Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"

26335 results found.

  1. Fermi GRB 251202B: Global MASTER-Net observations report
  2. IPN triangulation of GRB 251129B (short/hard)
  3. GRB251129A/EP251129a: Swift UVOT detection
  4. GRB 251202A: Fermi GBM Observation
  5. GRB 251202A: Swift/UVOT Detection
  6. GRB 251201B: Kilonova-Catcher optical afterglow detection
  7. GRB 251201B: Swift/UVOT Detection
  8. GRB 251130B: Glowbug gamma-ray detection
  9. EP251130a: continued NOT optical observations indicate steep fading phase
  10. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  11. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  12. GRB 251126A: SAO RAS optical marginal detection
  13. GRB 251202A: Swift-XRT afterglow detection
  14. EP251129a/GRB 251129A: NOWT Detection
  15. GRB 251126A: SVOM/VT optical observation
  16. EP251130a: SVOM/VT optical observation
  17. Fermi GRB 251202A: Global MASTER-Net observations report
  18. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  19. GRB 251201B: Swift-XRT refined Analysis
  20. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 251201A: SVOM/GRM observation of a burst
  22. GRB 251201B: SVOM/VT optical fading
  23. Swift GRB 251201B : MASTER optical counterpart detection
  24. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  25. Swift GRB 251201B: Global MASTER-Net observations report
  26. GRB 251201B: Enhanced Swift-XRT position
  27. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  28. GRB 251201B: Swift detection of a burst with an optical counterpart
  29. GRB 251201B: Fermi GBM Final Real-time Localization
  30. EP251130a: Mondy optical observations
  31. EP251130a: Optical detections with Kinder observations
  32. SVOM GRB251201.19: Global MASTER-Net observations report
  33. EP251130a: SAO RAS optical observations
  34. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  35. EP251130A: Optical observation from 1.3m DFOT
  36. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP251130a: JinShan optical observations
  38. GRB 251201A: MAXI/GSC detection
  39. Fermi GRB 251130B: Global MASTER-Net observations report
  40. GRB 251127A: SVOM/GRM observation
  41. IceCube Alert 251130.75: Global MASTER-Net observations report
  42. EP251130a: Swift-XRT counterpart detection
  43. EP251130a: Global MASTER-Net observations report
  44. EP251130a: COLIBRÍ optical counterpart candidate
  45. EP251130a: Einstein Probe detection of an X-ray transient
  46. GRB 251129A / EP251129a: SAO RAS optical observations
  47. GRB 251126A: SAO RAS optical observations
  48. GRB 251128A: SVOM/GRM observation of a long burst
  49. SVOM GRB 251129A : MASTER optical counterpart detection
  50. GRB 251129A: Swift-XRT afterglow detection
  51. EP251129a: Global MASTER-Net observations report
  52. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  53. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  54. GRB 251128A: Fermi GBM Observation
  55. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  56. GRB 251129A: SVOM detection of a burst
  57. SVOM GRB251129A: Global MASTER-Net observations report
  58. GRB 251129A: SVOM detection of a burst
  59. GRB 251126A: Swift-BAT refined analysis
  60. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  61. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  62. Fermi GRB 251128A: Global MASTER-Net observations report
  63. GRB 251127A: Glowbug gamma-ray detection
  64. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  65. GRB 251126A: further SAO RAS optical observations
  66. GRB 251126A NUTTelA-TAO Early Measurements
  67. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  68. GRB251126A: MAO/AZT-22 optical observations
  69. GRB251126A: Continued optical observation from 1.3m DFOT
  70. GRB 251126A: Swift/UVOT Detection
  71. GRB 251126A: Mondy and SAO RAS optical observations
  72. GRB 251126A: Swift-XRT refined Analysis
  73. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  74. GRB 251126A: NOT optical observations
  75. GRB 251126A: 1.3m DFOT optical afterglow detection
  76. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  77. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  78. Fermi GRB 251127A: Global MASTER-Net observations report
  79. GRB 251126A: Enhanced Swift-XRT position
  80. GRB 251126A: Kilonova-Catcher optical afterglow detection
  81. GRB 251126A: Nanshan/HMT optical afterglow detection
  82. Swift GRB 251126A: Global MASTER-Net observations report
  83. GRB 251121A: Fermi GBM Observation
  84. GRB 251126A: GIT discovery of the likely optical afterglow
  85. GRB 251126A: Swift detection of a burst
  86. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  87. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  88. EP251124b: NOT r- and z-band optical upper limits
  89. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  90. Fermi GRB 251125B: Global MASTER-Net observations report
  91. EP251124b: Global MASTER-Net observations report
  92. EP251124b: EP-WXT detection of a fast X-ray transient
  93. EP251124a: Xinglong GWAC-F60A optical observation
  94. Fermi GRB 251125A: Global MASTER-Net observations report
  95. EP251124a: NOT r- and z-band optical upper limits
  96. EP251124a: Global MASTER-Net observations report
  97. EP251124a: Swift-XRT observations
  98. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  99. EP251124a: Optical upper limit with Kinder observations
  100. Fermi GRB 251124a: Global MASTER-Net observations report

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