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Thoughts on the article MNRAS Vol. 443 474-484

Padovani and Resconi

Antoine KouchnerANTARES call, September 4th 2014

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Goal

• Find plausible astronomical counterparts in the GeV – TeV bands by looking for sources in the available large area high-energy γ -ray catalogues within the error circles of the IceCube events.

• Each IC event is treated independently and a flux associated is computed: “derived the flux per neutrino event assuming that the observed flux is spread over 1 dex in energy and that the spectrum is f(v) a v-1 (equivalent to dN/dE a E−2)

• All flavour flux? Guess so.

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Neutrino flux

• “Effective areas from the IceCube northern or southern hemisphere (depending on declination) and a live time of detection of 988 days (IceCube Collaboration 2014) were also used.”

• IceCube Collaboration, 2014, Physical Review Letters, submitted (arXiv:1405.5303)

• (Effective areas are in http://icecube.wisc.edu/science/data/HE-nu-2010-2012)

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Simplistic approach

• “We then performed an ‘energetic’ diagnostic by checking if a simple extrapolation succeeded in connecting the most energetic g-rays to the IceCube neutrino in the hybrid SED, taking into account the rather large uncertainty in the flux of the latter. If this was the case we considered the source to be a probable counterpart. Otherwise, we discarded the object.”

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Selected successful events

RA DEC

ANTARES looked for it (S. Adrian-Martinez et al., Astrophys. J. Lett. 786 L5, 2014 ) IceCube looked for it (Aartsen M. G., et al., 2013, ApJ, 779, 132)

Should we add in ANTARES list source, the one with dec<0 that we did not look at?

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Example of energetic diagnostic

Matchwhen correctedfor absorption

No Match

Nota: conversion from 10-11 erg cm-2 s-1 to 10-8 GeV (typo?)

ANTARES 90%CL limit (nm)

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Inferred Neutrino flux validity?• “For completeness, we have also checked that our neutrino fluxes

are consistent with the IceCube upper limits provided by Aartsen et al. (2013) (see their Tab. 2 and 3) assuming an E−2 (v−1) spectrum. This is especially important for the northern sources, where the neutrino non detections are particularly stringent and at the level of the fluxes here derived (within the rather larger error bars). If the proposed counterparts in Tab. 4 are indeed neutrino sources, this suggests that a direct detection by IceCube is within reach.”

• Really? What about Mkn421 and MGRO J1908+06?• No reference to ANTARES (nor to KM3NeT) in the paper !• Beware that in the upper limits from Antares and IC are given per

favour (nu_mu) while the fluxes associated to each IC event in the paper is probably all flavour… So IC and ANTARES limits should be multiplied by 3 for consistency

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Mkn 421 IC 90%CL limit (nm)

MGRO J1908 IC 90%CL limit (nm)

I would conclude that neither Mkn421 nor MGROJ1908can be responsible for the IC event? But factor 3…

ANTARES 90%CL limit (nm)

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ANTARES 90%CL limit (nm)

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My conclusions

• Can the extension of the source reconcile the neutrino fluxes and the upper limits?

• Or the energy range? But then the ‘energetic’ diagnostic becomes somewhat meaningless (and therefore the point of the paper)

• Should we add some interesting sources to the ANTARES list? Maybe even make a dedicated analysis for them, including the gamma shape spectrum and extension

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On the article “Neutrino Lighthouse

at Sagittarius A*” Y. Bai et al, arXiv:1407.2243

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abstract

• “investigate whether a subset of high-energy events observed by IceCube may be due to neutrinos from Sagittarius A*”.

• “Event 25 has a time very close to (around three hours after) the brightest X-ray are of Sagittarius A* observed by the Chandra X-ray Observatory (p-value of 0.9%). Furthermore, two of the seven events occurred within one day of each other (p-value 1.6% for a random distribution in time)”.

“smoking gun that Sagittarius A* is a point source of very high energy neutrinos”

ANTARES limits from the GC is not quoted (no mention of ANTARES)

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The IC events

“9 (7) IC NU events that are positionally consistent with the GC”: dark (light) blue shaded region within 30 (45) from the GC

ANTARES excludes a steady emission from GC

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Sgr A*

• “Sgr A* undergoes bursts of rapid variability in X-rays and gamma-rays; it is not visible in the optical and UV, and even in X-rays it is very dim”

• “To the best of our knowledge, precise theoretical calculations of the expected NU from Sgr A* have not been made”.

• “Most of the time Sgr A* emits at low luminosity, but in its flares the brightness increases are a hundred-fold. It is the giant flares of Sgr A* that are of prime interest in seeing if there is an association with IC events”

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Ex: Swift flares

“Because of the complex dynamics of the processes at the GC with X-rays of electromagnetic origin and NUs of hadronic origin, the somewhat inexact time coincidence of the X-ray activity and NU signal may not be surprising”

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Time clustering?

Small p-values for such a time distributionof the 7 events

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Conclusions• We proposed that the timings of IC NU events from Sgr A* are

sometimes correlated with the observed photon flaring in X-rays at the GC. In particular, we consider the timing and approximate positional coincidences of IC #25 and Chandra #14392 as an indicator that Sgr A* is the source of IC #25.

• We also investigated the idea that NU bursts from Sgr A* occur.• Unusual outbursts could serendipitously arise from disruptions of

asteroids, comets, planets or stars that approach the SMBH. A gas cloud of Earth-mass, called G2, is approaching Sgr A* [69, 70]. The trajectory of G2 is predicted to reach the pericenter of the orbit in 2014. It will be especially interesting if any high-energy NU events from Sgr A* occur that can be associated with its passage.°If our latest PS limit from the GC is not restrictive enough, we could make a dedicated study

during the flares mentioned to rule out this interpretation. (But what time window?)Were we taking data at that time? If yes, probably ruled out already.° Test time coincidence of our events close in space to IC events with these IC events.