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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"

44399 results found.

  1. GRB 250330A: Swift detection of a burst
  2. Swift GRB250330.26: Global MASTER-Net observations report
  3. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  4. GRB 250329B: SVOM/C-GFT optical upper limit
  5. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  6. GRB 250327B: ALMA detection
  7. GRB 250327B: VLA detection
  8. GRB 250329B: SVOM/VT optical upper limit
  9. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  10. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  11. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  12. GRB250329A: REM optical afterglow detection
  13. GRB 250329B: GWAC-F50A optical upper limit
  14. GRB 250329B: SVOM detection of a faint transient
  15. GRB 250329A: Swift-XRT afterglow detection
  16. GRB 250328A: SVOM/VT optical observation
  17. GRB 250329A: Fading optical counterpart detection by LCO.
  18. GRB 250328A: SVOM/C-GFT optical upper limit
  19. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  20. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  21. GRB 250329A: VLT/X-shooter redshift z = 2.921
  22. GRB 250329A: SVOM/VT optical counterpart confirmation
  23. GRB 250329A: SVOM detection of a burst
  24. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  25. GRB 250327B: J-band observations with WINTER
  26. GRB 250327B: MASTER detection of OT rebrightening
  27. GRB 250327B: LCO optical counterpart detection
  28. GRB 250328A: GWAC-F50A optical upper limit
  29. GRB 250328A: SVOM detection of a burst
  30. FRB 20250316A: FTW optical observations
  31. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  32. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  33. GRB 250327B: CrAO and SAO RAS Optical Observations
  34. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  35. GRB 250327B: further optical observations by LCOGT
  36. EP250315a: Pan-STARRS r and i-band imaging and photometry
  37. GRB 250327b: Liverpool Telescope optical observations
  38. GRB 250322A: GRANDMA/TNOT optical upper limits
  39. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  40. GRB 250327A: SVOM/VT upper limits on the XRT position
  41. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  42. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  43. GRB 250327B: Las Cumbres optical counterpart detection
  44. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  45. GRB 250327B: 1.6m Mephisto optical observations
  46. GRB 250327B: NOT spectroscopic redshift z = 3.035
  47. GRB 250327A: Swift-XRT refined Analysis
  48. GRB 250327B: GOTO optical counterpart detection
  49. GRB 250327B: SVOM/VT optically bright counterpart
  50. GRB 250327B: SAO RAS optical candidate
  51. GRB 250327B: SVOM detection of a burst
  52. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  53. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  54. GRB 250327A: J-band observations with WINTER
  55. GRB 250327A: SVOM/VT optical candidate
  56. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  57. GRB 250327A: Fermi GBM observation
  58. Fermi GRB 250327A: Global MASTER-Net observations report
  59. Swift GRB 250327A: Global MASTER-Net observations report
  60. GRB 250327A: DDOTI Optical Observations
  61. GRB 250327A: COLIBRÍ optical upper limit
  62. GRB 250327A: Swift detection of a burst
  63. GRB 250327A: Fermi GBM Final Real-time Localization
  64. Fermi trigger No 764700395: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  66. Konus-Wind detection of GRB 250322A (short)
  67. IPN triangulation of GRB 250322B
  68. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  69. EP250321a: Mondy AZT-33IK Continued Optical Observations
  70. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  71. GRB 250322A: third epoch of NOT optical observations
  72. GRB 250322A: Swift-BAT refined analysis
  73. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  74. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  75. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  76. GRB 250322A: further NOT optical observations
  77. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  78. GRB 250322A: Swift/UVOT Upper Limits
  79. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  80. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  81. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  82. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  83. GRB 250321B: Swift-XRT observations
  84. GRB 250322A: Swift-XRT refined Analysis
  85. EP250321a: TNOT Observation of Optical Counterpart
  86. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  87. GRB 250322A: Gemini-North redshift of candidate host galaxy
  88. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  89. SVOM/sb25032302: SVOM detection of a long X-ray transient
  90. GRB 250322A: AstroSat CZTI detection of a short burst
  91. GRB 250322B: AstroSat CZTI detection of a bright long burst
  92. GRB250322A: STEP/T80S optical limits
  93. GRB 250322A: Gemini-South optical observations
  94. GRB 250322A: VLT optical observations
  95. GRB 250322A: VLT near-infrared observations
  96. FRB 250316A: DDOTI Continued Optical Observations
  97. GRB 250322A: NOT optical upper limits
  98. GRB 250322A: Enhanced Swift-XRT position
  99. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  100. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060

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