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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"
  1. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  2. GRB 250217C: SVOM/GRM observation
  3. GRB 250217C: Tiled Swift observations
  4. GRB 250217C: Fermi GBM Observation
  5. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  6. IPN triangulation of GRB 250217C (short)
  7. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  8. SVOM/sb25021804: SVOM detection of a long X-ray transient
  9. GRB 250213A: Swift-XRT observations
  10. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  11. GRB 250216A: AstroSat CZTI detection
  12. GRB 250217C: AstroSat CZTI detection of a short burst
  13. Fermi GRB 250217C: Global MASTER-Net observations report
  14. GRB 250217C: Fermi GBM Final Real-time Localization
  15. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  16. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  17. Fermi GRB 250217A: Global MASTER-Net observations report
  18. GRANDMA/OPD observations of GRB250215A
  19. GRB 250217B: Fermi GBM Final Real-time Localization
  20. The EP-WXT trigger 01709131775 is likely a flaring star
  21. GRB 250217A: Fermi GBM Final Real-time Localization
  22. Fermi GRB 250216A: Global MASTER-Net observations report
  23. GRB 250215A / EP250215a: LCO detection of the afterglow
  24. GRB 250216A: Fermi GBM Final Real-time Localization
  25. EP250212a: FTW optical and NIR upper limits
  26. GRB 250215A: Swift/UVOT Upper Limits
  27. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  28. EP250215a / GRB 250215A : GTC redshift z = 4.61
  29. GRB 250215A: Fermi GBM Observation
  30. EP250215a / GRB 250215A : NOT optical observations
  31. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  32. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  33. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  34. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  35. GRB 250215A: Swift-XRT refined Analysis
  36. GRB 250215A: SVOM/GRM observation
  37. EP250215a / GRB 250215A: AstroSat CZTI detection
  38. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  39. EP250215a: Global MASTER-Net observations report
  40. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  41. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  42. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  43. Fermi GRB 250215A: Global MASTER-Net observations report
  44. GRB 250215A: Fermi GBM Final Real-time Localization
  45. Fermi trigger No 761206993: Global MASTER-Net observations report
  46. GRB 250213A：SVOM/VT optical candidate
  47. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  48. EP250207b: Xinglong optical upper limit
  49. Fermi GRB 250214A: Global MASTER-Net observations report
  50. GRB 250213A: Swift ToO observations
  51. GRB 250214A: Fermi GBM Final Real-time Localization
  52. EP250212a: Xinglong optical upper limit
  53. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  54. GRB 250213A: SVOM detection of a burst
  55. EP250212a: Global MASTER-Net observations report
  56. GRB 250205A: VIRT Optical Upper Limit
  57. GRB 250205A: Leavitt Observatory optical upper limit
  58. GRB 250210A: GRBAlpha detection
  59. EP250207B: Chandra localization of the X-ray counterpart
  60. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  61. EP250207b: VLA radio upper limits
  62. EP250212a: Liverpool Telescope optical upper limits
  63. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  64. GRB250101A: Radio upper limits from GMRT observations
  65. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  66. EP250207B: GTC z-band Observations
  67. Fermi GRB 250212A: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  69. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  70. Fermi trigger No 760945500: Global MASTER-Net observations report
  71. EP250207b: NOT optical counterpart candidate
  72. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  73. GRB 250211B: A long GRB detected by INTEGRAL
  74. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  75. GRB 250211A: Swift ToO observations
  76. Integral GRB250211.89: Global MASTER-Net observations report
  77. GRB 250212A: Fermi GBM Final Real-time Localization
  78. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  79. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  80. GRB 250207A: Fermi GBM Observation
  81. GRB 250206A: Fermi GBM Observation
  82. GRB 250205A / EP250205A: radio detection with the VLA
  83. IceCube-250207A: One candidate from the Zwicky Transient Facility
  84. EP250207b: Tentative z-band brightening source
  85. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  86. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  87. Konus-Wind detection of GRB 250207A
  88. Konus-Wind detection of GRB 250206A
  89. GRB 250210A: SVOM/GRM observation of a long burst
  90. EP250207b: Liverpool Telescope possible optical counterpart
  91. EP250207b: Global MASTER-Net observations report
  92. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  93. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  94. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  96. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  97. GRB 250207A: Skynet optical afterglow observations
  98. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  99. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  100. GRB 241128A: VIRT Optical Upper Limit

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