Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. 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"

41969 results found.

  1. GRB 250820A: Fermi GBM Final Real-time Localization
  2. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  3. GRB 250818B: TRT Optical Observation
  4. Fermi GRB 250816A: Global MASTER-Net observations report
  5. GRB 250818B: SAO RAS optical observations
  6. Swift GRB 250818A: Global MASTER-Net observations report
  7. GRB 250818B: NOT optical observations
  8. GRB 250818A: Swift-XRT refined Analysis
  9. GRB 250818B: EP-FXT counterpart detection
  10. GRB 250818A: Swift-BAT refined analysis
  11. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  12. GRB 250818C: Fermi GBM Final Real-time Localization
  13. GRB 250818B: Keck redshift of the optical afterglow
  14. Fermi trigger No 776849714: Global MASTER-Net observations report
  15. GRB 250818B: KAIT optical observations
  16. GRB 250818A: Swift/UVOT Upper Limits
  17. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  18. GRB 250818A: Enhanced Swift-XRT position
  19. GRB 250813B: SVOM/ECLAIRs refined analysis
  20. GRB 250818A: Fermi GBM Observation
  21. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  22. GRB 250818B: SVOM/VT optical observation
  23. GRB 250814A: Further GRAWITA TNG NIR observations
  24. GRB 250818B: Swift-XRT afterglow detection
  25. GRB 250818B: GOTO optical counterpart candidate
  26. GRB 250818B: SVOM detection of a short burst
  27. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  28. GRB 250818A: Swift detection of a burst
  29. GRB 250818A: Fermi GBM Final Real-time Localization
  30. sb25081602: Swift-XRT observations
  31. GRB 250816A: SVOM/GRM observation of a short burst
  32. SVOM/sb25081602: detection of a likely X-ray transient
  33. Fermi GRB 250814B: Global MASTER-Net observations report
  34. GRB 250816A: Fermi GBM Final Real-time Localization
  35. GRB 250814A: Swift-BAT refined analysis
  36. GRB 250815A: Fermi GBM Final Localization
  37. GRB 250813B: Liverpool Telescope optical upper limits
  38. GRB 250814A: Further COLIBRÍ optical upper limit
  39. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  40. GRB 250814A: GRAWITA TNG NIR observations
  41. GRB 250812A: SVOM/VT optical continued observation
  42. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  43. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  44. GRB250814A: TRT optical upper limits
  45. GRB 250814B: SVOM/GRM observation
  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 250813B: Fermi GBM Observation
  56. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  57. Fermi trigger No 776818276: Global MASTER-Net observations report
  58. Swift GRB250814.32: Global MASTER-Net observations report
  59. GRB 250814A: J-band upper limit from WINTER
  60. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 250813B: NOT observations of the optical afterglow
  62. GRB 250813B: SVOM/VT optical observations
  63. Subject GRB 250813B: SVOM/MXT refined analysis
  64. GRB 250814A: COLIBRÍ optical upper limit
  65. GRB 250814B: Fermi GBM Final Real-time Localization
  66. GRB 250813A: AstroSat CZTI detection
  67. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  68. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  69. GRB 250814A: DDOTI Optical Upper Limit
  70. GRB 250813B: EP-FXT counterpart detection
  71. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  72. GRB 250813B: Swift-XRT afterglow detection
  73. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  74. GRB 250814A: Fermi GBM Final Real-time Localization
  75. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  76. GRB 250813B: Ondrejov D50 fast decay
  77. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  78. GRB 250813B: Ondrejov D50 optical afterglow detection
  79. GRB 250813B: SVOM detection of a bright long burst
  80. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  81. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  82. EP250812a: Nickel optical upper limit
  83. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  84. GRB 250812A: NTT spectroscopic redshift z = 2.57
  85. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  86. EP250812a: NOT, NTT, and GS observations
  87. GRB 250812A: Swift/UVOT Detection
  88. GRB 250813A: Fermi GBM Final Localization
  89. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  90. EP250812a: Liverpool Telescope upper limits
  91. EP250812a: SVOM/VT optical counterpart
  92. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  93. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  94. IceCube Alert 250813.14: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  96. GRB 250812A: EP-FXT counterpart detection
  97. GRB 250812A: Swift ToO observations
  98. GRB 250807B: Swift-BAT refined analysis
  99. EP 250812a: GOTO optical upper limit
  100. GRB 250812A: Kilonova-Catcher optical afterglow detection

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