Skip to main content
Retirement of GCN Classic VOEvent Brokers. See news and announcements

GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 251126A: Swift-BAT refined analysis
  2. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  3. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  4. Fermi GRB 251128A: Global MASTER-Net observations report
  5. GRB 251127A: Glowbug gamma-ray detection
  6. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  7. GRB 251126A: further SAO RAS optical observations
  8. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  9. GRB 251126A NUTTelA-TAO Early Measurements
  10. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  11. GRB251126A: MAO/AZT-22 optical observations
  12. GRB 251128A: Fermi GBM Final Real-time Localization
  13. GRB251126A: Continued optical observation from 1.3m DFOT
  14. GRB 251126A: Swift/UVOT Detection
  15. EP251124a: Pan-STARRS ri-band imaging and photometry
  16. GRB 251126A: Mondy and SAO RAS optical observations
  17. GRB 251126A: Swift-XRT refined Analysis
  18. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  19. GRB 251126A: NOT optical observations
  20. GRB 251126A: 1.3m DFOT optical afterglow detection
  21. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  22. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  23. GRB 251125B: GECAM-B detection
  24. Fermi GRB 251127A: Global MASTER-Net observations report
  25. GRB 251127A: Fermi GBM Final Real-time Localization
  26. GRB 251126A: Enhanced Swift-XRT position
  27. GRB 251126A: Kilonova-Catcher optical afterglow detection
  28. GRB 251126A: Asiago i-band detection
  29. GRB 251126A: Nanshan/HMT optical afterglow detection
  30. Swift GRB 251126A: Global MASTER-Net observations report
  31. GRB 251121A: Fermi GBM Observation
  32. GRB 251126A: Prompt enhanced Swift-XRT position
  33. GRB 251126A: GIT discovery of the likely optical afterglow
  34. GRB 251126A: Swift detection of a burst
  35. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  36. EP251124b follow-up observation by EP-FXT
  37. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  38. EP251124b: NOT r- and z-band optical upper limits
  39. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  40. Fermi GRB 251125B: Global MASTER-Net observations report
  41. GRB 251125B: Fermi GBM Final Real-time Localization
  42. EP251124b: Global MASTER-Net observations report
  43. EP251124b: EP-WXT detection of a fast X-ray transient
  44. EP251124a: Xinglong GWAC-F60A optical observation
  45. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  46. Fermi GRB 251125A: Global MASTER-Net observations report
  47. GRB 251125A: Fermi GBM Final Real-time Localization
  48. EP251124a: NOT r- and z-band optical upper limits
  49. EP251124a: Global MASTER-Net observations report
  50. EP251124a: Swift-XRT observations
  51. GRB 251124A: Fermi GBM Localization by automated pipeline
  52. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  53. EP251124a: Optical upper limit with Kinder observations
  54. GRB 251122B: Fermi GBM Final Localization
  55. EP251118A: 6 GHz VLA Detection
  56. Fermi GRB 251124a: Global MASTER-Net observations report
  57. GRB 251124a: Fermi GBM Final Localization
  58. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  59. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  60. EP251124a: GROWTH-India Telescope optical upper limits
  61. EP251124a: Einstein Probe detection of an X-ray transient
  62. GRB 251116C: Swift-XRT confirmation of fading
  63. GRB 251122A/EP251122a: FTW optical and NIR observations
  64. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  65. The EP-WXT trigger 01709248783 is likely a flaring star
  66. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  67. EP251118A: 3.6m DOT optical afterglow detection
  68. GRB 251122A / EP251122a: EP-FXT counterpart detection
  69. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  70. GRB 251122A / EP251122a: WFST optical observations
  71. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  72. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  73. GRB 251122A / EP251122a: LCO optical upper limits
  74. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  75. EP251122a: Global MASTER-Net observations report
  76. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  77. GRB 251122A / EP251122a: SVOM detection of a long burst
  78. EP251122a: Einstein Probe detection of an X-ray transient
  79. EP251118a: Continued Optical Detection with Kinder observations
  80. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  81. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  82. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  83. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  84. EP251118a: Xinglong-2.16m optical observation
  85. GRB 251115A: Fermi GBM Observation
  86. The EP-WXT trigger 01709248635 is likely a flaring star
  87. GRB 251121A: Fermi GBM Final Real-time Localization
  88. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  89. Fermi trigger No 785388351: Global MASTER-Net observations report
  90. EP251118A: 1.3m DFOT optical afterglow detection
  91. GRB 251118A: Swift/UVOT Detection
  92. EP251118a / GRB 251118C: SAO RAS optical observations
  93. GRB 251118A: Glowbug gamma-ray detection
  94. GRB 251118A: Fermi GBM Observation
  95. GRB 251118A: Swift-XRT afterglow detection
  96. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  97. EP251118a: Optical detection with Kinder observations
  98. GRB 251118A: GECAM-B detection
  99. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  100. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov