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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"

24389 results found.

  1. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  3. GRB 250119B: VZLUSAT-2 detection
  4. GRB 250223C: Fermi GBM Final Real-time Localization
  5. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  6. GRB 250202B: VZLUSAT-2 detection
  7. GRB 250222A: SVOM/GRM observation of a burst
  8. GRB 250210A: VZLUSAT-2 detection
  9. GRB 250206A: VZLUSAT-2 detection
  10. EP250223a: REM NIR upper limit
  11. EP250223a: 1.6m Mephisto and 50cm array observations
  12. EP250223a: SVOM/VT optical observation
  13. 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
  14. EP250223a: Swift/XRT localization
  15. EP250223a: NOT optical afterglow candidate
  16. GRB 250223B: Fermi GBM Final Localization
  17. EP250223a: Global MASTER-Net observations report
  18. GRB 250221A: VLA radio detection
  19. Fermi GRB 250223A: Global MASTER-Net observations report
  20. Fermi trigger No 762020305: Global MASTER-Net observations report
  21. GRB 250223A: Fermi GBM Final Real-time Localization
  22. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  23. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  24. Konus-Wind detection of GRB 250221A
  25. EP250220a: FTW optical and NIR observations and upper limits
  26. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  27. GRB 250221A: VLT/X-shooter redshift z = 0.768
  28. Fermi trigger No 761805304: Global MASTER-Net observations report
  29. GRB 250221A: NOT optical observations
  30. GRB 250221A: 1.6m Mephisto optical detection
  31. GRB 250221A: AKO Optical Upper Limit
  32. GRB 250221A: REM optical/NIR afterglow detection
  33. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  34. EP250220a: 1.6m Mephisto observations
  35. EP250220a: Optical upper limit with Kinder observations
  36. SVOM/sb25022102: SVOM detection of an X-ray transient
  37. Swift GRB250221.15: Global MASTER-Net OT detection
  38. Swift GRB250221.15: Global MASTER-Net observations report
  39. EP250220a: Xinglong optical upper limit
  40. GRB 250220B: Fermi GBM Final Real-time Localization
  41. GRB 250220A: Fermi GBM Final Real-time Localization
  42. EP250220a: Global MASTER-Net observations report
  43. Konus-Wind detection of GRB 250217C (short)
  44. GRB 250219A: NOT optical observations
  45. GRB 250219A: 1.6m Mephisto optical upper limits
  46. GRB 250219A: SVOM/VT optical counterpart
  47. GRB 250219A: Swift-XRT observations
  48. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  49. GRB 250219A: SVOM detection of a burst
  50. Konus-Wind detection of GRB 250215A / EP250215a
  51. GRB 250217C: Swift-XRT observations
  52. GRB 250217C: SVOM/GRM observation
  53. GRB 250217C: Fermi GBM Observation
  54. IPN triangulation of GRB 250217C (short)
  55. SVOM/sb25021804: SVOM detection of a long X-ray transient
  56. GRB 250213A: Swift-XRT observations
  57. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  58. Fermi GRB 250217C: Global MASTER-Net observations report
  59. GRB 250217C: Fermi GBM Final Real-time Localization
  60. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  61. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  62. Fermi GRB 250217A: Global MASTER-Net observations report
  63. GRB 250217B: Fermi GBM Final Real-time Localization
  64. GRB 250217A: Fermi GBM Final Real-time Localization
  65. Fermi GRB 250216A: Global MASTER-Net observations report
  66. GRB 250216A: Fermi GBM Final Real-time Localization
  67. EP250212a: FTW optical and NIR upper limits
  68. GRB 250215A: Fermi GBM Observation
  69. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  70. GRB 250215A: SVOM/GRM observation
  71. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  72. EP250215a: Global MASTER-Net observations report
  73. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  74. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  75. Fermi GRB 250215A: Global MASTER-Net observations report
  76. GRB 250215A: Fermi GBM Final Real-time Localization
  77. Fermi trigger No 761206993: Global MASTER-Net observations report
  78. GRB 250213A:SVOM/VT optical candidate
  79. EP250207b: Xinglong optical upper limit
  80. Fermi GRB 250214A: Global MASTER-Net observations report
  81. GRB 250214A: Fermi GBM Final Real-time Localization
  82. EP250212a: Xinglong optical upper limit
  83. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  84. GRB 250213A: SVOM detection of a burst
  85. EP250212a: Global MASTER-Net observations report
  86. GRB 250205A: Leavitt Observatory optical upper limit
  87. GRB 250210A: GRBAlpha detection
  88. EP250207B: Chandra localization of the X-ray counterpart
  89. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  90. EP250207b: VLA radio upper limits
  91. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  92. GRB250101A: Radio upper limits from GMRT observations
  93. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  94. Fermi GRB 250212A: Global MASTER-Net observations report
  95. Fermi trigger No 760945500: Global MASTER-Net observations report
  96. EP250207b: NOT optical counterpart candidate
  97. GRB 250211B: A long GRB detected by INTEGRAL
  98. Integral GRB250211.89: Global MASTER-Net observations report
  99. GRB 250212A: Fermi GBM Final Real-time Localization
  100. LIGO/Virgo/KAGRA S250211be: Updated Sky localization

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