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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"

31738 results found.

  1. GRB 250221A: Swift/UVOT Detection
  2. EP250220a: Liverpool Telescope upper limits
  3. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  4. GRB 250221A: REM optical/NIR afterglow detection
  5. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  6. EP250220a: 1.6m Mephisto observations
  7. EP250220a: Liverpool Telescope optical upper limits
  8. EP250220a: Optical upper limit with Kinder observations
  9. SVOM trigger sb25022102 is not an astrophysical event
  10. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  11. EP250220a: Xinglong optical upper limit
  12. EP250220a: Global MASTER-Net observations report
  13. Konus-Wind detection of GRB 250217C (short)
  14. GRB 250219A: Swift/UVOT Upper Limits
  15. GRB 250219A: OHP/T193 optical upper limit
  16. GRB 250219A: NOT optical observations
  17. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  18. GRB 250219A: 1.6m Mephisto optical upper limits
  19. GRB 250219A: SVOM/VT optical counterpart
  20. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  21. GRB 250219A: Swift ToO observations
  22. Konus-Wind detection of GRB 250215A / EP250215a
  23. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  24. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  25. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  26. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  27. GRB 250217C: SVOM/GRM observation
  28. GRB 250217C: Tiled Swift observations
  29. GRB 250217C: Fermi GBM Observation
  30. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  31. IPN triangulation of GRB 250217C (short)
  32. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  33. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  34. GRB 250216A: AstroSat CZTI detection
  35. GRB 250217C: AstroSat CZTI detection of a short burst
  36. Fermi GRB 250217C: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  38. Fermi GRB 250217A: Global MASTER-Net observations report
  39. GRANDMA/OPD observations of GRB250215A
  40. Fermi GRB 250216A: Global MASTER-Net observations report
  41. GRB 250215A / EP250215a: LCO detection of the afterglow
  42. EP250212a: FTW optical and NIR upper limits
  43. GRB 250215A: Swift/UVOT Upper Limits
  44. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  45. EP250215a / GRB 250215A : GTC redshift z = 4.61
  46. GRB 250215A: Fermi GBM Observation
  47. EP250215a / GRB 250215A : NOT optical observations
  48. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  49. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  50. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  51. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  52. GRB 250215A: Swift-XRT refined Analysis
  53. GRB 250215A: SVOM/GRM observation
  54. EP250215a / GRB 250215A: AstroSat CZTI detection
  55. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  56. EP250215a: Global MASTER-Net observations report
  57. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  58. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  59. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  60. Fermi GRB 250215A: Global MASTER-Net observations report
  61. GRB 250213A：SVOM/VT optical candidate
  62. EP250207b: Xinglong optical upper limit
  63. Fermi GRB 250214A: Global MASTER-Net observations report
  64. GRB 250213A: Swift ToO observations
  65. EP250212a: Xinglong optical upper limit
  66. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  67. EP250212a: Global MASTER-Net observations report
  68. GRB 250205A: VIRT Optical Upper Limit
  69. GRB 250205A: Leavitt Observatory optical upper limit
  70. GRB 250210A: GRBAlpha detection
  71. EP250207B: Chandra localization of the X-ray counterpart
  72. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  73. EP250207b: VLA radio upper limits
  74. EP250212a: Liverpool Telescope optical upper limits
  75. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  76. GRB250101A: Radio upper limits from GMRT observations
  77. EP250207B: GTC z-band Observations
  78. Fermi GRB 250212A: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  80. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  81. EP250207b: NOT optical counterpart candidate
  82. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  83. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  84. GRB 250211A: Swift ToO observations
  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. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  100. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate

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