in 77% of our simulations. About half of our RdMs have kinematics that are consistent with ejection from the Galactic center. Seven of our RdMs have kinematics consistent with an ejection scenario from M31 or M32 to within 2{\sigma}, although our distance-limited survey makes such a realization unlikely. No more than four of our RdMs may have originated from the Leo stream. We propose that to within measurement errors, most of our bound RdMs are likely disk runaways or halo objects, and may have been accelerated through a series of multi-body interactions within the Galactic disk or possibly supernovae explosions., Comment: 17 pages, 5 figures, paper has been accepted for publication in the Astrophysical Journal

We present new radial velocity and trigonometric parallax measurements indicating that the unusually red and photometrically variable T2 dwarf 2MASS J13243553+6358281 is a member of the young (~150 Myr) AB Doradus moving group based on its space velocity. We estimate its model-dependent mass in the range 11-12 $M_{\rm Jup}$ at the age of the AB Doradus moving group, and its trigonometric parallax distance of 12.7 $\pm$ 1.5 pc makes it one of the nearest known isolated planetary-mass objects. The unusually red continuum of 2MASS J13243553+6358281 in the near-infrared was previously suspected to be caused by an unresolved L+T brown dwarf binary, although it was never observed with high-spatial resolution imaging. This new evidence of youth suggests that a low surface gravity may be sufficient to explain this peculiar feature. Using the new parallax we find that its absolute $J$-band magnitude is ~0.4 mag fainter than equivalent-type field brown dwarfs, suggesting that the binary hypothesis is unlikely. The fundamental properties of 2MASS J13243553+6358281 follow the spectral type sequence of other known high-likelihood members of the AB Doradus moving group. The effective temperature of 2MASS J13243553+6358281 provides the first precise constraint on the L/T transition at a known young age, and indicates that it happens at a temperature of ~1150 K at ~150 Myr, compared to ~1250 K for field brown dwarfs., Comment: 9 pages, 4 figures, 1 table. Accepted for publication in the Astrophysical Journal Letters

[not part of RNAAS note] We report the discovery of WISE J000100.45+065259.6 as a very low mass star/brown dwarf spectral binary candidate, on the basis of low resolution near-infrared spectroscopy obtained with IRTF/SpeX. Decomposition of the spectrum indicates component types of M8.5+T5 with a predicted $\Delta{J}$ = 3.5. As the majority of confirmed spectral binary candidates to date are very closely-separated systems ($\rho$ $\lesssim$ 3 AU; $P$ $\lesssim$ 15~yr), this source may provide mass measurements across the hydrogen burning limit within the decade.

We present the results of a Palomar Transient Factory (PTF) archival search for blue transients which lie in the magnitude range between "normal" core-collapse and superluminous supernovae (i.e. with $-21\,{\leq}M_{R\,(peak)}\,{\leq}-19$). Of the six events found after excluding all interacting Type~IIn and Ia-CSM supernovae, three (PTF09ge, 09axc and 09djl) are coincident with the centers of their hosts, one (10iam) is offset from the center, and for two (10nuj and 11glr) a precise offset can not be determined. All the central events have similar rise times to the He-rich tidal disruption candidate PS1-10jh, and the event with the best-sampled light curve also has similar colors and power-law decay. Spectroscopically, PTF09ge is He-rich, while PTF09axc and 09djl display broad hydrogen features around peak magnitude. All three central events are in low star-formation hosts, two of which are E+A galaxies. Our spectrum of the host of PS1-10jh displays similar properties. PTF10iam, the one offset event, is different photometrically and spectroscopically from the central events and its host displays a higher star formation rate. Finding no obvious evidence for ongoing galactic nuclei activity or recent star formation, we conclude that the three central transients likely arise from the tidal disruption of a star by a super-massive black hole. We compare the spectra of these events to tidal disruption candidates from the literature and find that all of these objects can be unified on a continuous scale of spectral properties. The accumulated evidence of this expanded sample strongly supports a tidal disruption origin for this class of nuclear transients., Comment: Minor changes and clarifications, added radio non-detection limits for one of the events, accepted to ApJ

Using the SDSS DR7 spectroscopic catalog, we searched the WISE AllWISE catalog to investigate the occurrence of warm dust, as inferred from IR excesses, around field M dwarfs (dMs). We developed SDSS/WISE color selection criteria to identify 175 dMs (from 70,841) that show IR flux greater than typical dM photosphere levels at 12 and/or 22 $\mu$m, including seven new stars within the Orion OB1 footprint. We characterize the dust populations inferred from each IR excess, and investigate the possibility that these excesses could arise from ultracool binary companions by modeling combined SEDs. Our observed IR fluxes are greater than levels expected from ultracool companions ($>3\sigma$). We also estimate that the probability the observed IR excesses are due to chance alignments with extragalactic sources is $, Comment: 27 pages, 21 figures, 12 tables, Accepted for publication in ApJ

Supernovae (SNe) are stellar explosions driven by gravitational or thermonuclear energy, observed as electromagnetic radiation emitted over weeks or more. In all known SNe, this radiation comes from internal energy deposited in the outflowing ejecta by either radioactive decay of freshly-synthesized elements (typically 56Ni), stored heat deposited by the explosion shock in the envelope of a supergiant star, or interaction between the SN debris and slowly-moving, hydrogen-rich circumstellar material. Here we report on a new class of luminous SNe whose observed properties cannot be explained by any of these known processes. These include four new SNe we have discovered, and two previously unexplained events (SN 2005ap; SCP 06F6) that we can now identify as members. These SNe are all ~10 times brighter than SNe Ia, do not show any trace of hydrogen, emit significant ultra-violet (UV) flux for extended periods of time, and have late-time decay rates which are inconsistent with radioactivity. Our data require that the observed radiation is emitted by hydrogen-free material distributed over a large radius (~10^15 cm) and expanding at high velocities (>10^4 km s^-1). These long-lived, UV-luminous events can be observed out to redshifts z>4 and offer an excellent opportunity to study star formation in, and the interstellar medium of, primitive distant galaxies., Accepted to Nature. Press embargoed until 2011 June 8, 18:00 UT

Many compute environments rely on centralized, network-facing services in order to work properly; examples are Web servers, Grid Compute Elements and Grid Storage Elements. Testing such services requires a large amount of geographically dispersed compute resources all interacting concurrently with the service to test. Grid resources provide an obvious candidate for such testing, but to the best of our knowledge there is no readily available tool for such testing. In this paper we present one such tool, based on Condor glideins.

The Open Science Grid relies on several network facing services to deliver resources to its users. The major services are the Compute Elements, Storage Elements, Workload Management Systems and Information Systems. All of these services are exposed to traffic coming from all over the world in an unmanaged way, so it is very important to know how they behave at different levels of load. In this paper we present the methodology and the results of scalability and reliability tests performed by OSG on some of the above services. The major services being tested are the Condor batch system, the GT2, GRAM5 and CREAM CEs, and the BeStMan SRM SE.