High Energy Network (HEN)

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Information on the observation and analysis of stars and other objects that are sources of x-rays and gamma rays.

59 289 By Bikeman 1 week 6 days ago

Observing optical transients from Astro-COLIBRI alerts

American Association of Variable Star Observers (AAVSO)
pbenni Tue, 11/28/2023 - 19:39

Responding to an Astro-COLIBRI alert, I imaged the unclassified optical transient AT 2023yoa in M31 using a Rc filter.  My general question about optical transients - are there any archives interested in saving an optical transient image?  I signed up for Kilonova Catcher / GRANDMA but noticed they are selective on what events they wish to archive observer images.  Are these optical transients of scientific interest?  I understand that afterglows from gravity waves, gamma ray bursts, and bright supernovas are of interest, but GWs and GRBs are difficult to capture because of the large field

Candidate optical counterpart for extragalactic neutrino event

American Association of Variable Star Observers (AAVSO)
Bikeman Fri, 10/20/2023 - 22:21

There is a possible optical counterpart (a supernova of type Ibn) that seems consistent with a neutrino event.



Unfortunately the SN is quite dim  (ca 20 mag in V and R ) and fading already, so amateur observations will be difficult except for those with really huge scopes....but it might be interesting to follow events.

Here is the link to the search for related GCN circulars: https://gcn.nasa.gov/circulars?query=+IC231004A&limit=100


Request for Complementary Observations of V404 Cygni for an Oct 14 campaign with JWST, XMM-Newton, Chandra, ALMA, the Very Large Array and GranTeCan

tjmaccarone Tue, 10/10/2023 - 14:42

On the evening of October 14 (JWST starts at 20:00 UT ), we'll have a coordinated campaign with all the telescopes above on V404 Cygni, which is a quiescent black hole X-ray binary.  It's about 16.6 in R in quiescence, and it's relatively red due to foreground extinction.  It would be great to have some folks in Europe get some additional photometry.  Hipercam on the Gran Telescopio Canarias will already be observing, but it would be good to have a backup in case of bad weather (which seems likely given forecasts for La Palma).  

A Binary Neutron Star merger alert from LIGO

American Association of Variable Star Observers (AAVSO)
Bikeman Mon, 09/18/2023 - 11:38

There was just now an alert about a BNS merger


but it's not a Gold plated one: There is a significant probability that this was just a false alarm, the sky localization is not great and partly in a part of the sky that is not easy to observe at the moment, and the distance could be rather far away.


Stay tuned!!



FWD: [vsnet-alert 27948] Swift J1727.8-1613: black-hole binary and V404 Cyg-like object ?

American Association of Variable Star Observers (AAVSO)
Bikeman Fri, 08/25/2023 - 23:42

This could be interesting: vsnet-alert 27948


Swift J1727.8-1613: black-hole binary and V404 Cyg-like object ?


Swift and MAXI detected an outburst in Swift J1727.8-1613.

This is a candidate for a black-hole binary and possibly similar to

V404 Cyg, a unique object known as a source of rapid variability.

A few seconds variability was already found in X-rays.

The most violent variability would be ~2 mag in several tens of min.

This is very bright. Currently, ~13 mag.

Gravitational Wave Observing Run O4: Latest Developments

American Association of Variable Star Observers (AAVSO)
Bikeman Thu, 05/11/2023 - 22:21

Observing Run O4 for the LIGO/Virgo/Kagra detector network ist set to begin on May 24th 2023. For amateurs of the High Energy Network this aboth could be an interesting time, The hope is that the gravitational wave detectors will detect two neutron stars merging during the next ca 18 months, hopefully in a galxy not too far away. Only one such event has even been observed in gravitational waves and in electromagnetic wavelengths, a second event would be extremely useful for astrophysicists.

Paper including amateur obs. of GRB 221009A published in ApJL

American Association of Variable Star Observers (AAVSO)
Bikeman Thu, 05/11/2023 - 16:37

Here's a recent success story for amateur GRB observations. A new paper has now been published in the journal "The Astrophysical Journal Letters" with the title

"GRANDMA and HXMT Observations of GRB 221009A: The Standard Luminosity Afterglow of a Hyperluminous Gamma-Ray Burst—In Gedenken an David Alexander Kann" [*]


GRB 230420A Outburst

American Association of Variable Star Observers (AAVSO)
daveh Fri, 04/21/2023 - 17:12

There have been numerous GCN Circulars announcing the outburst of GRB 230420A. The posted coordinates are 10:44:09.5, +32:06:38.3. This may be a good target for interested observers.

The GCN Circulars for this event can be found on the new GCN website. Go the the HEN page, click on Miscellaneous Links, GCN Circular Archive, then the "new GCN web site" where you can find the information for GRB 230420A.


Gravitational Wave Open Data Workshop

American Association of Variable Star Observers (AAVSO)
daveh Sat, 03/25/2023 - 23:22

It has come to my attention that in May there will be the 2023 Gravitational Wave Open Data Workshop. This would be an excellent opportunity for those interested in learning about gravitational waves and could possibly produce ideas for new projects or opportunities for AAVSO members. It is a free event that goes from May 15-May 17, 2023. This includes lectures, classes, tutorials, and study groups. The website is https://www.gw-openscience.org/odw/odw2023/. This is sponsored by the LIGO, Virgo and KAGRA (LVK) collaboration.

New schedule for the next gravitaonal wave obersvation run (Kilonovae !!!)

American Association of Variable Star Observers (AAVSO)
Bikeman Thu, 02/09/2023 - 19:48

One of the holy grails of "multimessenger astronomy" is the observation of a merger of two neutron stars resulting in a "kilonova" event. The event is observable in visible light, but to be sure it was really a merger of two neutron stars, you need to detect the gravitational waves generated during the merger. So this is a ideal use case for pro-am collaborations like the KILONOVA-CATCHERS discussed also in this forum: once the professional gravitational wave detectors issue public alarms about an event, amateurs can use their optical telescope to search for the optical counterpart.