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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"

22215 results found.

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

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