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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').
  1. IPN triangulation of GRB 250217C (short)
  2. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  3. SVOM/sb25021804: SVOM detection of a long X-ray transient
  4. GRB 250213A: Swift-XRT observations
  5. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  6. GRB 250216A: AstroSat CZTI detection
  7. GRB 250217C: AstroSat CZTI detection of a short burst
  8. Fermi GRB 250217C: Global MASTER-Net observations report
  9. GRB 250217C: Fermi GBM Final Real-time Localization
  10. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  11. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  12. Fermi GRB 250217A: Global MASTER-Net observations report
  13. GRANDMA/OPD observations of GRB250215A
  14. GRB 250217B: Fermi GBM Final Real-time Localization
  15. The EP-WXT trigger 01709131775 is likely a flaring star
  16. GRB 250217A: Fermi GBM Final Real-time Localization
  17. Fermi GRB 250216A: Global MASTER-Net observations report
  18. GRB 250215A / EP250215a: LCO detection of the afterglow
  19. GRB 250216A: Fermi GBM Final Real-time Localization
  20. EP250212a: FTW optical and NIR upper limits
  21. GRB 250215A: Swift/UVOT Upper Limits
  22. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  23. EP250215a / GRB 250215A : GTC redshift z = 4.61
  24. GRB 250215A: Fermi GBM Observation
  25. EP250215a / GRB 250215A : NOT optical observations
  26. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  27. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  28. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  29. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  30. GRB 250215A: Swift-XRT refined Analysis
  31. GRB 250215A: SVOM/GRM observation
  32. EP250215a / GRB 250215A: AstroSat CZTI detection
  33. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  34. EP250215a: Global MASTER-Net observations report
  35. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  36. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  37. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  38. Fermi GRB 250215A: Global MASTER-Net observations report
  39. GRB 250215A: Fermi GBM Final Real-time Localization
  40. Fermi trigger No 761206993: Global MASTER-Net observations report
  41. GRB 250213A：SVOM/VT optical candidate
  42. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  43. EP250207b: Xinglong optical upper limit
  44. Fermi GRB 250214A: Global MASTER-Net observations report
  45. GRB 250213A: Swift ToO observations
  46. GRB 250214A: Fermi GBM Final Real-time Localization
  47. EP250212a: Xinglong optical upper limit
  48. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  49. GRB 250213A: SVOM detection of a burst
  50. EP250212a: Global MASTER-Net observations report
  51. GRB 250205A: VIRT Optical Upper Limit
  52. GRB 250205A: Leavitt Observatory optical upper limit
  53. GRB 250210A: GRBAlpha detection
  54. EP250207B: Chandra localization of the X-ray counterpart
  55. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  56. EP250207b: VLA radio upper limits
  57. EP250212a: Liverpool Telescope optical upper limits
  58. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  59. GRB250101A: Radio upper limits from GMRT observations
  60. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  61. EP250207B: GTC z-band Observations
  62. Fermi GRB 250212A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  64. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  65. Fermi trigger No 760945500: Global MASTER-Net observations report
  66. EP250207b: NOT optical counterpart candidate
  67. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  68. GRB 250211B: A long GRB detected by INTEGRAL
  69. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  70. GRB 250211A: Swift ToO observations
  71. Integral GRB250211.89: Global MASTER-Net observations report
  72. GRB 250212A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  74. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  75. GRB 250207A: Fermi GBM Observation
  76. GRB 250206A: Fermi GBM Observation
  77. GRB 250205A / EP250205A: radio detection with the VLA
  78. IceCube-250207A: One candidate from the Zwicky Transient Facility
  79. EP250207b: Tentative z-band brightening source
  80. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  81. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  82. Konus-Wind detection of GRB 250207A
  83. Konus-Wind detection of GRB 250206A
  84. GRB 250210A: SVOM/GRM observation of a long burst
  85. EP250207b: Liverpool Telescope possible optical counterpart
  86. EP250207b: Global MASTER-Net observations report
  87. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  88. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  89. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  91. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  92. GRB 250207A: Skynet optical afterglow observations
  93. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  94. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  95. GRB 241128A: VIRT Optical Upper Limit
  96. EP250207b: Gemini GMOS-N z-band observations
  97. EP250207A: Upper limits from Fermi-GBM Observations
  98. GRB 250210A: INTEGRAL SPI-ACS detection
  99. GRB 250210A: AstroSat CZTI detection
  100. EP250207b: a new X-ray transient detected by Einstein Probe

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