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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"

35268 results found.

  1. GRB 250702B,D,E / EP250702a: ALMA detection
  2. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  3. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  4. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  5. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  6. GRB 250709A: Fermi GBM Final Localization
  7. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  8. GRB 250706B/C: Insight-HXMT detection
  9. EP250704a/GRB 250704B: 10 GHz VLA detection
  10. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  11. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  12. GRB 250704B / EP250704a: VLA radio detection
  13. Fermi GRB 250708A: Global MASTER-Net observations report
  14. EP250704a/GRB250704B : HCT optical and NIR upper limits
  15. GRB 250708A: Fermi GBM Final Real-time Localization
  16. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  17. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  18. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  19. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  20. GRB 250702F: radio detection with the VLA
  21. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  22. GRB 250706B/C: Fermi-LAT detection
  23. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  24. GRB 250706B: Swift/UVOT Detection
  25. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  26. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  27. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  28. GRB 250702F: GRANDMA observations
  29. GRB 250706A: Swift-XRT refined Analysis
  30. GRB 250706B: refined SVOM/MXT data analysis
  31. GRB 250706A: Swift/UVOT Upper Limits
  32. GRB 250706B: REM optical observations
  33. GRB 250706A: REM optical/NIR observations
  34. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  35. Swift GRB 250706A: Global MASTER-Net observations report
  36. GRB 250706A: JinShan optical upper limits
  37. GRB 250706A: SAO RAS optical observations
  38. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  39. GRB250706B: Swift-XRT counterpart detection
  40. GRB 250706B: iTelescope optical observations
  41. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  42. GRB 250706B: SVOM/VT optical observation
  43. GRB 250706B: TRT bright optical counterpart detection
  44. GRB 250706A: GROWTH-India Telescope optical upper limit
  45. GRB 250706B: SVOM detection of a long burst
  46. GRB 250706A: Swift detection of a burst
  47. GRB 250704B: Swift-XRT refined Analysis
  48. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  49. GRB 250703A: EIRSAT-1 GMOD Detection
  50. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  51. GRB 250704B: Swift/UVOT Upper Limits
  52. GRB 250704A: Swift/UVOT Detection
  53. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  54. GRB 250704B: Insight-HXMT detection
  55. Konus-Wind detection of GRB 250703A
  56. IPN triangulation of GRB 250703A
  57. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  58. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  59. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  60. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  61. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  62. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  63. GRB 250702F: Kilonova-Catcher optical afterglow detection
  64. GRB 250702F: Monte Agliale Observatory optical observations
  65. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  66. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  67. EP250704a / GRB 250704B: JinShan optical observations
  68. GRB 250704A: SVOM/VT optical observation
  69. EP250704a / GRB 250704B: SAO RAS optical observations
  70. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  71. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  72. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  73. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  74. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  75. GRB 250702A: Insight-HXMT detection
  76. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  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. EP250704a: Einstein Probe detection of an X-ray transient
  86. GRB 250704B: SVOM/GRM observation of a short burst
  87. GRB 250702F: optical photometry from Konkoly
  88. GRB 250704A: REM detection of the optical afterglow
  89. GRB 250702F: SVOM/VT optical observation
  90. GRB 250704A: SVOM detection of a burst
  91. GRB 250702F: Swift/UVOT Detection
  92. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  93. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  94. Fermi GRB 250703A: Global MASTER-Net observations report
  95. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  96. GRB 250702F: Swift-XRT refined Analysis
  97. GRB 250702F: Fermi GBM Observation
  98. GRB 250702F: Leavitt Observatory optical observations
  99. GRB 250702F: AKO Optical Afterglow Detection
  100. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate

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