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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"

24390 results found.

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

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