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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. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  2. GRB 250703A: EIRSAT-1 GMOD Detection
  3. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  4. GRB 250704B: Swift/UVOT Upper Limits
  5. GRB 250704A: Swift/UVOT Detection
  6. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  7. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  8. GRB 250704B: Insight-HXMT detection
  9. Konus-Wind detection of GRB 250703A
  10. IPN triangulation of GRB 250703A
  11. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  12. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  13. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  14. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  15. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  16. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  17. GRB 250702F: Kilonova-Catcher optical afterglow detection
  18. GRB 250702F: Monte Agliale Observatory optical observations
  19. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  20. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  21. EP250704a / GRB 250704B: JinShan optical observations
  22. GRB 250704A: SVOM/VT optical observation
  23. EP250704a / GRB 250704B: SAO RAS optical observations
  24. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  25. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  26. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  27. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  28. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  29. EP 250704a: BOOTES-5 optical detection
  30. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  31. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  32. GRB 250702A: Insight-HXMT detection
  33. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  34. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  35. EP250704a / GRB250704B: Swift-XRT counterpart detection
  36. GRB 250704A: Swift-XRT afterglow detection
  37. GRB 250702B / EP2050702a: FTW optical and NIR observations
  38. Konus-Wind detection of GRB 250702F
  39. EP250704a / GRB 250704B - REM observations
  40. GRB 250702F: GROWTH-India Telescope optical observations
  41. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  42. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  43. EP250702a: WFST optical observations
  44. EP250704a: COLIBRÍ optical counterpart candidate
  45. EP250704a: Einstein Probe detection of an X-ray transient
  46. GRB 250704B: SVOM/GRM observation of a short burst
  47. GRB 250702F: optical photometry from Konkoly
  48. GRB 250704A: REM detection of the optical afterglow
  49. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  50. GRB 250702F: SVOM/VT optical observation
  51. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  52. GRB 250704A: SVOM detection of a burst
  53. GRB 250702F: Swift/UVOT Detection
  54. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  55. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  56. Fermi GRB 250703A: Global MASTER-Net observations report
  57. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  58. GRB 250702F: Swift-XRT refined Analysis
  59. GRB 250702F: Fermi GBM Observation
  60. GRB 250702F: Leavitt Observatory optical observations
  61. GRB 250702F: AKO Optical Afterglow Detection
  62. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  63. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  64. GRB 250702A: GECAM-B detection
  65. GRB 250702F: Skynet Optical Observations
  66. GRB 250424A: VIRT Optical Upper Limit
  67. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  68. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  69. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  70. GRB 250702F: TRT Optical Observation
  71. GRB 250703A: DDOTI Optical Upper Limit
  72. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  73. GRB 250702F: REM optical afterglow detection
  74. EP250702a: Global MASTER-Net observations report
  75. GRB 250702F: DDOTI Optical Observation
  76. GRB 250702B,C,D,E / EP 250702: MAXI/GSC detection
  77. GRB 250703A: Fermi GBM Final Real-time Localization
  78. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  79. GRB 250702F: COLIBRÍ Observations of the Afterglow
  80. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  81. Fermi GRB 250702E: Global MASTER-Net observations report
  82. Fermi GRB 250702B: Global MASTER-Net observations report
  83. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  84. GRB 250702F: Enhanced Swift-XRT position
  85. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  86. GRB 250702F: NOT observations of the optical afterglow
  87. GRB 250702F: MASTER optical afterglow observation
  88. Fermi GRB 250702F: Global MASTER-Net observations report
  89. Fermi GRB 250702C: Global MASTER-Net observations report
  90. GRB 250702F: GOTO optical counterpart detection
  91. GRB 250702F: Ondrejov D50 optical afterglow detection
  92. GRB 250702F: Swift detection of a burst with an optical counterpart
  93. Swift GRB250702.88: Global MASTER-Net observations report
  94. GRB 250702F: Fermi GBM Final Real-time Localization
  95. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  96. GRB 250702E: Fermi GBM Final Real-time Localization
  97. Konus-Wind detection of GRB 250627A
  98. IPN triangulation of GRB 250627A (short)
  99. GRB 250702A: Fermi GBM Detection
  100. GRB 250702D: Fermi GBM Final Localization Correction

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