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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"

25043 results found.

  1. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  2. GRB 250717B: COLIBRÍ optical upper limit
  3. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  4. GRB 250717B: Swift-XRT observations
  5. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  6. Swift GRB250718.01: Global MASTER-Net observations report
  7. GRB 270713A: Kitab and AbAO Optical Observations
  8. GRB 250717B: Fermi GBM Observation
  9. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  10. GRB 250716A: Swift-XRT afterglow detection
  11. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  12. GRB 250716A: Fermi GBM Observation
  13. GRB 250714A: SVOM/GRM observation
  14. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  15. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  16. GRB 250713A: Mephisto optical upper limits
  17. GRB 250713A: SVOM/VT optical upper limit
  18. GRB 250713A: NOT optical upper limits
  19. GRB 250713A: OHP/T193 upper limit
  20. GRB 250713A: SVOM/C-GFT upper limit
  21. GRB 250706B/C: 7DT Follow-up Observations
  22. GRB 250713A: Swift-XRT observations
  23. GRB 250713A: EP-FXT counterpart detection
  24. EP250711a: COLIBRÍ continuous optical observations
  25. GRB 250706A: Swift-BAT refined analysis
  26. GRB 250702F: Swift-BAT refined analysis
  27. GRB 250628A: Swift-BAT refined analysis
  28. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  29. GRB 250713A: JinShan optical upper limits
  30. GRB 250713A: SVOM detection of a long burst
  31. EP250711a: Global MASTER-Net observations report
  32. GRB 250711A: DDOTI Optical Upper Limit
  33. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  34. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  35. GRB 250711A: SVOM/GRM observation
  36. EP250711a: NOT optical counterpart candidate
  37. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  38. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  39. GRB 250704A: GRANDMA observations
  40. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  41. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  42. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  43. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  44. IceCube-250708A: No Candidates from WINTER
  45. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  46. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  47. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  48. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  49. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  50. EP250704a/GRB 250704B: 10 GHz VLA detection
  51. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  52. IceCube-250706A: No Candidates from WINTER
  53. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  54. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  55. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  56. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  57. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  58. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  59. EP250704a/GRB250704B : HCT optical and NIR upper limits
  60. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  61. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  62. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  63. GRB 250702F: radio detection with the VLA
  64. IceCube-250706A: EP-FXT follow-up observations
  65. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  66. GRB 250706B/C: Fermi-LAT detection
  67. IceCube-250706A: Global MASTER-Net observations report
  68. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  69. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  70. GRB 250706B: Swift/UVOT Detection
  71. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250702F: GRANDMA observations
  73. GRB 250706A: Swift-XRT refined Analysis
  74. GRB 250706B: refined SVOM/MXT data analysis
  75. GRB 250706A: Swift/UVOT Upper Limits
  76. GRB 250706B: REM optical observations
  77. GRB 250706A: REM optical/NIR observations
  78. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  79. IceCube-250416A: DDOTI Optical Upper Limit
  80. IceCube-250706A: COLIBRÍ optical upper limits
  81. GRB 250706A: JinShan optical upper limits
  82. GRB 250706A: SAO RAS optical observations
  83. EP250704A: NOWT Detection
  84. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  85. GRB250706B: Swift-XRT counterpart detection
  86. GRB 250706B: iTelescope optical observations
  87. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  88. GRB 250706B: SVOM/VT optical observation
  89. GRB 250706B: TRT bright optical counterpart detection
  90. GRB 250706A: GROWTH-India Telescope optical upper limit
  91. GRB 250706B: SVOM detection of a long burst
  92. GRB 250706A: Swift detection of a burst
  93. GRB 250704B: Swift-XRT refined Analysis
  94. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  95. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  96. GRB 250703A: EIRSAT-1 GMOD Detection
  97. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  98. GRB 250704B: Swift/UVOT Upper Limits
  99. GRB 250704A: Swift/UVOT Detection
  100. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate

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