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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. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  2. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  3. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  4. GRB 250702F: Kilonova-Catcher optical afterglow detection
  5. GRB 250702F: Monte Agliale Observatory optical observations
  6. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  7. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  8. EP250704a / GRB 250704B: JinShan optical observations
  9. GRB 250704A: SVOM/VT optical observation
  10. EP250704a / GRB 250704B: SAO RAS optical observations
  11. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  12. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  13. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  14. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  15. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  16. EP 250704a: BOOTES-5 optical detection
  17. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  18. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  19. GRB 250702A: Insight-HXMT detection
  20. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  21. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  22. EP250704a / GRB250704B: Swift-XRT counterpart detection
  23. GRB 250704A: Swift-XRT afterglow detection
  24. GRB 250702B / EP2050702a: FTW optical and NIR observations
  25. Konus-Wind detection of GRB 250702F
  26. EP250704a / GRB 250704B - REM observations
  27. GRB 250702F: GROWTH-India Telescope optical observations
  28. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  29. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  30. EP250702a: WFST optical observations
  31. EP250704a: COLIBRÍ optical counterpart candidate
  32. EP250704a: Einstein Probe detection of an X-ray transient
  33. GRB 250704B: SVOM/GRM observation of a short burst
  34. GRB 250702F: optical photometry from Konkoly
  35. GRB 250704A: REM detection of the optical afterglow
  36. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  37. GRB 250702F: SVOM/VT optical observation
  38. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  39. GRB 250704A: SVOM detection of a burst
  40. GRB 250702F: Swift/UVOT Detection
  41. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  42. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  43. Fermi GRB 250703A: Global MASTER-Net observations report
  44. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  45. GRB 250702F: Swift-XRT refined Analysis
  46. GRB 250702F: Fermi GBM Observation
  47. GRB 250702F: Leavitt Observatory optical observations
  48. GRB 250702F: AKO Optical Afterglow Detection
  49. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  50. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  51. GRB 250702A: GECAM-B detection
  52. GRB 250702F: Skynet Optical Observations
  53. GRB 250424A: VIRT Optical Upper Limit
  54. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  55. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  56. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  57. GRB 250702F: TRT Optical Observation
  58. GRB 250703A: DDOTI Optical Upper Limit
  59. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  60. GRB 250702F: REM optical afterglow detection
  61. EP250702a: Global MASTER-Net observations report
  62. GRB 250702F: DDOTI Optical Observation
  63. GRB 250702B,C,D,E / EP 250702: MAXI/GSC detection
  64. GRB 250703A: Fermi GBM Final Real-time Localization
  65. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  66. GRB 250702F: COLIBRÍ Observations of the Afterglow
  67. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  68. Fermi GRB 250702E: Global MASTER-Net observations report
  69. Fermi GRB 250702B: Global MASTER-Net observations report
  70. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  71. GRB 250702F: Enhanced Swift-XRT position
  72. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  73. GRB 250702F: NOT observations of the optical afterglow
  74. GRB 250702F: MASTER optical afterglow observation
  75. Fermi GRB 250702F: Global MASTER-Net observations report
  76. Fermi GRB 250702C: Global MASTER-Net observations report
  77. GRB 250702F: GOTO optical counterpart detection
  78. GRB 250702F: Ondrejov D50 optical afterglow detection
  79. GRB 250702F: Swift detection of a burst with an optical counterpart
  80. Swift GRB 250702F: Global MASTER-Net observations report
  81. GRB 250702F: Fermi GBM Final Real-time Localization
  82. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  83. GRB 250702E: Fermi GBM Final Real-time Localization
  84. Konus-Wind detection of GRB 250627A
  85. IPN triangulation of GRB 250627A (short)
  86. GRB 250702A: Fermi GBM Detection
  87. GRB 250702D: Fermi GBM Final Localization Correction
  88. GRB 250702C: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  90. GRB 250702B: Fermi GBM Final Real-time Localization
  91. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  92. GRB 250702A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  95. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  96. GRB 250628B: Swift-XRT observations
  97. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  98. GRB 250628B: SVOM/VT optical upper limit
  99. GRB 250628B: EP-FXT counterpart detection
  100. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization

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