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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"

45447 results found.

  1. Konus-Wind detection of GRB 250217C (short)
  2. GRB 250219A: Swift/UVOT Upper Limits
  3. GRB 250219A: OHP/T193 optical upper limit
  4. GRB 250219A: NOT optical observations
  5. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. GRB 250219A: 1.6m Mephisto optical upper limits
  7. GRB 250219A: SVOM/VT optical counterpart
  8. GRB 250219A: Swift-XRT observations
  9. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  10. GRB 250219A: Swift ToO observations
  11. GRB 250219A: SVOM detection of a burst
  12. Konus-Wind detection of GRB 250215A / EP250215a
  13. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  14. GRB 250217C: Swift-XRT observations
  15. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  16. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  17. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  18. GRB 250217C: SVOM/GRM observation
  19. GRB 250217C: Tiled Swift observations
  20. GRB 250217C: Fermi GBM Observation
  21. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  22. IPN triangulation of GRB 250217C (short)
  23. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  24. SVOM/sb25021804: SVOM detection of a long X-ray transient
  25. GRB 250213A: Swift-XRT observations
  26. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  27. GRB 250216A: AstroSat CZTI detection
  28. GRB 250217C: AstroSat CZTI detection of a short burst
  29. Fermi GRB 250217C: Global MASTER-Net observations report
  30. GRB 250217C: Fermi GBM Final Real-time Localization
  31. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  32. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  33. Fermi GRB 250217A: Global MASTER-Net observations report
  34. GRANDMA/OPD observations of GRB250215A
  35. GRB 250217B: Fermi GBM Final Real-time Localization
  36. The EP-WXT trigger 01709131775 is likely a flaring star
  37. GRB 250217A: Fermi GBM Final Real-time Localization
  38. Fermi GRB 250216A: Global MASTER-Net observations report
  39. GRB 250215A / EP250215a: LCO detection of the afterglow
  40. GRB 250216A: Fermi GBM Final Real-time Localization
  41. EP250212a: FTW optical and NIR upper limits
  42. GRB 250215A: Swift/UVOT Upper Limits
  43. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  44. EP250215a / GRB 250215A : GTC redshift z = 4.61
  45. GRB 250215A: Fermi GBM Observation
  46. EP250215a / GRB 250215A : NOT optical observations
  47. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  48. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  49. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  50. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  51. GRB 250215A: Swift-XRT refined Analysis
  52. GRB 250215A: SVOM/GRM observation
  53. EP250215a / GRB 250215A: AstroSat CZTI detection
  54. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  55. EP250215a: Global MASTER-Net observations report
  56. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  57. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  58. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  59. Fermi GRB 250215A: Global MASTER-Net observations report
  60. GRB 250215A: Fermi GBM Final Real-time Localization
  61. Fermi trigger No 761206993: Global MASTER-Net observations report
  62. GRB 250213A：SVOM/VT optical candidate
  63. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  64. EP250207b: Xinglong optical upper limit
  65. Fermi GRB 250214A: Global MASTER-Net observations report
  66. GRB 250213A: Swift ToO observations
  67. GRB 250214A: Fermi GBM Final Real-time Localization
  68. EP250212a: Xinglong optical upper limit
  69. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  70. GRB 250213A: SVOM detection of a burst
  71. EP250212a: Global MASTER-Net observations report
  72. GRB 250205A: VIRT Optical Upper Limit
  73. GRB 250205A: Leavitt Observatory optical upper limit
  74. GRB 250210A: GRBAlpha detection
  75. EP250207B: Chandra localization of the X-ray counterpart
  76. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  77. EP250207b: VLA radio upper limits
  78. EP250212a: Liverpool Telescope optical upper limits
  79. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  80. GRB250101A: Radio upper limits from GMRT observations
  81. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  82. EP250207B: GTC z-band Observations
  83. Fermi GRB 250212A: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  85. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  86. Fermi trigger No 760945500: Global MASTER-Net observations report
  87. EP250207b: NOT optical counterpart candidate
  88. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  89. GRB 250211B: A long GRB detected by INTEGRAL
  90. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  91. GRB 250211A: Swift ToO observations
  92. Integral GRB250211.89: Global MASTER-Net observations report
  93. GRB 250212A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  95. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  96. GRB 250207A: Fermi GBM Observation
  97. GRB 250206A: Fermi GBM Observation
  98. GRB 250205A / EP250205A: radio detection with the VLA
  99. IceCube-250207A: One candidate from the Zwicky Transient Facility
  100. EP250207b: Tentative z-band brightening source

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