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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"

21953 results found.

  1. EP250223a: GOTO optical afterglow detections
  2. EP250223a: REM NIR upper limit
  3. EP250223a: TRT optical afterglow observation
  4. EP250223a: refined analysis of the EP-WXT and FXT observations
  5. EP250223a: 1.6m Mephisto and 50cm array observations
  6. EP250223a: SVOM/VT optical observation
  7. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  8. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  9. EP250223a: OASDG optical observations
  10. EP250223a: LCO detection of the afterglow
  11. EP250223a: NOT redshift z = 2.756
  12. EP250223a: NOT optical afterglow candidate
  13. EP250223a: Global MASTER-Net observations report
  14. GRB 250221A: VLA radio detection
  15. Fermi GRB 250223A: Global MASTER-Net observations report
  16. Fermi trigger No 762020305: Global MASTER-Net observations report
  17. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  18. GRB 250221A: continued Mondy optical observations, brightening afterglow
  19. GRB 250221A: Optical counterpart detection by LCO.
  20. GRB 250221A: Mondy optical observations
  21. GRB 250221A: Assy optical observations
  22. EP250220a: FTW optical and NIR observations and upper limits
  23. EP250220a: EP-FXT follow-up observations
  24. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  25. Fermi trigger No 761805304: Global MASTER-Net observations report
  26. GRB 250221A: NOT optical observations
  27. GRB 250221A: 1.6m Mephisto optical detection
  28. GRB 250221A: Swift/UVOT Detection
  29. EP250220a: Liverpool Telescope upper limits
  30. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  31. GRB 250221A: REM optical/NIR afterglow detection
  32. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  33. EP250220a: 1.6m Mephisto observations
  34. EP250220a: Optical upper limit with Kinder observations
  35. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  36. Swift GRB250221.15: Global MASTER-Net observations report
  37. EP250220a: Global MASTER-Net observations report
  38. GRB 250219A: Swift/UVOT Upper Limits
  39. GRB 250219A: OHP/T193 optical upper limit
  40. GRB 250219A: NOT optical observations
  41. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  42. GRB 250219A: 1.6m Mephisto optical upper limits
  43. GRB 250219A: SVOM/VT optical counterpart
  44. GRB 250219A: Swift-XRT observations
  45. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  46. GRB 250219A: Swift ToO observations
  47. GRB 250217C: Swift-XRT observations
  48. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  49. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  50. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  51. GRB 250217C: Tiled Swift observations
  52. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  53. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  54. GRB 250213A: Swift-XRT observations
  55. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  56. Fermi GRB 250217C: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  58. Fermi GRB 250217A: Global MASTER-Net observations report
  59. GRANDMA/OPD observations of GRB250215A
  60. Fermi GRB 250216A: Global MASTER-Net observations report
  61. GRB 250215A / EP250215a: LCO detection of the afterglow
  62. EP250212a: FTW optical and NIR upper limits
  63. GRB 250215A: Swift/UVOT Upper Limits
  64. EP250215a / GRB 250215A : NOT optical observations
  65. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  66. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  67. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  68. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  69. EP250215a: Global MASTER-Net observations report
  70. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  71. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  72. Fermi GRB 250215A: Global MASTER-Net observations report
  73. Fermi trigger No 761206993: Global MASTER-Net observations report
  74. GRB 250213A：SVOM/VT optical candidate
  75. Fermi GRB 250214A: Global MASTER-Net observations report
  76. GRB 250213A: Swift ToO observations
  77. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  78. EP250212a: Global MASTER-Net observations report
  79. GRB 250205A: Leavitt Observatory optical upper limit
  80. EP250207B: Chandra localization of the X-ray counterpart
  81. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  82. EP250207b: VLA radio upper limits
  83. GRB250101A: Radio upper limits from GMRT observations
  84. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  85. EP250207B: GTC z-band Observations
  86. Fermi GRB 250212A: Global MASTER-Net observations report
  87. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  88. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  89. Fermi trigger No 760945500: Global MASTER-Net observations report
  90. EP250207b: NOT optical counterpart candidate
  91. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  92. GRB 250211A: Swift ToO observations
  93. Integral GRB250211.89: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  95. GRB 250205A / EP250205A: radio detection with the VLA
  96. IceCube-250207A: One candidate from the Zwicky Transient Facility
  97. EP250207b: Tentative z-band brightening source
  98. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  99. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  100. EP250207b: Liverpool Telescope possible optical counterpart

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