Nova Sgr 2001 = V4643 Sgr

CCD image by S. Kiyota

(vsnet-alert 5713 = vsnet 2076)

Possible nova in Sgr

Date: Sat, 24 Feb 2001 16:58:06 -0500
From: "W.Liller" 
Subject: [vsnet 2076] Possible nova in Sgr

Hola everyone -

Surely someone else will have discovered this bright intruder already, but here is what I found:

There is an apparent nova (mag 7.7) on Technical Pan photographs taken on Feb. 24.3687 and 24.3709 UT with an 85mm camera (+orange filter). The approximate location of the star is R.A. = 17h 54.7m, Dec. = -26d 14'

(equinox 2000). Nothing brighter than mag 11.0 appears at this location on photographs taken on Feb. 14.

Confirmation is kindly requested. The star is approx. 3.0' east of GSC 6845 565. I will try for a more precise CCD position and magnitude tonight -- and a spectrogram if possible.

All the best to all, Bill Liller


(vsnet-alert 5721)

Kia ora everyone,

Clouds clearing.

Nova Sgr 2001

2001 February 25d15h04m UT Magnitude (visual) 8.9

Comparison stars Vj from Guide 7 CD ROM


Albert Jones

(vsnet-alert 5722)

Visual magnitude estimates by VSOLJ members

object         YYYYMMDD(UT)    mag   code
SGRnova2001    20010225.838     91   Mhh.VSOLJ  Seq. H/T

Observer: H.Maehara (Saitama, Japan)
Instruments: 20L

(vsnet-alert 5730)

Nova Sgr 2001 observation by K. Hirosawa

object         YYYYMMDD(UT)   mag  code
SGRnova2001    20010225.835    90  Hsk.VSOLJ

Observer's code:
  Hsk: Kenji Hirosawa (Aichi, Japan)  Instruments: 28cm SC

Independent detection

(vsnet-alert 5734)

Nova Sgr 2001: independent detection and prediscovery records by H. Nishimura

Hideo Nishimura (Kakegawa, Shizuoka, Japan) has reported he had detected the presence of the object on two photographs taken on Feb. 24 (see below for the details). The object was barely seen at the limit of detection on two photographs taken on Feb. 17.831 and 17.833 UT.

    The data:

    2001 Feb. 17.831 UT detected at the limit      exposure=40s
              17.833    detected at the limit      exposure=50s
              24.833    photographic magnitude 7.5 exposure=50s
              24.834    photographic magnitude 7.5 exposure=50s

    Instruments: 105mm F/5.6, T-Max 400 unfiltered
Relayed from Murai (Hamamatsu, Japan)

Spectroscopic confirmation as a nova!

(vsnet-alert 5723)

Dear colleagues,

We, K. Ayani and T. Kawabata (Bisei Astronomical Observatory) obtained a low-resolution spectrum (instrumental FWHM = 0.6nm; range 470-800nm) of possible nova Sgr 2001 at Feb. 25.88 UT with the Bisei Astronomical Observatory 1.01-m telescope. Strong and broad H-alpha and H-beta emission lines and broad emission feature at 784nm (O I 777.3 + Mg II 789.0 ?) are prominent. Fitting a gaussian, the equivalent width and FWHM of the H-alpha line are estimated to be 45nm and 4700 km/s, respectively. This object is truly a nova.

Best regards,

Kazuya Ayani
Bisei Astronomical Observatory

Prediscovery negative data

(vsnet-alert 5738)

Nova Sgr 2001 prediscovery negative observation by Takamizawa

Dear William,

Congratulations on your discovery!! This is a first galactic nova in 21th century.

The SASS(Saku All Sky Survey) image which was taken 5-min T-Max 400 film exposures on 2001 Feb. 19.831UT shows no object to mag 13.7 at the location Nova Sgr. 2001.

Best wishes,Kesao

Kesao Takamizawa    
SASS(Saku All Sky Survey)
Saku-machi, Nagano, 384-0502 Japan

Astrometry and identification

(vsnet-alert 5724)

Dear Colleagues,

Possible nova in Sgr: astrometry

2001 02 25.82760 UT
R.A.=17h54m40.42s Decl.=-26d14'15.2" (J2000.0)
12 reference stars from GSC-ACT. Mean residuals: 0.08" in R.A., 0.09" in Decl.
0.18-m f/5.5 reflector + CCD. 
K. Kadota, Ageo, Saitama, Japan.
Best regards,
K. Kadota

(vsnet-alert 5725)

There appears to be a USNO-A2.0 star at this position with magnitudes B = 17.4 and R = 15.8.

                             Yours sincerely,
                             Bjorn H. Granslo

(vsnet-alert 5727)

I note that Kadota-san's position is 0".4 from a moderately-bright USNO-A2.0 star (which looks real on the DSS image) at:

17 54 40.413 -26 14 15.38 (2000)

When reporting astrometry from CCD images, it would be best if several images were used to make the determination, particularly if the target were moved somewhat between frames, so that the reference net would also be shifted. The scatter in say three or four measurements would give a much better idea of the true uncertainty in the position than would a single frame using only the error in the fits to the reference stars.


(vsnet-alert 5728)

Dear all,

>Immediately neighbourhood of this position, an USNO_A2.0 star
>(position end figures 40s.414, 15".40, rmag = 15.8, bmag = 17.4)
>exists, which is the plausible counterpart at quiescent.
This star is really seen on DSS2R image. There seems to exist an dim (rmag about 18) star 2"-3" northeast of this USNO star, and no other object can be seen in 5" radius.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan

(vsnet-alert 5729)

Using K. Kadota's position of the new nova in Sgr (vsnet-alert 5724), the VizieR catalogue service at CDS Strasbourg returns the following potential precursor:

USNO-A2.0 0600-29446361 J2000 position RA 17 54 40.413, Dec -26 14 15.38
Blue plate mag 17.4 Red plate mag 15.8 

2MASSI J1754404-261415 J2000 position RA 17 54 40.42, Dec -26 14 15.5 
Jmag 12.950 +-0.050 Hmag 12.561 +-0.036 Kmag 12.268 +-0.067


James Bedient
Meteor Group Hawaii

(vsnet-alert 5733)

Nova Sgr 2001: revised astrometry by Kadota

K. Kadota, Ageo, Saitama, Japan has provided the following updated astrometry of Nova Sgr 2001. The position may be more accurate than the one previously reported (vsnet-alert 5724), which may have been affected by the image saturation.

2001 02 25.83346 UT
R.A.=17h54m40.43s  Decl.=-26d14'15.7" (J2000.0)
12 reference stars from GSC-ACT. Mean residuals: 0.12" in R.A., 0.13" in Decl.
0.18-m f/5.5 reflector. 
K. Kadota, Ageo, Saitama, Japan.

(vsnet-alert 5735)

Nova Sgr 2001: astrometry by Torii

K. Torii, NASDA, Japan has provided the following astrometry of Nova Sgr 2001. The position and error were estimated from 15 frames. Reference: USNO A2.0, software: Pixy-1

2001 02 25.826 UT
R.A.=17h54m40.41s  Decl.=-26d14'15.7" (J2000.0)
Error:  0.2" in R.A, 0.3" in Decl. (1-sigma)
0.2-m f/4 reflector + 1.4x teleconverter

Comparison star sequence

(vsnet-sequence 60)

***** Nova Sagittarii 2001 information and sequence *****

1748-26 NOVA SGR 2001 [R.A. = 17h54m40s.4, Decl. = -26o14'15" (2000)]

W. Liller has detected an apparent nova of mag. 7.7 on two exposures from Feb 24.47 UT using an 85-mm camera, Techical Pan film and an orange filter. No new object was present on Feb. 14 to a limiting magnitude of 11.0. [vsnet 2076].

The discovery has been confirmed by other observers. Observations by A. Jones, R. Stubbins and H. Maehara indicated mv=8.9-9.1 during Feb. 25.628-25.838 UT [vsnet 2077, vsnet 2078, vsnet-alert 5722].

Spectroscopic observations by K. Ayani and T. Kawabata confirm that the object is a nova. They found Doppler broadened emissions from H and possibly O I and Mg II [vsnet-alert 5723].

K. Kadota reports the following accurate position [vsnet-alert 5724]: R.A. = 17h54m40s.42s, Decl. = -26o14'15.2" (J2000.0). A USNO-A2.0 star (with magnitudes B=17.4 and R=15.8) and a 2MASS object is located very close to this position. The position end figures of these identifications are 40.41s, 15".4 and 40s.42, 15".5, respectively.

I have prepared a sequence based on astrometry and photometry from the Hipparcos (HIP) and Tycho-2 (TYC2) catalogues. This sequence is primary intended for visual observers, mainly due to the limited accuracy of the HIP/TYC2 photometry (with decreasing brightness from 0.02 to about 0.10 mag.). In order to minimize systematic differences between the Johnson V and visual magnitudes I have only included stars that are bluer than B-V = +1.0. In order to obtain V and B-V from the BT and VT magnitudes in TYC2 the standard transformation formulae have been used. B. Skiff (private communication 2001) has, however, pointed out that better results can be obtained by using the relations of M. Bessell in Publ. Ast. Soc. Pacific, 112, 961 (2000).

For more accurate photometry one may use the GSPC sequence prepared by Skiff [vsnet-alert 5710].

The numbers in last column refer to identifications (V magnitudes in units of 0.1 mag.) on the chart compiled by R. Bouma and E. van Dijk at [vsnet-alert 5719].

Id   R.A. (2000.0) Decl.  Star Name      V-mag   B-V   Ref   Bouma
    h  m   s    o  '  "                                      chart
A  17 56 24.4  -26 46 24  HIP 87824       7.39  +0.61  HIP    74
B  17 56 15.2  -25 40 22  HIP 87809       7.87  +0.06  HIP    79
C  17 54 30.1  -26 37 56  HIP 87679       8.55  +0.76  HIP    86
D  17 54 18.4  -25 57 44  HIP 87661       9.00  +0.60  HIP    90 
E  17 55 09.7  -26 18 11  TYC 6849-1798   9.13  +0.08  TYC2   92
F  17 56 41.0  -26 12 03  TYC 6845-0880   9.76  +0.75  TYC2   97
G  17 56 55.2  -26 07 06  TYC 6845-0562  10.14  +0.14  TYC2  102 
H  17 54 23.1  -26 42 58  TYC 6849-0872  10.28  +0.16  TYC2  103
I  17 55 10.4  -26 15 14  TYC 6849-1114  10.97  +0.78  TYC2  108
K  17 54 37.5  -26 16 36  TYC 6849-1825  11.06  +0.56  TYC2  ...

For this study I have made extensive use of the VizieR service of CDS ( and I wish to thank CDS for this service.

                                    Yours sincerely,
                                    Bjorn H. Granslo


(vsnet-alert 5719)

Following Liller's report of a possible nova in Sagittarius [vsnet 2076] we have prepared a chart (2.5 x 3 degrees) for visual observers, with comparison stars from Hipparcos/Tycho down to magnitude 10.8 and placed it the following URL:

Reinder Bouma/Edwin van Dijk

(vsnet-alert 5720)

For those not quite familiar with Sagittarius, we now have placed a finderchart (12x15 degrees) for the possible nova, with a few bright comparison stars down to magnitude 8.6, at:

VSNET light curve (requires Java)

Light curve

VSNET data search


Return to HomePage

Return to the Powerful Manager, Daisaku Nogami