arXiv subjects

R. M. Cutri

Publications and source records attributed to R. M. Cutri.

At least 37 records · Page 2Linked to original sources

arXiv2012

Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-Cryogenic Observations of Main Belt Asteroids

We present preliminary diameters and albedos for 13511 MBAs that were observed during the 3-Band Cryo phase of the WISE survey (after the outer cryogen tank was exhausted) and as part of the NEOWISE Post-Cryo Survey (after the inner cryogen tank was exhausted). With a reduced or complete loss of sensitivity in the two long wavelength channels of WISE, the uncertainty in our fitted diameters and albedos is increased to ~20% for diameter and ~40% for albedo. Diameter fits using only the 3.4 and 4.6 um channels are shown to be dependent on the literature optical H absolute magnitudes. These data allow us to increase the number of size estimates for large MBAs which have been identified as members of dynamical families. We present thermal fits for 14 asteroids previously identified as the parents of a dynamical family that were not observed during the fully cryogenic mission.

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arXiv2012

Characterizing Subpopulations within the Near Earth Objects with NEOWISE: Preliminary Results

We present the preliminary results of an analysis of the sub-populations within the near-Earth asteroids, including the Atens, Apollos, Amors, and those that are considered potentially hazardous using data from the Wide-field Infrared Survey Explorer (WISE). In order to extrapolate the sample of objects detected by WISE to the greater population, we determined the survey biases for asteroids detected by the project's automated moving object processing system (known as NEOWISE) as a function of diameter, visible albedo, and orbital elements. Using this technique, we are able to place constraints on the number of potentially hazardous asteroids (PHAs) larger than 100 m and find that there are $\sim4700\pm1450$ such objects. As expected, the Atens, Apollos, and Amors are revealed by WISE to have somewhat different albedo distributions, with the Atens being brighter than the Amors. The cumulative size distributions of the various near-Earth object (NEO) subgroups vary slightly between 100 m and 1 km. A comparison of the observed orbital elements of the various sub-populations of the NEOs with the current best model is shown.

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arXiv2012

Variability Flagging in the WISE Preliminary Data Release

The Wide-field Infrared Survey Explorer Preliminary Data Release Source Catalog contains over 257 million objects. We describe the method used to flag variable source candidates in the Catalog. Using a method based on the chi- square of single-exposure flux measurements, we generated a variability flag for each object, and have identified almost 460,000 candidates sources that exhibit significant flux variability with greater than \sim 7σ confidence. We discuss the flagging method in detail and describe its benefits and limitations. We also present results from the flagging method, including example light curves of several types of variable sources including Algol-type eclipsing binaries, RR Lyr, W UMa, and a blazar candidate.

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arXiv2011

NEOWISE Studies of Asteroids with Sloan Photometry: Preliminary Results

We have combined the NEOWISE and Sloan Digital Sky Survey data to study the albedos of 24,353 asteroids with candidate taxonomic classifications derived using Sloan photometry. We find a wide range of moderate to high albedos for candidate S-type asteroids that are analogous to the S-complex defined by previous spectrophotometrically-based taxonomic systems. The candidate C-type asteroids, while generally very dark, have a tail of higher albedos that overlaps the S types. The albedo distribution for asteroids with a photometrically derived Q classification is extremely similar to those of the S types. Asteroids with similar colors to (4) Vesta have higher albedos than the S types, and most have orbital elements similar to known Vesta family members. Finally, we show that the relative reflectance at 3.4 and 4.6 $μ$m is higher for D-type asteroids and suggest that their red visible and near-infrared spectral slope extends out to these wavelengths. Understanding the relationship between size, albedo, and taxonomic classification is complicated by the fact that the objects with classifications were selected from the visible/near-infrared Sloan Moving Object Catalog, which is biased against fainter asteroids, including those with lower albedos.

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arXiv2011

NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results

The NEOWISE dataset offers the opportunity to study the variations in albedo for asteroid classification schemes based on visible and near-infrared observations for a large sample of minor planets. We have determined the albedos for nearly 1900 asteroids classified by the Tholen, Bus and Bus-DeMeo taxonomic classification schemes. We find that the S-complex spans a broad range of bright albedos, partially overlapping the low albedo C-complex at small sizes. As expected, the X-complex covers a wide range of albedos. The multi-wavelength infrared coverage provided by NEOWISE allows determination of the reflectivity at 3.4 and 4.6 $μ$m relative to the visible albedo. The direct computation of the reflectivity at 3.4 and 4.6 $μ$m enables a new means of comparing the various taxonomic classes. Although C, B, D and T asteroids all have similarly low visible albedos, the D and T types can be distinguished from the C and B types by examining their relative reflectance at 3.4 and 4.6 $μ$m. All of the albedo distributions are strongly affected by selection biases against small, low albedo objects, as all objects selected for taxonomic classification were chosen according to their visible light brightness. Due to these strong selection biases, we are unable to determine whether or not there are correlations between size, albedo and space weathering. We argue that the current set of classified asteroids makes any such correlations difficult to verify. A sample of taxonomically classified asteroids drawn without significant albedo bias is needed in order to perform such an analysis.

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arXiv2011

NEOWISE Observations of Near-Earth Objects: Preliminary Results

With the NEOWISE portion of the \emph{Wide-field Infrared Survey Explorer} (WISE) project, we have carried out a highly uniform survey of the near-Earth object (NEO) population at thermal infrared wavelengths ranging from 3 to 22 $μ$m, allowing us to refine estimates of their numbers, sizes, and albedos. The NEOWISE survey detected NEOs the same way whether they were previously known or not, subject to the availability of ground-based follow-up observations, resulting in the discovery of more than 130 new NEOs. The survey's uniformity in sensitivity, observing cadence, and image quality have permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by NEOWISE during the fully cryogenic portion of the WISE mission to the larger population. We find that there are 981$\pm$19 NEAs larger than 1 km and 20,500$\pm$3000 NEAs larger than 100 m. We show that the Spaceguard goal of detecting 90% of all 1 km NEAs has been met, and that the cumulative size distribution is best represented by a broken power law with a slope of 1.32$\pm$0.14 below 1.5 km. This power law slope produces $\sim13,200\pm$1,900 NEAs with $D>$140 m. Although previous studies predict another break in the cumulative size distribution below $D\sim$50-100 m, resulting in an increase in the number of NEOs in this size range and smaller, we did not detect enough objects to comment on this increase. The overall number for the NEA population between 100-1000 m are lower than previous estimates. The numbers of near-Earth comets will be the subject of future work.

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arXiv2011

Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters

We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited to measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of Solar system objects. Using a NEATM thermal model fitting routine we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE dataset and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.

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arXiv2011

Thermal Model Calibration for Minor Planets Observed with WISE/NEOWISE: Comparison with IRAS

With thermal infrared observations detected by the NEOWISE project, we have measured diameters for 1742 minor planets that were also observed by the Infrared Astronomical Satellite (IRAS). We have compared the diameters and albedo derived by applying a spherical thermal model to the objects detected by NEOWISE and find that they are in generally good agreement with the IRAS values. We have shown that diameters computed from NEOWISE data are often less systematically biased than those found with IRAS. This demonstrates that the NEOWISE dataset can provide accurate physical parameters for the >157,000 minor planets that were detected by NEOWISE.

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arXiv2011

Thermal Model Calibration for Minor Planets Observed with WISE/NEOWISE

With the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010), we have observed over 157,000 minor planets (Mainzer et al. 2011). Included in these are a number of near-Earth objects, Main Belt Asteroids, and irregular satellites which have well-measured physical properties via radar, occultation and in situ imaging. We have used these objects to validate models of thermal models using the WISE measurements, as well as the color corrections derived in Wright et al. (2010) for the four WISE bandpasses as a function of effective temperature. We have used 50 objects with diameters measured by radar, occultation or in situ imaging to characterize the systematic errors implicit in using the WISE data with a faceted spherical NEATM model to compute diameters and albedos. By using the previously measured diameters and H magnitudes with a spherical NEATM model, we compute the predicted fluxes after applying the color corrections given in Wright et al. (2010) in the WISE bands and compare them to the measured magnitudes. We find minimum systematic flux errors of 5-10%, yielding minimum relative diameter and albedo errors of ~10% and ~20%, respectively. Visible albedos for the objects are computed and compared to the albedos at 3.4 and 4.6 microns, which contain a mix of reflected sunlight and thermal emission for most asteroids. We derive a linear relationship between subsolar temperature and effective temperature, which allows the color corrections given in Wright et al. (2010) to be used for asteroids by computing only subsolar temperature instead of a faceted thermal model. The thermal models derived in this paper are not intended to supplant previous measurements made using radar or spacecraft imaging; rather, we have used them to characterize the errors that should be expected when computing diameters and albedos of WISE asteroids using a spherical NEATM model.

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arXiv2011

An extremely luminous panchromatic outburst from the nucleus of a distant galaxy

Variable X-ray and gamma-ray emission is characteristic of the most extreme physical processes in the Universe, and studying the sources of these energetic photons has been a major driver in astronomy for the past 50 years. Here we present multiwavelength observations of a unique gamma-ray selected transient, discovered by Swift, which was accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z=0.3534. Its high-energy emission has lasted much longer than any gamma-ray burst, while its peak luminosity was about 100 times higher than the brightest active galactic nuclei. The association of the outburst with the center of its host galaxy suggests that this phenomenon has its origin in a new, rare mechanism associated with a massive black hole in the nucleus of a galaxy.

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arXiv2011

Preliminary Results from NEOWISE: An Enhancement to the Wide-field Infrared Survey Explorer for Solar System Science

The \emph{Wide-field Infrared Survey Explorer} has surveyed the entire sky at four infrared wavelengths with greatly improved sensitivity and spatial resolution compared to its predecessors, the \emph{Infrared Astronomical Satellite} and the \emph{Cosmic Background Explorer}. NASA's Planetary Science Division has funded an enhancement to the \WISE\ data processing system called "NEOWISE" that allows detection and archiving of moving objects found in the \WISE\ data. NEOWISE has mined the \WISE\ images for a wide array of small bodies in our Solar System, including Near-Earth Objects (NEOs), Main Belt asteroids, comets, Trojans, and Centaurs. By the end of survey operations in February 2011, NEOWISE identified over 157,000 asteroids, including more than 500 NEOs and $\sim$120 comets. The NEOWISE dataset will enable a panoply of new scientific investigations.

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arXiv2008

Absolute Physical Calibration in the Infrared

We determine an absolute calibration for the MIPS 24 microns band and recommend adjustments to the published calibrations for 2MASS, IRAC, and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of ~ 1.5% (rms) are placed on the intrinsic infrared SED variations in both A dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the infrared. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the sun to allow extending this work to any other infrared photometric system. They allow the recommended calibration to be applied from 1 to 25 microns with an accuracy of ~2 %, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 microns, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the infrared, making it problematic as the defining star for photometric systems. The integration of measurements of the sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 microns, which we show agrees with theoretical models.

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arXiv2008

2MASS J01542930+0053266 : A New Eclipsing M-dwarf Binary System

We report on 2MASS J01542930+0053266, a faint eclipsing system composed of two M dwarfs. The variability of this system was originally discovered during a pilot study of the 2MASS Calibration Point Source Working Database. Additional photometry from the Sloan Digital Sky Survey yields an 8-passband lightcurve, from which we derive an orbital period of 2.6390157 +/- 0.0000016 days. Spectroscopic followup confirms our photometric classification of the system, which is likely composed of M0 and M1 dwarfs. Radial velocity measurements allow us to derive the masses (M_1 = 0.66 +/- 0.03 M_sun; M_2 = 0.62 +/- 0.03 M_sun) and radii (R_1 = 0.64 +/- 0.08 R_sun; R_2 = 0.61 +/- 0.09 R_sun) of the components, which are consistent with empirical mass-radius relationships for low-mass stars in binary systems. We perform Monte Carlo simulations of the lightcurves which allow us to uncover complicated degeneracies between the system parameters. Both stars show evidence of H-alpha emission, something not common in early-type M dwarfs. This suggests that binarity may influence the magnetic activity properties of low-mass stars; activity in the binary may persist long after the dynamos in their isolated counterparts have decayed, yielding a new potential foreground of flaring activity for next generation variability surveys.

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arXiv2006

The Dipole Anisotropy of the 2mass Redshift Survey

We estimate the flux weighted acceleration on the Local Group (LG) from the near-infrared Two Micron All Sky Redshift Survey (2MRS). The near-infrared flux weighted dipoles are very robust because they closely approximate a mass weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. We use this method with the redshift information to determine the change in dipole with distance. The LG dipole seemingly converges by 60 Mpc/h. Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters Omega_m^0.6/b_L= 0.40+/-0.09.

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arXiv2006

The Dipole Anisotropy of the 2 Micron All-Sky Redshift Survey

We estimate the acceleration on the Local Group (LG) from the Two Micron All Sky Redshift Survey (2MRS). The sample used includes about 23,200 galaxies with extinction corrected magnitudes brighter than K_s=11.25 and it allows us to calculate the flux weighted dipole. The near-infrared flux weighted dipoles are very robust because they closely approximate a mass weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the CMB dipole drops to 12 degrees at around 50 Mpc/h, but then increases at larger distances, reaching 21 degrees at around 130 Mpc/h. Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to 14 degrees away from the CMB velocity dipole In both cases, the dipole seemingly converges by 60 Mpc/h. Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters Omega_m^0.6/b_L=0.40+/-0.09.

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arXiv2005

XMM-NEWTON Observations of Red AGN

XMM-Newton spectra of five red, 2MASS AGN, selected from a sample observed by Chandra to be relatively X-ray bright and to cover a range of hardness ratios, confirm the presence of substantial absorbing material in three sources with optical classifications ranging from Type 1 to Type 2. A flat (hard), power law continuum is observed in the other two. The combination of X-ray absorption and broad optical emission lines suggests either a small (nuclear) absorber or a favored viewing angle so as to cover the X-ray source but not the broad emission line region (BELR). A soft excess is detected in all three Type 1 sources. We speculate that this may arise in an extended region of ionised gas, perhaps linked with the polarised (scattered) optical light present in these sources. The spectral complexity revealed by XMM-Newton emphasizes the limitations of the low S/N \chandra data. The new results strengthen our earlier conclusions that the observed X-ray continua of red AGN are unusually hard at energies >2 keV. Their observed spectra are consistent with contributing significantly to the missing hard/absorbed population of the Cosmic X-ray Background (CXRB) although their intrinsic power law slopes are typical of broad-line (Type 1) AGN (Gamma ~1.7-1.9). This suggests that the missing X-ray-absorbed CXRB population may include Type 1 AGN/QSOs in addition to the Type 2 AGN generally assumed.

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arXiv2003

Host galaxies of 2MASS-selected QSOs to redshift 0.3

We present and discuss optical imaging of 76 AGN which represent the 2MASS-selected sample for z<0.3, from a full list of 243. They are found to have dust-obscured nuclei, residing in host galaxies that show a high fraction (>70%) of tidal interactions. The derived luminosities of the AGN and host galaxies are similar to traditionally-selected AGN, and they may comprise some 40% of the total AGN population at low redshift. We have measured a number of host galaxy properties, and discuss their distributions and interrelations. We compare the 2MASS AGN with optically selected samples and the IRAS-selected galaxy samples, and discuss the differences in terms of merger processes and initial conditions.

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arXiv2002

XMM-Newton observations of two hyperluminous IRAS galaxies: Compton-thick quasars with obscuring starbursts

We present XMM-Newton observations of two hyperluminous IRAS galaxies (L_Bol>1E13 L_sun), neither of which was previously detected by ROSAT. Published models of the infrared SEDs imply that a starburst and obscured quasar contribute equally to the power of each source. IRAS F12514+1027 (z=0.30) is detected in 18.6 ks with 130 EPIC-pn counts over 0.2-12 keV. The soft X-ray spectrum exhibits thermal emission from the starburst, with T=0.3 keV and L(0.5-2.0keV)=2.1E42 erg/s. With its Fe K-edge, the flat continuum above 2 keV is interpreted as cold reflection from a hidden AGN with an intrinsic L(2-10keV) of at least 1.8E44 erg/s. Comparison with the infrared power requires that the X-ray reflector subtend ~2pi/5 sr at the central engine. IRAS F00235+1024 (z=0.575) is not detected by the EPIC-pn in 15.9 ks; the limits imply that the starburst is X-ray weak, and (for the AGN) that any hard X-ray reflector subtend <2pi/5 sr. The direct lines of sight to the AGN in both objects are Compton-thick, and the presence of a reflection component in F12514+1027, but not in F00235+1024, suggests that the AGN in the latter object is more completely obscured. This is consistent with their Seyfert-2 and starburst optical spectra, respectively.

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