Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

3759 results found.

  1. GRB 251005C: AstroSat CZTI detection
  2. GRB 251003A: Swift-BAT refined analysis
  3. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  4. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  5. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  6. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  7. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  8. GRB 250924A: J-band detection with WINTER
  9. GRB 250920B: CrAO ZTSH optical observations
  10. Fermi trigger No 780156732: Global MASTER-Net observations report
  11. IPN triangulation of GRB 250920A (long/bright)
  12. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  13. GRB 250919A: Glowbug gamma-ray detection
  14. GRB 250919A: Fermi GBM Observation
  15. GRB 250919A: Fermi-LAT detection
  16. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  17. EP250919a: Global MASTER-Net observations report
  18. GRB 250919A: Fermi GBM Final Real-time Localization
  19. EP250827b: VLA Observations
  20. Fermi GRB 250912A: Global MASTER-Net observations report
  21. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  22. Fermi GRB 250910B: Global MASTER-Net observations report
  23. EP250911a: Einstein Probe detection of an X-ray transient
  24. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  25. Fermi GRB 250909A: Global MASTER-Net observations report
  26. GRB 250909A: Fermi GBM Final Real-time Localization
  27. EP250905b: Global MASTER-Net observations report
  28. EP250905b: EP-WXT detection of a fast X-ray transient
  29. EP250905a: FTW one optical and multiple NIR counterpart candidates
  30. EP250905a: JinShan likely optical counterpart detection
  31. IceCube Alert 250905.84: Global MASTER-Net observations report
  32. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  33. Fermi GRB 250902B: Global MASTER-Net observations report
  34. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  35. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 250831A: Swift-XRT counterpart detection
  37. GRB 250831A: SVOM detection of a soft burst
  38. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  39. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  40. EP250828a: KAIT optical upper limit
  41. EP250828a: Seimei/TriCCS optical counterpart detection
  42. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  43. EP250827a: LCO observations show fading optical counterpart
  44. GRB 250828A: Fermi GBM Final Localization
  45. EP250827a: Global MASTER-Net observations report
  46. Fermi GRB 250824B: Global MASTER-Net observations report
  47. GRB 250823A: SVOM/VT optical observation
  48. GRB 250823A: BOOTES6/DPRT early optical detection
  49. GRB 250821A: Prompt enhanced Swift-XRT position
  50. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  51. Fermi trigger No 776849714: Global MASTER-Net observations report
  52. GRB 250812A: NTT spectroscopic redshift z = 2.57
  53. IceCube Alert 250813.14: Global MASTER-Net observations report
  54. GRB 250702B: Chandra X-ray Detection
  55. Fermi GRB 250808A: Global MASTER-Net observations report
  56. Konus-Wind detection of GRB 250807A
  57. GRB 250805A: Kilonova-Catcher optical upper limits
  58. GRB 250804B: Swift-XRT observations
  59. GRB 250804B: SVOM/GRM observation of a short burst
  60. EP250711a: CrAO and Assy optical observations
  61. EP250730a: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  63. GRB 250725A: AstroSat CZTI detection
  64. GRB 250728A: Fermi GBM Observation
  65. Fermi trigger No 775387550: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  67. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  69. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  70. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  71. GRB 250721A: MAXI/GSC detection
  72. Fermi trigger No 774730635: Global MASTER-Net observations report
  73. Swift GRB250718.01: Global MASTER-Net observations report
  74. GRB 250711A: DDOTI Optical Upper Limit
  75. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  76. EP250711a: NOT optical counterpart candidate
  77. Fermi GRB 250711A: Global MASTER-Net observations report
  78. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  79. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  80. EP250704a / GRB 250704B - REM observations
  81. Fermi GRB 250702E: Global MASTER-Net observations report
  82. Fermi GRB 250702B: Global MASTER-Net observations report
  83. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  84. Fermi GRB 250702F: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  86. GRB 250628A: REM optical/NIR upper limits
  87. GRB 250628C: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  89. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  90. GRB 250628A: VLT/X-shooter upper limits
  91. Fermi GRB 250626A: Global MASTER-Net observations report
  92. Swift GRB 250628A: Global MASTER-Net observations report
  93. GRB 250625A: SVOM/C-GFT upper limit in early phase
  94. GRB 250625A: OHP/T193 optical detection
  95. Swift GRB 250625A: Global MASTER-Net observations report
  96. Fermi GRB 250623A: Global MASTER-Net observations report
  97. Fermi trigger No 772190032: Global MASTER-Net observations report
  98. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  99. Fermi trigger No 772058337: Global MASTER-Net observations report
  100. GRB 250617B: SAO RAS optical observations

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov