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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"
  1. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  2. GRB 250702F: Swift-XRT refined Analysis
  3. GRB 250702F: Fermi GBM Observation
  4. GRB 250702F: Leavitt Observatory optical observations
  5. GRB 250702F: AKO Optical Afterglow Detection
  6. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  7. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  8. GRB 250702A: GECAM-B detection
  9. GRB 250702F: Skynet Optical Observations
  10. GRB 250424A: VIRT Optical Upper Limit
  11. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  12. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  13. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  14. GRB 250702F: TRT Optical Observation
  15. GRB 250703A: DDOTI Optical Upper Limit
  16. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  17. GRB 250702F: REM optical afterglow detection
  18. EP250702a: Global MASTER-Net observations report
  19. GRB 250702F: DDOTI Optical Observation
  20. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  21. GRB 250703A: Fermi GBM Final Real-time Localization
  22. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  23. GRB 250702F: COLIBRÍ Observations of the Afterglow
  24. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  25. Fermi GRB 250702E: Global MASTER-Net observations report
  26. Fermi GRB 250702B: Global MASTER-Net observations report
  27. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  28. GRB 250702F: Enhanced Swift-XRT position
  29. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  30. GRB 250702F: NOT observations of the optical afterglow
  31. GRB 250702F: MASTER optical afterglow observation
  32. Fermi GRB 250702F: Global MASTER-Net observations report
  33. Fermi GRB 250702C: Global MASTER-Net observations report
  34. GRB 250702F: GOTO optical counterpart detection
  35. GRB 250702F: Ondrejov D50 optical afterglow detection
  36. GRB 250702F: Swift detection of a burst with an optical counterpart
  37. Swift GRB 250702F: Global MASTER-Net observations report
  38. GRB 250702F: Fermi GBM Final Real-time Localization
  39. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  40. GRB 250702E: Fermi GBM Final Real-time Localization
  41. Konus-Wind detection of GRB 250627A
  42. IPN triangulation of GRB 250627A (short)
  43. GRB 250702A: Fermi GBM Detection
  44. GRB 250702D: Fermi GBM Final Localization Correction
  45. GRB 250702C: Fermi GBM Final Real-time Localization
  46. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  47. GRB 250702B: Fermi GBM Final Real-time Localization
  48. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  49. GRB 250702A: Fermi GBM Final Real-time Localization
  50. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  52. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  53. GRB 250628B: Swift-XRT observations
  54. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  55. GRB 250628B: SVOM/VT optical upper limit
  56. GRB 250628B: EP-FXT counterpart detection
  57. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  58. GRB 250627A: Insight-HXMT detection
  59. GRB 250627A: SVOM/GRM detection of a short burst
  60. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  61. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  62. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  63. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  65. GRB 250628A: REM optical/NIR upper limits
  66. GRB 250628C: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  68. GRB 250628B: SVOM detection of a long burst
  69. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  70. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  71. GRB 250628A: VLT/X-shooter upper limits
  72. GRB 250628A: Swift/UVOT Upper Limits
  73. GRB 250628A: Swift-XRT refined Analysis
  74. Fermi GRB 250626A: Global MASTER-Net observations report
  75. Swift GRB 250628A: Global MASTER-Net observations report
  76. GRB 250628A: Enhanced Swift-XRT position
  77. GRB 250628A: Swift detection of a burst
  78. GRB 250625A: Swift-BAT refined analysis
  79. GRB 250625A: Leavitt Observatory afterglow detection
  80. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  81. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  82. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  83. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  84. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  85. GRB 250626A: Fermi GBM Final Real-time Localization
  86. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  87. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  88. GRB 250625A: SVOM/C-GFT upper limit in early phase
  89. GRB 250625A: GECAM-B detection
  90. GRB 250625A: Swift/UVOT Upper Limits
  91. GRB 250625A: ABObservatory afterglow detection
  92. GRB 250625A: OHP/T193 optical detection
  93. GRB 250625A: COLIBRÍ optical observations
  94. GRB 250625A: Fermi-LAT detection
  95. GRB 250625A: Swift-XRT refined Analysis
  96. GRB 250625A: JinShan optical observations
  97. GRB250625A: Fermi GBM Observation
  98. Swift GRB 250625A: Global MASTER-Net observations report
  99. GRB 250625A: NOT z-band upper limit
  100. GRB 250625A: SVOM/VT optical confirmation

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