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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

31634 results found.

  1. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  2. EP250220a: 1.6m Mephisto observations
  3. EP250220a: Liverpool Telescope optical upper limits
  4. EP250220a: Optical upper limit with Kinder observations
  5. SVOM trigger sb25022102 is not an astrophysical event
  6. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  7. EP250220a: Xinglong optical upper limit
  8. EP250220a: Global MASTER-Net observations report
  9. Konus-Wind detection of GRB 250217C (short)
  10. GRB 250219A: Swift/UVOT Upper Limits
  11. GRB 250219A: OHP/T193 optical upper limit
  12. GRB 250219A: NOT optical observations
  13. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  14. GRB 250219A: 1.6m Mephisto optical upper limits
  15. GRB 250219A: SVOM/VT optical counterpart
  16. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  17. GRB 250219A: Swift ToO observations
  18. Konus-Wind detection of GRB 250215A / EP250215a
  19. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  20. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  21. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  22. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  23. GRB 250217C: SVOM/GRM observation
  24. GRB 250217C: Tiled Swift observations
  25. GRB 250217C: Fermi GBM Observation
  26. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  27. IPN triangulation of GRB 250217C (short)
  28. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  29. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  30. GRB 250216A: AstroSat CZTI detection
  31. GRB 250217C: AstroSat CZTI detection of a short burst
  32. Fermi GRB 250217C: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  34. Fermi GRB 250217A: Global MASTER-Net observations report
  35. GRANDMA/OPD observations of GRB250215A
  36. Fermi GRB 250216A: Global MASTER-Net observations report
  37. GRB 250215A / EP250215a: LCO detection of the afterglow
  38. EP250212a: FTW optical and NIR upper limits
  39. GRB 250215A: Swift/UVOT Upper Limits
  40. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  41. EP250215a / GRB 250215A : GTC redshift z = 4.61
  42. GRB 250215A: Fermi GBM Observation
  43. EP250215a / GRB 250215A : NOT optical observations
  44. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  45. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  46. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  47. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  48. GRB 250215A: Swift-XRT refined Analysis
  49. GRB 250215A: SVOM/GRM observation
  50. EP250215a / GRB 250215A: AstroSat CZTI detection
  51. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  52. EP250215a: Global MASTER-Net observations report
  53. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  54. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  55. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  56. Fermi GRB 250215A: Global MASTER-Net observations report
  57. GRB 250213A：SVOM/VT optical candidate
  58. EP250207b: Xinglong optical upper limit
  59. Fermi GRB 250214A: Global MASTER-Net observations report
  60. GRB 250213A: Swift ToO observations
  61. EP250212a: Xinglong optical upper limit
  62. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  63. EP250212a: Global MASTER-Net observations report
  64. GRB 250205A: VIRT Optical Upper Limit
  65. GRB 250205A: Leavitt Observatory optical upper limit
  66. GRB 250210A: GRBAlpha detection
  67. EP250207B: Chandra localization of the X-ray counterpart
  68. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  69. EP250207b: VLA radio upper limits
  70. EP250212a: Liverpool Telescope optical upper limits
  71. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  72. GRB250101A: Radio upper limits from GMRT observations
  73. EP250207B: GTC z-band Observations
  74. Fermi GRB 250212A: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  76. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  77. EP250207b: NOT optical counterpart candidate
  78. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  79. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  80. GRB 250211A: Swift ToO observations
  81. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  82. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  83. GRB 250207A: Fermi GBM Observation
  84. GRB 250206A: Fermi GBM Observation
  85. GRB 250205A / EP250205A: radio detection with the VLA
  86. IceCube-250207A: One candidate from the Zwicky Transient Facility
  87. EP250207b: Tentative z-band brightening source
  88. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  89. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  90. Konus-Wind detection of GRB 250207A
  91. Konus-Wind detection of GRB 250206A
  92. GRB 250210A: SVOM/GRM observation of a long burst
  93. EP250207b: Liverpool Telescope possible optical counterpart
  94. EP250207b: Global MASTER-Net observations report
  95. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  96. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  97. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  98. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  99. GRB 250207A: Skynet optical afterglow observations
  100. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II

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