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5471. Radio observations of the HDFS region. I
ID:
ivo://CDS.VizieR/J/AJ/130/1358
Title:
Radio observations of the HDFS region. I
Short Name:
J/AJ/130/1358
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper is the first of a series describing the results of the Australia Telescope Hubble Deep Field-South radio survey. The survey was conducted at four wavelengths, 20, 11, 6, and 3cm, over a 4 year period and achieves an rms sensitivity of about 10{mu}Jy at each wavelength. We describe the observations and data reduction processes and present data on radio sources close to the center of the Hubble Deep Field-South. We discuss in detail the properties of a subset of these sources. The sources include both starburst galaxies and galaxies powered by an active galactic nucleus and range in redshift from 0.1 to 2.2. Some of them are characterized by unusually high radio-to-optical luminosities, presumably caused by dust extinction.
5472. Radio observations of the HDFS region. IV.
ID:
ivo://CDS.VizieR/J/AJ/135/2470
Title:
Radio observations of the HDFS region. IV.
Short Name:
J/AJ/135/2470
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Australia Telescope Hubble Deep Field-South (ATHDF-S) survey of the Hubble Deep Field-South (HDF-S) reaches sensitivities of ~10uJy at 1.4, 2.5, 5.2, and 8.7GHz, making the ATHDF-S one of the deepest surveys ever performed with the Australia Telescope Compact Array (ATCA). Here, we present the optical identifications of the ATHDF-S radio sources using data from the literature. We find that ~66% of the radio sources have optical counterparts to I=23.5mag. Deep Hubble Space Telescope (HST) imaging of the area identifies a further 12% of radio sources. We present new spectroscopic observations for 98 of the radio sources and supplement these spectroscopic redshifts with photometric ones calculated from five-band optical imaging.
5473. Radio observations of ultracool dwarf stars
ID:
ivo://CDS.VizieR/J/ApJ/746/23
Title:
Radio observations of ultracool dwarf stars
Short Name:
J/ApJ/746/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new radio survey of about 100 late-M and L dwarfs undertaken with the Very Large Array. The sample was chosen to explore the role of rotation in the radio activity of ultracool dwarfs. As part of the survey we discovered radio emission from three new objects, 2MASS J0518113-310153 (M6.5), 2MASS J0952219-192431 (M7), and 2MASS J1314203+132001 (M7), and made an additional detection of LP 349-25 (M8). Combining the new sample with results from our previous studies and from the literature, we compile the largest sample to date of ultracool dwarfs with radio observations and measured rotation velocities.
5474. Radio/Optical catalog of the SSA 13 field
ID:
ivo://CDS.VizieR/J/ApJS/167/103
Title:
Radio/Optical catalog of the SSA 13 field
Short Name:
J/ApJS/167/103
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a 1.4GHz catalog of 810 radio sources (560 sources in the complete sample) found in the SSA 13 field (RA=13:12, DE=42:38). The 1.4GHz radio image was obtained from a 91hr VLA integration with an rms noise level of 4.82uJy/beam at the field center. Optical images in the R band (6300{AA}) and z band (9200{AA}) with 3{sigma} detection magnitudes of 26.1 and 24.9, respectively, were obtained from three observing nights on the 8m Subaru Telescope. We find that 88%+/-2% of the radio sources are identified with an optical counterpart.
5475. Radio & optical observation of UX Arietis
ID:
ivo://CDS.VizieR/J/ApJ/439/983
Title:
Radio & optical observation of UX Arietis
Short Name:
J/ApJ/439/983
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have observed UX Arietis at C band (6cm) for 3 weeks with four VLA antennas. The temporal coverage during the program was approximately three scans per day. A few days into the VLA program, UX Ari began a radio flaring period which lasted for at least 2 weeks. All the radio fluxes were above the system noise during this episode, but the largest values (up to 270mJy) occurred close to 0.0 phase. This phasing is confirmed by the UX Ari radio observations of Neidhoefer, Massi, & Chiuderi-Drago (1993A&A...278L..51N). Visible-band light curves of UX Ari were obtained both during and after our radio observations; the peak-to-peak variation in all filters was ~0.2mag. The light curves indicate that the maximum starspot visibility occurred very close to 0.0 phase, the same phase as the radio maxima. Closer comparison of our radio and optical light curves indicates that they are almost perfectly anticorrelated. A similar radio/optical correlation has been found by Lim et al. (1992ApJ...388L..27L) and Lim et al. (1994ApJ...430..332L) for the single K0 V star AB Dor. We make the following conclusions from our observations. First, the episodes of long-term (~hours to days) radio flaring were modulated by stellar eclipses. Second, the flares were located close to the starspot groups. Third, the sizes of the flares were comparable to sizes of the starspot groups, which is consistent with nonthermal emission of brightness temperature T_b~10^10-10^13K. Fourth, the radio emission arose only from the midlatitude starspot groups. Last, the radio flares emitted their radiation nearly normal to the stellar surface.
5476. 58 radio sources near BNGSs
ID:
ivo://CDS.VizieR/J/ApJS/185/124
Title:
58 radio sources near BNGSs
Short Name:
J/ApJS/185/124
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a preliminary survey of 58 radio sources within the isoplanatic patches (r<25") of bright (11<R<12) stars suitable for use as natural guide stars with high-order adaptive optics (AO). An optical and near-infrared imaging survey was conducted utilizing tip-tilt corrections in the optical and AO in the near-infrared. Spectral energy distributions were fit to the multi-band data for the purpose of obtaining photometric redshifts using the Hyperz code. Several of these photometric redshifts were confirmed with spectroscopy, a result that gives more confidence to the redshift distribution for the whole sample. Additional long-wavelength data from Spitzer, SCUBA, SHARC2, and VLA supplement the optical and near-infrared data. We find the sample generally follows and extends the magnitude-redshift relation found for more powerful local radio galaxies. The survey has identified several reasonably bright (H=19-20) objects at significant redshifts (z>1) that are now within the capabilities of the current generation of AO-fed integral-field spectrographs. These objects constitute a unique sample that can be used for detailed ground-based AO studies of galactic structure, evolution, and active galactic nucleus formation at high redshift.
5477. Radio to UV observations of GRB 181201A
ID:
ivo://CDS.VizieR/J/ApJ/884/121
Title:
Radio to UV observations of GRB 181201A
Short Name:
J/ApJ/884/121
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present comprehensive multiwavelength radio to X-ray observations of GRB 181201A spanning from ~150s to ~163days after the burst, comprising the first joint ALMA-VLA-GMRT observations of a gamma-ray burst (GRB) afterglow. The radio and millimeter-band data reveal a distinct signature at ~3.9days, which we interpret as reverse-shock (RS) emission. Our observations present the first time that a single radio- frequency spectral energy distribution can be decomposed directly into RS and forward shock (FS) components. We perform detailed modeling of the full multiwavelength data set, using Markov Chain Monte Carlo sampling to construct the joint posterior density function of the underlying physical parameters describing the RS and FS synchrotron emission. We uncover and account for all discovered degeneracies in the model parameters. The joint RS-FS modeling reveals a weakly magnetized ({sigma}~3x10^-3^), mildly relativistic RS, from which we derive an initial bulk Lorentz factor of {Gamma}_0_~103 for the GRB jet. Our results support the hypothesis that low-density environments are conducive to the observability of RS emission. We compare our observations to other events with strong RS detections and find a likely observational bias selecting for longer lasting, nonrelativistic RSs. We present and begin to address new challenges in modeling posed by the present generation of comprehensive, multifrequency data sets.
5478. Radius relations for low-metallicity M-dwarf stars
ID:
ivo://CDS.VizieR/J/AJ/157/63
Title:
Radius relations for low-metallicity M-dwarf stars
Short Name:
J/AJ/157/63
Date:
21 Oct 2021
Publisher:
CDS
Description:
M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal-poor stars, hydrostatic equilibrium is reached at a smaller radius, leading to smaller radii for a given effective temperature. We compile a sample of 88 stars that span spectral classes K7 to M6 and include stars with metallicity classes from solar-metallicity dwarf stars to the lowest metallicity ultra subdwarfs to test how metallicity changes the stellar radius. We fit models to Palomar Double Spectrograph (DBSP) optical spectra to derive effective temperatures (T_eff_) and we measure bolometric luminosities (L_bol_) by combining broad wavelength-coverage photometry with Gaia parallaxes. Radii are then computed by combining the T_eff_ and L_bol_ using the Stefan-Boltzman law. We find that for a given temperature, ultra subdwarfs can be as much as five times smaller than their solar-metallicity counterparts. We present color-radius and color-surface brightness relations that extend down to [Fe/H] of -2.0 dex, in order to aid the radius determination of M subdwarfs, which will be especially important for the WFIRST exoplanetary microlensing survey.
5479. R- and I-band photometry of 506 asteroids with CNEOST
ID:
ivo://CDS.VizieR/J/AJ/160/73
Title:
R- and I-band photometry of 506 asteroids with CNEOST
Short Name:
J/AJ/160/73
Date:
09 Mar 2022
Publisher:
CDS
Description:
We initiated the bilateral collaboration between the Lulin Observatory and the Purple Mountain Observatory to collect asteroid lightcurves using the Chinese Near-Earth Object Survey Telescope at the Xuyi Observation Station. The primary goal of this collaboration was to discover super-fast rotators (SFRs) and study their physical properties. Two campaigns have been conducted: (a) a survey of ~45{deg}^2^ using 8minute cadence during 2017 February 26-March 2, and (b) a survey of ~60{deg}^2^ using 10minute cadence during 2018 March 9-12. Our samples are mainly main-belt asteroids and some Hildas and Jupiter Trojans. Out of 4522 collected lightcurves, 506 reliable rotation periods were obtained. Among the reliable rotation periods, we found 16 candidates with a possible rotation period of <2.2hr, in which (134291) 2006 DZ6 shows a very convincing folded lightcurve and the other 15 candidates only have a likely trend. Further confirmation is needed for the rotation periods of these SFR candidates. In addition, (2280) Kunikov seems to have an eclipsing feature on its lightcurve with a relatively long rotation period suggesting that it is likely a fully synchronized binary asteroid. When the preliminary spin-rate distributions were carried out for asteroids using different sizes, no obvious difference was found.
5480. Rapid optical variability in ultracool dwarfs
ID:
ivo://CDS.VizieR/J/MNRAS/428/2824
Title:
Rapid optical variability in ultracool dwarfs
Short Name:
J/MNRAS/428/2824
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, a summary of optical time-series photometry of 125 ultracool dwarfs is given. The observing strategy was to monitor each object continuously for 2-3h in order to ascertain whether it was rapidly variable. Many of the targets were observed at multiple epochs, to follow up possible short time-scale variability, or to test for slow brightness changes on longer time-scales. The 353 data sets obtained contain nearly 22000 individual measurements. Optical (I_C_) magnitudes, accurate to roughly 0.1-0.2mag, were derived for 21 objects for which there is no optical photometry in the literature. It is shown that photometry is affected by variable seeing in a large percentage of the time-series observations. Since this could give the appearance of variability intrinsic to the objects, magnitudes are modelled as functions of both time and seeing. Several ultracool dwarfs which had not been monitored before are variable, according to certain model-fitting criteria. A number of objects with multi-epoch observations appear to be variable on longer time-scales. Since testing for variability is far from being straightforward, the time-series data are made available so that interested readers can perform their own analyses.