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

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