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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"

27395 results found.

  1. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  2. IceCube-250706A: No Candidates from WINTER
  3. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  4. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  5. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  6. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  7. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  8. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  9. EP250704a/GRB250704B : HCT optical and NIR upper limits
  10. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  11. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  12. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  13. GRB 250702F: radio detection with the VLA
  14. IceCube-250706A: EP-FXT follow-up observations
  15. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  16. GRB 250706B/C: Fermi-LAT detection
  17. IceCube-250706A: Global MASTER-Net observations report
  18. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  19. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  20. GRB 250706B: Swift/UVOT Detection
  21. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 250702F: GRANDMA observations
  23. GRB 250706A: Swift-XRT refined Analysis
  24. GRB 250706B: refined SVOM/MXT data analysis
  25. GRB 250706A: Swift/UVOT Upper Limits
  26. GRB 250706B: REM optical observations
  27. GRB 250706A: REM optical/NIR observations
  28. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  29. IceCube-250416A: DDOTI Optical Upper Limit
  30. IceCube-250706A: COLIBRÍ optical upper limits
  31. GRB 250706A: JinShan optical upper limits
  32. GRB 250706A: SAO RAS optical observations
  33. EP250704A: NOWT Detection
  34. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  35. GRB250706B: Swift-XRT counterpart detection
  36. GRB 250706B: iTelescope optical observations
  37. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  38. GRB 250706B: SVOM/VT optical observation
  39. GRB 250706B: TRT bright optical counterpart detection
  40. GRB 250706A: GROWTH-India Telescope optical upper limit
  41. GRB 250706B: SVOM detection of a long burst
  42. GRB 250706A: Swift detection of a burst
  43. GRB 250704B: Swift-XRT refined Analysis
  44. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  45. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  46. GRB 250703A: EIRSAT-1 GMOD Detection
  47. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  48. GRB 250704B: Swift/UVOT Upper Limits
  49. GRB 250704A: Swift/UVOT Detection
  50. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  51. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  52. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  53. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  54. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  55. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  56. GRB 250702F: Kilonova-Catcher optical afterglow detection
  57. GRB 250702F: Monte Agliale Observatory optical observations
  58. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  59. EP250704a / GRB 250704B: JinShan optical observations
  60. EP250704a / GRB 250704B: SAO RAS optical observations
  61. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  62. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  63. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  64. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  65. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  66. EP250704a / GRB250704B: Swift-XRT counterpart detection
  67. GRB 250704A: Swift-XRT afterglow detection
  68. EP250704a / GRB 250704B - REM observations
  69. GRB 250702F: GROWTH-India Telescope optical observations
  70. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  71. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  72. EP250702a: WFST optical observations
  73. EP250704a: COLIBRÍ optical counterpart candidate
  74. EP250704a: Einstein Probe detection of an X-ray transient
  75. GRB 250704A: REM detection of the optical afterglow
  76. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  77. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  78. GRB 250704A: SVOM detection of a burst
  79. GRB 250702F: Swift/UVOT Detection
  80. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  81. GRB 250702F: Swift-XRT refined Analysis
  82. GRB 250702F: Fermi GBM Observation
  83. GRB 250702F: Leavitt Observatory optical observations
  84. GRB 250702F: AKO Optical Afterglow Detection
  85. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  86. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  87. GRB 250702F: Skynet Optical Observations
  88. GRB 250424A: VIRT Optical Upper Limit
  89. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  90. GRB 250702F: TRT Optical Observation
  91. GRB 250703A: DDOTI Optical Upper Limit
  92. GRB 250702F: REM optical afterglow detection
  93. EP250702a: Global MASTER-Net observations report
  94. GRB 250702F: DDOTI Optical Observation
  95. GRB 250702F: COLIBRÍ Observations of the Afterglow
  96. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  97. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  98. GRB 250702F: Enhanced Swift-XRT position
  99. GRB 250702F: NOT observations of the optical afterglow
  100. GRB 250702F: Swift detection of a burst with an optical counterpart

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