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91. A debris disk study of Praesepe
ID:
ivo://CDS.VizieR/J/ApJ/697/1578
Title:
A debris disk study of Praesepe
Short Name:
J/ApJ/697/1578
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 24um photometry of the intermediate-age open cluster Praesepe. We assemble a catalog of 193 probable cluster members that are detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24um, within an area of ~2.47deg^2^. Mid-IR excesses indicating debris disks are found for one early-type and for three solar-type stars. Corrections for sampling statistics yield a 24um excess fraction (debris disk fraction) of 6.5%+/-4.1% for luminous and 1.9%+/-1.2% for solar-type stars. The incidence of excesses is in agreement with the decay trend of debris disks as a function of age observed for other cluster and field stars.
92. A deep catalogue of classical Be stars
ID:
ivo://CDS.VizieR/J/MNRAS/446/274
Title:
A deep catalogue of classical Be stars
Short Name:
J/MNRAS/446/274
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of 247 photometrically and spectroscopically confirmed fainter classical Be stars (13<r<16) in the direction of the Perseus Arm of the Milky Way (1{deg}<b<+4{deg}, 120{deg}<l<140{deg}). The catalogue consists of 181 IPHAS-selected new classical Be stars, in addition to 66 objects that we studied in our previous work more closely, and three stars identified as classical Be stars in earlier work. This study more than doubles the number known in the region. Photometry spanning 0.6-5um, spectral types, and interstellar reddenings are given for each object. The spectral types were determined from low-resolution spectra ({lambda}/{Delta}_{lambda}~800-2000), to a precision of 1-3 subtypes. The interstellar reddenings are derived from the (r-i) colour, using a method that corrects for circumstellar disc emission. The colour excesses obtained range from E(B-V)=0.3 up to 1.6 a distribution that modestly extends the range reported in the literature for Perseus-Arm open clusters. For around half the sample, the reddenings obtained are compatible with measures of the total sightline Galactic extinction. Many of these are likely to lie well beyond the Perseus Arm.
93. A deep multicolor survey. I.
ID:
ivo://CDS.VizieR/J/ApJS/104/185
Title:
A deep multicolor survey. I.
Short Name:
J/ApJS/104/185
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Kitt Peak National Observatory 4m Mayall telescope to image 0.83 square degrees of sky in six fields at high Galactic latitude in six filters spanning 3000-10000A to magnitude limits ranging from 22.1 to 23.8. We have assembled a catalog of 21375 stellar objects detected in the fields for use primilary in conducting a multicolor search for quasars. This paper describes the data reduction techniques used on the CCD data, the methods used to construct the stellar object catalog, and the simulations performed to understand its completeness and contamination.
94. A deep multicolor survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/462/614
Title:
A deep multicolor survey. II.
Short Name:
J/ApJ/462/614
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Kitt Peak National Observatory 4m Mayall telescope to image 0.83 square degrees of sky in six fields at high galactic latitude in six filters spanning 3000-10000A to magnitude limits ranging from 22.1 to 23.8. As a first use of this database, we have conducted a multicolor survey for quasars. We discuss various methods of selecting outliers in different color-color diagrams and multicolor space that have been used to identify quasars at all redshifts from their colors alone. We discuss the initial results of our program of spectroscopic identification which has so far resulted in the identification of over 40 faint quasars, including one a z>4, a similar number of compact narrow emission-line galaxies, and a number of unusual and potentially interesting stars. We use these spectroscopic results, along with extensive simulations of quasar spectra, to study the efficiency of our candidate selection procedures. Finally, we compare the number counts of our quasars and quasar candidates to the expected numbers based on previous studies of the quasar luminosity function. The agreement of our observations with these expectations is good in most cases. However, we do estimate that our survey contains more quasars with B<21 and z<2.3 than expected from the results published by Koo & Kron in (1988ApJ...325...92K) and more z>3 quasars than expected from the results published by Warren, Hewett & Osmer in (1994ApJ...421..412W), both at the 3 {sigma} level. Additional spectroscopic observations will be required to confirm or refute these excesses.
95. A deep multicolor survey. III.
ID:
ivo://CDS.VizieR/J/AJ/114/2269
Title:
A deep multicolor survey. III.
Short Name:
J/AJ/114/2269
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have made spectroscopic identifications of 39 additional quasar candidates from the Deep Multicolor Survey (DMS) of Hall et al. (1996, Cat. <J/ApJ/462/614>). We have identified 9 new quasars with 0.3<z<2.8 and 16.8<B<21.6, all from the group of candidates with ultraviolet excess (UVX). No new quasars with z>3 were found among the observed candidates selected due to their red (B-R) and (V-R) colors. As a result, there are now 55 confirmed quasars in the survey: 42 with 0.3<z<2, nine with 2<z<3, three with 3<z<4, and 1 at z=4.3. One new quasar, DMS 0059-0055, is very bright with B=16.8 and z=0.3, making its detection by our survey very unexpected. Including this new spectroscopy, the results of the DMS are converging with the predicted space densities of other surveys. In particular, we no longer find an excess of quasars with z<2.3 and B<21 in the survey over predictions based on models by Koo & Kron (1988ApJ...325...92K). Also, the excess in the number of quasars seen at z>3 over predictions based on models by Warren et al. (1994ApJ...421..412W) is less than previously suggested. We also demonstrate the success of our quasar color modeling which is important in assessing the completeness of our survey.
96. A deep radio survey of Abell 2125. II
ID:
ivo://CDS.VizieR/J/AJ/129/31
Title:
A deep radio survey of Abell 2125. II
Short Name:
J/AJ/129/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using our extensive radio, optical, near-IR, and X-ray imaging and spectroscopy, we consider the reason for the unusually large number of radio-detected galaxies, mostly found outside the cluster core, in Abell 2125 (z=0.2465, richness class 4). With 20cm VLA data, we detect continuum emission from 90 cluster members. The multiwavelength properties of these galaxies suggest that most of the radio emission is due to an enhanced star formation rate. The recent dynamical study of Miller et al. (2004, Cat. <J/ApJ/613/841>) suggests that A2125 is undergoing a major cluster-cluster merger, with our view within 30{deg} of the merger axis and within 0.2Gyr of core passage. The combination of projection effects and the physical processes at work during this special time in the cluster's evolution seem likely to be responsible for the unusual level of activity we see in the cluster. We argue that tidal effects on individual cluster members, often far from the cluster core, are responsible for the increased star formation. Our results are consistent with the idea that disk galaxies during this phase of a cluster's evolution undergo rapid evolution through a burst of star formation on their way to becoming S0 galaxies.
97. A deep survey of galaxies
ID:
ivo://CDS.VizieR/J/AJ/88/1285
Title:
A deep survey of galaxies
Short Name:
J/AJ/88/1285
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of galaxies in six fields, each of area 2 sq deg, located in the North and South galactic polar caps. Photoelectrically calibrated photographic magnitudes and J-F colors have been determined for 512 galaxies brighter than completeness limits which range from F=16.5 to F=17.2 among the fields. Velocities, with typical accuracies of 150km/s have been obtained for 280 of the brighter galaxies. Using these data and previously published work, we determine the general galaxy luminosity function parameters to be M*_F_=-22.7, {alpha}=-1.25, and the mean visual luminosity density of the universe to be {rho}=2.3x10^8^hL_{sun}_/Mpc^3^. Assuming M/L_v_=300h, this implies {OMEGA}~0.26.
98. Adiabatic Mass Loss in Binary Stars. III.
ID:
ivo://CDS.VizieR/J/ApJ/899/132
Title:
Adiabatic Mass Loss in Binary Stars. III.
Short Name:
J/ApJ/899/132
Date:
14 Mar 2022 07:06:32
Publisher:
CDS
Description:
The distinguishing feature of the evolution of close binary stars is the role played by the mass exchange between the component stars. Whether or not the mass transfer is dynamically stable is one of the essential questions in binary evolution. In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We use the adiabatic mass-loss model to systematically survey the thresholds for dynamical timescale mass transfer over the entire span of possible donor star evolutionary states. We also simulate mass-loss process with isentropic envelopes, the specific entropy of which is fixed to be that at the base of the convective envelope, to artificially mimic the effect of such mass loss in superadiabatic surface convection regions, where the adiabatic approximation fails. We illustrate the general adiabatic response of 3.2M{odot} donor stars at different evolutionary stages. We extend our study to a grid of donor stars with different masses (from 0.1 to 100 M{sun} with Z=0.02) and at different evolutionary stages. We proceed to present our criteria for dynamically unstable mass transfer in both tabular and graphical forms. For red giant branch (RGB) and asymptotic giant branch (AGB) donors in systems with such mass ratios, they may have convective envelopes deep enough to evolve into common envelopes on a thermal timescale, if the donor star overfills its outer Lagrangian radius. Our results show that the RGB and AGB stars tend to be more stable than previously believed, and this may be helpful to explain the abundance of observed post-AGB binary stars with an orbital period of around 1000 days.
99. Ae/Be stars of Magellanic Bridge in JHKs
ID:
ivo://CDS.VizieR/J/ApJ/658/358
Title:
Ae/Be stars of Magellanic Bridge in JHKs
Short Name:
J/ApJ/658/358
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near-infrared camera SIRIUS and the 1.4m telescope IRSF, we surveyed ~3.0{deg}x1.3{deg} (24{deg}<~RA<~36{deg}, -75.0{deg}<~DE<~-73.7{deg}) in the J, H, and Ks bands. On the basis of colors and magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering the contaminations by miscellaneous sources, such as foreground stars and early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (#40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.
100. AEGIS-X: Chandra deep survey
ID:
ivo://CDS.VizieR/J/ApJS/180/102
Title:
AEGIS-X: Chandra deep survey
Short Name:
J/ApJS/180/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the EGIS-X survey, a series of deep Chandra ACIS-I observations of the Extended Groth Strip. The survey comprises pointings at eight separate positions, each with nominal exposure of 200ks, covering a total area of approximately 0.67deg^2^ in a strip of length 2 degrees. We describe in detail an updated version of our data reduction and point-source-detection algorithms used to analyze these data. A total of 1325 band-merged sources have been found to a Poisson probability limit of 4x10^-6^, with limiting fluxes of 5.3x10^-21^W/m2 in the soft (0.5-2keV) band and 3.8x10^-19^W/m2 in the hard (2-10keV) band. We present simulations verifying the validity of our source-detection procedure and showing a very small, <1.5%, contamination rate from spurious sources. Optical/NIR counterparts have been identified from the DEEP2, CFHTLS, and Spitzer/Infrared Array Camera (IRAC) surveys of the same region. Using a likelihood ratio method, we find optical counterparts for 76% of our sources, complete to R_AB_=24.1, and, of the 66% of the sources that have IRAC coverage, 94% have a counterpart to a limit of 0.9uJy at 3.6um (m_AB_=23.8). After accounting for (small) positional offsets in the eight Chandra fields, the astrometric accuracy of Chandra positions is found to be 0"8rms; however, this number depends both on the off-axis angle and the number of detected counts for a given source. All data products described in this paper are made available via a public Web site.