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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

43099 results found.

  1. GRB 250330A: Swift/UVOT Upper Limits
  2. GRB 250330A: Swift-XRT afterglow detection
  3. GRB 250328A: 1.6m Mephisto optical observations
  4. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  5. GRB 250330A: Fermi GBM Final Localization
  6. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  7. IceCube Alert 250330.35: Global MASTER-Net observations report
  8. GRB 250330A: VLT/FORS2 Optical Observations
  9. GRB 250330A: Prompt Swift-XRT position
  10. GRB 250329B: Swift-XRT afterglow detection
  11. GRB 250330A: Swift detection of a burst
  12. Swift GRB250330.26: Global MASTER-Net observations report
  13. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  14. GRB 250329B: SVOM/C-GFT optical upper limit
  15. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  16. GRB 250327B: ALMA detection
  17. GRB 250327B: VLA detection
  18. GRB 250329B: SVOM/VT optical upper limit
  19. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  20. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  21. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  22. GRB250329A: REM optical afterglow detection
  23. GRB 250329B: GWAC-F50A optical upper limit
  24. GRB 250329B: SVOM detection of a faint transient
  25. GRB 250329A: Swift-XRT afterglow detection
  26. GRB 250328A: SVOM/VT optical observation
  27. GRB 250329A: Fading optical counterpart detection by LCO.
  28. GRB 250328A: SVOM/C-GFT optical upper limit
  29. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  30. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  31. GRB 250329A: VLT/X-shooter redshift z = 2.921
  32. GRB 250329A: SVOM/VT optical counterpart confirmation
  33. GRB 250329A: SVOM detection of a burst
  34. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  35. GRB 250327B: J-band observations with WINTER
  36. GRB 250327B: MASTER detection of OT rebrightening
  37. GRB 250327B: LCO optical counterpart detection
  38. GRB 250328A: GWAC-F50A optical upper limit
  39. GRB 250328A: SVOM detection of a burst
  40. FRB 20250316A: FTW optical observations
  41. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  42. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  43. GRB 250327B: CrAO and SAO RAS Optical Observations
  44. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  45. GRB 250327B: further optical observations by LCOGT
  46. EP250315a: Pan-STARRS r and i-band imaging and photometry
  47. GRB 250327b: Liverpool Telescope optical observations
  48. GRB 250322A: GRANDMA/TNOT optical upper limits
  49. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  50. GRB 250327A: SVOM/VT upper limits on the XRT position
  51. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  52. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  53. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  54. GRB 250327B: 1.6m Mephisto optical observations
  55. GRB 250327B: NOT spectroscopic redshift z = 3.035
  56. GRB 250327A: Swift-XRT refined Analysis
  57. GRB 250327B: GOTO optical counterpart detection
  58. GRB 250327B: SVOM/VT optically bright counterpart
  59. GRB 250327B: SAO RAS optical candidate
  60. GRB 250327B: SVOM detection of a burst
  61. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  62. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  63. GRB 250327A: J-band observations with WINTER
  64. GRB 250327A: SVOM/VT optical candidate
  65. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  66. GRB 250327A: Fermi GBM observation
  67. Fermi GRB 250327A: Global MASTER-Net observations report
  68. Swift GRB 250327A: Global MASTER-Net observations report
  69. GRB 250327A: DDOTI Optical Observations
  70. GRB 250327A: COLIBRÍ optical upper limit
  71. GRB 250327A: Swift detection of a burst
  72. GRB 250327A: Fermi GBM Final Real-time Localization
  73. Fermi trigger No 764700395: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  75. Konus-Wind detection of GRB 250322A (short)
  76. IPN triangulation of GRB 250322B
  77. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  78. EP250321a: Mondy AZT-33IK Continued Optical Observations
  79. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  80. GRB 250322A: third epoch of NOT optical observations
  81. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  82. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  83. GRB 250322A: further NOT optical observations
  84. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  85. GRB 250322A: Swift/UVOT Upper Limits
  86. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  87. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  88. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  89. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  90. GRB 250321B: Swift-XRT observations
  91. GRB 250322A: Swift-XRT refined Analysis
  92. EP250321a: TNOT Observation of Optical Counterpart
  93. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  94. GRB 250322A: Gemini-North redshift of candidate host galaxy
  95. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  96. SVOM/sb25032302: SVOM detection of a long X-ray transient
  97. GRB 250322A: AstroSat CZTI detection of a short burst
  98. GRB 250322B: AstroSat CZTI detection of a bright long burst
  99. GRB250322A: STEP/T80S optical limits
  100. GRB 250322A: Gemini-South optical observations

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