Mechanical Cherry Harvesting

Markwardt, E. D.; Guest, R. W.; Cain, John C.; LaBelle, R. L.

doi:10.13031/2013.40699

Cited by 33 publications

(14 citation statements)

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“…The object Swift J1644+57 was found as both a source of X-rays and γ-rays by the Swift satellite, and thought initially to be a gamma-ray burst (GRB) (Markwardt et al 2011). However, the variability and longevity of the source soon proved that such an association was unlikely, and the proximity of the event to the nucleus of a host galaxy at redshift z = 0.354 led to the belief that the event was triggered by a TDE (Levan et al 2011).…”

Section: Swift J1644+57mentioning

confidence: 99%

Hyperaccretion During Tidal Disruption Events: Weakly Bound Debris Envelopes and Jets

Coughlin

Begelman

2014

ApJ

149

161

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After the destruction of the star during a tidal disruption event (TDE), the cataclysmic encounter between a star and the supermassive black hole (SMBH) of a galaxy, approximately half of the original stellar debris falls back onto the hole at a rate that can initially exceed the Eddington limit by orders of magnitude. We argue that the angular momentum of this matter is too low to allow it to attain a disk-like configuration with accretion proceeding at a mildly super-Eddington rate, the excess energy being carried away by a combination of radiative losses and radially distributed winds. Instead, we propose that the infalling gas traps accretion energy until it inflates into a weakly-bound, quasispherical structure with gas extending nearly to the poles. We study the structure and evolution of such "Zero-Bernoulli accretion" flows (ZEBRAs) as a model for the super-Eddington phase of TDEs. We argue that such flows cannot stop extremely super-Eddington accretion from occurring, and that once the envelope is maximally inflated, any excess accretion energy escapes through the poles in the form of powerful jets. We compare the predictions of our model to Swift J1644+57, the putative super-Eddington TDE, and show that it can qualitatively reproduce some of its observed features. Similar models, including self-gravity, could be applicable to gamma-ray bursts from collapsars and the growth of supermassive black hole seeds inside quasi-stars.

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Section: Swift J1644+57mentioning

confidence: 99%

Hyperaccretion During Tidal Disruption Events: Weakly Bound Debris Envelopes and Jets

Coughlin

Begelman

2014

ApJ

149

161

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“…A series of frames using polarizers with exposures growing from 10 s to 180 s were obtained over the next four hours (see table 4 of Gorbovskoy et al (2012a)). The duration of the GRB in the gamma-rays was T 90 = (114±1.6) s (Markwardt et al, 2010). Thus, the first three frames of the series were obtained simultaneously with the GRB.…”

Section: Grb100906amentioning

confidence: 99%

Optical polarization observations with the MASTER robotic net

et al. 2014

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We present results of optical polarization observations performed with the MASTER robotic net for three types of objects: gamma-ray bursts, supernovae, and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A, polarization observations were obtained during very early stages of optical emission. For GRB100906A it was the first prompt optical polarization observation in the world. Photometry in polarizers is presented for Type Ia Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the linear polarization of SN 2012bh at the early stage of the envelope expansion was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3, QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer the degree of the linear polarization and polarization angle. The blazars OC 457 and 3C 454.3 were observed during their periods of activity. The results show that MASTER is able to measure substantially polarized light; at the same time it is not suitable for determining weak polarization (less than 5%) of dim objects (fainter than 16$^m$). Polarimetric observations of the optical emission from gamma-ray bursts and supernovae are necessary to investigate the nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been correcte

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“…For most AMXPs, the duty cycle is a few weeks of outburst every few years. Taking into account the recent (2009 August and September respectively) discoveries of NGC 6440 X-2 Heinke et al 2009) and IGR J17511−305 (Markwardt et al 2009;Bozzo et al 2010), there are currently twelve known AMXPs (Wijnands et al 2008). Observationally, these systems have orbital periods of P orb ∼ 40 minutes -4 hours.…”

Section: Accreting Milli-second X-ray Pulsarsmentioning

confidence: 99%

“…This made it the fastest known AMXP (and the 6th one to be discovered). A sinusoidal frequency modulation of 147.4 minutes (2.46 hours) found in X-ray (by RXTE) was interpreted as the orbital period and no evidence of X-ray eclipses was present (Markwardt et al 2004b). The fast X-ray variability was stronger and had lower characteristic frequencies than any other neutron star LMXB, being more similar to that of black hole systems (Linares et al 2007).…”

Section: The Accreting Milli-second X-ray Pulsar Igr J00291+5934mentioning

confidence: 99%

The double-peaked 2008 outburst of the accreting milli-second X-ray pulsar, IGR J00291+5934

Lewis

Russell

Jonker

et al. 2010

A&A

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Context. In August 2008, the accreting milli-second X-ray pulsar (AMXP), IGR J00291+5934, underwent an outburst lasting ∼100 days, the first since its discovery in 2004. Aims. We present data from the 2008 double-peaked outburst of IGR J00291+5934 from Faulkes Telescope North, the Isaac Newton Telescope, the Keck Telescope, PAIRITEL, the Westerbork Synthesis Radio Telescope and the Swift, XMM-Newton and RXTE X-ray missions. We study the outburst's evolution at various wavelengths, allowing us to probe accretion physics in this AMXP. Methods. We study the light curve morphology, presenting the first radio-X-ray spectral energy Distributions (SEDs) for this source and the most detailed UV-IR SEDs for any outbursting AMXP. We show simple models that attempt to identify the emission mechanisms responsible for the SEDs. We analyse short-timescale optical variability, and compare a medium resolution optical spectrum with those from 2004. Results. The outburst morphology is unusual for an AMXP, comprising two peaks, the second containing a "plateau" of ∼10 days at maximum brightness within 30 days of the initial activity. This has implications on duty cycles of short-period X-ray transients. The X-ray spectrum can be fitted by a single, hard power-law. We detect optical variability of ∼0.05 mag, on timescales of minutes, but find no periodic modulation. In the optical, the SEDs contain a blue component, indicative of an irradiated disc, and a transient near-infrared (NIR) excess. This excess is consistent with a simple model of an optically thick synchrotron jet (as seen in other outbursting AMXPs), however we discuss other potential origins. The optical spectrum shows a double-peaked Hα profile, a diagnostic of an accretion disc, but we do not clearly see other lines (e.g. He I, II) that were reported in 2004. Conclusions. Optical/IR observations of AMXPs appear to be excellent for studying the evolution of both the outer accretion disc and the inner jet, and may eventually provide us with tight constraints to model disc-jet coupling in accreting neutron stars.

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Mechanical Cherry Harvesting

Cited by 33 publications

References 0 publications

Hyperaccretion During Tidal Disruption Events: Weakly Bound Debris Envelopes and Jets

Hyperaccretion During Tidal Disruption Events: Weakly Bound Debris Envelopes and Jets

Optical polarization observations with the MASTER robotic net

The double-peaked 2008 outburst of the accreting milli-second X-ray pulsar, IGR J00291+5934

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