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"
  1. EP251222a: Einstein Probe detection of an X-ray transient
  2. The EP-WXT trigger 01709250397 is likely a flaring star
  3. EP251221a: Global MASTER-Net observations report
  4. GRB 251222A: PRIME near-infrared detection
  5. EP251221a: NOT optical upper limit
  6. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  7. GRB 251222A: NOT optical observations
  8. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  9. IPN triangulation of GRB 251220B (short)
  10. GRB 251222A: Swift ToO observations
  11. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  12. GRB 251222A: SVOM/VT optical candidate
  13. GRB 251222A: SVOM detection of a long burst
  14. SVOM GRB251222A: Global MASTER-Net observations report
  15. GRB 251222A: Fermi GBM Final Real-time Localization
  16. EP251220a: PRIME upper limit
  17. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  18. GRB 251221A: PRIME near-infrared observation
  19. EP251220a: NOT optical observations
  20. EP251220a: FTW optical and NIR observations
  21. GRB 251221A: UAFO and Mondy optical upper limit
  22. GRB 251221A: Swift-XRT refined Analysis
  23. EP251221a: Einstein Probe detection of a fast X-ray transient
  24. GRB 251221A: Swift/UVOT Upper Limits
  25. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  26. GRB 251221A: Enhanced Swift-XRT position
  27. GRB 251221A: Fermi GBM Observation
  28. GRB 251221B: Fermi GBM Final Real-time Localization
  29. EP251220a: EP-FXT follow-up observation
  30. GRB 251220B: SVOM/GRM observation of a short burst
  31. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  32. EP 251220a: GOTO optical counterpart detection
  33. GRB 251221A: COLIBRÍ detection of the optical counterpart
  34. EP 251220a: COLIBRÍ detection of the optical counterpart
  35. GRB 251221A: Swift detection of a burst
  36. Swift GRB251221A: Global MASTER-Net observations report
  37. GRB 251221A: Fermi GBM Final Real-time Localization
  38. EP251220a: Global MASTER-Net observations report
  39. EP251220a: EP detection of a fast X-ray transient
  40. SVOM GRB251220.98: Global MASTER-Net observations report
  41. GRB 251220B: Fermi GBM Final Real-time Localization
  42. GRB 251219A: SVOM/GRM observation of a short burst
  43. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  44. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  45. GRB 251220A: MAXI/GSC detection
  46. GRB 251215A: Swift-XRT afterglow detection
  47. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  48. IceCube-251218A: COLIBRÍ optical upper limits
  49. SVOM GRB251219.11: Global MASTER-Net observations report
  50. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  51. IceCube Alert 251218.85: Global MASTER-Net observations report
  52. GRB 251214B: VIRT Optical Upper Limit
  53. Fermi trigger No 787736968: Global MASTER-Net observations report
  54. Fermi GRB 251217A: Global MASTER-Net observations report
  55. GRB 251217A: Fermi GBM Final Real-time Localization
  56. GRB 251215A: Swift/UVOT Upper LImits
  57. GRB 251215A: Fermi GBM Observation
  58. Fermi GRB 251216A: Global MASTER-Net observations report
  59. GRB 251202A/EP251202a: Koshka optical upper limit
  60. GRB 251214B: Mondy optical upper limit
  61. GRB 251215A: COLIBRÍ optical upper limit
  62. GRB 251216A: Fermi GBM Final Real-time Localization
  63. EP251214b: KAIT optical upper limit
  64. GRB 251215A: Swift-XRT observations
  65. Fermi GRB 251215A: Global MASTER-Net observations report
  66. EP251214a: Optical upper limit with Kinder observations
  67. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  68. GRB 251215A: Glowbug gamma-ray detection
  69. GRB 251214B: UAFO optical upper limit
  70. GRB 251214B: VLT/X-shooter observations
  71. GRB 251213A: GRID-10B observation
  72. GRB 251214B: Swift-BAT refined analysis
  73. GRB 251202A: radio detection with the VLA
  74. EP251214b: Global MASTER-Net observations report
  75. EP251214b : Einstein Probe detection of a fast X-ray transient
  76. EP251214b : Einstein Probe detection of a fast X-ray transient
  77. GRB 251214B: AbAO optical observations
  78. GRB 251214B: LCO detection of the optical counterpart
  79. GRB 251209A: GECAM-B observation of a long burst
  80. GRB 251214D: GECAM-B observation of a long burst
  81. GRB 251214B: Fermi GBM Observation
  82. GRB 251209A: Insight-HXMT/HE detection
  83. GRB 251215A: Swift ToO observations
  84. EP251214b (EP trigger 01709250023): LCO optical limits
  85. GRID detection of GRB 251213A
  86. GRB 251203B: AbAO optical observations
  87. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  88. GRB 251214B: GECAM-B observation of a long burst
  89. GRB 251214B: Swift-XRT refined Analysis
  90. GRB 251213A: SVOM/GRM observation
  91. EP251214a: KAIT optical upper limit
  92. GRB 251214D: AstroSat CZTI detection of a long burst
  93. GRB 251213A: AstroSat CZTI detection
  94. GRB 251214A: AstroSat CZTI detection
  95. GRB 251213A: GECAM-B detection
  96. GRB 251214B: Swift/UVOT Detection
  97. GRB 251215A: Fermi GBM Final Real-time Localization
  98. GRB 251214B: COLIBRÍ observations of the afterglow
  99. EP251214a: EP-FXT non-detection and upper limit
  100. GRB 251214A: GECAM-B observation of a likely long burst

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