Table of contents

We present Spitzer Space Telescope IRAC and MIPS observations of the Galactic globular cluster M15 (NGC 7078), one of the most metal-poor clusters, with a [Fe/H] = -2.4. Our Spitzer images reveal a population of dusty red giants near the cluster center, a previously detected planetary nebula designated K648, and a possible detection of the intracluster medium arising from mass-loss episodes from the evolved stellar population. Our analysis suggests that (9 ± 2) × 10^-4M_⊙ of dust is present in the core of M15, and that this material has accumulated over a period of ≈10⁶ yr, a timescale 10 times shorter than the last Galactic plane crossing event. We also present Spitzer IRS follow-up observations of K648, including the detection of the [Ne II] 12.81 μm line, and discuss abundances derived from infrared fine-structure lines.

We present I-band photometry, long-slit optical spectroscopy, and new aperture synthesis H I observations for eight late-type spiral galaxies with rotation velocities in the range 243 km s^-1 ≲ V_rot ≲ 308 km s^-1. The sample will be used to study the structure and angular momentum of disks at the high-mass end of the spiral galaxy population; here we discuss the basic properties of these "fast rotators" and derive hybrid optical/H I rotation curves for each. Despite the presence of H I warps and low-mass companions in many systems, their kinematics are regular and there is excellent agreement between optical and H I tracers near the optical radius r_opt. At high inclinations at which projection effects are negligible, the sample galaxies exhibit flat, featureless rotation curves out to their last measured points at 1.7r_opt-3.5r_opt. The intermediate-inclination systems are also consistent with a constant rotation amplitude for r ≳ 0.5r_opt. We therefore find no evidence for declining rotation curves at the high-mass end of the late-type spiral galaxy population. Combining our data with the compilation of spiral galaxies with reliable outer H I kinematics from the work of Casertano and van Gorkom, we find no convincing trends between logarithmic outer rotation curve slopes and rotation amplitudes or surface brightnesses for galaxies with V_rot ≳ 220 km s^-1. Correlations between these slopes and morphological types or disk scale lengths are also marginal in this regime.

We have increased the spectral resolution and accuracy of the absolute infrared spectral flux for a subset of stellar standards created by Cohen and his collaborators in previous papers in this series. We combined the moderate-resolution (λ/Δλ ∼ 400) spectroscopy obtained on infrared standard stars by the Short Wavelength Spectrometer on the Infrared Space Observatory with high-quality photometry that is tied to our recent absolute calibration from the Midcourse Space Experiment. New spectra were created for 33 stars, 9 of which are Cohen et al. secondary standards and another 20 of which are tertiary standards for which Cohen adopted spectral templates. The effective temperatures and angular diameters for the stars are derived from the absolute spectra and compare favorably with independent measures of these quantities in the literature. The present spectra display systematic differences with those of Cohen and colleagues in that they have 4%-7% lower fluxes in the 1-4 μm spectral region. Our spectra remove the A-K star calibration bias recently noted in the calibration of the Spitzer Space Telescope camera.

We have detected FIRST J101614.3+520916 with the XMM-Newton X-ray observatory. FIRST J101614.3+520916, one of the most extreme radio-loud, broad absorption line (BAL) quasars so far discovered, is also a Fanaroff-Riley type II radio source. We find that, compared to its estimated intrinsic X-ray flux, the observed X-rays are likely suppressed and that the observed hardness ratio indicates significant soft X-ray photons. This is inconsistent with the simplest model, a normal quasar spectrum absorbed by a large neutral H I column density, which would primarily absorb the softer photons. More complex models, involving partial covering, an ionized absorber, ionized mirror reflection, or jet contributions need to be invoked to explain this source. The suppressed but soft X-ray emission in this radio-loud BAL quasar is consistent with the behavior displayed by other BAL quasars, both radio-loud and radio-quiet.

We attempt to select new candidate intrinsic and extrinsic S stars in the General Catalogue of Galactic S Stars (GCGSS) by combining data from the Two Micron All Sky Survey, the Infrared Astronomical Satellite, and the Midcourse Space Experiment. Catalog entries are cross-identified, yielding 528 objects, out of which 29 are known extrinsic S stars and 31 are known intrinsic S stars. Their color-color diagrams, (H - [12])-(K - [12]) and (K - [12])-(J - [25]), are drawn and used to identify a new sample of 147 extrinsic and 256 intrinsic S star candidates, while the nature of 65 stars remains identified. We infer that about 38% ± 10% of the GCGSS objects are of extrinsic type. Moreover, we think that colors such as J - [25] can be used to split off the two categories of S stars, while single colors are not appropriate. The color-color diagrams, such as (H - [12])-(K - [12]) and (K - [12])-(J - [25]), are proven to be powerful tools for distinguishing the two kinds of S stars.

We present a sample of 1744 type 1 active galactic nuclei (AGNs) from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) spectroscopic catalog with X-ray counterparts in the White-Giommi-Angelini Catalog (WGACAT) of ROSAT PSPC pointed observations. Of 1744 X-ray sources, 1410 (80.9%) are new AGN identifications. Of 4574 SDSS DR4 AGNs for which we found radio matches in the catalog of radio sources from the Faint Images of the Radio Sky at Twenty cm survey, 224 turned up in our sample of SDSS X-ray AGNs. The sample objects are given in a catalog that contains optical and X-ray parameters and supporting data, including redshifts; it also contains radio emission parameters where available. We illustrate the content of our catalog and its potential for AGN science by providing statistical relationships for the catalog data. The potential of the morphological information is emphasized by confronting the statistics of optically resolved, mostly low-redshift AGNs with unresolved AGNs that occupy a much wider redshift range. The immediate properties of the catalog objects include significant correlation of X-ray and optical fluxes, which is consistent with expectations. Also expected is the decrease of X-ray flux toward higher redshifts. The X-ray-to-optical flux ratio for the unresolved AGNs exhibits a decline toward higher redshifts, in agreement with previous results. The resolved AGNs, however, display the opposite trend. The X-ray hardness ratio shows a downward trend with increasing low-energy X-ray flux and no obvious dependence on redshift. At a given optical brightness, X-ray fluxes of radio-loud AGNs are, on average, higher than those of radio-quiet AGNs by a factor of 2. We caution, however, that because of the variety of selection effects present in both the WGACAT and the SDSS, the interpretation of any relationships based on our sample of X-ray AGNs requires a careful analysis of these effects.

The maximum amplitude of a solar activity cycle is found to be inversely correlated (r = -0.769) with the newly defined max-max cycle length two cycles earlier in a 13 month mean of monthly sunspot numbers. Meanwhile, a 14 cycle periodicity is found in the fitted residuals. The max-max cycle length can be used as one of the indicators to predict amplitudes. As a result, the amplitudes of cycles 24 and 25 are estimated to be 150.3 ± 22.4 and 102.6 ± 22.4, respectively, where the indicated error is the standard error.

From two sets of radial velocities we have obtained the orbital elements of HR 1613. This single-lined binary has an orbital period of 8.11128 days and a nearly circular orbit. The primary has an A9 V spectral type and a v sin i value of 11 km s^-1, while the unseen secondary is likely a K or M dwarf. Spectral classifications and spectrum synthesis analysis indicate that the abundances of the primary are normal. We reject the possibility that the primary of HR 1613 is seen nearly pole-on and instead argue that its rotational inclination is at least 20°, resulting in an equatorial rotational velocity of 30 km s^-1 or less. Slowly rotating A stars almost always have spectrum peculiarities, being classified as either Ap or Am stars, but HR 1613, with its essentially solar abundances, appears to be an exception.

Type II quasars are luminous active galactic nuclei (AGNs) whose centers are obscured by large amounts of gas and dust. In this paper we present three-band Hubble Space Telescope images of nine type II quasars with redshifts 0.2 < z < 0.4 selected from the Sloan Digital Sky Survey based on their emission-line properties. The intrinsic luminosities of these AGNs are estimated to be -24 > M_B > -26, but optical obscuration allows their host galaxies to be studied unencumbered by bright nuclei. Each object has been imaged in three continuum filters ("UV," "blue," and "yellow") placed between the strong emission lines. The spectacular, high-quality images reveal a wealth of details about the structure of the host galaxies and their environments. Six of the nine galaxies in the sample are elliptical galaxies with de Vaucouleurs light profiles, one object has a well-defined disk component, and the remaining two have marginal disks. Stellar populations of type II quasar hosts are more luminous (by a median of 0.3-0.7 mag, depending on the wavelength) and bluer (by about 0.4 mag) than are M_* galaxies at the same redshift. When smooth fits to stellar light are subtracted from the images, we find both positive and negative residuals that become more prominent toward shorter wavelengths. We argue that the negative residuals are due to kiloparsec-scale dust obscuration, while most positive residuals are due to the light from the nucleus scattered off interstellar material in the host galaxy. Scattered light makes a significant contribution to the broadband continuum emission and can be the dominant component of the extended emission in the UV in extreme cases.

Spectroscopy of 222 late-type dwarfs in the Praesepe open cluster is used to measure the strengths of molecular and atomic features and to examine their sensitivity to chromospheric activity as measured by the strength of Hα emission. For this cluster we confirm the results of Hawley and coworkers that some TiO features are selectively weakened among active field stars. However, a similar effect for CaOH is only weakly confirmed. Using differential measures of the strengths of features with respect to the median in narrow color bins, we also find that absorption in the Ca II IR triplet is selectively weakened in more active stars, while absorption at K I and Na I is strengthened. A comparison of the distribution of the Hα strengths with V - I color in Praesepe and the similarly aged Hyades cluster indicates that the onset of M dwarf activity occurs at a significantly redder color in Praesepe than in the Hyades. Analysis of similar data on eight clusters from the literature is used to explore the relationship between age and activity in open clusters. We quantify the dependence on cluster age of the location along the main sequence for the onset of activity, confirming that the critical color at which activity becomes prominent is a nearly linear function of the logarithm of the age.

HD 5980 is a unique system containing one massive star (star A) that is apparently entering the luminous blue variable phase and an eclipsing companion (star B) that may have already evolved beyond this phase to become a Wolf-Rayet star. In this paper we present the results from FUSE observations obtained in 1999, 2000, and 2002, and one far-UV observation obtained by ORFEUS BEFS in 1993 shortly before the first eruption of HD 5980. The eight phase-resolved spectra obtained by FUSE in 2002 are analyzed in the context of a wind-eclipse model. This analysis shows that the wind of the eruptor obeyed a very fast velocity law in 2002, which is consistent with the line-driving mechanism. Large-amplitude line-profile variations on the orbital period are shown to be due to the eclipse of star B by the wind of star A, although the eclipse due to gas flowing in the direction of star B is absent. This can only be explained if the wind of star A is not spherically symmetric or if the eclipsed line radiation is "filled in" by emission originating from somewhere else in the system, e.g., in the wind-wind collision region. Except for a slightly lower wind speed, the ORFEUS BEFS spectrum is very similar to the spectrum obtained by FUSE at the same orbital phase; there is no indication of the impending eruption. However, the trend for decreasing wind velocity suggests the occurrence of the "bistability" mechanism, which in turn implies that the restructuring of the circumbinary environment caused by the transition from fast, rarefied wind to slow, dense wind was observed as the eruptive event. The underlying mechanism responsible for the long-term decrease in wind velocity that precipitated this change remains an open issue.

Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for nine contact binaries: V1464 Aql, V759 Cen, DE Oct, MW Pav, BQ Phe, EL Aqr, SX Crv, VZ Lib, and GR Vir. For the first five of these, our observations are the first available radial velocity data. For the three remaining radial velocity variables, CE Hyi is a known visual binary, while CL Cet and V1084 Sco are suspected to be multiple systems in which the contact binary is spectrally dominated by its companion (which itself is a binary in V1084 Sco). Five additional variable stars, V872 Ara, BD Cap, HIP 69300, BX Ind, and V388 Pav, are of unknown type, but most are pulsating stars; we give their mean radial velocities and V sin i.

We study the temperature and density sensitivities of the ratios of Si XI soft X-ray emission lines in the wavelength range of 43-54 Å. The typical temperature of formation of the analyzed lines is around 1.6 MK, which makes this analysis complementary to the analysis of He-like triplets, which are sensitive to hotter plasma. We present theoretical calculations and compare them with ratios obtained from high-resolution X-ray spectra of five solar-like stars: Procyon, α Cen A, α Cen B, Eri, and Capella. We find that our results are in good agreement with results obtained by other authors through different diagnostics, namely, the analysis of density- and temperature-sensitive He-like triplet lines. We further estimate the coronal pressure and filling factors from Si XI lines in this study.

A variability study of the young cluster IC 348 at Van Vleck Observatory has been extended to a total of 7 yr. Twelve new periodic stars have been found in the last 2 yr, bringing the total discovered by this program to 40. In addition, we confirm 16 of the periods reported by others and resolve some discrepancies. The total number of known rotation periods in the cluster from all studies has now reached 70. This is sufficient to demonstrate that the parent population of K5-M2 stars is rotationally indistinguishable from that in the Orion Nebula Cluster, even though their radii are 20% smaller and they would be expected to spin about twice as fast if angular momentum were conserved. The median radius and therefore the inferred age of the IC 348 stars actually closely matches that of NGC 2264, but the stars spin significantly more slowly. This suggests that another factor besides mass and age plays a role in establishing the rotation properties within a cluster, and we suggest that it is environment. If disk locking were to persist for longer times in less harsh environments because the disks themselves persist for longer times, it could explain the generally slower rotation rates observed for stars in this cluster, whose earliest type star is of class B5. We have also obtained radial velocities, the first for pre-main-sequence stars in IC 348, and v sin i measurements for 30 cluster stars to assist in the study of rotation and as an independent check on stellar radii. Several unusual variable stars are discussed; in some or all cases their behavior may be linked to occultations by circumstellar material. A strong correlation exists between the range of photometric variability and the slope of the spectral energy distribution in the infrared. Nineteen of the 21 stars with I ranges exceeding 0.4 mag show infrared evidence for circumstellar disks.

The satellite systems of M31 and the Galaxy are compared. It is noted that all five of the suspected stripped dwarf spheroidal (dSph) cores of M31's companions are located within a projected distance of 40 kpc from the nucleus of this galaxy, whereas the normal dSph companions to this object have distances >40 kpc from the center of M31. All companions within 200 kpc < D_M31 < 600 kpc are late-type objects. In one respect the companions to the Galaxy appear to exhibit different systematics, with the irregular LMC and SMC being located at small galactocentric distance R_gc. It is speculated that this difference might be accounted for by assuming that the Magellanic Clouds are interlopers that were originally formed in the outer reaches of the Local Group. The radial distribution of the total sample of 40 companions of M31 and the Galaxy, which we show in a figure, hints at the possibility that these objects contain distinct populations of core (R < 25 kpc) and halo (R > 25 kpc) satellites.

The 2005 July 11 C313.2 stellar occultation by Charon was observed by three separate research groups, including our own, at observatories throughout South America. Here, the published timings from the three data sets have been combined to more accurately determine the mean radius of Charon: 606.0 ± 1.5 km. Our analysis indicates that a slight oblateness in the body (0.006 ± 0.003) best matches the data, with a confidence level of 86%. The oblateness has a pole position angle of 714 ± 104 and is consistent with Charon's pole position angle of 67°. Charon's mean radius corresponds to a bulk density of 1.63 ± 0.07 g cm^-3, which is significantly less than Pluto's (1.92 ± 0.12 g cm^-3). This density differential favors an impact formation scenario for the system in which at least one of the impactors was differentiated. Finally, unexplained differences between chord timings measured at Cerro Pachón and the rest of the data set could be indicative of a depression as deep as 7 km on Charon's limb.

This paper studies the nearby interacting group the Leo Triplet using multicolor photometry data obtained with the National Astronomical Observatories of China 60 cm/90 cm Schmidt telescope. The observation covers the entire area of the three galaxies (NGC 3623, NGC 3627, and NGC 3628), and spectral energy distributions (SEDs) of each galaxy are obtained. By comparing the observed SEDs of each part of the galaxies with the theoretical ones generated by instantaneous burst evolutionary synthesis models with different metallicities (Z = 0.0001, 0.008, 0.02, and 0.05), two-dimensional relative age distribution maps of the three galaxies were obtained. NGC 3623 exhibits a very weak age gradient from the bulge to the disk. This gradient is absent in NGC 3627. The ages of the dominant stellar populations of NGC 3627 and NGC 3628 are consistent, and this consistency is model independent (0.5-0.6 Gyr, Z = 0.02), but the ages of NGC 3623 are systematically older (0.7-0.9 Gyr, Z = 0.02). The results indicate that NGC 3627 and NGC 3628 have undergone synchronous evolution and that the interaction has likely triggered starbursts in both galaxies. For NGC 3623, however, the weak age gradient may indicate recent star formation in its bulge, which has caused its color to turn blue. Evidence is found for a potential bar existing in the bulge of NGC 3623, and my results support the view that NGC 3623 does interact with NGC 3627 and NGC 3628.

A detailed imaging analysis of the globular cluster (GC) system of the Sombrero galaxy (NGC 4594) has been accomplished using a six-image mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The quality of the data is such that contamination by foreground stars and background galaxies is negligible for all but the faintest 5% of the GC luminosity function. This enables the study of an effectively pure sample of 659 GCs until ∼2 mag fainter than the turnover magnitude, which occurs at M = -7.60 ± 0.06 for an assumed m - M = 29.77. Two GC metallicity subpopulations are easily distinguishable, with the metal-poor subpopulation exhibiting a smaller intrinsic dispersion in color compared to the metal-rich subpopulation. There are three new discoveries. (1) A metal-poor GC color-magnitude trend has been observed. (2) The fact that the metal-rich GCs are ∼17% smaller than the metal-poor ones for small projected galactocentric radii (less than ∼2') has been confirmed. However, the median half-light radii of the two subpopulations become identical at ∼3' from the center. This is most easily explained if the size difference is the result of projection effects. (3) The brightest (M_V < -9.0) members of the GC system show a size-magnitude upturn, where the average GC size increases with increasing luminosity. Evidence is presented that supports an intrinsic origin for this feature rather than being a result of accreted dwarf elliptical nuclei. In addition, the metal-rich GCs show a shallower positive size-magnitude trend, similar to what is found in previous studies of young star clusters.

We present 3.6, 4.5, 5.8, 8.0, 24, and 70 μm images of the Crab Nebula obtained with the Spitzer Space Telescope IRAC and MIPS cameras, low- and high-resolution Spitzer IRS spectra of selected positions within the nebula, and a near-infrared ground-based image made in the light of [Fe II] 1.644 μm. The 8.0 μm image, made with a bandpass that includes [Ar II] 7.0 μm, resembles the general morphology of visible Hα and near-IR [Fe II] line emission, while the 3.6 and 4.5 μm images are dominated by continuum synchrotron emission. The 24 and 70 μm images show enhanced emission that may be due to line emission or the presence of a small amount of warm dust in the nebula on the order of less than 1% of a solar mass. The ratio of the 3.6 and 4.5 μm images reveals a spatial variation in the synchrotron power-law index ranging from approximately 0.3 to 0.8 across the nebula. Combining this information with optical and X-ray synchrotron images, we derive a broadband spectrum that reflects the superposition of the flatter spectrum of the jet and torus with the steeper spectrum of the diffuse nebula. We also see suggestions of the expected pileup of relativistic electrons just before the exponential cutoff in the X-ray. The pulsar, and the associated equatorial toroid and polar jet structures seen in Chandra and Hubble Space Telescope images (Hester et al. 2002), can be identified in all of the IRAC images. We present the IR photometry of the pulsar. The forbidden lines identified in the high-resolution IR spectra are all double due to Doppler shifts from the front and back of the expanding nebula and give an expansion velocity of ≈1264 km s^-1.

Planet-crossing object 2005 UD is dynamically similar to purported Geminid meteor-stream parent 3200 Phaethon, suggesting an association between the two. We present new physical observations taken to characterize 2005 UD when at 1.6 AU from the Sun. Assuming equal albedos, 2005 UD is about 4 times smaller than 3200 Phaethon, with a diameter of ∼1.3 ± 0.1 km. The body shows periodic brightness variations of 0.4 mag that are compatible with an aspherical nucleus in rotation with a period near 5.2 hr. At optical wavelengths, 2005 UD is similar to or slightly bluer than the Sun. This property is relatively uncommon among near-Earth objects but is shared by Phaethon, strengthening the association between the two. No evidence for ongoing mass loss at rates as small as 0.01 kg s^-1 is found in the surface brightness profile, and we conclude that the fraction of the surface that is losing mass is not greater than 10^-4. Overall, we conclude that the dynamical similarities between 2005 UD and 3200 Phaethon are matched by physical similarities between these bodies, except that the former contains only about 2% of the mass of the latter. Phaethon, 2005 UD, and the Geminid meteoroids may be fragments produced by the breakup of a precursor object.

Using the FORS2 instrument on the Very Large Telescope, we have obtained near-infrared spectra for more than 200 stars in 28 populous LMC clusters. This cluster sample spans a large range of ages (∼1-13 Gyr) and metallicities (-0.3 ≳ [Fe/H] ≳ -2.0) and has good areal coverage of the LMC disk. The strong absorption lines of the Ca II triplet are used to derive cluster radial velocities and abundances. We determine mean cluster velocities to typically 1.6 km s^-1 and mean metallicities to 0.04 dex (random error). For eight of these clusters, we report the first spectroscopically determined metallicities based on individual cluster stars, and six of these eight have no published radial velocity measurements. Combining our data with archival Hubble Space Telescope WFPC2 photometry, we find that the newly measured cluster, NGC 1718, is one of the most metal-poor ([Fe/H] ∼ -0.80) intermediate-age (∼2 Gyr) inner disk clusters in the LMC. Similar to what was found by previous authors, this cluster sample has radial velocities consistent with that of a single rotating disk system, with no indication that the newly reported clusters exhibit halo kinematics. In addition, our findings confirm previous results that show that the LMC lacks the metallicity gradient typically seen in nonbarred spiral galaxies, suggesting that the bar is driving the mixing of stellar populations in the LMC. However, in contrast to previous work, we find that the higher metallicity clusters (≳-1.0 dex) in our sample show a very tight distribution (mean [Fe/H] = -0.48, σ = 0.09), with no tail toward solar metallicities. The cluster distribution is similar to what has been found for red giant stars in the bar, which indicates that the bar and the intermediate-age clusters have similar star formation histories. This is in good agreement with recent theoretical models that suggest the bar and intermediate-age clusters formed as a result of a close encounter with the SMC ∼4 Gyr ago.

We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, and surface gravity) of up to one million stars using the Six Degree Field multiobject spectrograph on the 1.2 m UK Schmidt Telescope of the Anglo-Australian Observatory. The RAVE program started in 2003, obtaining medium-resolution spectra (median R = 7500) in the Ca-triplet region (8410-8795 Å) for southern hemisphere stars drawn from the Tycho-2 and SuperCOSMOS catalogs, in the magnitude range 9 < I < 12. The first data release is described in this paper and contains radial velocities for 24,748 individual stars (25,274 measurements when including reobservations). Those data were obtained on 67 nights between 2003 April 11 and 2004 April 3. The total sky coverage within this data release is ∼4760 deg². The average signal-to-noise ratio of the observed spectra is 29.5, and 80% of the radial velocities have uncertainties better than 3.4 km s^-1. Combining internal errors and zero-point errors, the mode is found to be 2 km s^-1. Repeat observations are used to assess the stability of our radial velocity solution, resulting in a variance of 2.8 km s^-1. We demonstrate that the radial velocities derived for the first data set do not show any systematic trend with color or signal-to-noise ratio. The RAVE radial velocities are complemented in the data release with proper motions from Starnet 2.0, Tycho-2, and SuperCOSMOS, in addition to photometric data from the major optical and infrared catalogs (Tycho-2, USNO-B, DENIS, and the Two Micron All Sky Survey). The data release can be accessed via the RAVE Web site.

In this paper we study the evolution of the core and corona of nine open clusters using the projected radial density profiles derived from homogeneous CCD photometric data obtained with the 105 cm Kiso Schmidt telescope. The age and galactocentric distance of the target clusters vary from 16 to 2000 Myr and 9 to 10.8 kpc, respectively. Barring Be 62, which is a young open cluster, other clusters show a uniform reddening across the cluster region. The reddening in Be 62 varies from E(B - V)_min = 0.70 mag to E(B - V)_max = 1.00 mag. The coronae of six of the clusters in the present sample are found to be elongated; however, on the basis of the present sample it is not possible to establish any correlation between the age and shape of the core. The elongated core in the case of the young cluster Be 62 may reflect the initial conditions in the parental molecular cloud. The other results of the present study are as follows: (1) Core radius r_c and corona size r_cn/cluster radius r_cl are linearly correlated. (2) The r_c, r_cn, and r_cl are linearly correlated with the number of stars in that region. (3) In the age range 10-1000 Myr, the core and corona shrink with age. (4) We find that in the galactocentric distance range 9-10 kpc, the core and corona/cluster extent of the clusters increase with the galactocentric distance.

We present new candidates for protostars and embedded clusters detected in our deep near-infrared (J, H, K_S) imaging survey of cloud C of the Vela Molecular Ridge (Vela C). We selected protostar candidates on the basis of positional coincidences with Midcourse Space Experiment (MSX) and/or IRAS sources and the slopes of their spectral energy distributions from 2 to 25 μm. For embedded clusters, we selected them on the basis of positional coincidence with MSX and/or IRAS sources and enhancement of stellar number densities. We identified 31 sources as protostar candidates and 5 clusters as embedded clusters; 28 protostar candidates and 3 embedded clusters were newly identified. Most of them are associated with the C¹⁸O clumps distributed throughout Vela C. We calculated the bolometric luminosities of the protostar candidates by integrating the observed fluxes from near- to far-infrared, and then estimated the mass range to be from 0.9 to 4.0 M_⊙, assuming their ages at the birth line. There is a correlation between the number of members and the K_S magnitude of the brightest star in the embedded clusters.

We compare the rise times of nearby and distant Type Ia supernovae (SNe Ia) as a test for evolution using 73 high-redshift spectroscopically confirmed SNe Ia from the first 2 years of the 5 year Supernova Legacy Survey (SNLS) and published observations of nearby SNe. Because of the "rolling" search nature of the SNLS, our measurement is approximately 6 times more precise than previous studies, allowing for a more sensitive test of evolution between nearby and distant SNe. Adopting a simple t² early-time model (as in previous studies), we find that the rest-frame B rise times for a fiducial SN Ia at high and low redshift are consistent, with values 19.10 ± 0.2 and 19.58 days, respectively; the statistical significance of this difference is only 1.4 σ. The errors represent the uncertainty in the mean rather than any variation between individual SNe. We also compare subsets of our high-redshift data set based on decline rate, host galaxy star formation rate, and redshift, finding no substantive evidence for any subsample dependence.

We have conducted a photometric and high-resolution spectroscopic analysis of the high-latitude (l = 1°, b = -55°) metal-poor RR Lyrae star TY Gru (=CS 22881-071). We find this star to have large overabundances of carbon and neutron-capture elements. Mass transfer from an asymptotic giant branch binary companion prior to its RR Lyrae evolutionary state is the simplest explanation of this circumstance. Unfortunately, TY Gru is afflicted by the Blazhko effect, which greatly complicates accurate measurement of the motion of its center of mass. We have not yet detected the small orbital motion that would be produced by a distant degenerate companion of TY Gru.