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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"

44282 results found.

  1. GRB 250702F: REM optical afterglow detection
  2. EP250702a: Global MASTER-Net observations report
  3. GRB 250702F: DDOTI Optical Observation
  4. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  5. GRB 250703A: Fermi GBM Final Real-time Localization
  6. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  7. GRB 250702F: COLIBRÍ Observations of the Afterglow
  8. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  9. Fermi GRB 250702E: Global MASTER-Net observations report
  10. Fermi GRB 250702B: Global MASTER-Net observations report
  11. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  12. GRB 250702F: Enhanced Swift-XRT position
  13. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  14. GRB 250702F: NOT observations of the optical afterglow
  15. GRB 250702F: MASTER optical afterglow observation
  16. Fermi GRB 250702F: Global MASTER-Net observations report
  17. Fermi GRB 250702C: Global MASTER-Net observations report
  18. GRB 250702F: GOTO optical counterpart detection
  19. GRB 250702F: Ondrejov D50 optical afterglow detection
  20. GRB 250702F: Swift detection of a burst with an optical counterpart
  21. Swift GRB 250702F: Global MASTER-Net observations report
  22. GRB 250702F: Fermi GBM Final Real-time Localization
  23. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  24. GRB 250702E: Fermi GBM Final Real-time Localization
  25. Konus-Wind detection of GRB 250627A
  26. IPN triangulation of GRB 250627A (short)
  27. GRB 250702A: Fermi GBM Detection
  28. GRB 250702D: Fermi GBM Final Localization Correction
  29. GRB 250702C: Fermi GBM Final Real-time Localization
  30. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  31. GRB 250702B: Fermi GBM Final Real-time Localization
  32. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  33. GRB 250702A: Fermi GBM Final Real-time Localization
  34. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  36. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  37. GRB 250628B: Swift-XRT observations
  38. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  39. GRB 250628B: SVOM/VT optical upper limit
  40. GRB 250628B: EP-FXT counterpart detection
  41. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  42. GRB 250627A: Insight-HXMT detection
  43. GRB 250627A: SVOM/GRM detection of a short burst
  44. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  45. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  47. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  48. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  49. GRB 250628A: REM optical/NIR upper limits
  50. GRB 250628C: Fermi GBM Final Real-time Localization
  51. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  52. GRB 250628B: SVOM detection of a long burst
  53. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  54. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  55. GRB 250628A: VLT/X-shooter upper limits
  56. GRB 250628A: Swift/UVOT Upper Limits
  57. GRB 250628A: Swift-XRT refined Analysis
  58. Fermi GRB 250626A: Global MASTER-Net observations report
  59. Swift GRB 250628A: Global MASTER-Net observations report
  60. GRB 250628A: Enhanced Swift-XRT position
  61. GRB 250628A: Swift detection of a burst
  62. GRB 250625A: Swift-BAT refined analysis
  63. GRB 250625A: Leavitt Observatory afterglow detection
  64. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  65. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  66. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  67. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  68. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  69. GRB 250626A: Fermi GBM Final Real-time Localization
  70. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  71. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  72. GRB 250625A: SVOM/C-GFT upper limit in early phase
  73. GRB 250625A: GECAM-B detection
  74. GRB 250625A: Swift/UVOT Upper Limits
  75. GRB 250625A: ABObservatory afterglow detection
  76. GRB 250625A: OHP/T193 optical detection
  77. GRB 250625A: COLIBRÍ optical observations
  78. GRB 250625A: Fermi-LAT detection
  79. GRB 250625A: Swift-XRT refined Analysis
  80. GRB 250625A: JinShan optical observations
  81. GRB250625A: Fermi GBM Observation
  82. Swift GRB 250625A: Global MASTER-Net observations report
  83. GRB 250625A: NOT z-band upper limit
  84. GRB 250625A: SVOM/VT optical confirmation
  85. GRB 250620B: Fermi GBM Observation
  86. GRB 250625A: SAO RAS possible optical afterglow
  87. GRB 250625A: Enhanced Swift-XRT position
  88. Fermi GRB 250625A: Global MASTER-Net observations report
  89. GRB 250625A: Swift detection of a burst
  90. GRB 250625A: Fermi GBM Final Real-time Localization
  91. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  92. GRB 250620A: AstroSat CZTI detection
  93. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  94. GRB 241018A: Maidanak optical observations
  95. GRB 250620C: AstroSat CZTI detection
  96. Fermi GRB 250624A: Global MASTER-Net observations report
  97. GRB 250624A: Fermi GBM Final Real-time Localization
  98. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  99. Fermi GRB 250623A: Global MASTER-Net observations report
  100. GRB 250623A: Fermi GBM Final Real-time Localization

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