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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"

18100 results found.

  1. GRB 250713A: SVOM/VT optical upper limit
  2. GRB 250713A: NOT optical upper limits
  3. GRB 250713A: OHP/T193 upper limit
  4. GRB 250713A: SVOM/C-GFT upper limit
  5. GRB 250706B/C: 7DT Follow-up Observations
  6. GRB 250713A: EP-FXT counterpart detection
  7. EP250711a: COLIBRÍ continuous optical observations
  8. GRB 250713A: JinShan optical upper limits
  9. GRB 250713A: SVOM detection of a short burst
  10. GRB 250711A: DDOTI Optical Upper Limit
  11. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  12. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  13. GRB 250711A: SVOM/GRM observation
  14. EP250711a: NOT optical counterpart candidate
  15. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  16. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  17. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  18. GRB 250704A: GRANDMA observations
  19. GRB 250704A: SVOM/ECLAIRs refined analysis
  20. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  21. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  22. IceCube-250708A: No Candidates from WINTER
  23. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  24. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  25. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  26. EP250704a/GRB 250704B: 10 GHz VLA detection
  27. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  28. IceCube-250706A: No Candidates from WINTER
  29. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  30. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  31. EP250704a/GRB250704B : HCT optical and NIR upper limits
  32. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  33. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  34. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  35. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  36. GRB 250702F: radio detection with the VLA
  37. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  38. GRB 250706B/C: Fermi-LAT detection
  39. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  40. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  41. GRB 250706B: Swift/UVOT Detection
  42. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 250702F: GRANDMA observations
  44. GRB 250706A: Swift/UVOT Upper Limits
  45. GRB 250706B: REM optical observations
  46. GRB 250706A: REM optical/NIR observations
  47. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  48. IceCube-250416A: DDOTI Optical Upper Limit
  49. IceCube-250706A: COLIBRÍ optical upper limits
  50. GRB 250706A: JinShan optical upper limits
  51. GRB 250706A: SAO RAS optical observations
  52. EP250704A: NOWT Detection
  53. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  54. GRB 250706B: iTelescope optical observations
  55. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  56. GRB 250706B: SVOM/VT optical observation
  57. GRB 250706B: TRT bright optical counterpart detection
  58. GRB 250706A: GROWTH-India Telescope optical upper limit
  59. GRB 250706B: SVOM detection of a long burst
  60. GRB 250706A: Swift detection of a burst
  61. GRB 250704B: Swift-XRT refined Analysis
  62. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  63. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  64. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  65. GRB 250704B: Swift/UVOT Upper Limits
  66. GRB 250704A: Swift/UVOT Detection
  67. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  68. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  69. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  70. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  71. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  72. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  73. GRB 250702F: Kilonova-Catcher optical afterglow detection
  74. GRB 250702F: Monte Agliale Observatory optical observations
  75. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  76. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  77. EP250704a / GRB 250704B: JinShan optical observations
  78. EP250704a / GRB 250704B: SAO RAS optical observations
  79. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  80. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  81. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  82. EP 250704a: BOOTES-5 optical detection
  83. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  84. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  85. GRB 250704A: Swift-XRT afterglow detection
  86. EP250704a / GRB 250704B - REM observations
  87. GRB 250702F: GROWTH-India Telescope optical observations
  88. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  89. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  90. EP250702a: WFST optical observations
  91. EP250704a: COLIBRÍ optical counterpart candidate
  92. EP250704a: Einstein Probe detection of an X-ray transient
  93. GRB 250704A: REM detection of the optical afterglow
  94. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  95. GRB 250704A: SVOM detection of a burst
  96. GRB 250702F: Swift/UVOT Detection
  97. GRB 250702F: Leavitt Observatory optical observations
  98. GRB 250702F: AKO Optical Afterglow Detection
  99. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  100. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation

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