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4811. Opt. & UV evolution of the TDE iPTF15af
ID:
ivo://CDS.VizieR/J/ApJ/873/92
Title:
Opt. & UV evolution of the TDE iPTF15af
Short Name:
J/ApJ/873/92
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present multiwavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by the intermediate Palomar Transient Factory survey at redshift z=0.07897. The optical and ultraviolet (UV) light curves of the transient show a slow decay over 5 months, in agreement with previous optically discovered TDEs. It also has a comparable blackbody peak luminosity of L_peak_~1.5x10^44^erg/s. The inferred temperature from the optical and UV data shows a value of (3-5)x10^4^K. The transient is not detected in X-rays up to L_X_<3x10^42^erg/s within the first 5 months after discovery. The optical spectra exhibit two distinct broad emission lines in the HeII region, and at later times also H{alpha} emission. Additionally, emission from [NIII] and [OIII] is detected, likely produced by the Bowen fluorescence effect. UV spectra reveal broad emission and absorption lines associated with high-ionization states of NV, CIV, SiIV, and possibly PV. These features, analogous to those of broad absorption line quasars (BAL QSOs), require an absorber with column densities N_H_>10^23^cm^-2^. This optically thick gas would also explain the nondetection in soft X-rays. The profile of the absorption lines with the highest column density material at the largest velocity is opposite that of BAL QSOs. We suggest that radiation pressure generated by the TDE flare at early times could have provided the initial acceleration mechanism for this gas. Spectral UV line monitoring of future TDEs could test this proposal.
4812. OQ Dra V light curve
ID:
ivo://CDS.VizieR/J/other/NewA/49.28
Title:
OQ Dra V light curve
Short Name:
J/other/NewA/49.
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present study is an analysis of V-band CCD observations of new W UMa contact binary OQ Dra. To carry out the analysis, Primary and secondary minimum were obtained and new epoch was calculated. The computed period of system was 0.33967 day. Light curve analysis was performed using Binary Maker 3 and PHOEBE that uses the latest Wilson-Devinney code. We obtained photometric mass ratio of q_ptm_=0.55. O'Connell effect also was seen in the fitted model. Finally, the best model was achieved by introducing 2 spots on each component.
4813. Orbital eccentricities of 31535 G-dwarfs
ID:
ivo://CDS.VizieR/J/ApJ/725/L186
Title:
Orbital eccentricities of 31535 G-dwarfs
Short Name:
J/ApJ/725/L186
Date:
21 Oct 2021
Publisher:
CDS
Description:
We test four competing models that aim to explain the nature of stars in spiral galaxies that are well away (>1kpc) from the midplane, the so-called thick disk: the stars may have gotten there through orbital migration, through satellite mergers and accretion, or through heating of pre-existing thin disk stars. The eccentricity distribution of thick disk stars has recently been proposed as a diagnostic to differentiate between these mechanisms. Drawing on SDSS-DR7, we have assembled a sample of 31535 G-dwarfs with six-dimensional phase-space information and metallicities and have derived the orbital eccentricities for them.
4814. Orbital elements of TNOs from the Dark Energy Survey
ID:
ivo://CDS.VizieR/J/AJ/159/133
Title:
Orbital elements of TNOs from the Dark Energy Survey
Short Name:
J/AJ/159/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
The outer solar system contains a large number of small bodies (known as trans-Neptunian objects or TNOs) that exhibit diverse types of dynamical behavior. The classification of bodies in this distant region into dynamical classes-subpopulations that experience similar orbital evolution-aids in our understanding of the structure and formation of the solar system. In this work, we propose an updated dynamical classification scheme for the outer solar system. This approach includes the construction of a new (automated) method for identifying mean motion resonances. We apply this algorithm to the current data set of TNOs observed by the Dark Energy Survey (DES) and present a working classification for all of the DES TNOs detected to date. Our classification scheme yields 1 inner centaur, 19 outer centaurs, 21 scattering disk objects, 47 detached TNOs, 48 securely resonant objects, 7 resonant candidates, and 97 classical belt objects. Among the scattering and detached objects, we detect 8 TNOs with semimajor axes greater than 150au.
4815. ORICAT Catalog of Stars in Orion Great Nebula
ID:
ivo://CDS.VizieR/J/AZh/88/143
Title:
ORICAT Catalog of Stars in Orion Great Nebula
Short Name:
J/AZh/88/143
Date:
21 Oct 2021
Publisher:
CDS
Description:
Six Tautenburg 2-m Schmidt telescope plates have been used to derive proper motions for 12740 stars down to Blim=18.5 in the region centered at RA=83.45grad, Dec=-5.20grad of the Great Nebula in Orion. Each plate covers a 3x3 grad region of sky, with a scale of 51.4"/mm. The largest difference between the epochs is 36 years. The photographic plates were scanned using Tautenburg Observatory plate scanner. The accuracy of the scans was 0.5micron, and the scale was 1000pixels/mm. The rectangular coordinates x, y and instrumental magnitudes were then determined using a dedicated software. To convert the scanned positions to the equatorial coordinates we adopt reference stars from the ACT catalog. Mean errors of position determinations are 3-4mas. The components of the proper motions and their rms uncertainties were obtained via linear least-squares fit to individual rectangular coordinates as a function of the observing epoch with no less than three epochs for every proper motion. The mean measurement uncertainty is 3.5mas/yr in magnitude interval 15-19 and 5.0mas/yr outside this interval. The photometry has been taken from Walker (1969) for B-magnitudes, and from USNO-A2.0 for R-magnitudes. Mean errors for photometry are 0.03mag in B and 0.25mag in R. The ORICAT is supplemented with the data of Parenago (1954) (stars with numbers greater 17000), and includes 13 577 stars in total. ACKNOWLEDGMENTS. We thank E. Schilbach, N.V. Kharchenko, and R.D. Scholz for numerous discussions of the results, and J. Brunzendorf and H. Meusinger for help in organizing the work at Jena Observatory.
4816. Origin of nuclear activity in low-power radio galaxies
ID:
ivo://CDS.VizieR/J/AJ/155/188
Title:
Origin of nuclear activity in low-power radio galaxies
Short Name:
J/AJ/155/188
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using large samples containing nearly 2300 active galaxies of low radio luminosity (1.4 GHz luminosity between 2x10^23^ and 3x10^25^ W/Hz, essentially low-excitation radio galaxies) at z~<0.3, we present a self-contained analysis of the dependence of the nuclear radio activity on both intrinsic and extrinsic properties of galaxies, with the goal of identifying the best predictors of the nuclear radio activity. While confirming the established result that stellar mass must play a key role on the triggering of radio activities, we point out that for the central, most massive galaxies, the radio activity also shows a strong dependence on halo mass, which is not likely due to enhanced interaction rates in denser regions in massive, cluster-scale halos. We thus further investigate the effects of various properties of the intracluster medium (ICM) in massive clusters on the radio activities, employing two standard statistical tools, principle component analysis and logistic regression. It is found that ICM entropy, local cooling time, and pressure are the most effective in predicting the radio activity, pointing to the accretion of gas cooling out of a hot atmosphere to be the likely origin in triggering such activities in galaxies residing in massive dark matter halos. Our analysis framework enables us to logically discern the mechanisms responsible for the radio activity separately for central and satellite galaxies.
4817. 25 Ori group low-mass stars
ID:
ivo://CDS.VizieR/J/MNRAS/444/1793
Title:
25 Ori group low-mass stars
Short Name:
J/MNRAS/444/1793
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a survey of the low-mass star and brown dwarf population of the 25 Orionis group. Using optical photometry from the CIDA (Centro de Investigaciones de Astronomia Francisco J. Duarte, Merida, Venezuela) Deep Survey of Orion, near-IR photometry from the Visible and Infrared Survey Telescope for Astronomy and low-resolution spectroscopy obtained with Hectospec at the MMT telescope, we selected 1246 photometric candidates to low-mass stars and brown dwarfs with estimated masses within 0.02<~M/M_{sun}_<~0.8 and spectroscopically confirmed a sample of 77 low-mass stars as new members of the cluster with a mean age of ~7Myr. We have obtained a system initial mass function of the group that can be well described by either a Kroupa power-law function with indices {alpha}3=-1.73+/-0.31 and {alpha}2=0.68+/-0.41 in the mass ranges 0.03<=M/M_{sun}_<=0.08 and 0.08<=M/M_{sun}_<=0.5, respectively, or a Scalo lognormal function with coefficients m_c_=0.21^+0.02^_-0.02_ and {sigma}=0.36+/-0.03 in the mass range 0.03<=M/M_{sun}_<=0.8. From the analysis of the spatial distribution of this numerous candidate sample, we have confirmed the east-west elongation of the 25 Orionis group observed in previous works, and rule out a possible southern extension of the group. We find that the spatial distributions of low-mass stars and brown dwarfs in 25 Orionis are statistically indistinguishable. Finally, we found that the fraction of brown dwarfs showing IR excesses is higher than for low-mass stars, supporting the scenario in which the evolution of circumstellar discs around the least massive objects could be more prolonged.
4818. Ori OB1 IRAC/MIPS observations
ID:
ivo://CDS.VizieR/J/ApJ/671/1784
Title:
Ori OB1 IRAC/MIPS observations
Short Name:
J/ApJ/671/1784
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new Spitzer observations of two fields in the Orion OB1 association. We report IRAC/MIPS observations for 115 confirmed members and 41 photometric candidates of the ~10Myr 25 Orionis aggregate in the OB1a subassociation, and 106 confirmed members and 65 photometric candidates of the 5Myr region located in the OB1b subassociation.
4819. Orion Nebula Cluster members VRI photometry
ID:
ivo://CDS.VizieR/J/MNRAS/468/931
Title:
Orion Nebula Cluster members VRI photometry
Short Name:
J/MNRAS/468/931
Date:
21 Oct 2021
Publisher:
CDS
Description:
Very young stars, like the Orion Nebula Cluster (ONC) members analysed in the present study, exhibit photometric variability with a wide range of amplitudes. Such a prominent variability reflects in the inferred values of stellar colours and luminosities and, in turn, in the inferred stellar ages and masses. In this study, we measure the amplitudes of the photometric variability in V, R and I optical bands of a sample of 346 ONC members. We use these measurements to investigate how this variability affects the inferred masses and ages and whether it alone can account for the age spread among ONC members reported by earlier studies. We make use of colour-magnitude and Hertzprung-Russell (HR) diagrams. We find that members that show periodic and smooth photometric rotational modulation have masses and ages that are unaffected by variability when theoretical isochrones and evolutionary mass tracks are used in either colour-magnitude or HR diagrams. On the other hand, members with periodic but very scattered photometric rotational modulation and non-periodic members have masses and ages that are significantly affected. Moreover, using HR diagrams, we find that the observed I-band photometric variability can take account of only a fraction (~50 per cent) of the inferred age spread, whereas the V-band photometric variability is large enough to mask any age spread.
4820. Orion Nebula Cluster PMs with HST Treasury Program
ID:
ivo://CDS.VizieR/J/AJ/159/272
Title:
Orion Nebula Cluster PMs with HST Treasury Program
Short Name:
J/AJ/159/272
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of high-precision proper motions in the Orion Nebula Cluster (ONC), based on Treasury Program observations with the Hubble Space Telescope's (HST) ACS/WFC camera. Our catalog contains 2454 objects in the magnitude range of 14.2<m_F775W_<24.7, thus probing the stellar masses of the ONC from ~0.4M{sun} down to ~0.02M{sun} over an area of ~550arcmin^2^. We provide a number of internal velocity dispersion estimates for the ONC that indicate a weak dependence on stellar location and mass. There is good agreement with the published velocity dispersion estimates, although nearly all of them (including ours at {sigma }_{v,x}_=0.94 and {sigma}_{v,y}_=1.25mas/yr) might be biased by the overlapping young stellar populations of Orion A. We identified four new ONC candidate runaways based on HST and the Gaia DR 2 data, all with masses less than ~1M{sun}. The total census of known candidate runaway sources is 10-one of the largest samples ever found in any Milky Way open star cluster. Surprisingly, none of them have tangential velocities exceeding 20km/s. If most of them indeed originated in the ONC, it may compel the re-examination of dynamical processes in very young star clusters. It appears that the mass function of the ONC is not significantly affected by the lost runaways.