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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"

24776 results found.

  1. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  2. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  3. GRB 250312A: Swift-XRT refined Analysis
  4. GRB 250312A: Enhanced Swift-XRT position
  5. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  6. GRB 250226B: Fermi GBM Observation
  7. GRB 250302A: Fermi GBM Observation
  8. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  9. GRB 250312A: Swift detection of a burst
  10. GRB 241213A: VIRT Optical Upper Limit
  11. GRB 241228A: VIRT Optical Upper Limit
  12. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  13. GRB 250311A: Swift-XRT observations
  14. GRB 230509B: 1.3m DFOT Optical observations
  15. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  19. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  20. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  21. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250309B: PRIME near-infrared detection
  23. GRB 250225B: Swift-BAT refined analysis
  24. GRB 250311A/EP250311a: TRT optical upper limit
  25. EP250311a/GRB 250311A: EP-WXT detection
  26. GRB 250311B: SVOM detection of a burst
  27. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  28. GRB 250309B / AT2025dws: further SAO RAS optical observations
  29. EP250308a: 1.6m Mephisto optical upper limits
  30. Konus-Wind detection of GRB 250309B
  31. IPN triangulation of GRB 250308A (short)
  32. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  33. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  34. GRB 250309B: Swift-XRT refined Analysis
  35. GRB 250309B / IceCube-250309A: GECAM-B observations
  36. GRB 250309B / AT2025dws: SAO RAS optical observations
  37. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  38. GRB 250309B: Fermi GBM Observation
  39. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  40. IceCube-250309A: No candidates from the Zwicky Transient Facility
  41. Fermi-LAT gamma-ray observations of IceCube-250309A
  42. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  44. EP250308a: GSP optical upper limit
  45. EP250308a: Einstein Probe detection of an X-ray transient
  46. EP250308a: NOT optical upper limit
  47. GRB 250306A: EIRSAT-1 GMOD detection
  48. GRB 250306A: Swift-BAT refined analysis
  49. GRB 250306A: NuSTAR detection of the prompt emission
  50. EP250304a: MeerKAT detection of a possible radio counterpart
  51. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  52. GRB 250305A: AstroSat CZTI detection
  53. EP250302a:Xinglong optical observations
  54. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  55. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  56. GRB250101A: Radio upper limits from VLA observations
  57. GRB 250305A: SVOM/GRM observation of a burst
  58. The EP-WXT trigger 01709132323 is likely a flaring star
  59. EP250304A: Upper limits from Fermi-GBM Observations
  60. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  61. EP250302a: Optical Observations at CrAO and SAO RAS
  62. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  63. EP 250304A: Optical counterpart detection by LCO
  64. EP250302A: 1.3m DFOT optical afterglow detection
  65. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  66. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  67. EP250304a: REM NIR upper limits
  68. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  69. EP250302a: Mondy Continued Optical Observations
  70. EP250304a: Swift-XRT detection of a fading X-ray source
  71. EP250304a: TRT optical counterpart detection
  72. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  73. EP250304a: Einstein Probe detection of an X-ray transient
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  75. EP250302a: SAO RAS optical observations
  76. EP250302a : GIT optical follow-up
  77. EP250225a: the candidate optical counterpart is an AGN
  78. EP250302a: Kinder optical follow-up observations
  79. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  80. EP250302a: Swift/UVOT detection
  81. EP250302a: optical observation from the INAF Asiago Observatory
  82. EP250302a: REM NIR upper limits
  83. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  84. EP250302a: Mondy Observations and Optical Light Curve
  85. EP250302a: VLT/MUSE optical redshift z = 1.131
  86. EP250302A: VLT near-infrared observations
  87. EP250302A: VLT/X-shooter tentative redshift
  88. EP250302a: OHP/T193 optical and spectroscopic observations
  89. EP250302a: Swift-XRT observations of a fading X-ray source
  90. EP250302a: Einstein Probe detection of an X-ray transient
  91. EP250302a: SVOM/C-GFT optical observations
  92. GRB 250226A: GRANDMA Optical Observations
  93. EP250302a: Montarrenti Observatory optical detection
  94. EP250302a: Nanshan/HMT optical counterpart detection
  95. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  96. GRB 250225B: VLT near-infrared afterglow confirmation
  97. EP250228a: Optical observations with Kinder and Swift/UVOT
  98. Konus-Wind detection of GRB 250226A
  99. GRB 250225B: EIRSAT-1 GMOD Detection
  100. GRB 250226A: KAO Optical Upper Limit

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