Archive for neutron star

Weekly Update from the Open Journal of Astrophysics – 31/05/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , on May 31, 2025 by telescoper

Once again it’s time for the weekly Saturday morning update of papers published at the Open Journal of Astrophysics. Since the last update we have published five new papers, which brings the number in Volume 8 (2025) up to 67; the total so far published by OJAp has passed the 300 mark and is now up to 302. If we keep up at the same rate for the rest of the year as we did for the first five months now completed, we will publish around 160 papers altogether in 2025.

In chronological order of publication, the five papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is “Which is the most eccentric binary known? Insights from the 2023/4 pericenter passages of Zeta Boötis and Eta Ophiuchi” by Idel Waisberg, Ygal Klein and Boaz Katz (Weizmann Institute of Science, Israel).  This is a report of interferometric observations of two very eccentric binary star systems, published on Tuesday 27th May 2025 in the folder Solar and Stellar Astrophysics. The overlay is here:

You can read the final accepted version on arXiv here.

The second paper to report is “On the full non-Gaussian Surprise statistic and the cosmological concordance between DESI, SDSS and Pantheon+” by Pedro Riba Mello & Miguel Quartin (Universidade Federal do Rio de Janeiro, Brazil), and Bjoern Malte Schaefer & Benedikt Schosser (Heidelberg, Germany). This paper is in the folder Cosmology and NonGalactic Astrophysics and was published on Tuesday 27th May 2025. The paper presents an application of the “Surprise Statistic”, based on the Kullback-Leibler divergence, as a measure of the difference between results inferred from different data sets.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

The third paper we published last week, and our 300th overall, is “Cosmic Ray Feedback in Massive Halos: Implications for the Distribution of Baryons” by Eliot Quataert (Princeton, USA) and Philip F. Hopkins (Caltech, USA).  This was published on Thursday 29th May in the folder Cosmology and NonGalactic Astrophysics. The paper discusses the effects of cosmic rays produced by massive black holes on the structure of the baryonic component of galaxies and how these might affect cosmological parameter estimation. The overlay is here:

 

You can read the officially accepted version of this paper on arXiv here.

The next one to report is “Mixing neutron star material into the jets in the common envelope jets supernova r-process scenario” by Noam Soker (Technion, Israel). This was published on Thursday 27th May in the folder High-Energy Astrophysical Phenomena; it presents a discussion of the chemical enrichment of an evolved star consequent upon its ingestion of a neutron star.

The overlay is here:

You can find the officially accepted version on arXiv here.

Last, but by no means least, for this week we have “Dark Energy Survey Year 6 Results: Synthetic-source Injection Across the Full Survey Using Balrog” by Dhayaa Anbajagane (Kavli Institute, Chicago) et al. (81 authors) on behalf of the Dark Energy Survey Collaboration. It was also  published on Thursday 27th May  2025, but in the folder Cosmology and NonGalactic Astrophysics. It is about testing the Dark Energy Survey analysis pipeline using synthetic sources.

The overlay is here:

 

You can find the officially accepted version on arXiv here.

That’s all the papers for this week. I’ll post another update next weekend.

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Newsflash: another Neutron Star – Black Hole merger?

Posted in The Universe and Stuff with tags , , , , , on May 18, 2023 by telescoper
Fanciful “artist’s impression” of a Neutron Star – Black Hole merger (from last time).

It seems that the engineering data ahead of the imminent observing run from the newly refurbished LIGO gravitational wave observatory has just triggered an alert for astronomers to look for an electromagnetic counterpart. The code number for this candidate event is S230518h. If confirmed this could very well be another Neutron-Star – Black Hole merger event. The search area is rather large, with the 90% probability region being about 1002 square degrees on the sky:

For more details, see here.

I’m reminded about the excitement surrounding the first Neutron Star merger way back in 2017. In fact, rumours started to spread via this blog as people outside the LIGO/transient source community used a comments thread here to share information of where telescopes were looking. Those were the days. Was that really 6 years ago?

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What kind of thing is GW190814?

Posted in The Universe and Stuff with tags , , , , , , , on June 24, 2020 by telescoper

There’s been a lot of interest in the past day or two over an event that occurred in the LIGO detectors last August, entitled GW190814. A paper has appeared declaring this to be “the observation of a compact binary coalescence involving a 22.2–24.3 M ⊙ black hole and a compact object with a mass of 2.50–2.67 M ⊙“. That would be interesting of course because the smaller object is smaller than the black holes involved in previous detections and its mass suggests the possibility that it may be a neutron star, although no electromagnetic counterpart has yet been detected.  It’s a mystery.

I was quite excited when I saw the announcement about this yesterday but my enthusiasm was dampened a bit when I saw the data from the two LIGO detectors at Hanford and Livingston in the USA and the Virgo detector in Italy.

Visually, the Livingston detection seems reasonably firm, but the paper notes that there were thunderstorms in the area at the time of  GW190814 which affected the low-frequency data. There doesn’t look like anything at all but noise in the Virgo channel. The Hanford data may show something but, according to the paper, the detector was “not in nominal observing mode at the time of GW190814” so the data from this detector require special treatment. What you see in the Hanford channel looks rather similar to the two (presumably noise) features seen to the left in the Livingston plot.

I know that – not for the first time – I’m probably going to incur the wrath of my colleagues in the gravitational waves community but I have to sound a note of caution. Before asking whether the event involves a black hole or a neutron star you have to be convinced that the event is an event at all.  Fortunately, at least some of the data relating to this have been released and will no doubt be subjected to independent scrutiny.

Now I’m going to retreat into my bunker and hide from the inevitable comments…

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