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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. Fermi GRB 250711A: Global MASTER-Net observations report
  2. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  3. GRB 250704A: GRANDMA observations
  4. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  5. GRB 250711A: Fermi GBM Final Real-time Localization
  6. GRB 250704A: SVOM/ECLAIRs refined analysis
  7. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  8. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  9. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  10. GRB 250702B,D,E / EP250702a: ALMA detection
  11. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  12. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  13. IceCube-250708A: No Candidates from WINTER
  14. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  15. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  16. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  17. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 250709A: Fermi GBM Final Localization
  19. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  20. GRB 250706B/C: Insight-HXMT detection
  21. EP/WXT 01709181970: GOTO observations confirm stellar variability
  22. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  23. EP250704a/GRB 250704B: 10 GHz VLA detection
  24. The EP-WXT trigger 01709181970 is likely a flaring star
  25. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  26. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  27. IceCube-250706A: No Candidates from WINTER
  28. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  29. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  30. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 250704B / EP250704a: VLA radio detection
  32. Fermi GRB 250708A: Global MASTER-Net observations report
  33. IceCube-250708A: Global MASTER-Net observations report
  34. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  35. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  36. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  37. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  38. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  39. EP250704a/GRB250704B : HCT optical and NIR upper limits
  40. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  41. GRB 250708A: Fermi GBM Final Real-time Localization
  42. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  43. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  44. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  45. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  46. GRB 250702F: radio detection with the VLA
  47. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  48. IceCube-250706A: EP-FXT follow-up observations
  49. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  50. GRB 250706B/C: Fermi-LAT detection
  51. IceCube-250706A: Global MASTER-Net observations report
  52. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  54. GRB 250706B: Swift/UVOT Detection
  55. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  56. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  57. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  58. GRB 250702F: GRANDMA observations
  59. GRB 250706A: Swift-XRT refined Analysis
  60. GRB 250706B: refined SVOM/MXT data analysis
  61. GRB 250706A: Swift/UVOT Upper Limits
  62. GRB 250706B: REM optical observations
  63. GRB 250706A: REM optical/NIR observations
  64. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  65. IceCube-250416A: DDOTI Optical Upper Limit
  66. IceCube-250706A: COLIBRÍ optical upper limits
  67. Swift GRB 250706A: Global MASTER-Net observations report
  68. GRB 250706A: JinShan optical upper limits
  69. GRB 250706A: SAO RAS optical observations
  70. EP250704A: NOWT Detection
  71. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  72. The EP-WXT trigger 01709181580 is likely a flaring star
  73. GRB250706B: Swift-XRT counterpart detection
  74. GRB 250706B: iTelescope optical observations
  75. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  76. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  77. GRB 250706B: SVOM/VT optical observation
  78. GRB 250706B: TRT bright optical counterpart detection
  79. GRB 250706A: GROWTH-India Telescope optical upper limit
  80. GRB 250706B: SVOM detection of a long burst
  81. GRB 250706A: Swift detection of a burst
  82. GRB 250704B: Swift-XRT refined Analysis
  83. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  84. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  85. GRB 250703A: EIRSAT-1 GMOD Detection
  86. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  87. GRB 250704B: Swift/UVOT Upper Limits
  88. GRB 250704A: Swift/UVOT Detection
  89. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  90. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  91. GRB 250704B: Insight-HXMT detection
  92. Konus-Wind detection of GRB 250703A
  93. IPN triangulation of GRB 250703A
  94. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  95. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  96. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  98. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  99. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  100. GRB 250702F: Kilonova-Catcher optical afterglow detection

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