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"

28229 results found.

  1. Fermi GRB 260506A: Global MASTER-Net observations report
  2. IceCube Alert 260505A: Global MASTER-Net observations report
  3. GRB 260430B: Glowbug gamma-ray detection
  4. GRB 260421B: radio observation with the VLA
  5. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  6. GRB 260430B: AstroSat CZTI detection of a long burst
  7. GRB 260502A: SVOM/GRM observation of a short GRB
  8. GRB 260503A: SVOM/GRM observation of a GRB
  9. Konus-Wind detection of GRB 260411C
  10. GRB 260504B: REM optical/NIR observations
  11. GRB 260504B: LCO z-band upper limit
  12. SVOM GRB 260504B: MASTER-OAFA optical observations
  13. GRB 260504B: SVOM detection of a short burst
  14. Fermi GRB 260504A: Global MASTER-Net observations report
  15. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  16. GRB 260429B / EP260429a: EP-FXT follow-up observation
  17. EP260502a: Einstein Probe detection of an X-ray transient
  18. GRB 260429A: SVOM/GRM observation of a short burst
  19. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  20. EP260429a: Global MASTER-Net observations report
  21. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  22. GRB 260424B: AstroSat CZTI detection
  23. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  24. EP260429a: LCO optical upper limits
  25. EP260430a: LCO optical upper limits
  26. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  27. GRB 260429A: Fermi GBM Detection
  28. Fermi GRB 260429A: Global MASTER-Net observations report
  29. EP260430a: Global MASTER-Net observations report
  30. EP260430a: Einstein Probe detection of an X-ray transient
  31. EP260429a: EP-WXT detection of a fast X-ray transient
  32. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  33. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  34. Fermi GRB 260428A: Global MASTER-Net observations report
  35. EP260416a: Mondy and Terskol optical upper limits
  36. GRB 260424B: Glowbug gamma-ray detection of a short burst
  37. GRB 260424B: COLIBRÍ optical upper limit
  38. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  39. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  40. IceCube Alert 260425A: Global MASTER-Net observations report
  41. Fermi trigger No 798737427: Global MASTER-Net observations report
  42. GRB 260401A: cubesat Avion detection
  43. EP260321a: Upper limits from ATCA radio observations
  44. GRB 260421B: Kilonova-Catcher optical afterglow detection
  45. The EP-WXT trigger 01709258652: Mondy optical observations
  46. EP260416a: Mondy optical observations
  47. GRB 260421B: 3.6m DOT optical observation
  48. EP260416a: ZTSh R band observations
  49. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 260421B: SVOM/GRM observation
  51. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  52. GRB 260421B: EP-FXT follow-up observation
  53. GOTO26djh/AT2026jpw: ATCA radio detection
  54. GRB 260421B: J-band upper limit with WINTER
  55. GRB 260421B: LCO optical counterpart detection
  56. GRB 260421B: Fermi GBM Observation
  57. GOTO26djh/AT2026jpw: radio detection at 15GHz
  58. GRB 260421B: SVOM/VT optical observations
  59. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  60. GRB 260310A: Late-time Chandra X-ray Detection
  61. EP260416a: 1.3m DFOT optical observation
  62. Fermi GRB 260421C: Global MASTER-Net observations report
  63. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  64. Fermi GRB 260421B: Global MASTER-Net observations report
  65. GRB 260421B: LCO optical afterglow confirmation
  66. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  67. GRB 260421B: TRT optical counterpart detection
  68. GRB 260421B: SVOM detection of a long burst
  69. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  70. Fermi GRB 260421A: Global MASTER-Net observations report
  71. EP260321a: VLA radio follow-up
  72. GRB 260412A: LCOGT Optical Upper Limits
  73. EP260416a: Optical follow-up observations with Kinder
  74. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  75. GRB 260417A: SVOM/GRM observation
  76. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  77. Fermi trigger No 798275385: Global MASTER-Net observations report
  78. EP260417a: GROWTH-India Telescope optical upper limit
  79. Fermi GRB 260417B: Global MASTER-Net observations report
  80. EP260417b: GROWTH-India Telescope optical upper limit
  81. EP260416a: Ondrejov D50 optical detection
  82. EP260417a: Global MASTER-Net observations report
  83. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  84. EP260416a: GMG Optical Observation
  85. Fermi GRB 260417A: Global MASTER-Net observations report
  86. EP260416a: LCO observations confirm end of flaring phase
  87. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  88. EP260417a: TRT optical counterpart detection
  89. EP260417a: Einstein Probe detection of an X-ray transient
  90. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  91. EP260417b: Einstein Probe detection of a fast X-ray transient
  92. EP260416a: KAIT optical upper limit
  93. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  94. EP260416a: WFST optical observations and rebrightening
  95. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  96. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  97. GRB 260415B: Glowbug gamma-ray detection
  98. GRB 260411B: Glowbug gamma-ray detection
  99. EP260416a: COLIBRÍ optical counterpart candidate
  100. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw

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