Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe double-peaked radio light curve of PTF11qcj
102
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present continued radio follow-up observations of PTF11qcj, a highly energetic broad-lined Type Ic supernova (SN), with a radio peak luminosity comparable to that of the $gamma$-ray burst (GRB) associated SN 1998bw. The latest observations, carried out with the Karl G. Jansky Very Large Array (VLA), extend up to $sim$5 years after the PTF11qcj optical discovery. The radio light curve shows a double-peak profile, possibly associated with density variations in the circumstellar medium (CSM), or with the presence of an off-axis GRB jet. Optical spectra of PTF11qcj taken during both peaks of the radio light curve do not show the broad H$alpha$ features typically expected from H-rich circumstellar interaction. Modeling of the second radio peak within the CSM interaction scenario requires a flatter density profile and an enhanced progenitor mass-loss rate compared to those required to model the first peak. Although our radio data alone cannot rule out the alternative scenario of an off-axis GRB powering the second radio peak, the implied off-axis GRB parameters are unusual compared to typical values found for cosmological long GRBs. Deep X-ray observations carried out around the time of the second radio peak could have helped distinguish between the density variation and off-axis GRB scenarios. Future VLBA measurements of the PTF11qcj radio ejecta may unambiguously rule out the off-axis GRB jet scenario.
rate research
Read More
We present observations made with the Australia Telescope Compact Array (ATCA), the Jansky Very Large Array (JVLA) and the Giant Metre-Wave Telescope of the radio source within the galaxy WISE~J071634.59-190039.2, claimed to be host of FRB~150418 by Keane et al. (2016). We have established a common flux density scale between the ATCA and JVLA observations, the main result of which is to increase the flux densities obtained by Keane et al. At a frequency of 5.5 GHz, the source has a mean flux density of 140uJy and is variable on short timescales with a modulation index of 0.36. Statistical analysis of the flux densities shows that the variations seen are consistent with refractive interstellar scintillation of the weak active galactic nucleus at the centre of the galaxy. It may therefore be the case that the FRB and the galaxy are not associated. However, taking into account the rarity of highly variable sources in the radio sky, and our lack of knowledge of the progenitors of FRBs as a class, the association between WISE~J071634.59-190039.2 and FRB~150418 remains a possibility.
The dominant radioactive energy source powering Type Ia supernova light curves is expected to switch from the decay of $^{56}$Co to $^{57}$Co at very late epochs. We use archival HST images of SN1992A obtained more than 900 days after explosion to constrain its cobalt isotopic abundance ratio and compare it to the well-studied event SN2011fe. We confirm the $^{57}$Co / $^{56}$Co ratio for SN2011fe of $0.026pm 0.004$ found by arXiv:1608.01155, consistent with a double degenerate progenitor scenario. For SN1992A, we find a ratio of $0.034pm 0.010$, but the large uncertainty does not allow us to differentiate between progenitor models
We revisit the evidence for the contribution of the long-lived radioactive nuclides 44Ti, 55Fe, 56Co, 57Co, and 60Co to the UVOIR light curve of SN 1987A. We show that the V-band luminosity constitutes a roughly constant fraction of the bolometric luminosity between 900 and 1900 days, and we obtain an approximate bolometric light curve out to 4334 days by scaling the late time V-band data by a constant factor where no bolometric light curve data is available. Considering the five most relevant decay chains starting at 44Ti, 55Co, 56Ni, 57Ni, and 60Co, we perform a least squares fit to the constructed composite bolometric light curve. For the nickel isotopes, we obtain best fit values of M(56Ni) = (7.1 +- 0.3) x 10^{-2} Msun and M(57Ni) = (4.1 +- 1.8) x 10^{-3} Msun. Our best fit 44Ti mass is M(44Ti) = (0.55 +- 0.17) x 10^{-4} Msun, which is in disagreement with the much higher (3.1 +- 0.8) x 10^{-4} Msun recently derived from INTEGRAL observations. The associated uncertainties far exceed the best fit values for 55Co and 60Co and, as a result, we only give upper limits on the production masses of M(55Co) < 7.2 x 10^{-3} Msun and M(60Co) < 1.7 x 10^{-4} Msun. Furthermore, we find that the leptonic channels in the decay of 57Co (internal conversion and Auger electrons) are a significant contribution and constitute up to 15.5% of the total luminosity. Consideration of the kinetic energy of these electrons is essential in lowering our best fit nickel isotope production ratio to [57Ni/56Ni]=2.5+-1.1, which is still somewhat high but is in agreement with gamma-ray observations and model predictions.
We present optical, radio, and X-ray observations of SN2020bvc (=ASASSN20bs; ZTF20aalxlis), a nearby ($z=0.0252$; $d$=114 Mpc) broad-lined (BL) Type Ic supernova (SN). Our observations show that SN2020bvc shares several properties in common with the Ic-BL SN2006aj, which was associated with the low-luminosity gamma-ray burst (LLGRB) 060218. First, the 10 GHz radio light curve is on the faint end of LLGRB-SNe ($L_mathrm{radio} approx 10^{37}$erg/s): we model our VLA observations (spanning 13-43 d) as synchrotron emission from a mildly relativistic ($v gtrsim 0.3c$) forward shock. Second, with Swift and Chandra we detect X-ray emission ($L_X approx 10^{41}$erg/s) that is not naturally explained as inverse Compton emission or as part of the same synchrotron spectrum as the radio emission. Third, high-cadence ($6times$/night) data from the Zwicky Transient Facility (ZTF) shows a double-peaked optical light curve, the first peak from shock-cooling emission from extended low-mass material (mass $M<10^{-2} M_odot$ at radius $R>10^{12}$cm) and the second peak from the radioactive decay of Ni-56. SN2020bvc is the first confirmed double-peaked Ic-BL SN discovered without a GRB trigger, and shows X-ray and radio emission similar to LLGRB-SNe: this is consistent with models in which the same mechanism produces both the LLGRB and the shock-cooling emission. For four of the five other nearby ($zlesssim0.05$) Ic-BL SNe with ZTF high-cadence data, we rule out a first peak like that seen in SN2006aj and SN2020bvc, i.e. that lasts $approx 1$d and reaches a peak luminosity $M approx -18$. X-ray and radio follow-up observations of future such events will establish whether double-peaked optical light curves are indeed predictive of LLGRB-like X-ray and radio emission.
The quasar SDSS J153636.22+044127.0, exhibiting peculiar broad emission-line profiles with multiple components, was proposed as a candidate sub-parsec binary supermassive black hole system. More recently, imaging revealed two spatially distinct sources, leading some to suggest the system to be a quasar pair separated by ~5 kpc. We present Palomar and Keck optical spectra of this system from which we identify a third velocity component to the emission lines. We argue that the system is more likely an unusual member of the class of active galactic nuclei (AGNs) known as double-peaked emitters than a sub-parsec black hole binary or quasar pair. We find no significant velocity evolution of the two main peaks over the course of 0.95 yr, with a 3-sigma upper limit on any secular change of 70 km/s/yr. We also find that the three velocity components of the emission lines are spatially coincident to within 0.015 along the slit, apparently ruling out the double-quasar hypothesis.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
