Archive for July 26, 2016

#LeaveTheDark: Easy social media shares

Posted in Uncategorized on July 26, 2016 by telescoper

My blog may be called “In The Dark” but that won’t stop me sharing this.

#LeaveTheDark

Yesterday we had a request for a shareable summary of the #LeaveTheDark manifesto. That’s quite difficult to do in brief. There’s a lot to it. A more complete manifesto will follow within the next few days.

But in the meantime we thought these little images might be helpful for people who’d like to spread the word a bit. There’s no issue with copyright or anything like that. We want and need people to share our stuff. That’s the only way we’ll reach enough people to turn last week’s idea into next year’s reality! And we will make this a reality.

So feel free to download and share these images across your networks. The more the merrier…

Leavethedark we are that movement we believe.pngleaveTheDark join us we are memeleaveTheDark Join us we need

Thankyou! Together we really can make a difference and turn back the growing swell of hatred that threatens to engulf our society.

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The 3.5 keV “Line” that (probably) wasn’t…

Posted in Bad Statistics, The Universe and Stuff with tags , , , , , , , on July 26, 2016 by telescoper

About a year ago I wrote a blog post about a mysterious “line” in the X-ray spectra of galaxy clusters corresponding to an energy of around 3.5 keV. The primary reference for the claim is a paper by Bulbul et al which is, of course, freely available on the arXiv.

The key graph from that paper is this:

XMMspectrum

The claimed feature – it stretches the imagination considerably to call it a “line” – is shown in red. No, I’m not particularly impressed either, but this is what passes for high-quality data in X-ray astronomy!

Anyway, there has just appeared on the arXiv a paper by the Hitomi Collaboration describing what are basically the only set of science results that the Hitomi satellite managed to obtain before it fell to bits earlier this year. These were observations of the Perseus Cluster.

Here is the abstract:

High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E=3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported flux level. The high flux derived with XMM MOS for the Perseus region covered by Hitomi is excluded at >3-sigma within the energy confidence interval of the most constraining previous study. If XMM measurement uncertainties for this region are included, the inconsistency with Hitomi is at a 99% significance for a broad dark-matter line and at 99.7% for a narrow line from the gas. We do find a hint of a broad excess near the energies of high-n transitions of Sxvi (E=3.44 keV rest-frame) – a possible signature of charge exchange in the molecular nebula and one of the proposed explanations for the 3.5 keV line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.

And here is the killer plot:

Perseus_Hitomi

The spectrum looks amazingly detailed, which makes the demise of Hitomi all the more tragic, but the 3.5 keV is conspicuous by its absence. So there you are, yet another supposedly significant feature that excited a huge amount of interest turns out to be nothing of the sort. To be fair, as the abstract states, the anomalous line was only seen by stacking spectra of different clusters and might still be there but too faint to be seen in an individual cluster spectrum. Nevertheless I’d say the probability of there being any feature at 3.5 keV has decreased significantly after this observation.

P.S. rumours suggest that the 750 GeV diphoton “excess” found at the Large Hadron Collider may be about to meet a similar fate.

2016 ‘Beards, Shorts & Sandals’ season reaches peak

Posted in Beards on July 26, 2016 by telescoper

The Great Question of the day..

Kmflett's Blog

Beard Liberation Front

26th July Contact Keith Flett 07803 167266

2016 ‘BEARDS, SHORTS & SANDALS’ SEASON REACHES PEAK

corbynsandals

BLF permission given for official engagements only

The Beard Liberation Front, the informal network of beard wearers, has said that the 2016 Beards, Shorts and Sandals season has reached its peak in the recent warm weather in some parts of the UK.

The campaigners say that with temperatures well above 20C in some places the rise in the wearing of beards, shorts and sandals has been significant

Shorts and sandals may be worn all day until 9pm at the discretion of the wearer.

The campaigners say that the image of organic beard, shorts and sandals is one of the key male fashions of 2016 not just in Hackney and Dalston but across large parts of the UK as fashions change and develop.

The official season traditionally runs until August 31st. During…

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