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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"

27220 results found.

  1. GRB 250221A: Optical counterpart detection by LCO.
  2. EP250220a: FTW optical and NIR observations and upper limits
  3. EP250220a: EP-FXT follow-up observations
  4. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  5. GRB 250221A: GRANDMA/TAROT Detection
  6. Fermi trigger No 761805304: Global MASTER-Net observations report
  7. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  8. GRB 250221A: Swift-XRT refined Analysis
  9. GRB 250221A: NOT optical observations
  10. GRB 250221A: 1.6m Mephisto optical detection
  11. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  12. GRB 250221A: AKO Optical Upper Limit
  13. GRB 250221A: Swift/UVOT Detection
  14. EP250220a: Liverpool Telescope upper limits
  15. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  16. GRB 250221A: REM optical/NIR afterglow detection
  17. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  18. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  19. EP250220a: 1.6m Mephisto observations
  20. EP250220a: Optical upper limit with Kinder observations
  21. SVOM trigger sb25022102 is not an astrophysical event
  22. SVOM/sb25022102: SVOM detection of an X-ray transient
  23. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  24. GRB 250221A: Swift detection of a burst with an optical counterpart
  25. Swift GRB250221.15: Global MASTER-Net OT detection
  26. Swift GRB250221.15: Global MASTER-Net observations report
  27. EP250220a: Xinglong optical upper limit
  28. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  29. GRB 250220B: Fermi GBM Final Real-time Localization
  30. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  31. GRB 250220A: Fermi GBM Final Real-time Localization
  32. EP250220a: Global MASTER-Net observations report
  33. EP250220a: EP-WXT detection of a fast X-ray transient
  34. GRB 250219A: Swift/UVOT Upper Limits
  35. GRB 250219A: OHP/T193 optical upper limit
  36. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  37. GRB 250219A: 1.6m Mephisto optical upper limits
  38. GRB 250219A: SVOM/VT optical counterpart
  39. GRB 250219A: SVOM detection of a burst
  40. Konus-Wind detection of GRB 250215A / EP250215a
  41. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  42. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  43. GRB 250217C: SVOM/GRM observation
  44. GRB 250217C: Fermi GBM Observation
  45. IPN triangulation of GRB 250217C (short)
  46. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  47. SVOM/sb25021804: SVOM detection of a long X-ray transient
  48. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  49. Fermi GRB 250217C: Global MASTER-Net observations report
  50. GRB 250217C: Fermi GBM Final Real-time Localization
  51. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  52. Fermi GRB 250217A: Global MASTER-Net observations report
  53. GRB 250217B: Fermi GBM Final Real-time Localization
  54. The EP-WXT trigger 01709131775 is likely a flaring star
  55. GRB 250217A: Fermi GBM Final Real-time Localization
  56. Fermi GRB 250216A: Global MASTER-Net observations report
  57. GRB 250215A / EP250215a: LCO detection of the afterglow
  58. GRB 250216A: Fermi GBM Final Real-time Localization
  59. EP250212a: FTW optical and NIR upper limits
  60. GRB 250215A: Swift/UVOT Upper Limits
  61. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  62. GRB 250215A: Fermi GBM Observation
  63. EP250215a / GRB 250215A : NOT optical observations
  64. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  65. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  66. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  67. GRB 250215A: Swift-XRT refined Analysis
  68. GRB 250215A: SVOM/GRM observation
  69. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  70. EP250215a: Global MASTER-Net observations report
  71. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  72. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  73. Fermi GRB 250215A: Global MASTER-Net observations report
  74. GRB 250215A: Fermi GBM Final Real-time Localization
  75. Fermi trigger No 761206993: Global MASTER-Net observations report
  76. GRB 250213A：SVOM/VT optical candidate
  77. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  78. EP250207b: Xinglong optical upper limit
  79. Fermi GRB 250214A: Global MASTER-Net observations report
  80. GRB 250214A: Fermi GBM Final Real-time Localization
  81. EP250212a: Xinglong optical upper limit
  82. GRB 250213A: SVOM detection of a burst
  83. EP250212a: Global MASTER-Net observations report
  84. GRB 250205A: Leavitt Observatory optical upper limit
  85. EP250207B: Chandra localization of the X-ray counterpart
  86. EP250207b: VLA radio upper limits
  87. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  88. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  89. EP250207B: GTC z-band Observations
  90. Fermi GRB 250212A: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  92. Fermi trigger No 760945500: Global MASTER-Net observations report
  93. EP250207b: NOT optical counterpart candidate
  94. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  95. Integral GRB250211.89: Global MASTER-Net observations report
  96. GRB 250212A: Fermi GBM Final Real-time Localization
  97. GRB 250207A: Fermi GBM Observation
  98. GRB 250206A: Fermi GBM Observation
  99. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  100. GRB 250210A: SVOM/GRM observation of a long burst

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