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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: Insight-HXMT detection
  2. EP/WXT 01709181970: GOTO observations confirm stellar variability
  3. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  4. EP250704a/GRB 250704B: 10 GHz VLA detection
  5. The EP-WXT trigger 01709181970 is likely a flaring star
  6. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  7. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  8. IceCube-250706A: No Candidates from WINTER
  9. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  10. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  11. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 250704B / EP250704a: VLA radio detection
  13. Fermi GRB 250708A: Global MASTER-Net observations report
  14. IceCube Alert 250708.59: Global MASTER-Net observations report
  15. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  16. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  17. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  18. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  19. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  20. EP250704a/GRB250704B : HCT optical and NIR upper limits
  21. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  22. GRB 250708A: Fermi GBM Final Real-time Localization
  23. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  24. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  25. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  26. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  27. GRB 250702F: radio detection with the VLA
  28. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  29. IceCube-250706A: EP-FXT follow-up observations
  30. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  31. GRB 250706B/C: Fermi-LAT detection
  32. IceCube Alert 250706.55: Global MASTER-Net observations report
  33. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  35. GRB 250706B: Swift/UVOT Detection
  36. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  37. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  38. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  39. GRB 250702F: GRANDMA observations
  40. GRB 250706A: Swift-XRT refined Analysis
  41. GRB 250706B: refined SVOM/MXT data analysis
  42. GRB 250706A: Swift/UVOT Upper Limits
  43. GRB 250706B: REM optical observations
  44. GRB 250706A: REM optical/NIR observations
  45. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  46. IceCube-250416A: DDOTI Optical Upper Limit
  47. IceCube-250706A: COLIBRÍ optical upper limits
  48. Swift GRB 250706A: Global MASTER-Net observations report
  49. GRB 250706A: JinShan optical upper limits
  50. GRB 250706A: SAO RAS optical observations
  51. EP250704A: NOWT Detection
  52. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  53. The EP-WXT trigger 01709181580 is likely a flaring star
  54. GRB250706B: Swift-XRT counterpart detection
  55. GRB 250706B: iTelescope optical observations
  56. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  57. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  58. GRB 250706B: SVOM/VT optical observation
  59. GRB 250706B: TRT bright optical counterpart detection
  60. GRB 250706A: GROWTH-India Telescope optical upper limit
  61. GRB 250706B: SVOM detection of a long burst
  62. GRB 250706A: Swift detection of a burst
  63. GRB 250704B: Swift-XRT refined Analysis
  64. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  65. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  66. GRB 250703A: EIRSAT-1 GMOD Detection
  67. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  68. GRB 250704B: Swift/UVOT Upper Limits
  69. GRB 250704A: Swift/UVOT Detection
  70. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  71. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  72. GRB 250704B: Insight-HXMT detection
  73. Konus-Wind detection of GRB 250703A
  74. IPN triangulation of GRB 250703A
  75. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  76. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  77. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  78. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  79. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  80. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  81. GRB 250702F: Kilonova-Catcher optical afterglow detection
  82. GRB 250702F: Monte Agliale Observatory optical observations
  83. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  84. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  85. EP250704a / GRB 250704B: JinShan optical observations
  86. GRB 250704A: SVOM/VT optical observation
  87. EP250704a / GRB 250704B: SAO RAS optical observations
  88. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  89. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  90. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  91. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  92. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  93. EP 250704a: BOOTES-5 optical detection
  94. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  95. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  96. GRB 250702A: Insight-HXMT detection
  97. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  98. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  99. EP250704a / GRB250704B: Swift-XRT counterpart detection
  100. GRB 250704A: Swift-XRT afterglow detection

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