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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"

32508 results found.

  1. IPN triangulation of GRB 250217C (short)
  2. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  3. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  4. GRB 250216A: AstroSat CZTI detection
  5. GRB 250217C: AstroSat CZTI detection of a short burst
  6. Fermi GRB 250217C: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  8. Fermi GRB 250217A: Global MASTER-Net observations report
  9. GRANDMA/OPD observations of GRB250215A
  10. Fermi GRB 250216A: Global MASTER-Net observations report
  11. GRB 250215A / EP250215a: LCO detection of the afterglow
  12. EP250212a: FTW optical and NIR upper limits
  13. GRB 250215A: Swift/UVOT Upper Limits
  14. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  15. EP250215a / GRB 250215A : GTC redshift z = 4.61
  16. GRB 250215A: Fermi GBM Observation
  17. EP250215a / GRB 250215A : NOT optical observations
  18. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  19. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  20. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  21. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  22. GRB 250215A: Swift-XRT refined Analysis
  23. GRB 250215A: SVOM/GRM observation
  24. EP250215a / GRB 250215A: AstroSat CZTI detection
  25. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  26. EP250215a: Global MASTER-Net observations report
  27. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  28. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  29. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  30. Fermi GRB 250215A: Global MASTER-Net observations report
  31. GRB 250213A:SVOM/VT optical candidate
  32. EP250207b: Xinglong optical upper limit
  33. Fermi GRB 250214A: Global MASTER-Net observations report
  34. GRB 250213A: Swift ToO observations
  35. EP250212a: Xinglong optical upper limit
  36. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  37. EP250212a: Global MASTER-Net observations report
  38. GRB 250205A: VIRT Optical Upper Limit
  39. GRB 250205A: Leavitt Observatory optical upper limit
  40. GRB 250210A: GRBAlpha detection
  41. EP250207B: Chandra localization of the X-ray counterpart
  42. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  43. EP250207b: VLA radio upper limits
  44. EP250212a: Liverpool Telescope optical upper limits
  45. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  46. GRB250101A: Radio upper limits from GMRT observations
  47. EP250207B: GTC z-band Observations
  48. Fermi GRB 250212A: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  50. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  51. EP250207b: NOT optical counterpart candidate
  52. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  53. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  54. GRB 250211A: Swift ToO observations
  55. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  56. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  57. GRB 250207A: Fermi GBM Observation
  58. GRB 250206A: Fermi GBM Observation
  59. GRB 250205A / EP250205A: radio detection with the VLA
  60. IceCube-250207A: One candidate from the Zwicky Transient Facility
  61. EP250207b: Tentative z-band brightening source
  62. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  63. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  64. Konus-Wind detection of GRB 250207A
  65. Konus-Wind detection of GRB 250206A
  66. GRB 250210A: SVOM/GRM observation of a long burst
  67. EP250207b: Liverpool Telescope possible optical counterpart
  68. EP250207b: Global MASTER-Net observations report
  69. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  70. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  72. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  73. GRB 250207A: Skynet optical afterglow observations
  74. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  75. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  76. GRB 241128A: VIRT Optical Upper Limit
  77. EP250207b: Gemini GMOS-N z-band observations
  78. EP250207A: Upper limits from Fermi-GBM Observations
  79. GRB 250210A: INTEGRAL SPI-ACS detection
  80. GRB 250210A: AstroSat CZTI detection
  81. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  82. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  83. Fermi GRB 250210A: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  85. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  86. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  87. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  88. GRB 250204B: GRBAlpha detection
  89. GRB 250204A: GRBAlpha detection
  90. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  91. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  92. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  93. GRB 250207A: 1.3m DFOT Optical observations
  94. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  95. GRB 250129A: GRANDMA Continued Afterglow Detection
  96. GRB 250207A: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  98. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  100. GRB 250205A: 1.3m DFOT optical upper limit

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