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"

19218 results found.

  1. GRB 250821A: Kilonova-Catcher optical upper limits
  2. EP250821a: Swift/XRT counterpart fading
  3. GRB 250821A: Swift-BAT refined analysis
  4. EP250821a: Swift/UVOT further observations.
  5. GRB 250821A: VLT/FORS2 Optical Observation
  6. GRB 250821A: GECAM-B detection
  7. EP250821a: SVOM/VT optical observation
  8. GRB 250821A: NOT z-band upper limit
  9. GRB 250821A: Swift-XRT refined Analysis
  10. Swift GRB 250821A: Global MASTER-Net observations report
  11. GRB 250821A: Enhanced Swift-XRT position
  12. GRB 250821A: Swift/UVOT Upper Limits
  13. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  14. EP250821a: Swift XRT and UVOT counterpart detection
  15. GRB 250821A: LCOGT Optical Upper Limits
  16. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  17. GRB 250821A: Prompt enhanced Swift-XRT position
  18. GRB 250821A: Swift detection of a burst
  19. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  20. GRB 250814A: Swift/UVOT Upper Limits
  21. GRB 250813B: Swift/UVOT Upper Limit
  22. IPN triangulation of GRB 250814C (short)
  23. IPN triangulation of GRB 250804B (short)
  24. GRB 250818B: Kilonova-Catcher optical afterglow detection
  25. GRB 250818A: AstroSat CZTI detection
  26. GRB 250818B: Swift/UVOT Detection
  27. GRB 250818B: SAO RAS optical observations
  28. Swift GRB 250818A: Global MASTER-Net observations report
  29. GRB 250818A: Swift-XRT refined Analysis
  30. GRB 250818A: Swift-BAT refined analysis
  31. GRB 250818B: Keck redshift of the optical afterglow
  32. GRB 250818A: Swift/UVOT Upper Limits
  33. GRB 250818A: Enhanced Swift-XRT position
  34. GRB 250818A: Fermi GBM Observation
  35. GRB 250818B: SVOM/VT optical observation
  36. GRB 250814A: Further GRAWITA TNG NIR observations
  37. GRB 250818B: Swift-XRT afterglow detection
  38. GRB 250818A: Swift detection of a burst
  39. sb25081602: Swift-XRT observations
  40. GRB 250814A: Swift-BAT refined analysis
  41. GRB 250814A: Further COLIBRÍ optical upper limit
  42. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  43. GRB 250814A: GRAWITA TNG NIR observations
  44. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  45. GRB250814A: TRT optical upper limits
  46. GRB 250814C: SVOM/GRM observation of a short burst
  47. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  48. GRB 250813B: SVOM/GRM observation
  49. GRB 250814A: P200/WIRC observations of the afterglow candidate
  50. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  51. GRB 250814A: KAIT optical upper limit
  52. GRB 250814A: Swift-XRT refined Analysis
  53. GRB 240814A: Fermi GBM Observation
  54. GRB 250814A: Possible afterglow candidate from P200/WIRC
  55. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  56. Swift GRB250814.32: Global MASTER-Net observations report
  57. GRB 250814A: J-band upper limit from WINTER
  58. GRB 250813B: SVOM/VT optical observations
  59. GRB 250814A: COLIBRÍ optical upper limit
  60. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  61. GRB 250814A: DDOTI Optical Upper Limit
  62. GRB 250813B: Swift-XRT afterglow detection
  63. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  64. EP250812a: NOT, NTT, and GS observations
  65. GRB 250812A: Swift/UVOT Detection
  66. EP250812a: SVOM/VT optical counterpart
  67. GRB 250812A: Swift ToO observations
  68. GRB 250807B: Swift-BAT refined analysis
  69. EP 250812a: GOTO optical upper limit
  70. GRB 250812A: Kilonova-Catcher optical afterglow detection
  71. EP250812a: Swift-XRT counterpart detection
  72. GRB 250812A: SVOM/VT optical afterglow confirmation
  73. GRB 250812A: Swift-XRT afterglow detection
  74. GRB 250809A: Swift-BAT refined analysis
  75. GRB 250807A: Swift-BAT refined analysis
  76. GRB 250809A: Swift/UVOT Detection
  77. Corrected Swift-XRT Refined Analysis of GRB 250809A
  78. GRB 250809A: Swift-XRT refined Analysis
  79. GRB 250807B: SVOM/VT optical observation
  80. GRB 250809A: LCOGT Optical Upper Limits
  81. GRB 250702B: Chandra X-ray Detection
  82. GRB 250808A: VLT X-shooter candidate counterpart
  83. GRB 250809A: Prompt enhanced Swift-XRT position
  84. GRB 250809A: Swift detection of a gamma ray burst
  85. GRB 250808A: Swift-XRT candidate counterpart detection
  86. GRB 250807A: SVOM/VT optical continued observation
  87. Konus-Wind detection of GRB 250807A
  88. GRB 250807B: Swift/UVOT Detection
  89. GRB 250807B: Kilonova-Catcher optical afterglow detection
  90. GRB 250807A: Swift/UVOT Detection
  91. GRB 250807A: Swift-XRT refined Analysis
  92. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  93. GRB 250806A: SVOM/MXT refined analysis
  94. GRB 250806A: SVOM/ECLAIRs refined analysis
  95. GRB 250807A: SVOM/GRM observation
  96. Swift GRB250807.45: Global MASTER-Net observations report
  97. GRB 250807A: AstroSat CZTI detection of bright long burst
  98. GRB 250807B: Swift-XRT refined Analysis
  99. GRB 250807B: NTT optical observations
  100. GRB 250807A: SVOM/VT optical observation

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