- ID:
- ivo://CDS.VizieR/J/ApJ/816/53
- Title:
- Multiwavelength obs. of BL Lac in 2012-2013
- Short Name:
- J/ApJ/816/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BL Lac, the eponymous blazar, flared to historically high levels at millimeter, infrared, X-ray, and gamma-ray wavelengths in 2012. We present observations made with Herschel, Swift, NuSTAR, Fermi, the Submillimeter Array, CARMA, and the VLBA in 2012-2013, including three months with nearly daily sampling at several wavebands. We have also conducted an intensive campaign of 30 hr with every-orbit observations by Swift and NuSTAR, accompanied by Herschel, and Fermi observations. The source was highly variable at all bands. Time lags, correlations between bands, and the changing shapes of the spectral energy distributions can be explained by synchrotron radiation and inverse Compton emission from nonthermal seed photons originating from within the jet. The passage of four new superluminal very long baseline interferometry knots through the core and two stationary knots about 4 pc downstream accompanied the high flaring in 2012-2013. The seed photons for inverse Compton scattering may arise from the stationary knots and from a Mach disk near the core where relatively slow-moving plasma generates intense nonthermal radiation. The 95 spectral energy distributions obtained on consecutive days form the most densely sampled, broad wavelength coverage for any blazar. The observed spectral energy distributions and multi-waveband light curves are similar to simulated spectral energy distributions and light curves generated with a model in which turbulent plasma crosses a conical shock with a Mach disk.
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- ID:
- ivo://CDS.VizieR/J/ApJ/852/108
- Title:
- Multiwavelength obs. of gamma-ray NOVA Sco 2012
- Short Name:
- J/ApJ/852/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production of gamma-rays are still not well understood. We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty FeII-type nova, with a maximum ejecta velocity of 2600km/s and an ejecta mass of a few x10^-5^M_{sun}_. There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324 Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324 Sco with other gamma-ray-detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma-rays in novae.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/94
- Title:
- Multiwavelength obs. of GRB 161219B
- Short Name:
- J/ApJ/862/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed multiwavelength observations of GRB 161219B at z=0.1475, spanning the radio to X-ray regimes, and the first Atacama Large Millimeter/submillimeter Array (ALMA) light curve of a {gamma}-ray burst (GRB) afterglow. The centimeter- and millimeter-band observations before 8.5 days require emission in excess of that produced by the afterglow forward shock (FS). These data are consistent with radiation from a refreshed reverse shock (RS) produced by the injection of energy into the FS, signatures of which are also present in the X-ray and optical light curves. We infer a constant- density circumburst environment with an extremely low density, n_0_~3x10^-4^cm^-3^, and show that this is a characteristic of all strong RS detections to date. The Karl G. Lansky Very Large Array (VLA) observations exhibit unexpected rapid variability on roughly minute timescales, indicative of strong interstellar scintillation. The X-ray, ALMA, and VLA observations together constrain the jet break time, t_jet_~32 days, yielding a wide jet opening angle of {theta}_jet_~13{deg}, implying beaming-corrected {gamma}-ray and kinetic energies of E_{gamma}~4.9x10^48^erg and E_K_~1.3x10^50^erg, respectively. Comparing the RS and FS emission, we show that the ejecta are only weakly magnetized, with relative magnetization, R_B_~1, compared to the FS. These direct, multifrequency measurements of a refreshed RS spanning the optical to radio bands highlight the impact of radio and millimeter data in probing the production and nature of GRB jets.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/125
- Title:
- 2014-2018 multiwavelength obs. of PKS 1502+106
- Short Name:
- J/ApJ/881/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the multiband activities (outbursts/flares) of blazars is still a heavily debated topic. Shock and magnetic reconnection have long been considered as possible triggers of the multiband activities. In this paper, we present an exploration of the origin of multiband activities for a high-redshift (z=1.8385) flat-spectrum radio quasar PKS 1502+106. Utilizing multiband data from radio to {gamma}-ray and optical polarization observations, we investigate two dramatic activities in detail: a {gamma}-ray- dominated outburst in 2015 and an optical-dominated outburst in 2017. Our main results are as follows. (I) A fast {gamma}-ray flare with a flux-doubling timescale as short as 1 hr in 2015 is discovered. Based on the variability timescale, the physical parameters of the flaring region (e.g., minimum Doppler factor, emission region size, etc.) are constrained. At the peak of the flare, the {gamma}-ray spectrum hardens to {Gamma}_{gamma}_=1.82+/-0.04 and exhibits an obvious curvature/break characteristic that is caused by the typical "cooling break." Modeling of multiband spectral energy distributions reveal a very hard electronic energy spectrum with the electronic spectral index of 1.07+/-0.53. This result suggests that this fast {gamma}-ray flare may be triggered by magnetic reconnection. (II) During the outburst in 2017, the degree of optical polarization and optical fluxes showed a very tight correlation. By analyzing the Stokes parameters of polarization observations, our results show that this outburst could be triggered by a transverse shock with a compression ratio of {eta}>2.2, and the magnetic field intensity of the shock emission region is about 0.032G.
- ID:
- ivo://CDS.VizieR/J/AJ/156/148
- Title:
- Multiwavelength photometry of RCB stars
- Short Name:
- J/AJ/156/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of extended, cold dust envelopes surrounding R Coronae Borealis (RCB) stars began with their discovery by the Infrared Astronomical Satellite. RCB stars are carbon-rich supergiants characterized by their extreme hydrogen deficiency and their irregular and spectacular declines in brightness (up to 9 mag). We have analyzed new and archival Spitzer Space Telescope and Herschel Space Observatory data of the envelopes of seven RCB stars to examine the morphology and investigate the origin of these dusty shells. Herschel, in particular, has revealed the first-ever bow shock associated with an RCB star with its observations of SU Tauri. These data have allowed the assembly of the most comprehensive spectral energy distributions (SEDs) of these stars with multiwavelength data from the ultraviolet to the submillimeter. Radiative transfer modeling of the SEDs implies that the RCB stars in this sample are surrounded by an inner warm (up to 1200 K) and an outer cold (up to 200 K) envelope. The outer shells are suggested to contain up to 10^-3^ M_{sun}_ of dust and have existed for up to 10^5^ years depending on the expansion rate of the dust. This age limit indicates that these structures have most likely been formed during the RCB phase.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/2502
- Title:
- Multiwavelength study of HII region S311
- Short Name:
- J/MNRAS/461/2502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength investigation of the young stellar population and star formation activities around the HII region Sharpless 311. Using our deep near-infrared observations and archival Spitzer-IRAC observations, we have detected a total of 125 young stellar objects (YSOs) in an area of ~86 arcmin^2^. The YSO sample includes eight Class I and 117 Class II candidate YSOs. The mass completeness of the identified YSO sample is estimated to be 1.0M_{sun}_. The ages and masses of the majority of the candidate YSOs are estimated to be in the range ~0.1-5Myr and ~0.3-6M_{sun}_, respectively. The 8um image of S311 displays an approximately spherical cavity around the ionizing source, which was possibly created by the expansion of the H ii region. The spatial distribution of the candidate YSOs reveals that a significant number of them are distributed systematically along the 8-{mu}m emission with a majority clustered around the eastern border of the HII region. Four clumps/compact HII regions are detected in the radio continuum observations at 1280MHz, which may have been formed during the expansion of the HII region. The estimated dynamical age of the region, main-sequence lifetime of the ionizing source, the spatial distribution and ages of the candidate YSOs indicate triggered star formation in the complex.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1279
- Title:
- Multiwavelength study of NGC 7419
- Short Name:
- J/MNRAS/391/1279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new UBVRI H{alpha} CCD photometric observations and the archival infrared and X-ray data, we have carried out a multiwavelength study of a Perseus arm young open star cluster NGC 7419. Using XMM-Newton observations, we found several X-ray sources in the cluster region but none of the Herbig Ae/Be stars is detected in X-rays.
- ID:
- ivo://CDS.VizieR/J/PASJ/64/107
- Title:
- Multiwavelength study of NGC 281 complex
- Short Name:
- J/PASJ/64/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of the NGC 281 complex, which contains the young cluster IC 1590 at the center, using deep wide-field optical UBVIc photometry, slitless spectroscopy along with archival data sets in the near-infrared (NIR) and X-ray regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/664/777
- Title:
- Multiwavelength study of RX J1117.4+0743
- Short Name:
- J/ApJ/664/777
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of the poor cluster RX J1117.4+0743 ([VMF98] 097) at z=0.485, based on GMOS/Gemini South g' and r' photometry and spectroscopy, and XMM-Newton observations. We examine its nature and surroundings by analyzing the projected galaxy distribution, the galaxy velocity distribution, the weak-lensing mass reconstruction, and the X-ray spectroscopy and imaging.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/81
- Title:
- Multiwavelength survey of HII regions in NGC 300
- Short Name:
- J/ApJ/789/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 H II regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250pc scales using pointed CO(J=2-1) observations with the Atacama Pathfinder Experiment telescope. We detect CO in 42 of our targets, deriving molecular gas masses ranging from our sensitivity limit of ~10^5^M_{sun}_ to 7x10^5^M_{sun}_. We find a clear decline in the CO detection rate with galactocentric distance, which we attribute primarily to the decreasing radial metallicity gradient in NGC 300. We combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24{mu}m, and H{alpha} narrowband imaging to measure the star formation activity in our sample. We have developed a new direct modeling approach for computing star formation rates (SFRs) that utilizes these data and population synthesis models to derive the masses and ages of the young stellar clusters associated with each of our H II region targets. We find a characteristic gas depletion time of 230Myr at 250pc scales in NGC 300, more similar to the results obtained for Milky Way giant molecular clouds than the longer (>2Gyr) global depletion times derived for entire galaxies and kiloparsec-sized regions within them. This difference is partially due to the fact that our study accounts for only the gas and stars within the youngest star-forming regions. We also note a large scatter in the NGC 300 SFR-molecular gas mass scaling relation that is furthermore consistent with the Milky Way cloud results. This scatter likely represents real differences in giant molecular cloud physical properties such as the dense gas fraction.
