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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 250706B/C: Konus-Wind analysis of the prompt emission
  2. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  3. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  4. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  5. GRB 250702F: radio detection with the VLA
  6. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  7. IceCube-250706A: EP-FXT follow-up observations
  8. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  9. GRB 250706B/C: Fermi-LAT detection
  10. IceCube-250706A: Global MASTER-Net observations report
  11. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  12. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  13. GRB 250706B: Swift/UVOT Detection
  14. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  15. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  16. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  17. GRB 250702F: GRANDMA observations
  18. GRB 250706A: Swift-XRT refined Analysis
  19. GRB 250706B: refined SVOM/MXT data analysis
  20. GRB 250706A: Swift/UVOT Upper Limits
  21. GRB 250706B: REM optical observations
  22. GRB 250706A: REM optical/NIR observations
  23. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  24. IceCube-250416A: DDOTI Optical Upper Limit
  25. IceCube-250706A: COLIBRÍ optical upper limits
  26. Swift GRB 250706A: Global MASTER-Net observations report
  27. GRB 250706A: JinShan optical upper limits
  28. GRB 250706A: SAO RAS optical observations
  29. EP250704A: NOWT Detection
  30. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  31. The EP-WXT trigger 01709181580 is likely a flaring star
  32. GRB250706B: Swift-XRT counterpart detection
  33. GRB 250706B: iTelescope optical observations
  34. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  35. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  36. GRB 250706B: SVOM/VT optical observation
  37. GRB 250706B: TRT bright optical counterpart detection
  38. GRB 250706A: GROWTH-India Telescope optical upper limit
  39. GRB 250706B: SVOM detection of a long burst
  40. GRB 250706A: Swift detection of a burst
  41. GRB 250704B: Swift-XRT refined Analysis
  42. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  43. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  44. GRB 250703A: EIRSAT-1 GMOD Detection
  45. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  46. GRB 250704B: Swift/UVOT Upper Limits
  47. GRB 250704A: Swift/UVOT Detection
  48. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  49. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  50. GRB 250704B: Insight-HXMT detection
  51. Konus-Wind detection of GRB 250703A
  52. IPN triangulation of GRB 250703A
  53. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  54. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  55. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  56. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  57. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  58. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  59. GRB 250702F: Kilonova-Catcher optical afterglow detection
  60. GRB 250702F: Monte Agliale Observatory optical observations
  61. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  62. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  63. EP250704a / GRB 250704B: JinShan optical observations
  64. GRB 250704A: SVOM/VT optical observation
  65. EP250704a / GRB 250704B: SAO RAS optical observations
  66. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  67. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  68. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  69. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  70. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  71. EP 250704a: BOOTES-5 optical detection
  72. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  73. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  74. GRB 250702A: Insight-HXMT detection
  75. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  76. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  77. EP250704a / GRB250704B: Swift-XRT counterpart detection
  78. GRB 250704A: Swift-XRT afterglow detection
  79. GRB 250702B / EP2050702a: FTW optical and NIR observations
  80. Konus-Wind detection of GRB 250702F
  81. EP250704a / GRB 250704B - REM observations
  82. GRB 250702F: GROWTH-India Telescope optical observations
  83. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  84. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  85. EP250702a: WFST optical observations
  86. EP250704a: COLIBRÍ optical counterpart candidate
  87. EP250704a: Einstein Probe detection of an X-ray transient
  88. GRB 250704B: SVOM/GRM observation of a short burst
  89. GRB 250702F: optical photometry from Konkoly
  90. GRB 250704A: REM detection of the optical afterglow
  91. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  92. GRB 250702F: SVOM/VT optical observation
  93. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  94. GRB 250704A: SVOM detection of a burst
  95. GRB 250702F: Swift/UVOT Detection
  96. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  97. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  98. Fermi GRB 250703A: Global MASTER-Net observations report
  99. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  100. GRB 250702F: Swift-XRT refined Analysis

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