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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.

Advanced Search Examples (click to copy):

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

45477 results found.

  1. EP250212a: Global MASTER-Net observations report
  2. GRB 250205A: VIRT Optical Upper Limit
  3. GRB 250205A: Leavitt Observatory optical upper limit
  4. GRB 250210A: GRBAlpha detection
  5. EP250207B: Chandra localization of the X-ray counterpart
  6. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  7. EP250207b: VLA radio upper limits
  8. EP250212a: Liverpool Telescope optical upper limits
  9. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  10. GRB250101A: Radio upper limits from GMRT observations
  11. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  12. EP250207B: GTC z-band Observations
  13. Fermi GRB 250212A: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  15. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  16. Fermi trigger No 760945500: Global MASTER-Net observations report
  17. EP250207b: NOT optical counterpart candidate
  18. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  19. GRB 250211B: A long GRB detected by INTEGRAL
  20. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  21. GRB 250211A: Swift ToO observations
  22. Integral GRB250211.89: Global MASTER-Net observations report
  23. GRB 250212A: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  25. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  26. GRB 250207A: Fermi GBM Observation
  27. GRB 250206A: Fermi GBM Observation
  28. GRB 250205A / EP250205A: radio detection with the VLA
  29. IceCube-250207A: One candidate from the Zwicky Transient Facility
  30. EP250207b: Tentative z-band brightening source
  31. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  32. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  33. Konus-Wind detection of GRB 250207A
  34. Konus-Wind detection of GRB 250206A
  35. GRB 250210A: SVOM/GRM observation of a long burst
  36. EP250207b: Liverpool Telescope possible optical counterpart
  37. EP250207b: Global MASTER-Net observations report
  38. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  39. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  40. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  41. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  42. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  43. GRB 250207A: Skynet optical afterglow observations
  44. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  45. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  46. GRB 241128A: VIRT Optical Upper Limit
  47. EP250207b: Gemini GMOS-N z-band observations
  48. EP250207A: Upper limits from Fermi-GBM Observations
  49. GRB 250210A: INTEGRAL SPI-ACS detection
  50. GRB 250210A: AstroSat CZTI detection
  51. EP250207b: a new X-ray transient detected by Einstein Probe
  52. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  53. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  54. Fermi GRB 250210A: Global MASTER-Net observations report
  55. GRB 250210A: Fermi GBM Final Real-time Localization
  56. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  57. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  58. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  60. IceCube Alert 250207.09: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  62. GRB 250204B: GRBAlpha detection
  63. GRB 250204A: GRBAlpha detection
  64. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  65. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  66. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  67. GRB 250207A: 1.3m DFOT Optical observations
  68. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  69. GRB 250206A: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  71. GRB 250129A: GRANDMA Continued Afterglow Detection
  72. GRB 250207A: Swift-BAT refined analysis
  73. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  74. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  75. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  76. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  77. GRB 250205A: 1.3m DFOT optical upper limit
  78. GRB 250206A: Tiled Swift observations
  79. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  81. GRB 250206A: EIRSAT-1 GMOD Detection
  82. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  83. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  84. GRB 250206A: Fermi-LAT detection
  85. GRB 250207B: Swift-XRT observations
  86. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  87. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  88. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  89. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  90. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  91. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  92. GRB 250208A: Fermi GBM Final Real-time Localization
  93. EP250207a: EP-WXT detection and XRT follow-up observation
  94. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  96. GRB 250207A: Swift-XRT refined Analysis
  97. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  98. EP-WXT trigger 01709131361: correction to GCN 39214
  99. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  100. GRB 250207A: Enhanced Swift-XRT position

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