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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"

20387 results found.

  1. EP250711a: NOT optical counterpart candidate
  2. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  3. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  4. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  5. GRB 250704A: GRANDMA observations
  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. IceCube-250708A: No Candidates from WINTER
  10. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  11. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  12. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  13. EP250704a/GRB 250704B: 10 GHz VLA detection
  14. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  15. IceCube-250706A: No Candidates from WINTER
  16. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  17. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  18. EP250704a/GRB250704B : HCT optical and NIR upper limits
  19. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  20. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  21. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  23. GRB 250702F: radio detection with the VLA
  24. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  25. GRB 250706B/C: Fermi-LAT detection
  26. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  27. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  28. GRB 250706B: Swift/UVOT Detection
  29. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  30. GRB 250702F: GRANDMA observations
  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. IceCube-250416A: DDOTI Optical Upper Limit
  36. IceCube-250706A: COLIBRÍ optical upper limits
  37. GRB 250706A: JinShan optical upper limits
  38. GRB 250706A: SAO RAS optical observations
  39. EP250704A: NOWT Detection
  40. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  41. GRB 250706B: iTelescope optical observations
  42. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  43. GRB 250706B: SVOM/VT optical observation
  44. GRB 250706B: TRT bright optical counterpart detection
  45. GRB 250706A: GROWTH-India Telescope optical upper limit
  46. GRB 250706B: SVOM detection of a long burst
  47. GRB 250706A: Swift detection of a burst
  48. GRB 250704B: Swift-XRT refined Analysis
  49. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  50. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  51. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  52. GRB 250704B: Swift/UVOT Upper Limits
  53. GRB 250704A: Swift/UVOT Detection
  54. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  55. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  56. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  57. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  58. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  59. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  60. GRB 250702F: Kilonova-Catcher optical afterglow detection
  61. GRB 250702F: Monte Agliale Observatory optical observations
  62. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  63. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  64. EP250704a / GRB 250704B: JinShan optical observations
  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: Pan-STARRS iz-band imaging and photometry
  69. EP 250704a: BOOTES-5 optical detection
  70. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  71. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  72. GRB 250704A: Swift-XRT afterglow detection
  73. EP250704a / GRB 250704B - REM observations
  74. GRB 250702F: GROWTH-India Telescope optical observations
  75. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  76. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  77. EP250702a: WFST optical observations
  78. EP250704a: COLIBRÍ optical counterpart candidate
  79. EP250704a: Einstein Probe detection of an X-ray transient
  80. GRB 250704A: REM detection of the optical afterglow
  81. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  82. GRB 250704A: SVOM detection of a burst
  83. GRB 250702F: Swift/UVOT Detection
  84. GRB 250702F: Leavitt Observatory optical observations
  85. GRB 250702F: AKO Optical Afterglow Detection
  86. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  87. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  88. GRB 250702F: Skynet Optical Observations
  89. GRB 250424A: VIRT Optical Upper Limit
  90. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  91. GRB 250702F: TRT Optical Observation
  92. GRB 250703A: DDOTI Optical Upper Limit
  93. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  94. GRB 250702F: REM optical afterglow detection
  95. GRB 250702F: DDOTI Optical Observation
  96. GRB 250702F: COLIBRÍ Observations of the Afterglow
  97. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  98. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  99. GRB 250702F: Enhanced Swift-XRT position
  100. GRB 250702F: NOT observations of the optical afterglow

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