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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. GRB 250219A: Swift ToO observations
  2. GRB 250219A: SVOM detection of a burst
  3. Konus-Wind detection of GRB 250215A / EP250215a
  4. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  5. GRB 250217C: Swift-XRT observations
  6. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  7. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  8. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  9. GRB 250217C: SVOM/GRM observation
  10. GRB 250217C: Tiled Swift observations
  11. GRB 250217C: Fermi GBM Observation
  12. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  13. IPN triangulation of GRB 250217C (short)
  14. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  15. SVOM/sb25021804: SVOM detection of a long X-ray transient
  16. GRB 250213A: Swift-XRT observations
  17. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  18. GRB 250216A: AstroSat CZTI detection
  19. GRB 250217C: AstroSat CZTI detection of a short burst
  20. Fermi GRB 250217C: Global MASTER-Net observations report
  21. GRB 250217C: Fermi GBM Final Real-time Localization
  22. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  23. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  24. Fermi GRB 250217A: Global MASTER-Net observations report
  25. GRANDMA/OPD observations of GRB250215A
  26. GRB 250217B: Fermi GBM Final Real-time Localization
  27. The EP-WXT trigger 01709131775 is likely a flaring star
  28. GRB 250217A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 250216A: Global MASTER-Net observations report
  30. GRB 250215A / EP250215a: LCO detection of the afterglow
  31. GRB 250216A: Fermi GBM Final Real-time Localization
  32. EP250212a: FTW optical and NIR upper limits
  33. GRB 250215A: Swift/UVOT Upper Limits
  34. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  35. EP250215a / GRB 250215A : GTC redshift z = 4.61
  36. GRB 250215A: Fermi GBM Observation
  37. EP250215a / GRB 250215A : NOT optical observations
  38. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  39. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  40. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  41. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  42. GRB 250215A: Swift-XRT refined Analysis
  43. GRB 250215A: SVOM/GRM observation
  44. EP250215a / GRB 250215A: AstroSat CZTI detection
  45. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  46. EP250215a: Global MASTER-Net observations report
  47. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  48. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  49. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  50. Fermi GRB 250215A: Global MASTER-Net observations report
  51. GRB 250215A: Fermi GBM Final Real-time Localization
  52. Fermi trigger No 761206993: Global MASTER-Net observations report
  53. GRB 250213A：SVOM/VT optical candidate
  54. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  55. EP250207b: Xinglong optical upper limit
  56. Fermi GRB 250214A: Global MASTER-Net observations report
  57. GRB 250213A: Swift ToO observations
  58. GRB 250214A: Fermi GBM Final Real-time Localization
  59. EP250212a: Xinglong optical upper limit
  60. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  61. GRB 250213A: SVOM detection of a burst
  62. EP250212a: Global MASTER-Net observations report
  63. GRB 250205A: VIRT Optical Upper Limit
  64. GRB 250205A: Leavitt Observatory optical upper limit
  65. GRB 250210A: GRBAlpha detection
  66. EP250207B: Chandra localization of the X-ray counterpart
  67. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  68. EP250207b: VLA radio upper limits
  69. EP250212a: Liverpool Telescope optical upper limits
  70. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  71. GRB250101A: Radio upper limits from GMRT observations
  72. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  73. EP250207B: GTC z-band Observations
  74. Fermi GRB 250212A: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  76. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  77. Fermi trigger No 760945500: Global MASTER-Net observations report
  78. EP250207b: NOT optical counterpart candidate
  79. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  80. GRB 250211B: A long GRB detected by INTEGRAL
  81. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  82. GRB 250211A: Swift ToO observations
  83. Integral GRB250211.89: Global MASTER-Net observations report
  84. GRB 250212A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  86. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  87. GRB 250207A: Fermi GBM Observation
  88. GRB 250206A: Fermi GBM Observation
  89. GRB 250205A / EP250205A: radio detection with the VLA
  90. IceCube-250207A: One candidate from the Zwicky Transient Facility
  91. EP250207b: Tentative z-band brightening source
  92. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  93. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  94. Konus-Wind detection of GRB 250207A
  95. Konus-Wind detection of GRB 250206A
  96. GRB 250210A: SVOM/GRM observation of a long burst
  97. EP250207b: Liverpool Telescope possible optical counterpart
  98. EP250207b: Global MASTER-Net observations report
  99. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  100. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)

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