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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 250217B: Fermi GBM Final Real-time Localization
  2. The EP-WXT trigger 01709131775 is likely a flaring star
  3. GRB 250217A: Fermi GBM Final Real-time Localization
  4. Fermi GRB 250216A: Global MASTER-Net observations report
  5. GRB 250215A / EP250215a: LCO detection of the afterglow
  6. GRB 250216A: Fermi GBM Final Real-time Localization
  7. EP250212a: FTW optical and NIR upper limits
  8. GRB 250215A: Swift/UVOT Upper Limits
  9. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  10. EP250215a / GRB 250215A : GTC redshift z = 4.61
  11. GRB 250215A: Fermi GBM Observation
  12. EP250215a / GRB 250215A : NOT optical observations
  13. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  14. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  15. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  16. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  17. GRB 250215A: Swift-XRT refined Analysis
  18. GRB 250215A: SVOM/GRM observation
  19. EP250215a / GRB 250215A: AstroSat CZTI detection
  20. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  21. EP250215a: Global MASTER-Net observations report
  22. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  23. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  24. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  25. Fermi GRB 250215A: Global MASTER-Net observations report
  26. GRB 250215A: Fermi GBM Final Real-time Localization
  27. Fermi trigger No 761206993: Global MASTER-Net observations report
  28. GRB 250213A：SVOM/VT optical candidate
  29. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  30. EP250207b: Xinglong optical upper limit
  31. Fermi GRB 250214A: Global MASTER-Net observations report
  32. GRB 250213A: Swift ToO observations
  33. GRB 250214A: Fermi GBM Final Real-time Localization
  34. EP250212a: Xinglong optical upper limit
  35. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  36. GRB 250213A: SVOM detection of a burst
  37. EP250212a: Global MASTER-Net observations report
  38. GRB 250205A: VIRT Optical Upper Limit
  39. GRB 250205A: Leavitt Observatory optical upper limit
  40. GRB 250210A: GRBAlpha detection
  41. EP250207B: Chandra localization of the X-ray counterpart
  42. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  43. EP250207b: VLA radio upper limits
  44. EP250212a: Liverpool Telescope optical upper limits
  45. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  46. GRB250101A: Radio upper limits from GMRT observations
  47. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  48. EP250207B: GTC z-band Observations
  49. Fermi GRB 250212A: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  51. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. Fermi trigger No 760945500: Global MASTER-Net observations report
  53. EP250207b: NOT optical counterpart candidate
  54. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  55. GRB 250211B: A long GRB detected by INTEGRAL
  56. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  57. GRB 250211A: Swift ToO observations
  58. Integral GRB250211.89: Global MASTER-Net observations report
  59. GRB 250212A: Fermi GBM Final Real-time Localization
  60. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  61. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  62. GRB 250207A: Fermi GBM Observation
  63. GRB 250206A: Fermi GBM Observation
  64. GRB 250205A / EP250205A: radio detection with the VLA
  65. IceCube-250207A: One candidate from the Zwicky Transient Facility
  66. EP250207b: Tentative z-band brightening source
  67. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  68. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  69. Konus-Wind detection of GRB 250207A
  70. Konus-Wind detection of GRB 250206A
  71. GRB 250210A: SVOM/GRM observation of a long burst
  72. EP250207b: Liverpool Telescope possible optical counterpart
  73. EP250207b: Global MASTER-Net observations report
  74. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  75. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  76. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  78. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  79. GRB 250207A: Skynet optical afterglow observations
  80. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  81. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  82. GRB 241128A: VIRT Optical Upper Limit
  83. EP250207b: Gemini GMOS-N z-band observations
  84. EP250207A: Upper limits from Fermi-GBM Observations
  85. GRB 250210A: INTEGRAL SPI-ACS detection
  86. GRB 250210A: AstroSat CZTI detection
  87. EP250207b: a new X-ray transient detected by Einstein Probe
  88. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  89. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  90. Fermi GRB 250210A: Global MASTER-Net observations report
  91. GRB 250210A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  93. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  94. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  96. IceCube Alert 250207.09: Global MASTER-Net observations report
  97. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  98. GRB 250204B: GRBAlpha detection
  99. GRB 250204A: GRBAlpha detection
  100. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy

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