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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

22214 results found.

  1. EP250226a/GRB 250226A: Kinder optical follow-up observations
  2. Fermi GRB 250226B: Global MASTER-Net observations report
  3. GRB 250221A: ATCA Detections and Upper Limits
  4. GRB 250225B: REM NIR upper limits
  5. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  6. GRB 250225B: VLT optical and near-infrared candidate counterpart
  7. GRB 250225B: VLT/FORS2 candidate optical afterglow
  8. GRB 250221A: EP-FXT detection of the X-ray afterglow
  9. EP250226a/GRB 250226A: GSP detects optical counterpart
  10. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  11. EP250226a: Global MASTER-Net observations report
  12. Swift GRB 250225B: Global MASTER-Net observations report
  13. Fermi GRB 250226A: Global MASTER-Net observations report
  14. Fermi trigger No 762205158: Global MASTER-Net observations report
  15. EP250225a: Global MASTER-Net observations report
  16. EP250225a: GSP optical upper limit
  17. EP250225a: Einstein Probe detected of a fast X-ray transient
  18. Fermi GRB 250225A: Global MASTER-Net observations report
  19. EP250223a: GROWTH-India Telescope optical observations
  20. EP250215A: J band upper limit by SYSU 80cm telescope
  21. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  22. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  23. EP250223a: Kinder optical follow-up observations
  24. GRB 250207a: ATCA Radio Upper Limits
  25. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  27. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  28. EP250223a: GOTO optical afterglow detections
  29. EP250223a: REM NIR upper limit
  30. EP250223a: TRT optical afterglow observation
  31. EP250223a: refined analysis of the EP-WXT and FXT observations
  32. EP250223a: 1.6m Mephisto and 50cm array observations
  33. EP250223a: SVOM/VT optical observation
  34. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  35. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  36. EP250223a: OASDG optical observations
  37. EP250223a: LCO detection of the afterglow
  38. EP250223a: NOT redshift z = 2.756
  39. EP250223a: NOT optical afterglow candidate
  40. EP250223a: Global MASTER-Net observations report
  41. GRB 250221A: VLA radio detection
  42. Fermi GRB 250223A: Global MASTER-Net observations report
  43. Fermi trigger No 762020305: Global MASTER-Net observations report
  44. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  45. GRB 250221A: continued Mondy optical observations, brightening afterglow
  46. GRB 250221A: Optical counterpart detection by LCO.
  47. GRB 250221A: Mondy optical observations
  48. GRB 250221A: Assy optical observations
  49. EP250220a: FTW optical and NIR observations and upper limits
  50. EP250220a: EP-FXT follow-up observations
  51. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  52. Fermi trigger No 761805304: Global MASTER-Net observations report
  53. GRB 250221A: NOT optical observations
  54. GRB 250221A: 1.6m Mephisto optical detection
  55. GRB 250221A: Swift/UVOT Detection
  56. EP250220a: Liverpool Telescope upper limits
  57. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  58. GRB 250221A: REM optical/NIR afterglow detection
  59. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  60. EP250220a: 1.6m Mephisto observations
  61. EP250220a: Optical upper limit with Kinder observations
  62. Swift GRB250221.15: Global MASTER-Net observations report
  63. EP250220a: Global MASTER-Net observations report
  64. GRB 250219A: Swift/UVOT Upper Limits
  65. GRB 250219A: OHP/T193 optical upper limit
  66. GRB 250219A: NOT optical observations
  67. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  68. GRB 250219A: 1.6m Mephisto optical upper limits
  69. GRB 250219A: SVOM/VT optical counterpart
  70. GRB 250219A: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  72. GRB 250219A: Swift ToO observations
  73. Konus-Wind detection of GRB 250215A / EP250215a
  74. GRB 250217C: Swift-XRT observations
  75. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  76. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  77. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  78. GRB 250217C: Tiled Swift observations
  79. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  80. GRB 250213A: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  82. Fermi GRB 250217C: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  84. Fermi GRB 250217A: Global MASTER-Net observations report
  85. GRANDMA/OPD observations of GRB250215A
  86. Fermi GRB 250216A: Global MASTER-Net observations report
  87. GRB 250215A / EP250215a: LCO detection of the afterglow
  88. EP250212a: FTW optical and NIR upper limits
  89. GRB 250215A: Swift/UVOT Upper Limits
  90. EP250215a / GRB 250215A : NOT optical observations
  91. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  92. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  93. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  94. EP250215a: Global MASTER-Net observations report
  95. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  96. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  97. Fermi GRB 250215A: Global MASTER-Net observations report
  98. Fermi trigger No 761206993: Global MASTER-Net observations report
  99. GRB 250213A：SVOM/VT optical candidate
  100. Fermi GRB 250214A: Global MASTER-Net observations report

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