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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. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  2. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  3. EP250704a / GRB 250704B: JinShan optical observations
  4. GRB 250704A: SVOM/VT optical observation
  5. EP250704a / GRB 250704B: SAO RAS optical observations
  6. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  7. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  8. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  9. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  10. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  11. EP 250704a: BOOTES-5 optical detection
  12. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  13. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  14. GRB 250702A: Insight-HXMT detection
  15. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  16. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  17. EP250704a / GRB250704B: Swift-XRT counterpart detection
  18. GRB 250704A: Swift-XRT afterglow detection
  19. GRB 250702B / EP2050702a: FTW optical and NIR observations
  20. Konus-Wind detection of GRB 250702F
  21. EP250704a / GRB 250704B - REM observations
  22. GRB 250702F: GROWTH-India Telescope optical observations
  23. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  24. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  25. EP250702a: WFST optical observations
  26. EP250704a: COLIBRÍ optical counterpart candidate
  27. EP250704a: Einstein Probe detection of an X-ray transient
  28. GRB 250704B: SVOM/GRM observation of a short burst
  29. GRB 250702F: optical photometry from Konkoly
  30. GRB 250704A: REM detection of the optical afterglow
  31. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  32. GRB 250702F: SVOM/VT optical observation
  33. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  34. GRB 250704A: SVOM detection of a burst
  35. GRB 250702F: Swift/UVOT Detection
  36. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  37. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  38. Fermi GRB 250703A: Global MASTER-Net observations report
  39. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  40. GRB 250702F: Swift-XRT refined Analysis
  41. GRB 250702F: Fermi GBM Observation
  42. GRB 250702F: Leavitt Observatory optical observations
  43. GRB 250702F: AKO Optical Afterglow Detection
  44. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  45. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  46. GRB 250702A: GECAM-B detection
  47. GRB 250702F: Skynet Optical Observations
  48. GRB 250424A: VIRT Optical Upper Limit
  49. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  50. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  51. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  52. GRB 250702F: TRT Optical Observation
  53. GRB 250703A: DDOTI Optical Upper Limit
  54. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  55. GRB 250702F: REM optical afterglow detection
  56. EP250702a: Global MASTER-Net observations report
  57. GRB 250702F: DDOTI Optical Observation
  58. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  59. GRB 250703A: Fermi GBM Final Real-time Localization
  60. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  61. GRB 250702F: COLIBRÍ Observations of the Afterglow
  62. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  63. Fermi GRB 250702E: Global MASTER-Net observations report
  64. Fermi GRB 250702B: Global MASTER-Net observations report
  65. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  66. GRB 250702F: Enhanced Swift-XRT position
  67. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  68. GRB 250702F: NOT observations of the optical afterglow
  69. GRB 250702F: MASTER optical afterglow observation
  70. Fermi GRB 250702F: Global MASTER-Net observations report
  71. Fermi GRB 250702C: Global MASTER-Net observations report
  72. GRB 250702F: GOTO optical counterpart detection
  73. GRB 250702F: Ondrejov D50 optical afterglow detection
  74. GRB 250702F: Swift detection of a burst with an optical counterpart
  75. Swift GRB 250702F: Global MASTER-Net observations report
  76. GRB 250702F: Fermi GBM Final Real-time Localization
  77. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  78. GRB 250702E: Fermi GBM Final Real-time Localization
  79. Konus-Wind detection of GRB 250627A
  80. IPN triangulation of GRB 250627A (short)
  81. GRB 250702A: Fermi GBM Detection
  82. GRB 250702D: Fermi GBM Final Localization Correction
  83. GRB 250702C: Fermi GBM Final Real-time Localization
  84. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  85. GRB 250702B: Fermi GBM Final Real-time Localization
  86. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  87. GRB 250702A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  89. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  90. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  91. GRB 250628B: Swift-XRT observations
  92. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  93. GRB 250628B: SVOM/VT optical upper limit
  94. GRB 250628B: EP-FXT counterpart detection
  95. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  96. GRB 250627A: Insight-HXMT detection
  97. GRB 250627A: SVOM/GRM detection of a short burst
  98. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)

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