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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"

26507 results found.

  1. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  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. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  8. IceCube-250708A: No Candidates from WINTER
  9. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  10. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  11. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  12. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  13. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  14. EP250704a/GRB 250704B: 10 GHz VLA detection
  15. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  16. IceCube-250706A: No Candidates from WINTER
  17. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  18. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  19. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  20. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  21. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  22. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  23. EP250704a/GRB250704B : HCT optical and NIR upper limits
  24. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  25. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  26. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  27. GRB 250702F: radio detection with the VLA
  28. IceCube-250706A: EP-FXT follow-up observations
  29. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  30. GRB 250706B/C: Fermi-LAT detection
  31. IceCube-250706A: Global MASTER-Net observations report
  32. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  34. GRB 250706B: Swift/UVOT Detection
  35. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  36. GRB 250702F: GRANDMA observations
  37. GRB 250706A: Swift-XRT refined Analysis
  38. GRB 250706B: refined SVOM/MXT data analysis
  39. GRB 250706A: Swift/UVOT Upper Limits
  40. GRB 250706B: REM optical observations
  41. GRB 250706A: REM optical/NIR observations
  42. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  43. IceCube-250416A: DDOTI Optical Upper Limit
  44. IceCube-250706A: COLIBRÍ optical upper limits
  45. GRB 250706A: JinShan optical upper limits
  46. GRB 250706A: SAO RAS optical observations
  47. EP250704A: NOWT Detection
  48. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  49. GRB250706B: Swift-XRT counterpart detection
  50. GRB 250706B: iTelescope optical observations
  51. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  52. GRB 250706B: SVOM/VT optical observation
  53. GRB 250706B: TRT bright optical counterpart detection
  54. GRB 250706A: GROWTH-India Telescope optical upper limit
  55. GRB 250706B: SVOM detection of a long burst
  56. GRB 250706A: Swift detection of a burst
  57. GRB 250704B: Swift-XRT refined Analysis
  58. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  59. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  60. GRB 250703A: EIRSAT-1 GMOD Detection
  61. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  62. GRB 250704B: Swift/UVOT Upper Limits
  63. GRB 250704A: Swift/UVOT Detection
  64. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  65. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  66. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  67. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  68. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  69. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  70. GRB 250702F: Kilonova-Catcher optical afterglow detection
  71. GRB 250702F: Monte Agliale Observatory optical observations
  72. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  73. EP250704a / GRB 250704B: JinShan optical observations
  74. EP250704a / GRB 250704B: SAO RAS optical observations
  75. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  76. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  77. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  78. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  79. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  80. EP250704a / GRB250704B: Swift-XRT counterpart detection
  81. GRB 250704A: Swift-XRT afterglow detection
  82. EP250704a / GRB 250704B - REM observations
  83. GRB 250702F: GROWTH-India Telescope optical observations
  84. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  85. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  86. EP250702a: WFST optical observations
  87. EP250704a: COLIBRÍ optical counterpart candidate
  88. EP250704a: Einstein Probe detection of an X-ray transient
  89. GRB 250704A: REM detection of the optical afterglow
  90. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  91. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  92. GRB 250704A: SVOM detection of a burst
  93. GRB 250702F: Swift/UVOT Detection
  94. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  95. GRB 250702F: Swift-XRT refined Analysis
  96. GRB 250702F: Fermi GBM Observation
  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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