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- ID:
- ivo://CDS.VizieR/J/ApJ/704/652
- Title:
- Radio transients in a 1.4GHz drift-scan survey
- Short Name:
- J/ApJ/704/652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report two new radio transients at high Galactic latitude, WJN J0951+3300 (RA=09h51m22s+/-10s, DE=33{deg}00'+/-0.4{deg}, b=50{deg}54.2') and WJN J1039+3300 (RA=10h39m26s+/-10s, DE=33{deg}00'+/-0.4{deg}, b=60{deg}58.5'), which were detected by interferometric drift-scan observations at 1.4GHz at the Waseda Nasu Pulsar Observatory. WJN J0951+3300 was detected at 16:49:32UT on 2006 January 12 with the flux density of approximately 1760.5+/-265.9mJy, and WJN J1039+3300 was detected at 17:13:32UT on 2006 January 18 with the flux density of approximately 2242.5+/-228.7mJy. Both of them lasted for a short duration (<=2 days). The possibility that the distribution of the WJN radio transients is isotropic was suggested in a previous study. Having re-evaluated the log N-log S relation with the addition of the two new objects reported in this paper, we find that the slope is consistent with a slope of -1.5 and the previous result. Additionally, although there are several counterparts to WJN radio transients, we found that one of the quasar counterparts within the positional error of WJN J0951+3300 could be a radio-loud quasar. We have discussed whether or not WJN J0951+3300 could be of this quasar origin.
- ID:
- ivo://CDS.VizieR/J/AJ/142/108
- Title:
- Radio variability of compact, flat-spectrum AGNs
- Short Name:
- J/AJ/142/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 4.9GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in interstellar scintillation (ISS) for sources at redshifts z>~2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the intergalactic medium (IGM) in excess of the expected (1+z)^1/2^ angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9GHz and 8.4GHz observations and data analysis for a sample of 140 compact, flat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A169
- Title:
- Radio variability to identifying changing jets
- Short Name:
- J/A+A/654/A169
- Date:
- 16 Mar 2022 00:56:46
- Publisher:
- CDS
- Description:
- Supermassive black holes can launch highly relativistic jets with velocities reaching Lorentz factors of as high as {GAMMA}>50. How the jets accelerate to such high velocities and where along the jet they reach terminal velocity are open questions that are tightly linked to their structure as well as their launching and dissipation mechanisms. Changes in the beaming factor along the jets could potentially reveal jet acceleration, deceleration, or bending. We aim to (1) quantify the relativistic effects in multiple radio frequencies and (2) study possible jet velocity-viewing angle variations at parsec scales. We used the state-of-the-art code Magnetron to model light curves from the University of Michigan Radio Observatory and the Metsahovi Radio Observatory's monitoring programs in five frequencies covering about 25 years of observations in the 4.8 to 37GHz range for 61 sources. We supplement our data set with high-frequency radio observations in the 100-340GHz range from ALMA, CARMA, and SMA. For each frequency we estimate the Doppler factor which we use to quantify possible changes in the relativistic effects along the jets. The majority of our sources do not show any statistically significant difference in their Doppler factor across frequencies. This is consistent with constant velocity in a conical jet structure, as expected at parsec scales. However, our analysis reveals 17 sources where relativistic beaming changes as a function of frequency. In the majority of cases, the Doppler factor increases towards lower frequencies. Only 1253-053 shows the opposite behavior. By exploring their jet properties we find that the jet of 0420-014 is likely bent across the 4.8-340GHz range. For 0212+735, the jet is likely parabolic, and still accelerating in the 4.8-37GHz range. We discuss possible interpretations for the trends found in the remaining sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/307
- Title:
- Radio variations of Cygnus X-3
- Short Name:
- J/MNRAS/406/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus X-3 is one of the brightest X-ray and radio sources in the Galaxy and is well known for its erratic behaviour in X-rays as well as in the radio, occasionally producing major radio flares associated with relativistic ejections. However, even after many years of observations in various wavelength bands Cyg X-3 still eludes clear physical understanding. Studying different emission bands simultaneously in microquasars has proved to be a fruitful approach towards understanding these systems, especially by shedding light on the accretion disc/jet connection. We continue this legacy by constructing a hardness-intensity diagram (HID) from archival Rossi X-ray Timing Explorer data and linking simultaneous radio observations to it. We find that surprisingly Cyg X-3 sketches a similar shape in the HID to that seen in other transient black hole X-ray binaries during outburst but with distinct differences.
- ID:
- ivo://CDS.VizieR/J/A+A/472/805
- Title:
- Radio-X-ray sources in the HDF(N) region.
- Short Name:
- J/A+A/472/805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue lists the properties of 62 radio sources in the Hubble Deep Field (North) and Flanking Fields (HDFN) which were also detected by the Chandra X-ray satellite (see Alexander et al., 2003, Cat. <J/AJ/126/539>, file cdfn). This includes 55/92 sources brighter than 40uJy detected by MERLIN+VLA at 1.4GHz (see Muxlow et al., 2005, Cat. <J/MNRAS/358/1159>, Richards, 2000, Cat. <J/ApJ/533/611>); some were also detected by the VLA at 8.4GHz (Richards et al., 1998AJ....116.1039R) including 7 selected at this frequency. The cross-matching, derivation of properties and analysis are described fully in the paper. The radio data have a positional accuracy of 15 mas with respect to the ICRS (Muxlow et al., 2005, Cat. <J/MNRAS/358/1159>) but data using the GOODS HST ACS (Giavalisco et al., 2004, Cat. <II/261>) positions requires a shift of -342mas in Declination for alignment with the ICRS. We use measurements taken from the radio observations and from the literature to compile the flux densities, sizes and spectral/photon indices of the cross-matched radio+X-ray sources and their redshifts (where available), enabling us to derive the rest-frame luminosities. The 1.4-GHz detections are all resolved at 0.2-2arcsec resolution. The radio emission was classified using the source morphologies and radio spectral indices; optical and IR information was used as supporting evidence only. On this basis, starbursts outnumber radio AGN 3:1. The high-redshift starbursts have typical sizes of 5-10kpc and star formation rates of around 1000 Msun/yr, an order of magnitude more extended and intense than in the local universe. The X-ray sources are unresolved but their luminosity and spectral indices allows X-ray AGN and obscured (Type II) AGN to be identified (2004A&A...424..545P). In this way, we can distinguish between the origins of radio and X-ray emission from the same object. There is no obvious correlation between radio and X-ray luminosities nor spectral indices at z>1.3. About 70% of both the radio-selected AGN and the starburst samples were detected by Chandra. The X-ray luminosity indicates the presence of an AGN in at least half of the 45 cross-matched radio starbursts. Eleven of these are type-II AGN, of which 7 are at z>1.5. This distribution overlaps closely with the X-ray detected radio sources which were also detected by SCUBA. Almost all extended radio starbursts at z>1.3 host X-ray selected obscured AGN. The radio emission from most of these ultra-luminous objects is dominated by star formation although the highest redshift (z=4.424) source has a substantial AGN contribution. Star-formation appears to contribute less than 1/3 of their X-ray luminosity. Our results support the inferences from SCUBA and IR data, that at z>1.5, star formation is observably more extended and more copious, it is closely linked to AGN activity and it is triggered differently, compared with star formation at lower redshifts.
- ID:
- ivo://CDS.VizieR/J/A+AS/87/1
- Title:
- RATAN-600 7.6 cm catalog of radio sources
- Short Name:
- J/A+AS/87/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog containing 840 radio sources obtained during the Experiment Cold-80 at 7.6 cm wavelength using RATAN-600 are presented. The completeness of the list in the central zone is about 0.7-0.8 for sources with flux density 7.5-15 mJy. For sources brighter than 15 mJy the completeness reaches one. The number of sources-flux density differential curve is constructed. Spectra are given for 230 sources.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/72.150
- Title:
- RATAN COLD Reined (RCR) catalogue
- Short Name:
- J/other/AstBu/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the additional list of radio sources of the RCR (RATAN Cold Refined) catalog. The sources was obtained on the observation data of the COLD experiment which included a series of surveys carried out in 1980-1999 on the RATAN-600 radio telescope. This part of RCR catalogue contains the right ascensions, integrated flux densities at 7.6cm (3.94GHz) and their spectral indices 3.94 and 0.5GHz of 269 objects detected in the right-ascension interval 2h<R.A.<7h and also additional 24 radio sources found in only one survey and 3 transient candidates in the right-ascension interval 2h<R.A.<17h. We constructed radio spectra of the sources using data of the catalogues from CATS and VizieR databases which the strip of COLD surveys overlays, and, in cases of weak sources, for this purpose we used the flux density values estimated from VLSSr, GLEAM, TGSS, and GB6 survey maps. 6% of the sources, which are mostly weaker than 30 mJy at 3.94GHz, have flux density data only at two frequencies - 1.4 and 3.94GHz. About 30% of these sources have flat or inverse spectra (alpha>-0.5) at 3.94GHz. We verified the reliability of identifications of the sources detected in the scans by comparing the coordinates and integrated flux densities with the corresponding parameters of the sources of the NVSS catalogue. In the central 10'-part of the strip at 10mJy level completness of the catalogue is about 90% and we found no objects that lack in decimeter-wave catalogues.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/2658
- Title:
- RATAN-600 flux densities of 123 blazars
- Short Name:
- J/MNRAS/450/2658
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the correlation between gamma-ray and radio band radiation for 123 blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data obtained at the same period of time (within a few months).
- ID:
- ivo://CDS.VizieR/J/other/AstBu/69.266
- Title:
- RATAN-600 flux densities of 37 blazars
- Short Name:
- J/other/AstBu/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the correlation between the emission from the broad-line region (BLR) and the emission in other wavelength ranges (from radio to x-ray) for the sample of 37 blazars (25 flat-spectrum radio quasars (FSRQs) and 10 BL Lac blazars). Studying the relation between luminosities in various wavebands and the BLR luminosity is an effective method to examine the connection between the accretion rate and the luminosity of the jet.We used simultaneous RATAN-600measurements of blazar flux densities at six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7GHz. The observational data from other bands was taken from the literature. To determine the effect produced by the state of the object on the correlation, for the radio data we used the measurements obtained with the RATAN-600 in two states-namely, the maximum and minimum flux density values.We show that at some frequencies of the radio band, there exists a correlation of emission with the emission in the BLR for two types of blazars. In the FSRQ and BL Lac blazars, the correlation between the flux from the BLR and the flux in the radio band is indistinguishable in all cases, except for the case when a strong flux density variation was considered for the BL Lac-type of blazars (tens of percent). At the same time, the levels of significance for BL Lac (at certain frequencies p is worse than 0.05) in the active state indicate only the probable presence of connection. On the example of the sample, we show that the variability of emission significantly affects the level of correlation. Our results are consistent with the theoretical predictions about the close relationship of the accretion disk and the jet in blazars.
