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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. GRB 250706A: Swift detection of a burst
  2. GRB 250704B: Swift-XRT refined Analysis
  3. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  4. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  5. GRB 250703A: EIRSAT-1 GMOD Detection
  6. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  7. GRB 250704B: Swift/UVOT Upper Limits
  8. GRB 250704A: Swift/UVOT Detection
  9. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  10. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  11. GRB 250704B: Insight-HXMT detection
  12. Konus-Wind detection of GRB 250703A
  13. IPN triangulation of GRB 250703A
  14. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  15. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  16. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  17. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  18. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  19. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  20. GRB 250702F: Kilonova-Catcher optical afterglow detection
  21. GRB 250702F: Monte Agliale Observatory optical observations
  22. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  23. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  24. EP250704a / GRB 250704B: JinShan optical observations
  25. GRB 250704A: SVOM/VT optical observation
  26. EP250704a / GRB 250704B: SAO RAS optical observations
  27. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  28. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  29. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  30. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  31. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  32. EP 250704a: BOOTES-5 optical detection
  33. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  34. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  35. GRB 250702A: Insight-HXMT detection
  36. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  37. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  38. EP250704a / GRB250704B: Swift-XRT counterpart detection
  39. GRB 250704A: Swift-XRT afterglow detection
  40. GRB 250702B / EP2050702a: FTW optical and NIR observations
  41. Konus-Wind detection of GRB 250702F
  42. EP250704a / GRB 250704B - REM observations
  43. GRB 250702F: GROWTH-India Telescope optical observations
  44. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  45. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  46. EP250702a: WFST optical observations
  47. EP250704a: COLIBRÍ optical counterpart candidate
  48. EP250704a: Einstein Probe detection of an X-ray transient
  49. GRB 250704B: SVOM/GRM observation of a short burst
  50. GRB 250702F: optical photometry from Konkoly
  51. GRB 250704A: REM detection of the optical afterglow
  52. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  53. GRB 250702F: SVOM/VT optical observation
  54. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  55. GRB 250704A: SVOM detection of a burst
  56. GRB 250702F: Swift/UVOT Detection
  57. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  58. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  59. Fermi GRB 250703A: Global MASTER-Net observations report
  60. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  61. GRB 250702F: Swift-XRT refined Analysis
  62. GRB 250702F: Fermi GBM Observation
  63. GRB 250702F: Leavitt Observatory optical observations
  64. GRB 250702F: AKO Optical Afterglow Detection
  65. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  66. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  67. GRB 250702A: GECAM-B detection
  68. GRB 250702F: Skynet Optical Observations
  69. GRB 250424A: VIRT Optical Upper Limit
  70. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  71. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  72. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  73. GRB 250702F: TRT Optical Observation
  74. GRB 250703A: DDOTI Optical Upper Limit
  75. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  76. GRB 250702F: REM optical afterglow detection
  77. EP250702a: Global MASTER-Net observations report
  78. GRB 250702F: DDOTI Optical Observation
  79. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  80. GRB 250703A: Fermi GBM Final Real-time Localization
  81. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  82. GRB 250702F: COLIBRÍ Observations of the Afterglow
  83. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  84. Fermi GRB 250702E: Global MASTER-Net observations report
  85. Fermi GRB 250702B: Global MASTER-Net observations report
  86. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  87. GRB 250702F: Enhanced Swift-XRT position
  88. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  89. GRB 250702F: NOT observations of the optical afterglow
  90. GRB 250702F: MASTER optical afterglow observation
  91. Fermi GRB 250702F: Global MASTER-Net observations report
  92. Fermi GRB 250702C: Global MASTER-Net observations report
  93. GRB 250702F: GOTO optical counterpart detection
  94. GRB 250702F: Ondrejov D50 optical afterglow detection
  95. GRB 250702F: Swift detection of a burst with an optical counterpart
  96. Swift GRB 250702F: Global MASTER-Net observations report
  97. GRB 250702F: Fermi GBM Final Real-time Localization
  98. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  99. GRB 250702E: Fermi GBM Final Real-time Localization
  100. Konus-Wind detection of GRB 250627A

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