Statistical Re-examination of Reported Emission Lines in the X-ray Afterglow of GRB 011211

(abridged) A 0.2-12 keV spectrum obtained with the XMM EPIC/pn instrument of GRB 011211 was found by Reeves et al. (2002) to contain emission lines which were interpreted to be from Mg XI, Si XIV, S XVI, Ar XVIII, and Ca XX, at a lower redshift (z_{obs}=1.88) than the host galaxy (z_{host}=2.14). We examine the spectrum independently, and find that the claimed lines would not be discovered in a blind search. Specifically, Monte Carlo simulations show that they would be observed in 10% of featureless spectra with the same signal-to-noise. Imposing a model in which the two brightest lines would be Si XIV and S XVI K-alpha emission possibly velocity shifted to between z=1.88--2.40, such features would be found in between ~1.2-2.6% of observed featureless spectra. We find the detection significances to be insufficient to justify the claim of detection and the model put forth to explain them. K-alpha line complexes are also found at z=1.2 and z=2.75 of significance equal to or greater than that at z=1.88. If one adopts the z=1.88 complex as significant, one must also adopt the other two complexes to be significant. The interpretation of these data in the context of the model proposed by Reeves et al. is therefore degenerate, and cannot be resolved by these data alone.Comment: 23 pages, 4 figures. MNRAS, accepted. Expanded discussio

XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources

The 18806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-ray sources are quantitatively cross-associated with near-infrared (NIR) sources from the Two Micron All Sky Survey Point Source Catalog (2MASS/PSC). An association catalog is presented, listing the most likely counterpart for each RASS/BSC source, the probability Pid that the NIR source and X-ray source are uniquely associated, and the probability Pnoid that none of the 2MASS/PSC sources are associated with the X-ray source. The catalog includes 3853 high quality (Pid>0.98) X-ray--NIR matches, 2280 medium quality (0.98>Pid>0.9) matches, and 4153 low quality (0.9>Pid>0.5) matches. Of the high quality matches, 1418 are associations that are not listed in the SIMBAD database, and for which no high quality match with a USNO-A2 optical source was presented for the RASS/BSC source in previous work. The present work offers a significant number of new associations with RASS/BSC objects that will require optical/NIR spectroscopy for classification. For example, of the 6133 Pid>0.9 2MASS/PSC counterparts presented in the association catalog, 2411 have no classification listed in the SIMBAD database. These 2MASS/PSC sources will likely include scientifically useful examples of known source classes of X-ray emitters (white dwarfs, coronally active stars, active galactic nuclei), but may also contain previously unknown source classes. It is determined that all coronally active stars in the RASS/BSC should have a counterpart in the 2MASS/PSC, and that the unique association of these RASS/BSC sources with their NIR counterparts thus is confusion limited.Comment: 14 pages, 13 figures, 5 table

First Record of the Soybean Aphid, \u3ci\u3eAphis Glycines\u3c/i\u3e (Hemiptera: Sternorrhyncha: Aphididae) in Connecticut and Massachusetts

The soybean aphid, Aphis glycines Matsumara, was first found in the United States in Wisconsin in the summer of 2000. Since that time it has spread to 21 states, primarily in the upper Midwest and 3 Canadian provinces. The predicted range of soybean aphid includes all of New England, but it had not yet been reported from Connecticut and Massachusetts. I surveyed two sites in each state during the summer of 2004: Hamden, CT on 4 August, Cromwell, CT on 1 September, and Plainfield, MA and Conway, MA on 10 September. Soybean aphids were present at all four sites. This is the first report of soybean aphid for Connecticut and Massachusetts

Time-Variable Emission from Transiently Accreting Neutron Stars In Quiescence due to Deep Crustal Heating

Transiently accreting neutron stars in quiescence (Lx<10^34 erg/s) have been observed to vary in intensity by factors of few, over timescales of days to years. If the quiescent luminosity is powered by a hot NS core, the core cooling timescale is much longer than the recurrence time, and cannot explain the observed, more rapid variability. However, the non-equilibrium reactions which occur in the crust during outbursts deposit energy in iso-density shells, from which the thermal diffusion timescale to the photosphere is days to years. The predicted magnitude of variability is too low to explain the observed variability unless - as is widely believed - the neutrons beyond the neutron-drip density are superfluid. Even then, variability due to this mechanism in models with standard core neutrino cooling processes is less than 50 per cent - still too low to explain the reported variability. However, models with rapid core neutrino cooling can produce variability by a factor as great as 20, on timescales of days to years following an outburst. Thus, the factors of few intensity variability observed from transiently accreting neutron stars can be accounted for by this mechanism only if rapid core cooling processes are active.Comment: 12 pages, 5 figures, submitted to MNRA

Planar sandwich antennas for submillimeter applications

A planar receiving antenna with a predictable pattern at submillimeter wavelength is demonstrated experimentally for the first time. It is single lobed and efficient, with a gain of approximately 8 dB at a wavelength of 119 µm

Gamma-Ray Bursts and the Cosmic Star Formation Rate

We have tested several models of GRB luminosity and redshift distribution functions for compatibility with the BATSE 4B number versus peak flux relation. Our results disagree with recent claims that current GRB observations can be used to strongly constrain the cosmic star formation history. Instead, we find that relaxing the assumption that GRBs are standard candles renders a very broad range of models consistent with the BATSE number-flux relation. We explicitly construct two sample distributions, one tracing the star formation history and one with a constant comoving density. We show that both distributions are compatible with the observed fluxes and redshifts of the bursts GRB970508, GRB971214, and GRB980703, and we discuss the measurements required to distinguish the two models.Comment: 12 pages, 2 postscript figures, uses AAS LaTex macros v4.0. To be published in Astrophysical Journal Letters, accepted August 20, 1998. Revised for publicatio

Discovery of an Isolated Compact Object at High Galactic Latitude

We report discovery of a compact object at high Galactic latitude. The object was initially identified as a ROSAT All-Sky Survey Bright Source Catalog X-ray source, 1RXS J141256.0+792204, statistically likely to possess a high X-ray to optical flux ratio. Further observations using {\em Swift}, Gemini-North, and the Chandra X-ray Observatory refined the source position and confirmed the absence of any optical counterpart to an X-ray to optical flux ratio of F_X/F_V > 8700 (3 sigma). Interpretation of 1RXS J141256.0+792204 -- which we have dubbed Calvera -- as a typical X-ray-dim isolated neutron star would place it at z ~ 5.1 kpc above the Galactic disk -- in the Galactic halo -- implying that it either has an extreme space velocity (v_z >~ 5100 km s-1) or has failed to cool according to theoretical predictions. Interpretations as a persistent anomalous X-ray pulsar, or a ``compact central object'' present conflicts with these classes' typical properties. We conclude the properties of Calvera are most consistent with those of a nearby (80 to 260 pc) radio pulsar, similar to the radio millisecond pulsars of 47 Tuc, with further observations required to confirm this classification. If it is a millisecond pulsar, it has an X-ray flux equal to the X-ray brightest millisecond pulsar (and so is tied for highest flux); is the closest northern hemisphere millisecond pulsar; and is potentially the closest known millisecond pulsar in the sky, making it an interesting target for X-ray-study, a radio pulsar timing array, and LIGO.Comment: ApJ, in press. We are grateful to the anonymous referee, who pointed us toward a better XRT response matrix which changes our quantitative conclusions somewha

Measurement of the Radius of Neutron Stars with High S/N Quiescent Low-mass X-ray Binaries in Globular Clusters

This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter -- present in the core of NSs -- is best described by "normal matter" equations of state (EoSs). Such EoSs predict that the radii of NSs, Rns, are quasi-constant (within measurement errors, of ~10%) for astrophysically relevant masses (Mns > 0.5 Msun). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single Rns value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov-Chain Monte-Carlo approach, we produce the marginalized posterior distribution for Rns, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions,we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, Rns=9.1(+1.3)(-1.5) km (90%-confidence). Such a value is consistent with low-res equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.Comment: Accepted to Apj. 31 pages, 17 figures, 8 table