scholarly journals The precessing jets of classical nova YZ Reticuli

2021 ◽  
Vol 503 (1) ◽  
pp. 704-714
Author(s):  
Dominic McLoughlin ◽  
Katherine M Blundell ◽  
Steven Lee ◽  
Chris McCowage
Keyword(s):  
Rapid Evolution ◽  
Accretion Disc ◽  
Line Of Sight ◽  
Central Component ◽  
Time Resolved ◽  
Spectral Signatures ◽  
Classical Novae ◽  
Classical Nova ◽  
Large Perturbation ◽  
Evolution With Time

ABSTRACT The classical nova YZ Reticuli was discovered in 2020 July. Shortly after this, we commenced a sustained, highly time-sampled coverage of its subsequent rapid evolution with time-resolved spectroscopy from the Global Jet Watch observatories. Its H-alpha complex exhibited qualitatively different spectral signatures in the following weeks and months. We find that these H-alpha complexes are well described by the same five Gaussian emission components throughout the six months following eruption. These five components appear to constitute two pairs of lines, from jet outflows and an accretion disc, together with an additional central component. The correlated, symmetric patterns that these jet/accretion disc pairs exhibit suggest precession, probably in response to the large perturbation caused by the nova eruption. The jet and accretion disc signatures persist from the first 10 d after brightening – evidence that the accretion disc survived the disruption. We also compare another classical nova (V6568 Sgr) that erupted in 2020 July whose H-alpha complex can be described analogously, but with faster line-of-sight jet speeds exceeding 4000 km s−1. We suggest that classical novae with higher mass white dwarfs bridge the gap between recurrent novae and classical novae such as YZ Reticuli.

First Demonstration of an Acousto-Optically Modulated Quantum Cascade Laser As a Broadband, Time-Resolved Combustion Diagnostic

2018 ◽  
Author(s):  
Zachary E. Loparo ◽  
Kareem Ahmed ◽  
Subith S. Vasu ◽  
Andrey V. Muraviev ◽  
Pedro Figueiredo ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Gas Turbines ◽  
Chemical Kinetic ◽  
Single Line ◽  
Line Of Sight ◽  
Spectral Measurements ◽  
Time Resolved ◽  
Quantum Cascade ◽  
No Formation ◽  
Multiple Species

We provide the first demonstration of an acousto-optically modulated quantum cascade laser (AOM QCL) system as a diagnostic for combustion by measuring nitric oxide (NO), a highly-regulated emission produced in gas turbines. The system provides time-resolved broadband spectral measurements of the present gas species via a single line of sight measurement, offering advantages over widely used narrowband absorption spectroscopy (e.g., the potential for simultaneous multi-species measurements using a single laser) and considerably faster (> 15kHz rates and potentially up to MHz) than sampling techniques which employ FTIR or GC/MS. The developed AOM QCL system yields fast tunable output covering a spectral range of 1725–1930 cm−1 with a linewidth of 10–15 cm−1. For the demonstration experiment, the AOM QCL system has been used to obtain time-resolved spectral measurements of NO formation during the shock heating of mixture of a 10% nitrous oxide (N2O) in a balance of argon over a temperature range of 1245–2517 K and a pressure range of 3.6–5.8 atm. Results were in good agreement with chemical kinetic simulations. The system shows revolutionary promise for making simultaneous time-resolved measurements of multiple species concentrations and temperature with a single line of sight measurement.

scholarly journals Chromatic Amplitudes and Line-of-Sight Velocity Variations for the Pulsating DB White Dwarf GD 358

2002 ◽  
Vol 185 ◽  
pp. 380-381
Author(s):  
R. Kotak
Keyword(s):  
Optical Spectroscopy ◽  
White Dwarf ◽  
Line Of Sight ◽  
Time Resolved ◽  
Preliminary Results ◽  
Velocity Variations

AbstractWe report on preliminary results from time-resolved optical spectroscopy of the He-rich variable white dwarf GD 358.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

Shock Tube Demonstration of Acousto-Optically Modulated Quantum Cascade Laser as a Broadband, Time-Resolved Combustion Diagnostic

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Zachary E. Loparo ◽  
Andrey V. Muraviev ◽  
Pedro Figueiredo ◽  
Arkadiy Lyakh ◽  
Robert E. Peale ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Gas Turbines ◽  
Chemical Kinetic ◽  
Single Line ◽  
Line Of Sight ◽  
Spectral Measurements ◽  
Time Resolved ◽  
Quantum Cascade ◽  
No Formation ◽  
Multiple Species

We provide the first demonstration of an acousto-optically modulated quantum cascade laser (AOM QCL) system as a diagnostic for combustion by measuring nitric oxide (NO), a highly regulated emission produced in gas turbines. The system provides time-resolved broadband spectral measurements of the present gas species via a single line of sight measurement, offering advantages over widely used narrowband absorption spectroscopy (e.g., the potential for simultaneous multispecies measurements using a single laser) and considerably faster (>15 kHz rates and potentially up to MHz) than sampling techniques, which employ fourier transform infrared (FTIR) or GC/MS. The developed AOM QCL system yields fast tunable output covering a spectral range of 1725–1930 cm−1 with a linewidth of 10–15 cm−1. For the demonstration experiment, the AOM QCL system has been used to obtain time-resolved spectral measurements of NO formation during the shock heating of mixture of a 10% nitrous oxide (N2O) in a balance of argon over a temperature range of 1245–2517 K and a pressure range of 3.6–5.8 atm. Results were in good agreement with chemical kinetic simulations. The system shows revolutionary promise for making simultaneous time-resolved measurements of multiple species concentrations and temperature with a single line of sight measurement.

scholarly journals Detection of a double-peaked H α component from the accretion disc of NGC 4958

2019 ◽  
Vol 486 (1) ◽  
pp. 1138-1145
Author(s):  
T V Ricci ◽  
J E Steiner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Outer Radius ◽  
Accretion Disc ◽  
Line Of Sight ◽  
Broad Component ◽  
Line Region ◽  
Inner Radius ◽  
The Galaxy ◽  
Narrow Line Region

Abstract Active Galactic Nuclei are objects associated with the presence of an accretion disc around supermassive black holes found in the very central region of galaxies with a well-defined bulge. In the optical range of the spectrum, a possible signature of the accretion disc is the presence of a broad double-peaked component that is mostly seen in H α. In this paper, we report the detection of a double-peaked feature in the H α line in the nucleus of the galaxy NGC 4958. The narrow-line region of this object has an emission that is typical of a low-ionization nuclear emission-line region galaxy, which is the usual classification for double-peaked emitters. A central broad component, related to the broad-line region of this object, is seen in H α and also in H β. We concluded that the double-peaked emission is emitted by a circular relativistic Keplerian disc with an inner radius ξi  = 570 ± 83, an outer radius ξo  = 860 ± 170 (both in units of GMSMBH/c2), an inclination to the line of sight i = 27.2 ± 0.7° and a local broadening parameter σ  = 1310 ± 70 km s−1.

scholarly journals VVV-WIT-01: highly obscured classical nova or protostellar collision?

2020 ◽  
Vol 492 (4) ◽  
pp. 4847-4857
Author(s):  
P W Lucas ◽  
D Minniti ◽  
A Kamble ◽  
D L Kaplan ◽  
N Cross ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Single Event ◽  
Dark Cloud ◽  
Continuum Source ◽  
Classical Novae ◽  
Classical Nova ◽  
Low Mass ◽  
Compact Array

ABSTRACT A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H − Ks = 5.2). It peaked before March 2010, then faded by ∼9.5 mag over the following 2 yr. The 1.6–22 μm spectral energy distribution in March 2010 was well fit by a highly obscured blackbody with T ∼ 1000 K and $A_{K_s} \sim 6.6$ mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062−0.294. The chance projection probability is small for any single event (p ≈ 0.01–0.02), which suggests a physical association, e.g. a collision between low mass protostars. However, blackbody emission at T ∼ 1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve due to condensation of dust ∼30–60 d after the explosion. Radio follow-up with the Australia Telescope Compact Array detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p = 0.13–0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.

scholarly journals The Variable Ṁ Scenario for Nova Outbursts

1987 ◽  
Vol 93 ◽  
pp. 419-429
Author(s):  
A. Kovetz ◽  
D. Prialnik ◽  
M.M. Shara
Keyword(s):  
Mass Transfer ◽  
High Rate ◽  
Transfer Rates ◽  
Classical Novae ◽  
Binary Separation ◽  
Classical Nova ◽  
The One ◽  
Thermonuclear Runaway ◽  
Mass Ejection ◽  
Nova Outbursts

AbstractAn evolutionary scenario for classical novae is proposed, which is intended to solve the discrepancies that exist between theory and observations: the space densities of classical novae deduced from surveys in the solar neighbourhood are lower by about two orders of magnitude than those predicted theoretically, and the mass transfer rates in nova binaries, as estimated from observed luminosities in quiescence, are higher than those allowed by the thermonuclear runaway model for nova outbursts. These discrepancies disappear if mass transfer (at a high rate) takes place for only a few hundred years before and a few hundred years after an eruption, but declines afterwards and remains off for most of the time between outbursts. We show that such a behavior is to be expected if one takes into account the variation of binary separation, due to mass ejection on the one hand and angular momentum losses on the other hand.One of the aspects of this scenario, on which we report in more detail, is the possibility of enhanced Roche-lobe overflow of the secondary, due to its expansion that results from irradiation by the high nova luminosity. We followed the evolution of a 0.5M⊙ main sequence star illuminated by a changing flux, typical of a classical nova. The numerical results indicate that, in spite of the slight binary separation that may occur after eruption, mass loss from the irradiated and thus bloated secondary should continue for a few hundred years. Other aspects of the variable Ṁ scenario are briefly summarized.

scholarly journals A dataset for benchmarking time-resolved non-line-of-sight imaging

2019 ◽  
Author(s):  
Miguel Galindo ◽  
Julio Marco ◽  
Matthew O'Toole ◽  
Gordon Wetzstein ◽  
Diego Gutierrez ◽  
...  
Keyword(s):  
Line Of Sight ◽  
Time Resolved ◽  
Non Line Of Sight

scholarly journals The binary millisecond pulsar PSR J1023+0038 – II. Optical spectroscopy

2019 ◽  
Vol 488 (1) ◽  
pp. 198-212 ◽  
Author(s):  
T Shahbaz ◽  
M Linares ◽  
P Rodríguez-Gil ◽  
J Casares
Keyword(s):  
Radial Velocity ◽  
Optical Spectroscopy ◽  
State Transition ◽  
High Energy ◽  
Accretion Disc ◽  
Millisecond Pulsar ◽  
Mass Ratio ◽  
Time Resolved ◽  
Type Change ◽  
Model Predictions

ABSTRACT We present time-resolved optical spectroscopy of the ‘redback’ binary millisecond pulsar system PSR J1023+0038 during both its radio pulsar (2009) and accretion disc states (2014 and 2016). We provide observational evidence for the companion star being heated during the disc state. We observe a spectral type change along the orbit, from ∼G5 to ∼F6 at the secondary star’s superior and inferior conjunction, respectively, and find that the corresponding irradiating luminosity can be powered by the high-energy accretion luminosity or the spin-down luminosity of the neutron star. We determine the secondary star’s radial velocity semi-amplitude from the metallic (primarily Fe and Ca) and Hα absorption lines during these different states. The metallic and Hα radial velocity semi-amplitude determined from the 2009 pulsar-state observations allows us to constrain the secondary star’s true radial velocity K2 = 276.3 ± 5.6  km s−1 and the binary mass ratio q = 0.137 ± 0.003. By comparing the observed metallic and Hα absorption-line radial velocity semi-amplitudes with model predictions, we can explain the observed semi-amplitude changes during the pulsar state and during the pulsar/disc-state transition as being due to different amounts of heating and the presence of an accretion disc, respectively.

scholarly journals Cataclysmic variables as possible counterparts of ancient Far Eastern guest stars

2020 ◽  
Vol 494 (4) ◽  
pp. 5775-5786 ◽  
Author(s):  
Susanne M Hoffmann ◽  
Nikolaus Vogt
Keyword(s):  
Cataclysmic Variables ◽  
Supplementary Information ◽  
Future Research ◽  
Historical Events ◽  
Significant Excess ◽  
Classical Novae ◽  
Classical Nova ◽  
Intermediate Polars ◽  
Far Eastern

ABSTRACT Continuing our efforts to select possible classical nova candidates among Far Eastern guest stars and to identify them with modern cataclysmic variables (CVs), we present a search for counterparts in 24 promising areas of the sky corresponding to ancient observations between 204 bce and 1690 ce. These areas were derived by us in a previous paper. Based on the physical entities of the CVs in our areas and reasonable magnitude limits compatible with the distribution of known eruption amplitudes of telescopic classical novae, we present a catalogue of a total of 80 CVs and related targets that could possibly have caused the historical sightings. This list could potentially be reduced by additionally discussing further information such as brightness or duration. In some cases, we present a detailed discussion of the interpretation of ancient sources comparing them with properties of the brightest CVs in the field. In order to estimate whether this list is representative, we discuss the distribution of CV types in our catalogue of counterparts for the historical events. Compared to the entire sky, the surface densities of most CV subtypes in our search fields reveal similar values, except for polars and intermediate polars, i.e. strongly magnetic CVs, for which a significant excess in our search fields was detected. Finally, we give an outlook towards future research in this topic, and provide in the online supplementary information a complete atlas of the celestial maps of all 24 guest star events, displaying the search areas and locations of CVs within them.

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