Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

27572 results found.

  1. GRB 260504A: Fermi GBM Final Real-time Localization
  2. GRB 260503A: Fermi GBM Final Real-time Localization
  3. GRB 260502A: Fermi GBM Final Localization
  4. The EP-WXT trigger 01709261576 is likely a flaring star
  5. GRB 260429B / EP260429a: EP-FXT follow-up observation
  6. EP260502a: BOOTES-7: early optical upper limit
  7. EP260502a: Las Cumbres upper limit
  8. GRB 260429A: SVOM/GRM observation of a short burst
  9. EP260429a: Global MASTER-Net observations report
  10. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  11. EP260429a: LCO optical upper limits
  12. EP260430a: LCO optical upper limits
  13. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  14. GRB 260429A: Fermi GBM Detection
  15. Fermi GRB 260429A: Global MASTER-Net observations report
  16. EP260430a: Global MASTER-Net observations report
  17. EP260430a: Einstein Probe detection of an X-ray transient
  18. GRB 260429A: Fermi GBM Final Real-time Localization
  19. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  20. Fermi GRB 260428A: Global MASTER-Net observations report
  21. GRB 260424B: COLIBRÍ optical upper limit
  22. GRB 260428A: Fermi GBM Final Real-time Localization
  23. GRB 260424C: Fermi GBM Final Localization
  24. GRB 260424B: SVOM/GRM detection of a short burst
  25. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  26. IceCube Alert 260425A: Global MASTER-Net observations report
  27. Fermi trigger No 798737427: Global MASTER-Net observations report
  28. The EP-WXT trigger 01709258652: Mondy optical observations
  29. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  30. GRB 260421B: SVOM/ECLAIRs refined analysis
  31. GRB 260421B: 3.6m DOT optical observation
  32. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  33. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  34. GRB 260421B: SVOM/GRM observation
  35. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  36. GRB 260421B: EP-FXT follow-up observation
  37. The EP-WXT trigger 01709260362 is likely a flaring star
  38. GRB 260421B: J-band upper limit with WINTER
  39. GRB 260421B: LCO optical counterpart detection
  40. GRB 260421B: Fermi GBM Observation
  41. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  42. GRB 260412A: SVOM/ECLAIRs refined analysis
  43. GRB 260421B: SVOM/VT optical observations
  44. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  45. GRB 260310A: Late-time Chandra X-ray Detection
  46. EP260416a: 1.3m DFOT optical observation
  47. Fermi GRB 260421C: Global MASTER-Net observations report
  48. GRB 260421C: Fermi GBM Final Real-time Localization
  49. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  50. Fermi GRB 260421B: Global MASTER-Net observations report
  51. GRB 260421B: LCO optical afterglow confirmation
  52. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  53. GRB 260421B: SVOM detection of a long burst
  54. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  55. GRB 260421B: Fermi GBM Final Real-time Localization
  56. Fermi GRB 260421A: Global MASTER-Net observations report
  57. GRB 260421A: Fermi GBM Final Real-time Localization
  58. EP260321a: VLA radio follow-up
  59. GRB 260412A: LCOGT Optical Upper Limits
  60. The EP-WXT trigger 01709260314 is likely a flaring star
  61. EP-WXT trigger 01709260303: KAIT optical observations
  62. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  63. The EP-WXT trigger 01709260303 is likely a flaring star
  64. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  65. GRB 260419B: Fermi GBM Final Real-time Localization
  66. GRB 260419A: Fermi GBM Final Real-time Localization
  67. Fermi trigger No 798275385: Global MASTER-Net observations report
  68. EP260417a: GROWTH-India Telescope optical upper limit
  69. Fermi GRB 260417B: Global MASTER-Net observations report
  70. EP260417b: GROWTH-India Telescope optical upper limit
  71. EP260416a: Ondrejov D50 optical detection
  72. GRB 260418B: Fermi GBM Final Real-time Localization
  73. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  74. EP260417a: Global MASTER-Net observations report
  75. GRB 260418A: Fermi GBM Final Real-time Localization
  76. EP260416a: GMG Optical Observation
  77. Fermi GRB 260417A: Global MASTER-Net observations report
  78. GRB 260417B: Fermi GBM Final Real-time Localization
  79. EP260416a: LCO observations confirm end of flaring phase
  80. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  81. EP260417a: TRT optical counterpart detection
  82. EP-WXT trigger 01709259586: KAIT optical observations
  83. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  84. EP260416a: WFST optical observations and rebrightening
  85. GRB 260417A: Fermi GBM Final Real-time Localization
  86. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  87. GRB 260415B: Glowbug gamma-ray detection
  88. EP260416a: COLIBRÍ optical counterpart candidate
  89. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  90. EP260416a: Global MASTER-Net observations report
  91. GRB 260415B: NuSTAR detection of long prompt emission
  92. GRB 260415B: Fermi GBM Final Localization
  93. GRB 260415A: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 797912738: Global MASTER-Net observations report
  95. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  96. GRB 260414A: Fermi GBM Final Real-time Localization
  97. The EP-WXT trigger 01709260122 is likely a flaring star
  98. Fermi GRB 260413A: Global MASTER-Net observations report
  99. GRB 260413A: Fermi GBM Final Real-time Localization
  100. EP260321a: SVOM/VT optical observations and color changes around peak

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