- ID:
- ivo://CDS.VizieR/J/ApJ/895/23
- Title:
- Radio observation of the transient CSS161010
- Short Name:
- J/ApJ/895/23
- Date:
- 16 Mar 2022 00:23:37
- Publisher:
- CDS
- Description:
- We present X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010J045834-081803 (CSS161010 hereafter) at t=69-531days. CSS161010 shows luminous X-ray (Lx~5x1039erg/s) and radio (L{nu}~1029erg/s/Hz) emission. The radio emission peaked at ~100days post-transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blast wave. CSS161010 launched a mildly relativistic outflow with velocity {Gamma}{beta}c>~0.55c at ~100days. This is faster than the non- relativistic AT 2018cow ({Gamma}{beta}c~0.1c) and closer to ZTF18abvkwla ({Gamma}{beta}c>~0.3c at 63days). The inferred initial kinetic energy of CSS161010 (Ek>~1051erg) is comparable to that of long gamma-ray bursts, but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger (~0.01-0.1M{odot}). This is consistent with the lack of observed {gamma}-rays. The luminous X-rays were produced by a different emission component to the synchrotron radio emission. CSS161010 is located at ~150Mpc in a dwarf galaxy with stellar mass M*~107M{sun} and specific star formation rate sSFR~0.3/Gyr. This mass is among the lowest inferred for host galaxies of explosive transients from massive stars. Our observations of CSS161010 are consistent with an engine-driven aspherical explosion from a rare evolutionary path of a H-rich stellar progenitor, but we cannot rule out a stellar tidal disruption event on a centrally located intermediate-mass black hole. Regardless of the physical mechanism, CSS161010 establishes the existence of a new class of rare (rate<0.4% of the local core-collapse supernova rate) H-rich transients that can launch mildly relativistic outflows.
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- ID:
- ivo://CDS.VizieR/J/ApJ/903/132
- Title:
- Radio & optical observations of supernova SN2020oi
- Short Name:
- J/ApJ/903/132
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We report the discovery and panchromatic follow-up observations of the young Type Ic supernova (SNIc) SN2020oi in M100, a grand-design spiral galaxy at a mere distance of 14Mpc. We followed up with observations at radio, X-ray, and optical wavelengths from only a few days to several months after explosion. The optical behavior of the supernova is similar to those of other normal SNeIc. The event was not detected in the X-ray band but our radio observations revealed a bright mJy source (L_{nu}_~1.2x10^27^erg/s/Hz). Given the relatively small number of stripped envelope SNe for which radio emission is detectable, we used this opportunity to perform a detailed analysis of the comprehensive radio data set we obtained. The radio-emitting electrons initially experience a phase of inverse Compton cooling, which leads to steepening of the spectral index of the radio emission. Our analysis of the cooling frequency points to a large deviation from equipartition at the level of {epsilon}_e_/{epsilon}_B_>~200, similar to a few other cases of stripped envelope SNe. Our modeling of the radio data suggests that the shock wave driven by the SN ejecta into the circumstellar matter (CSM) is moving at ~3x10^4^km/s. Assuming a constant mass loss from the stellar progenitor, we find that the mass-loss rate is M~1.4x10^-4^M{sun}/yr for an assumed wind velocity of 1000km/s. The temporal evolution of the radio emission suggests a radial CSM density structure steeper than the standard r-2.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A45
- Title:
- R Crt and RT Vir Medicina spectra
- Short Name:
- J/A+A/644/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Water masers emitting at a radiofrequency of 22GHz are often found in the circumstellar envelopes of evolved stars. We monitored the H_2_O maser emission of a larger sample of evolved stars of different types to study the maser properties as a function of stellar type. We wish to understand the origin and evolution of the H_2_O masers in circumstellar envelopes. In this paper, we take a closer look at R Crt and RT Vir, two nearby (<250pc) semi-regular variable stars. The findings complement our monitoring results for RX Boo and SV Peg, two other semi-regular variable stars that we have discussed in a previous paper. Within the framework of the Medicina/Effelsberg H_2_O maser monitoring programme, we observed the maser emission of R Crt and RT Vir for more than two decades with single-dish telescopes. To get insights into the distribution of maser spots in the circumstellar envelopes at different times, to get an idea of their longevity, and, where possible, to be able to link the phenomena seen in our observations to maser locations within the envelopes, we collected interferometric data for these stars, taken within the same period, from the literature. The H_2_O masers in R Crt and RT Vir exhibit brightness variations on a variety of timescales. We confirm short-time variations of individual features on timescales of months to up to 1.5 years, as seen by previous monitoring programmes. Also decade-long variations of the general brightness level, independent from individual features, were seen in both stars. These long-term variations are attributed to brightness variations occurring independently from each other in selected velocity ranges and they are independent of the optical light curve of the stars. Expected drifts in velocity of individual features are usually masked by the blending of other features with similar velocities. However, in RT Vir, we found the exceptional case of a single feature with a constant velocity over 7.5 years (<0.06km/s/yr). We attribute the long-term brightness variations to the presence of regions with higher-than-average density in the stellar wind and hosting several clouds which emit maser radiation on short timescales. These regions typically need ~20 years to cross the H_2_O maser shell, where the right conditions for exciting H_2_O masers are present. Different clouds contained in such a region all move within a narrow range of velocities, and so does their maser emission. This sometimes gives the impression of longer-living features in single-dish spectra, in spite of the short lifetimes of the individual components that lie at their origin, thus, naturally explaining the longer timescales observed. The constant velocity feature (11km/s) is likely to come from a single maser cloud, which moved through about half of RT Vir's H_2_O maser shell without changing its velocity. From this, we infer that its path was located in the outer part of the H_2_O maser shell, where RT Vir's stellar wind has, apparently, already reached its terminal outflow velocity. This conclusion is independently corroborated by the observation that the highest H_2_O maser outflow velocity in RT Vir approaches the terminal outflow velocity, as given by OH and CO observations. This is generally not observed in other semi-regular variable stars. All four stars in our study are of optical variability type SRb, indicating the absence of periodic large-amplitude variations. Therefore, any likely responses of the maser brightness to variations of the optical emission are masked by the strong short-term maser fluctuations.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A72
- Title:
- Resolved molecular line observations
- Short Name:
- J/A+A/646/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Physical processes that govern the star and planet formation sequence influence the chemical composition and evolution of protoplanetary disks. Recent studies allude to an early start to planet formation already ongoing during the formation of a disk. To understand the chemical composition of protoplanets, we need to constrain the composition and structure of the disks from whence they are formed. We aim to determine the molecular abundance structure of the young disk around the TMC1A protostar on au scales in order to understand its chemical structure and any possible implications for disk formation. We present spatially resolved Atacama Large Millimeter/submillimeter Array observations of CO, HCO^+^, HCN, DCN, and SO line emission, as well as dust continuum emission, in the vicinity of TMC1A. Molecular column densities are estimated both under the assumption of optically thin emission from molecules in local thermodynamical equilibrium (LTE) as well as through more detailed non-LTE radiative transfer calculations. From the derived HCO^+^ abundance, we estimate the ionization fraction of the disk surface and find values that imply that the accretion process is not driven by the magneto-rotational instability. The molecular abundances averaged over the TMC1A disk are similar to its protostellar envelope and other, older Class II disks. We meanwhile find a discrepancy between the young disk's molecular abundances relative to Solar System objects. Abundance comparisons between the disk and its surrounding envelope for several molecular species reveal that the bulk of planet-forming material enters the disk unaltered. Differences in HCN and H_2_O molecular abundances between the disk around TMC1A, Class II disks, and Solar System objects trace the chemical evolution during disk and planet formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/9
- Title:
- Rotational frequencies of TiO isotopologues
- Short Name:
- J/ApJ/833/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pure rotational spectra of the rare isotopologues of titanium oxide, ^46^TiO, ^47^TiO, ^49^TiO, and ^50^TiO, have been recorded using a combination of Fourier transform millimeter-wave (FTmmW) and millimeter/submillimeter direct absorption techniques in the frequency range 62-538GHz. This study is the first complete spectroscopic characterization of these species in their X^3^{Delta}_r_ ground electronic states. The isotopologues were created by the reaction of N_2_O or O_2_ and titanium vapor, produced either by laser ablation or in a Broida-type oven, and observed in the natural Ti isotopic abundances. Between 10 and 11 rotational transitions J+1<->J were measured for each species, typically in all 3 spin-orbit ladders {Omega}=1, 2, and 3. For ^47^TiO and ^49^TiO, hyperfine structure was resolved, originating from the titanium-47 and titanium-49 nuclear spins of I=5/2 and 7/2, respectively. For the {Omega}=1 and 3 components, the hyperfine structure was found to follow a classic Lande pattern, while that for {Omega}=2 appeared to be perturbed, likely a result of mixing with the nearby isoconfigurational a^1^{Delta} state. The spectra were analyzed with a case (a) Hamiltonian, and rotational, spin-orbit, and spin-spin parameters were determined for each species, as well as magnetic hyperfine and electric quadrupole constants for the two molecules with nuclear spins. The most abundant species, ^48^TiO, has been detected in circumstellar envelopes. These measurements will enable other titanium isotopologues to be studied at millimeter wavelengths, providing Ti isotope ratios that can test models of nucleosynthesis.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/26
- Title:
- Rotational spectra of aminoacetonitrile
- Short Name:
- J/ApJS/229/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a detailed spectroscopic investigation of the interstellar aminoacetonitrile, a possible precursor molecule of glycine. Using a combination of Stark and frequency-modulation microwave and millimeter wave spectroscopies, we observed and analyzed the room-temperature rotational spectra of 29 excited states with energies up to 1000cm^-1^. We also observed the ^13^C isotopologues in the ground vibrational state in natural abundance (1.1%). The extensive data set of more than 2000 new rotational transitions will support further identifications of aminoacetonitrile in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1120
- Title:
- Rotational spectrum and DCOOCH_3_ in Orion
- Short Name:
- J/ApJ/714/1120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New centimeter-wave (7-80GHz) and submillimeter-wave (580-661GHz) spectra of a deuterated species of methyl formate (DCOOCH_3_) have been measured. Transitions with a maximum value of J=64 and K=36 have been assigned and fitted together with previous measurements. The internal rotation of this compound was treated using the so-called rho axis method (RAM). A total of 1703 transitions were fitted using this method. Only 24 parameters were employed in the final fit, which has an rms deviation of 94.2kHz. The dipole moment and the nuclear quadrupole coupling constants of the deuterated species have also been obtained. This new study has permitted a tentative detection of DCOOCH_3_ in Orion with the IRAM 30m telescope based on the observation of more than 100 spectral features with low blending effects among the 400 lines expected in the observed frequency domain (for which over 300 are heavily blended with other species). These 100 transitions are above noise and confusion limited without heavy blending and cannot be assigned to any other species. Moreover, none of the strongest unblended transitions is missing. The derived source-averaged total column density for DCOOCH_3_ is 7.8x10^14^cm^-2^ and the DCOOCH_3_/HCOOCH_3_ column density ratio varies between 0.02 and 0.06 in the different cloud components of Orion. This value is consistent with the deuteration enhancement found for other species in this cloud.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/315
- Title:
- Rotational spectrum of H^13^COOCH_3_
- Short Name:
- J/ApJS/190/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A compilation of the available spectroscopic millimeter- and submillimeter-wave data of the ground and first excited states of ^13^C_1_-methyl formate (H^13^COOCH_3_) has been carried out. The exhaustive analysis of the available transition lines of H^13^COOCH_3_ has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method (RAM) and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous H^13^COOCH_3_ spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new H^13^COOCH_3_ lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/42
- Title:
- Rotational spectrum of vinyl formate (CH_2_=CHOCHO)
- Short Name:
- J/ApJ/832/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous detections of methyl and ethyl formate make other small substituted formates potential candidates for observation in the interstellar medium. Among them, vinyl formate is one of the simplest unsaturated carboxylic ester. The aim of this work is to provide direct experimental frequencies of the ground vibrational state of vinyl formate in a large spectral range for astrophysical use. The room-temperature rotational spectrum of vinyl formate has been measured from 80 to 360GHz and analyzed in terms of Watson's semirigid rotor Hamiltonian. Two thousand six hundred transitions within J=3-88 and K_a_=0-28 were assigned to the most stable conformer of vinyl formate and a new set of spectroscopic constants was accurately determined. Spectral features of vinyl formate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of vinyl formate are provided.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A142
- Title:
- SDC G335.579-0.292 ALMA images and datacubes
- Short Name:
- J/A+A/645/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The infrared dark cloud (IRDC) SDC335.579-0.292 (hereafter, SDC335) is a massive (~5000 solar masses) star-forming cloud which has been found to be globally collapsing towards one of the most massive star forming cores in the Galaxy, which is located at its centre. SDC335 is known to host three high-mass protostellar objects at early stages of their evolution and archival ALMA Cycle 0 data (at ~5 arcsecond resolution) indicate the presence of at least one molecular outflow in the region detected in HNC. Observations of molecular outflows from massive protostellar objects allow us to estimate the accretion rates of the protostars as well as to assess the disruptive impact that stars have on their natal clouds during their formation. The aim of this work is to identify and analyse the properties of the protostellar-driven molecular outflows within SDC335 and use these outflows to help refine the properties of the young massive protostars in this cloud. We imaged the molecular outflows in SDC335 using new data from the Australia Telescope Compact Array (ATCA) of SiO and Class I CH_3_OH maser emission (at a resolution of ~3 arcsecond) alongside} observations of four CO transitions made with the Atacama Pathfinder EXperiment (APEX) and archival Atacama Large Millimeter/submillimeter Array (ALMA) CO, 13CO (~1 arcsecond), and HNC data. We introduced a generalised argument to constrain outflow inclination angles based on observed outflow properties. We then used the properties of each outflow to infer the accretion rates on the protostellar sources driving them. These accretion properties allowed us to deduce the evolutionary characteristics of the sources. Shock-tracing SiO emission and CH_3_OH Class I maser emission allowed us to locate regions of interaction between the outflows and material infalling to the central region via the filamentary arms of SDC335.
