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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').
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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"

44433 results found.

  1. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  2. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  3. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  4. GRB 250217C: SVOM/GRM observation
  5. GRB 250217C: Tiled Swift observations
  6. GRB 250217C: Fermi GBM Observation
  7. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  8. IPN triangulation of GRB 250217C (short)
  9. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  10. SVOM/sb25021804: SVOM detection of a long X-ray transient
  11. GRB 250213A: Swift-XRT observations
  12. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  13. GRB 250216A: AstroSat CZTI detection
  14. GRB 250217C: AstroSat CZTI detection of a short burst
  15. Fermi GRB 250217C: Global MASTER-Net observations report
  16. GRB 250217C: Fermi GBM Final Real-time Localization
  17. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  18. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  19. Fermi GRB 250217A: Global MASTER-Net observations report
  20. GRANDMA/OPD observations of GRB250215A
  21. GRB 250217B: Fermi GBM Final Real-time Localization
  22. The EP-WXT trigger 01709131775 is likely a flaring star
  23. GRB 250217A: Fermi GBM Final Real-time Localization
  24. Fermi GRB 250216A: Global MASTER-Net observations report
  25. GRB 250215A / EP250215a: LCO detection of the afterglow
  26. GRB 250216A: Fermi GBM Final Real-time Localization
  27. EP250212a: FTW optical and NIR upper limits
  28. GRB 250215A: Swift/UVOT Upper Limits
  29. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  30. EP250215a / GRB 250215A : GTC redshift z = 4.61
  31. GRB 250215A: Fermi GBM Observation
  32. EP250215a / GRB 250215A : NOT optical observations
  33. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  34. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  35. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  36. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  37. GRB 250215A: Swift-XRT refined Analysis
  38. GRB 250215A: SVOM/GRM observation
  39. EP250215a / GRB 250215A: AstroSat CZTI detection
  40. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  41. EP250215a: Global MASTER-Net observations report
  42. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  43. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  44. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  45. Fermi GRB 250215A: Global MASTER-Net observations report
  46. GRB 250215A: Fermi GBM Final Real-time Localization
  47. Fermi trigger No 761206993: Global MASTER-Net observations report
  48. GRB 250213A：SVOM/VT optical candidate
  49. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  50. EP250207b: Xinglong optical upper limit
  51. Fermi GRB 250214A: Global MASTER-Net observations report
  52. GRB 250213A: Swift ToO observations
  53. GRB 250214A: Fermi GBM Final Real-time Localization
  54. EP250212a: Xinglong optical upper limit
  55. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  56. GRB 250213A: SVOM detection of a burst
  57. EP250212a: Global MASTER-Net observations report
  58. GRB 250205A: VIRT Optical Upper Limit
  59. GRB 250205A: Leavitt Observatory optical upper limit
  60. GRB 250210A: GRBAlpha detection
  61. EP250207B: Chandra localization of the X-ray counterpart
  62. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  63. EP250207b: VLA radio upper limits
  64. EP250212a: Liverpool Telescope optical upper limits
  65. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  66. GRB250101A: Radio upper limits from GMRT observations
  67. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  68. EP250207B: GTC z-band Observations
  69. Fermi GRB 250212A: Global MASTER-Net observations report
  70. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  71. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  72. Fermi trigger No 760945500: Global MASTER-Net observations report
  73. EP250207b: NOT optical counterpart candidate
  74. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  75. GRB 250211B: A long GRB detected by INTEGRAL
  76. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  77. GRB 250211A: Swift ToO observations
  78. Integral GRB250211.89: Global MASTER-Net observations report
  79. GRB 250212A: Fermi GBM Final Real-time Localization
  80. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  81. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  82. GRB 250207A: Fermi GBM Observation
  83. GRB 250206A: Fermi GBM Observation
  84. GRB 250205A / EP250205A: radio detection with the VLA
  85. IceCube-250207A: One candidate from the Zwicky Transient Facility
  86. EP250207b: Tentative z-band brightening source
  87. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  88. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  89. Konus-Wind detection of GRB 250207A
  90. Konus-Wind detection of GRB 250206A
  91. GRB 250210A: SVOM/GRM observation of a long burst
  92. EP250207b: Liverpool Telescope possible optical counterpart
  93. EP250207b: Global MASTER-Net observations report
  94. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  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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