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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"
  1. EP250220a: Xinglong optical upper limit
  2. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  3. GRB 250220B: Fermi GBM Final Real-time Localization
  4. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  5. GRB 250220A: Fermi GBM Final Real-time Localization
  6. EP250220a: Global MASTER-Net observations report
  7. EP250220a: EP-WXT detection of a fast X-ray transient
  8. Konus-Wind detection of GRB 250217C (short)
  9. GRB 250219A: Swift/UVOT Upper Limits
  10. GRB 250219A: OHP/T193 optical upper limit
  11. GRB 250219A: NOT optical observations
  12. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  13. GRB 250219A: 1.6m Mephisto optical upper limits
  14. GRB 250219A: SVOM/VT optical counterpart
  15. GRB 250219A: Swift-XRT observations
  16. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  17. GRB 250219A: Swift ToO observations
  18. GRB 250219A: SVOM detection of a burst
  19. Konus-Wind detection of GRB 250215A / EP250215a
  20. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  21. GRB 250217C: Swift-XRT observations
  22. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  23. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  24. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  25. GRB 250217C: SVOM/GRM observation
  26. GRB 250217C: Tiled Swift observations
  27. GRB 250217C: Fermi GBM Observation
  28. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  29. IPN triangulation of GRB 250217C (short)
  30. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  31. SVOM/sb25021804: SVOM detection of a long X-ray transient
  32. GRB 250213A: Swift-XRT observations
  33. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  34. GRB 250216A: AstroSat CZTI detection
  35. GRB 250217C: AstroSat CZTI detection of a short burst
  36. Fermi GRB 250217C: Global MASTER-Net observations report
  37. GRB 250217C: Fermi GBM Final Real-time Localization
  38. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  39. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  40. Fermi GRB 250217A: Global MASTER-Net observations report
  41. GRANDMA/OPD observations of GRB250215A
  42. GRB 250217B: Fermi GBM Final Real-time Localization
  43. The EP-WXT trigger 01709131775 is likely a flaring star
  44. GRB 250217A: Fermi GBM Final Real-time Localization
  45. Fermi GRB 250216A: Global MASTER-Net observations report
  46. GRB 250215A / EP250215a: LCO detection of the afterglow
  47. GRB 250216A: Fermi GBM Final Real-time Localization
  48. EP250212a: FTW optical and NIR upper limits
  49. GRB 250215A: Swift/UVOT Upper Limits
  50. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  51. EP250215a / GRB 250215A : GTC redshift z = 4.61
  52. GRB 250215A: Fermi GBM Observation
  53. EP250215a / GRB 250215A : NOT optical observations
  54. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  55. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  56. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  57. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  58. GRB 250215A: Swift-XRT refined Analysis
  59. GRB 250215A: SVOM/GRM observation
  60. EP250215a / GRB 250215A: AstroSat CZTI detection
  61. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  62. EP250215a: Global MASTER-Net observations report
  63. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  64. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  65. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  66. Fermi GRB 250215A: Global MASTER-Net observations report
  67. GRB 250215A: Fermi GBM Final Real-time Localization
  68. Fermi trigger No 761206993: Global MASTER-Net observations report
  69. GRB 250213A：SVOM/VT optical candidate
  70. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  71. EP250207b: Xinglong optical upper limit
  72. Fermi GRB 250214A: Global MASTER-Net observations report
  73. GRB 250213A: Swift ToO observations
  74. GRB 250214A: Fermi GBM Final Real-time Localization
  75. EP250212a: Xinglong optical upper limit
  76. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  77. GRB 250213A: SVOM detection of a burst
  78. EP250212a: Global MASTER-Net observations report
  79. GRB 250205A: VIRT Optical Upper Limit
  80. GRB 250205A: Leavitt Observatory optical upper limit
  81. GRB 250210A: GRBAlpha detection
  82. EP250207B: Chandra localization of the X-ray counterpart
  83. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  84. EP250207b: VLA radio upper limits
  85. EP250212a: Liverpool Telescope optical upper limits
  86. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  87. GRB250101A: Radio upper limits from GMRT observations
  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. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  93. Fermi trigger No 760945500: Global MASTER-Net observations report
  94. EP250207b: NOT optical counterpart candidate
  95. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  96. GRB 250211B: A long GRB detected by INTEGRAL
  97. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  98. GRB 250211A: Swift ToO observations
  99. Integral GRB250211.89: Global MASTER-Net observations report
  100. GRB 250212A: Fermi GBM Final Real-time Localization

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