Skip to main content
New JavaScript client! 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. AT 2026wki: EP/FXT follow-up observations
  2. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  3. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  4. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  5. GRB 260804A: Fermi GBM Final Real-time Localization
  6. GRB 260708A: LCO further optical observations show supernova features
  7. GRB 260803A: Fermi GBM Final Real-time Localization
  8. Fermi GRB 260802B: Global MASTER-Net observations report
  9. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  10. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  11. GRB 260802A: SVOM/VT optical upper limits from VHF data
  12. GRB 260802A: LCO optical upper limits
  13. GRB 260802B: Fermi GBM Final Localization
  14. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. The EP-WXT trigger 01709277420 is likely a flaring star
  16. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  17. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  18. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  19. GRB 260731A: AstroSat CZTI detection of a long burst
  20. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  21. GRB 260730B: AstroSat CZTI detection
  22. EP260731a: COLIBRÍ optical upper limit
  23. EP260731a: NOT optical upper limit
  24. GRB 260730B: NuSTAR detection of prompt emission
  25. EP260731a: Einstein Probe detection of an X-ray transient
  26. GRB 260727A: SVOM/ECLAIRs refined analysis
  27. GRB 260726A: SVOM/ECLAIRs refined analysis
  28. GRB260730A: Fermi GBM Final Localization
  29. EP260728a: COLIBRÍ optical upper limit
  30. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  31. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  32. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  33. EP260729a: Einstein Probe detection of an X-ray transient
  34. EP260727a: SAO RAS optical observations
  35. GRB 260727A: AbAO and SAO RAS optical observations
  36. EP260728a: EP-FXT follow-up observation
  37. GRB 260726A: EP-FXT follow-up observations
  38. EP260728a: Einstein Probe detection of a fast X-ray transient
  39. GRB 260727A: SVOM/GRM observation
  40. GRB 260726A: Fermi GBM Observation
  41. EP260727a: 1.5m OSN optical counterpart detection
  42. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  43. EP260727a: OHP/T193 optical observations
  44. Konus-Wind detection of GRB 260727A
  45. GRB 260726A: Liverpool Telescope optical observations
  46. GRB 260727A: Liverpool Telescope optical upper limits
  47. EP260727a: Liverpool Telescope confirmation of optical counterpart
  48. EP260727a: NUTTELA-TAO Early Optical Limits
  49. GRB 260728A: Fermi GBM Final Localization
  50. GRB 260727A: EP/FXT follow-up observations
  51. EP260727a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  53. GRB 260727A: Glowbug gamma-ray detection
  54. GRB 260726A: J-band upper limit with WINTER
  55. GRB 260727A: J-band upper limit with WINTER
  56. GRB 260726A: SVOM/VT optical candidate
  57. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  58. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  59. EP260723a: SVOM/ECLAIRs Upper Limit
  60. GRB 260727A: GOTO early optical upper limit
  61. GRB 260727A: AstroSat CZTI detection
  62. GRB 260727A: Kilonova-Catcher optical upper limit
  63. GRB 260727A: LCO optical upper limits
  64. GRB 260727B: Fermi GBM Final Real-time Localization
  65. Fermi GRB 260726A: Global MASTER-Net observations report
  66. GRB 260727A: SVOM detection of a bright long burst
  67. GRB 260726A: SVOM detection of a burst
  68. GRB 260726A: Fermi GBM Final Real-time Localization
  69. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  70. EP260723a: further EP-FXT follow-up observation
  71. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  72. EP260725a: EP-WXT detection of an X-ray transient
  73. GRB 260616A: cubesat Avion detection
  74. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  75. GRB 260602B: cubesat Avion detection
  76. GRB 260601A: cubesat Avion detection
  77. EP260723a: EP-FXT follow-up observation
  78. IPN triangulation of GRB 260706B
  79. GRB 260718A: SVOM/ECLAIRs refined analysis
  80. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  81. EP260723a: SVOM/VT optical observation
  82. EP260723a: COLIBRÍ optical observations
  83. EP260723a: NOT optical conterpart confirmation
  84. EP260723a: Liverpool Telescope likely optical counterpart
  85. EP260723a: EP-WXT detection of a fast X-ray transient
  86. GRB 260723A: Fermi GBM Final Localization
  87. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  88. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  89. IceCube Alert 260722A: Global MASTER-Net observations report
  90. Konus-Wind detection of GRB 260721A
  91. GRB 260722A: Fermi GBM Final Real-time Localization
  92. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  93. Fermi GBM trigger 806384210/260722151 is not a GRB
  94. GRB 260721A: NuSTAR detection of prompt emission
  95. Konus-Wind detection of GRB 260714B
  96. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  97. GRB 260705A: Retraction of optical counterpart
  98. GRB 260714B: Insight-HXMT/HE detection
  99. GRB 260718A: EP-FXT follow-up observation
  100. Fermi trigger No 806104130: Global MASTER-Net observations report

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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