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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"

32500 results found.

  1. Fermi GRB 250217A: Global MASTER-Net observations report
  2. GRANDMA/OPD observations of GRB250215A
  3. Fermi GRB 250216A: Global MASTER-Net observations report
  4. GRB 250215A / EP250215a: LCO detection of the afterglow
  5. EP250212a: FTW optical and NIR upper limits
  6. GRB 250215A: Swift/UVOT Upper Limits
  7. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  8. EP250215a / GRB 250215A : GTC redshift z = 4.61
  9. GRB 250215A: Fermi GBM Observation
  10. EP250215a / GRB 250215A : NOT optical observations
  11. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  12. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  13. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  14. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  15. GRB 250215A: Swift-XRT refined Analysis
  16. GRB 250215A: SVOM/GRM observation
  17. EP250215a / GRB 250215A: AstroSat CZTI detection
  18. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  19. EP250215a: Global MASTER-Net observations report
  20. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  21. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  22. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  23. Fermi GRB 250215A: Global MASTER-Net observations report
  24. GRB 250213A:SVOM/VT optical candidate
  25. EP250207b: Xinglong optical upper limit
  26. Fermi GRB 250214A: Global MASTER-Net observations report
  27. GRB 250213A: Swift ToO observations
  28. EP250212a: Xinglong optical upper limit
  29. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  30. EP250212a: Global MASTER-Net observations report
  31. GRB 250205A: VIRT Optical Upper Limit
  32. GRB 250205A: Leavitt Observatory optical upper limit
  33. GRB 250210A: GRBAlpha detection
  34. EP250207B: Chandra localization of the X-ray counterpart
  35. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  36. EP250207b: VLA radio upper limits
  37. EP250212a: Liverpool Telescope optical upper limits
  38. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  39. GRB250101A: Radio upper limits from GMRT observations
  40. EP250207B: GTC z-band Observations
  41. Fermi GRB 250212A: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  43. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  44. EP250207b: NOT optical counterpart candidate
  45. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  46. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  47. GRB 250211A: Swift ToO observations
  48. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  49. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  50. GRB 250207A: Fermi GBM Observation
  51. GRB 250206A: Fermi GBM Observation
  52. GRB 250205A / EP250205A: radio detection with the VLA
  53. IceCube-250207A: One candidate from the Zwicky Transient Facility
  54. EP250207b: Tentative z-band brightening source
  55. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  56. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  57. Konus-Wind detection of GRB 250207A
  58. Konus-Wind detection of GRB 250206A
  59. GRB 250210A: SVOM/GRM observation of a long burst
  60. EP250207b: Liverpool Telescope possible optical counterpart
  61. EP250207b: Global MASTER-Net observations report
  62. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  63. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  65. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  66. GRB 250207A: Skynet optical afterglow observations
  67. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  68. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  69. GRB 241128A: VIRT Optical Upper Limit
  70. EP250207b: Gemini GMOS-N z-band observations
  71. EP250207A: Upper limits from Fermi-GBM Observations
  72. GRB 250210A: INTEGRAL SPI-ACS detection
  73. GRB 250210A: AstroSat CZTI detection
  74. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  75. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  76. Fermi GRB 250210A: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  78. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  79. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  80. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  81. GRB 250204B: GRBAlpha detection
  82. GRB 250204A: GRBAlpha detection
  83. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  84. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  85. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  86. GRB 250207A: 1.3m DFOT Optical observations
  87. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  88. GRB 250129A: GRANDMA Continued Afterglow Detection
  89. GRB 250207A: Swift-BAT refined analysis
  90. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  91. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  92. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  93. GRB 250205A: 1.3m DFOT optical upper limit
  94. GRB 250206A: Tiled Swift observations
  95. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  96. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  97. GRB 250206A: EIRSAT-1 GMOD Detection
  98. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  99. GRB 250206A: Fermi-LAT detection
  100. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification

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